Vol. 24 No. 02 Apr-Jun 2015

Samira Adnan ¹                                        BDS,FCPS

Farhan Raza Khan²                               BDS, MS, MCPS, FCPS

CASE REPORT

A 27 year old female came to our dental clinic having an otherwise healthy dentition, with only her upper left 2nd premolar exhibiting grade III mobility. This was her chief complaint, that the tooth had becoming excessively mobile and was bothering her while chewing. On further inquiry, it was found the some months before, this particular tooth was fine. One night, in a hypnagogic state, she had the urge of wriggling this tooth with her finger. After this specific episode, she established a habit of playing with this tooth, wriggling and twisting it all day long with her finger and tongue. Now the tooth had become so mobile that it was causing her discomfort, interfering with her bite and she wanted to get it extracted (figure 1, 2). Unfortunately, nothing could be done as to

save the tooth as it was just attached with the gingiva with no surrounding bone. Usually, cases of dental selfmutilation or auto-extraction have been reported more frequently in patients with either psychotic illnesses¹, autism^2-4 or those succumbing to peer-pressure⁵. This case is unusual because the patients had no history of psychiatric problem or sleep disorders, and was fully conscience of the fact that she was causing self-harm. Yet she was unable to stop herself from damaging the supporting tissues of the tooth, and had caused injury to such an extent that the tooth had become unsalvageable. The tooth in question was extracted after explaining to the patient the extreme damage that had resulted from her habit, and advising that if she developed the urge to practice such a self-destructive

routine on any other tooth, she should not only seek dental consultation but also consult with a psychiatrist in order to assess the reason behind the self-mutilating behaviour. Her pre-extraction radiograph was taken but unfortunately wasnot properly saved in the clinic computer and thus got misplaced.

REFERENCES

1. Altom RL, DiAngelis AJ. Multiple autoextractions: oral self-mutilation reviewed. Oral Surg Oral Med Oral Pathol. 1989; 67:271-274.
2. Armstrong D, Matt M. Autoextraction in an autistic dental patient: a case report. Spec Care Dentist. 1999;19:7274.
3. Ross-Russell M, Sloan P. Autoextraction in a child with autistic spectrum disorder. Br Dent J. 2005;198:473474.
4. Williams AC. Autoextraction of twelve permanent teeth in a child with autistic spectrum disorder.Int J Paediatr Dent. 2015; doi: 10.1111/ipd.12161.
5. Agrawal A, Gupta SK, Saxena P, Agrawal S. Selfmutilation of teeth due to peer pressure: an aspect of child psychology. Brit Med J Case Rep. 2014; doi: 10.1136/bcr2014-203624.

1. Former Chief Resident, Operative Dentistry, Aga Khan University, Karachi, Pakistan. < nnmst@hotmail.com >
2. Assistant Professor, Operative Dentistry Dental Section, Aga Khan University, Karachi, Pakistan.

Corresponding author: “Dr Farhan Raza Khan ” < farhan.raza@aku.edu  >

Farhan Raza Khan ¹                                BDS, MCPS, MS, FCPS

Tashfeen Ahmad²                                   MBBS, FCPS, PhD

Rabia Hussain³                                        MSc, PhD

Zulfiqar Ahmed Bhutta⁴                      MBBS,FCPS,FRCP,FRCPCH, PhD                        

INTRODUCTION

Among all study designs, randomized controlled clinical trial (RCT) is considered as the gold standard^[1]. Researchers put substantial effort in designing and conducting RCTs to generate high quality scientific evidence that helps to shape the future of the healthcare^[2]. It’s likely that the subjects enrolled in a clinical trial are diagnosed with certain health conditions that are unrelated to the main research objective but otherwise are fairly treatable and manageable; this poses a dilemma to the investigators. It becomes more relevant when the trial is being conducted in a community where basic health facilities are extinct or at least not readily available.

The good clinical practice (GCP) guidelines for trials suggests that “during and following a subject’s participation in a trial, the investigator/institution should ensure that adequate medical care is provided to a subject for any adverse events, including clinically significant laboratory values, related to the trial”. However, provision of care for a health condition that is relatively “unrelated” to the primary objective of the study is not discussed in thatguidelines^[3]. Here, we report the dental services rendered to the participants enrolled in a community based, double blind, randomized controlled trial that was conducted atdistrict Jhelum. The pregnant women from 12-16 weeks of gestation were inducted. The objective of the primary study was to determine the effect of oral vitamin D supplementation on the pregnancy outcomes. The detailed results are published elsewhere^[4].

METHODOLGY

A total of 85 pregnant women were recruited in the study that was duly approved by Aga Khan University Ethics review committee (AKU-ERC,ref# 147-Ped-ERC2010) and trial protocol was registered at the clinicaltrials.gov bearing ID# NCT01422122⁵

A large proportion of the females enrolled in the trial had some dental problems but their access to the professional dental care wasrestricted. There was no qualified & registered dental practitioner in that area. This compelled them to travel to over hundred miles to get oral care at any setting that has any reasonableinfection control practices.Both the access and the financial affordability of professional dental care werequestionable. Moreover, during prospective assessment of the subjects on regular time points, the trial participants started to expect some form of dental treatment.  Although, it was not part of the original study protocol, but we discussed this within our team to provide some help to the participants so that a community service elementis added to our research. This made it possible for not only the trial participants but their immediate household to get basic dental care.

A mobile dental operatory that was originally acquired for Aga Khan Health services in Northern areas of Pakistan and was attained at the trial site. The permission was obtained to use that mobile dental operatory (with all instruments, accessories, materials along with an autoclave sterilizer) for delivering the baseline dental care to the study participants at the community trial site.A dentist and a dental assistant (both full time employed at university) visited the PindDadan Khan for 10 days. The project office of the women and child health division at trial site was used as the base camp to install the dental operatory.The treatment delivery visit was confined to serve the pregnant females already registered in the trial with no intentions to carry out any new research.Study participants were brought into the office by the project transport.

RESULTS

We planned to deliver required oral care to 85 females

Basic dental care to pregnant women in a trial

out of which 70 turned up. However, 26 males were also seen. These males were the immediate family members of the study participants. There were 13 other females

examined who were either local residents or were close relative (sister or sister in law) of the study participant andwere accompanied with the participants. Thus, a total of 109 subjects were attended.

DISCUSSION

Pakistan is a resource constraint country. The model of health care in rural districts of the country is such that public hospitals are already over-burdened. Limited funds, deficiency of health care staff and long distances between clusters of population and health care facility makes the accessibility of care a challenge. Moreover, the health insurance or any third party coverage is nonexisting in the underdeveloped areas. This makes the provision of clinical care to the participants already enrolled in a randomized trial an uphill task. Although, investigators, ethics review committee and the data safety monitoring units, all work as a team to design and take up appropriate measures to ensure safety of the participants but it’s not uncommon for anystudy participant to develop a health condition that is albeit manageable but is somewhat unrelated to the primary research objective.

In the present study, scaling was the most frequent service (n=42, 38.5%) that was being offered. This reveals that hygiene related periodontal problems were prevalent in the sample. Those who presented with minor periodontal deposits were advised oral hygiene instruction and education on tooth brushing and flossing (n=39, 35.7%). Extractions under local anesthetic were done on 20

(18.3%) subjects. There were 8 subjects (7.4%) who did not gave consent for any intervention primarily because of the fear that they will get any injection during treatment. Their decision was respected and no intervention carried out on this subset. The most important limitation in the course of this exercise was our inability to offer dental restorations (fillings). We didn’t carry any mercury disposal system with us; so amalgam restorations were not done. Similarly, lack of polymerization light guide tip prevented us from carrying out resin based composite fillings too.

There was a warm response among the local residents who requested contacted clinical trial project office to get their families examined but it was not possible to expand the services because of limited resources including time available to us. However, providing the baseline dental care to the under privileged community was an excellent gratifying experience.

CONCLUSIONS

We inferred that whenever possible, a service component should be added to the community based studies. This not only ensuresparticipants’ interest, but adds value of community service to the research and above all, it rewards the investigators with a satisfying experience.

GRANT INFORMATION

The main study was supported by a grant from Pakistan Initiative for Mothers and Newborns (PAIMAN). The USAID-funded Pakistan Initiative for Mothers and Newborns (PAIMAN) project has served various districts in Pakistan. Professor Zulfiqar A. Bhutta is the recipient of the grant.

ACKNOWLEDGEMENTS

Authors acknowledge the kind help of Dr Sajid Soofi and Dr Atif Habib at the Women and Child Health Division, Aga Khan University and Mr Didar Alam at the Nutrition Research Laboratory of the Aga Khan University, Karachi for the conduct of this study

AUTHOR’S CONTRIBUTION

Dr Zulfiqar Ahmed Bhutta received the grant, planned and supervised the main vitamin D study.Dr Farhan Raza Khan did the periodontal assessment of pregnant females and wrote this manuscript. Dr Rabia Hussain contributed by doing the multiplex inflammatory biomarkers analysis for development of periodontitis among study participants.Dr Tashfeen Ahmed did the statistical analysis of study data and supervised of the dental aspect of study.

CONFLICT OF INTEREST DISCLOSURE

The authors declare that there is no conflict of interest regarding the publication of this article.

REFERENCES

1. Sackett DL, Rosenberg WM, Gray JA, Haynes RB, Richardson WS. Evidence based medicine: what it is and what it isn’t. Brit Med J 1996; 312: 71-72.
2. Evidence-Based Medicine Working Group. Evidence based medicine. A new approach to teaching the practice of medicine. J Am Med Assoc 1992; 268: 2420-2425.
3. http://www.fda.gov/downloads/Drugs/Guidances/ ucm073122.pdf. Page 14.
4. Khan FR, Ahmad T, Hussain R, Bhutta ZA. Effect of vitamin D supplementation on the periodontal status of pregnant females- A randomized clinical trial. (unpublished data) J Periodontol.
5. Khan FR, Bhutta ZA. Study of Vitamin D Supplementation on Improvement of Gums Health. www.clinicaltrials.gov: Identifier: NCT01422122.

1. Assistant Professor, Dentistry, Department of Surgery Aga Khan University & Hospital, Stadium Road, Karachi 74800, Pakistan.
2. Orthopedics Section, Department of Surgery, Aga Khan University, Karachi, Pakistan.
3. Immunology Section, Department of Pathology, Aga Khan University, Karachi, Pakistan.
4. Center of Excellence in Women & Child Health, Aga Khan University, Karachi, Pakistan.
Corresponding author: “Dr Farhan Raza Khan” <farhan.raza@aku.edu >

Abdul Bari Memon ¹                                 BDS, MSc

Abdul Jabbar ²                                           BDS, FCPS 

Irfan Ahmed Sheikh ³                             BDS, FCPS 

Waheed Murad Dahri ⁴                          BDS

Permanand Malhi ⁵                                 BDS, MSc  

Sadam Hussain Rind ⁶                           BDS                          

INTRODUCTION

It is important to maintain better oral hygiene during orthodontic treatment. Fixed orthodontic appliances cause difficulty in tooth brushing which lead to accumulation of plaque.  Emphasis must be given on oral hygiene maintenance, including both professional tooth cleaning and home care instructions^1-3.

There is direct correlation between oral hygiene and periodontal health⁴. Orthodontic appliances such as brackets and bands trap food and other debris under wir e which makes it challenging for patient to maintain oral hygiene⁵. Good oral hygiene is hallmark for good dental and periodontal health during orthodontic treatment^6-8. Brackets, arch wires and other orthodontic gadgets are main focal points for  accumulation of plaque and also acts as  obstacle to control the  plaque  hence enhancing gingivitis⁹. Plaque also carries cariogenic bacteria which are capable of developing white spot lesions around brackets margins^7,8. Fixed orthodontic treatment increases risk of enamel demineralization which is evident in patients with compromised oral hygiene¹⁰.

A recent review of literature concluded that fixed orthodontic treatment may cause few detrimental effects  to the periodontium¹¹. Along with that in another study it is also stated that periodontitis due to orthodontic fixed appliance therapy may be avoided if basic oral hygiene maintenance protocol is followed¹². It is observed that a significant percentage of orthodontic patients feel difficulty in maintaining oral hygiene and exhibit adverse effects¹³.

Tooth brushing is the principal tool  used for plaque control, however regular tooth brush does not remove inter-dental plaque adequetly¹⁴. Therefore inter-dental plaque controlling aids such as flossing and inter-dental brushing should be added along with regular brush. Oral hygiene instructions are frequently demonstrated by orthodontists to their patients routinely to motivate them for oral hygiene improvement¹⁵. Aim of our research was to assess the plaque score in the fixed orthodontic patients in relation to gender, age and duration of orthodontic treatment.

METHODOLOGY

A cross sectional study was conducted from spetember 2013 to march 2014 at the Department of Orthodontics, Liaquat Medical University Hospital and private orthodontic clinics in Hyderabad. Permission was obtained from the ethical review committee and informed written consent was taken from all participants.

The online Epi calculator was used to calculate sample size. The sample size was calculated at a 95% confidence interval, with 0.3% estimated proportion of plaque and 0.05 desired precision of estimate from the 1000 population size. The required sample size was 245.

Non-probability purposive sampling technique was used to select 245 orthodontic patients. Orthodontics patients having fixed orthodontics appliances, age ranges from 13 to 25 years of either gender, permanent dentition up to 2^nd molar, having no enamel defects or no restorations involving facial surface and good general health were included in study. Patients having crown, bridge, removable appliances or clear liners and mouth washes used in last four weeks were excluded from study.

Mouth mirror and profound light were used to examine patients individually. Selected patients were asked to chew the plaque disclosing tablet (Eviplac Pastilhas), swish it for thirty seconds, spit out and wash once with clean water to decrease the false positive results. Facial, palatal and lingual surfaces were examined to calculate the plaque score. Turseky modification of Quigley Hein Plaque index was used to calculate plaque score using the following formulae:

Index = Total score / number of surfaces Examined The data was analyzed by Statistical Package for Social Sciences (SPSS) version 16. Categorical variables like gender and cleaning of teeth are presented in frequencies. Numerical variables like age and plaque score were recorded as mean and SD. Independent T test was used to check significance of plaque score in male and female. One way ANOVA test was applied among plaque score and duration of fixed appliance to assess the plaque score. Correlation analysis was done between the age of patients and plaque index score. The level of significance was set to < 0.05 at 95% Confidence Interval.

RESULTS

Mean plaque score was 4.29+1.58 and mean age 19.1+2.47 years. Mean values of plaque for male 2.42+0.70 and female 2.51+1.99 were statistically not significant. (Table-1).

Male and female patients were 42% and 58% respectively. Majority of Male and female patients were cleaning their teeth once a day and very less number of patients were cleaning their teeth thrice a day. (Table-2)

The analysis of variance (ANOVA) test showed insignificant differences in plaque score and duration of fixed appliance. (Table-3)

There was insignificant (r=0.035, p = 0.581) correlation between age and plaque score. (Table-4)

DISCUSSION

For the correction of skeletal, dental and facial problems an effective cooperation is required between orthodontist, hygienist, patient and specialist of related fields linked to that problem¹⁶. If patient is motivated and keen to control plaque effectively he may keep his dentition for life time¹⁷. Orthodontic treatment becomes complicated and develop undesirable effects if oral hygiene is not maintained¹⁸.

Most of the periodontal diseases and dental caries are caused by plaque. Therefore, plaque control must be insisted in avoiding periodontal problems during orthodontic treatment⁴.

There was insignificant difference of plaque score between different genders. The findings of this study are in agreement with the study of Sukhia HR¹⁹ and Attasi F, Awartani F²⁰. In comparison of brushing frequency, females brushed more than male counterparts which can be compared with the research of Sukhia HR¹⁹ and Da’ameh M D²¹. This might be due to the fact that females are more conscious about their hygiene as compared to males. Very few patients were irregular in cleaning their teeth on daily basis.

The current study found that plaque score does not increase with increase in treatment duration, this finding is not in harmony with other studies^9-22,24.  Optimal oral hygiene can be achieved when proper measures are  used25-26.

There was insignificant (r=0.035, p = 0.581) correlation between age and plaque score. This finding was in contrast with the study results of Al-Hadad KA et²⁷ al and a study conducted on subjects in Sana’a²⁸. However some

researchers have reported similar results as ours ^29,30. These variations may be attributed to differences in methodology or age of study samples and may also reflect genuine differences in oral hygiene practices, culture, and food habits. This study was conducted on orthodontic fixed appliances patients so the results of our research may not be valid for patients using clear aligners and removable appliances. The data was collected by single researcher so operator bias could not be eliminated.

CONCLUSION

It is concluded that:

• Plaque score was not influenced by age or gender of our study subjects
• Plaque score did not increase with increased duration of orthodontic treatment.

REFRENCES

1. Gold SL. Plaque-control motivation in orthodontic practice. Am J Orthod. 1975 ;68:8-14.
2. Clark JR. Oral hygiene in the orthodontic practice: Motivation, responsibilities, and concepts. Am J Orthod. 1976 ;69:72-82.
3. Yeung SC, Howell S, Fahey P. Oral hygiene program for orthodontic patients. Am J Orthod Dentofacial Orthop. 1989 ;96:208-213.
4. Kloehn JS, Pfeifer JS. The effect of orthodontic treatment on the periodontium. Angle Orthod 1974;44:127134.
5. RafeZvi, Vardimon Alexander, Ashkenazi Malka. Comparative study of 3 types of toothbrushes in patients with fixed orthodontic appliances. Am J Orthod Dentofac Orthop 2006;130: 92-95.
6. Zachrisson BU. Cause and prevention of injuries to teeth and supporting structures during orthodontic treatment. Am J Orthod 1976;69: 285-300.
7. Mitchell L. Decalcification during orthodontic treatment with fixed appliances: An overview. Br J Orthod 1992;19:199-205.
8. Atack NE, Sandy JR, Addy M. Periodontal and microbiological changes associated with the placement of orthodontic appliances: A review. J Periodontol 1996;67:78-85.
9. Zachrisson S, Zachrisson BU. Gingival condition associated with orthodontic treatment. Angle Orthod 1972;42:26-34.
10. Costa MR, da Silva VC, Miqui MN, Colombo AP, Cirelli JA. Effects of ultrasonic, electric, and manual toothbrushes on subgingival plaque composition in orthodontically banded molars. Am J Orthod Dentofacial Orthop. 2010;137:229-235
11. Boyd R. enhancing the value of orthodontic treatment: incorporating effective preventive dentistry into treatment. Am J Orthod 2000:117;601-603.
12. Laher A, Kroon J, Booyens SJ. Effectiveness of four manual toothbrushes in a cohort of patients undergoing fixed orthodontic treatment in an academic training hospital. SADJ. 2003;58:231, 234-237.
13. Quigley GA, Hein JW. Comparative cleansing efficiency of manual and power brushing. J Am Dent Assoc. 1962;65:26-29.
14. Bimstein E, Needleman HL, Karimbux N, Van Dyke TE. Periodontal and gingival health and diseases. London NW1 0AE: Martin Dunitz Ltd; 2001
15. Lees A, Rock WP. A comparison between written, verbal, and videotape oral hygiene instruction for patient with fixed appliances. J Orthod 2000;27:323-328.
16. Kharsa MAI. The importance of oral hygiene in orthodontic treatment. The Orthodontic SYPER J, 2007.
17. Schwaninger B, Vickers-Schwaninger N. Developing an effective oral hygiene program for the orthodontic patient: review, rationale, and recommendations. AM J Orthod1979;75:447-452.
18. Machen, DE. Periodontal evaluation and updates: don’t abdicate your duty to diagnose and supervise. Am J Orthod DentofacOrthoped 1990;98:84-85.
19. Sukhia HR. Oral hygiene evaluation in orthodontic practice. Pak Oral Dent J. 2002;22:31-38.
20. Attasi F, Awartani F. Oral hygine status among orthodontic patients. J Contemp Dent Pract 2010;11:2532.
21. Da’ameh M D, Al-Shorman I, Al-Shdeifat N, Fnaish MM. Oral hygiene measures in orthodontic treatment in Northern Jordan. Pak Ora Dent J.2011;31:336-339.
22. Zachrisson BU. Clinical implications of recent orthodontic periodontic research findings. Semin Orthod 1996;2:4-12.
23. Huser MC, Baehni PC, Lang R. Effects of orthodontic bands on microbiologic and clinical parameters. Am J Orthod Dento facial Orthop 1990;97:213-218.
24. Kloehn JS, Pfeifer JS. The effect of orthodontic treatment on the periodontium. Angle Orthod 1974;44:127134.
25. Speer C, Pelz K, Hopfenmuller W, Holtgrave EA. Investigations on the influencing of the subgingivalmicroflora in chronic periodontitis. A study in adult patients during fixed appliance therapy [in English and German]. J Oro fac Orthop 2004;65:34-47.
26. McGlynn FD, LeCompte EJ, Thomas RG, Courts FJ, Melamed BG. Effects of behavioral self-management on oral hygiene adherence among orthodontic patients. Am J Orthod Dento facial Orthop 1987;91:15-21.
27. Al-Haddad KA, Ibrahim YT, Al-Haddad AM, AlHebshi NN. Assessment of Gingival Health Status among 5- and 12-Year-Old Children in Yemen: A Cross-Sectional Study. ISRN dentistry 2013 (2013).
28. Clerehugh, U. Laryea, and H. V. Worthington, “Periodontal condition and comparison of toothcleaning using chewing sponge, chewing sticks and toothbrushes in 14-year-old schoolchildren in Ghana,” Commun Dent Oral Epidemiol 1995 23:319-320.
29. Cahen PM, Turlot JC, Frank RM, Obry-Musset AM. National survey of caries prevalence in 6-15-year-old children in France. J Dent Res. 1989;68:64-68.
30. R. D. Emslie, A dental health survey in the Republic of the Sudan, Brit Dent J, 1966; 120:167-178.

1. PhD Scholar, Medical Research Center, Liaquat University of Medical & Health Sciences Jamshoro Sindh.
2. Assistant professor, Liaquat University of medical and Health Sciences Jamshoro Cell: +92-333-2608489
3. Assistant Professor, Isra Dental College Hyderabad Sindh. Email: irfanahmedshaikh80@yahoo.com
4. Lecturer, Bhittai Medical and Dental College Mirpurkhas Sindh. Email: waheedmuraddahri@yahoo.com
5. Assistant Professor, Bhittai Medical and Dental College Mirpurkhas Sindh. Email: kumarsaein@yahoo.com
6. Post graduate trainee, Liaquat University of medical and Health Sciences Jamshoro Email: sadamhussain84@hotmail.com

Corresponding author: “Dr Ahmed Bari Memon ” < drabmemon@yahoo.com >

Ahmed Qannam ¹                                 BDS, MSc                                 

INTRODUCTION

Although children suffer from manyoral diseases found in adults there are undoubtedly some difference in prevalence of various lesions in comparison to the latter¹. In addition, there are lesions relatively unique to the pediatric population^2,3. There have been various studies on the frequency of oral lesions in children from various continents of the world.These studies have highlighted differences in racial and regional differences in the prevalence of oral lesions^4-14. A common denominator with all the studies is the lack of unanimity in defining what constitutes the pediatric age group, in the classification of various disease entities and in the time period over which the data was collected⁸. This lack of unanimity in study design makes it difficult to make relatively valid comparison between studies.In dentistry, the pediatric age is generally considered as between 0-18 years, encompassing such periods as the infancy, childhood and adolescence.

Most of the previous studies have reported biopsies involving hard and soft tissues although a few have concentrated on specific group of lesions such as salivary gland lesions¹⁵, odontogenic^16,17 and non-odontogenic tumors¹⁸. There has been no study dedicated to examining only the range of diagnosis of soft tissue lesions in children. Most previous studies have reported them in the context of all lesions including hard tissue and dental lesions.With this method there is a strong likelihood that soft tissue lesions are often overlooked¹⁹.

Studies on soft tissue lesions^19,20 are often based mainly on clinical examinations as the only tool for diagnosis. Although a substantial proportion of soft tissue lesions do not require tissue biopsies, many of them are only conclusively diagnosed histologically. Therefore a study of the range of diagnoses of soft tissue lesions submitted to an oral pathology service will complement those based on clinical diagnoses in giving a true picture of soft tissue lesions in children. This will probably have greater influence in designing a more coherent public health policy for tackling oral disease in pediatric patients.

With the knowledge that similar studies have not been undertaken previously in Saudi Arabia,this study aimed to determine the frequency of soft tissue lesions histologicallydiagnosed and relate this to the age (age group), gender and site of the biopsy in patients between 0 and 18 years old in the College of Dentistry, King Saud University over a 30 year period (1984-2013).  An additional aim is to make a comparison with the soft tissue biopsies in previous reports of pediatric oral lesions in the English literature.

METHODOLOGY

Study Setting

The setting of the study is the biopsy service at the College of Dentistry, King Saud University, Riyadh, Saudi Arabia. Many of the cases come from university staff and relations, the general public and a few of them seen as cases for consultation from other centers that also run their own biopsy services.Ethical permission was sought and obtained from the local Institutional Review Board (College of Dentistry Research Center, FR 0181).

General Evaluation

The biopsy records of patients between 0 and 18 years of age were retrieved from the archives

of the above named service spanning the period 1984 to 2013.  All cases that were reported as soft tissue lesions with complete record of the patient’s gender, anatomic site of lesion and histopathologic diagnosis clearly stated were included in this study.As the author alongside a colleague arepracticing oral pathologists, all slides (including those with special stains and immunohistochemical staining) were then recalled to re-check the histopathologic diagnoses. New diagnoses based on current knowledge were reassigned to many lesions including to those cases with previously inconclusive diagnoses, where possible.Data was presented as frequencies and percentages. Associations between variables were tested by Pearson chi-square test or Fisher’s exact test where necessary. A p value of less than 0.05 was considered statistically significant. Analyses was done using IBM SPSS software version 20.

RESULTS

Two hundred and eighty patients comprising 119 (42.5%) males and 161(57.5%) females met the inclusion criteria for this study. The mean age of the study subjects was 12 years (range: 2 weeks to 18 years). Majority of the specimens were obtained from the age group 6-12 years (Table 1). Most lesions were located in the gingiva, the lips, buccal mucosa and the tongue (Table 2). Among the categories of lesions, reactive lesions accounted for slightly more than half (51%) of the biopsies reported in this study group followed by salivary gland-related

lesions (including benign and malignant salivary gland tumors; 26.8%) (Table 1). Lesions were generally more common in females except epithelial alterations and vascular lesions (Table 1). However there was no statistical significant difference in the gender distribution of lesions (Pearson Chi square = 9.87; P = 0.195)nor in the distribution of lesions between the different age groups (Pearson Chi square = 18.90; P = 0.579)

Reactive lesions accounted for the largest group of lesions and comprised mainly pyogenic granuloma and fibroma. Three-fifth (60%) of these lesions occurred in the gingiva followed by the buccal mucosa (15%) and tongue (13%). The salivary gland lesions were the second most common. Thisheterogeneousgroup of lesions constituted 26 % of total biopsies. A disproportionate amount of these lesions were located in the lips (62%) with the floor of the mouth a distant second (16%) followed by major salivary glands (11%). Mucous extravasation phenomenon (76%) was by far the dominant lesion followed by chronic sialadenitis (10%). All cases of the former that were seen occurred on the lower lip. Mucoepidermoid carcinoma and pleomorphic adenoma found in 3 patients (4%) were the only salivary gland tumors seen (Table 3).

Benign tumors of non-salivary gland origin accounted for 18 cases (6.4% of total biopsies). This rises to 31 cases (11% of total biopsies) if vascular benign tumors (hemangioma and lymphangioma) are added to this group as was done in many previous studies. The gingiva, buccal mucosa and tongue were the most commonly affected sites. The two most common were squamous papilloma and lymphangioma (Table 3).

As expected, malignant tumors were rarely seen in

Abbreviations: PGCG, peripheral giant cell granuloma; POF, peripheral ossifying fibroma; MNTI, melanotic neuroectodermal tumor of infancy; SCN, solitary circumscribed neuroma.

^aEpulis granulomatosa is an unusual for of pyogenic granuloma occurring in extraction sockets

*Alveolar ridge

pediatric patients. Only six cases were found. They were mainly located on the gingiva (50%) with the remaining half distributed equally in 3 other oral sites. There were 3 cases of rhabdomyosarcoma, 2 cases of Non-Hodgkin’s lymphoma as well as a case of squamous cell carcinoma of the dorsal tongue (Table 3). Pigmented lesions were rare (9 cases in all) although it is noteworthy that in this

group of lesions, melanoticneuroectodermal tumor of infancy was well represented (3 cases) as a pigmented disorder seen commonly in infants.

DISCUSSION

This study reviewed the profile of oral soft tissue biopsies received and diagnosed in a University-based oral biopsy service in Saudi Arabia over a 30 year period.Due to the fact that there are no well-documented reports on pediatric oral diseases in the country as well as cultural and environmental differences which presumably may influence the pattern and prevalence of lesions in pediatric patients, studies like these are needed to help define future pediatric healthcare needs.

Previous studies, as in this study, have identified that the age-group most commonly associated with increased number of oral lesions in the pediatric age is the 6-12 year old group^6,7,14. The differences seems to be much greater when the latter group are compared to the 0-5 years but rather attenuated when compared to those of 13-15 year old group or even older. This seemed to underline the continuous role being played by dentition in the evolution of some of the most common lesions. The mixed dentition stage is characterized by teeth resorption, crowding and even carious lesions which provides a good etiologic source (plaque and calculus accumulation, jagged teeth) for the reactive and inflammatory soft tissue lesions²¹. This may reduce slightly, albeit not significantly, as the permanent dentition comes into play in the older age groups. Moreover, to again emphasize the effect of the mixed dentition stage of tooth development regarding reactive and inflammatory lesions, some lesions which are exclusive to infants and children less than 5 year old who have not yet reached mixed dentition stageare tumors (e.g. congenital epulis, melanoticneuroectodermal tumor of infancy) and not reactive lesions.

Like in most previous studies, the most common lesions are the reactive lesions which constituted 51% of the total lesions in this study. However, in African children the most prevalent lesions were neoplastic⁹,possibly due to oversized role of some tumors such as Burkitt’s lymphoma that are environmentally endemic in sub-Saharan Africa²². Pyogenic granuloma and fibroma were by far the two most common lesions among the reactive lesions. As alluded to previously, trauma and chronic irritation (often as a result of the presence of gradually changing dentition) are the main etiologic sources of these lesions²³.Gultekin et al (2003)⁷found giant cell granuloma as the most prevalent reactive lesion in their study of the Turkish population. Regarding the location of these lesions, the great majority were found on the gingiva. Fibromas were reported to accounted for 36% of such lesions. It is probable that in many studies, vascular anomaly has been reported under hemangioma, as often some pathologists still refer to vascular malformation as a form of hemangioma²⁵. It is also probable that lymphangioma may also probably be more commonin Saudi children. It is noteworthy that apart from lesions associated with infancy (melanoticneuroectodermal tumor of infancy and congenital epulis),lymphangioma had the lowest mean age among the other lesions (Table 4).

In virtually all previous studies, benign tumors vastly

Abbreviations: PGCG, peripheral giant cell granuloma; POF, peripheral ossifying fibroma; MNTI, melanotic neuroectodermal tumor of infancy
*These lesions were selected randomly from other lesions having the same prevalence

be more commonly found in the buccal mucosa in Thai children⁶.

Vascular lesions were in general fairly common in this study, being the fourth most common group. In many studies despite being classified as benign non-odontogenic tumor, hemangioma tends to be relatively very common in pediatric patients and may even sometimes be almost as common as reactive lesions, while lymphangiomas are much less common^1,6,7,14,24. In this study however, lymphangioma was more common than hemangioma. In addition, in previous studies arteriovenous malformation were rarely found in children.Jones and Franklin 2006 reported that vascular anomalies constituted 8% of connective tissue lesions in children while hemangioma outnumber malignant tumors in pediatric patients. The main reason is that the range and pattern of benign tumors that may be seen in pediatric patients is wide compared to the very narrow range of malignant tumors^1,6,7. In this study, benign tumors are 3 times likely to be encountered than malignant tumors, and if neoplastic vascular lesions are added as was done in some studies, then the benign tumors are at least 5 times as common as malignant tumors. Although this is less than in most studies where the ratio ranged from 8:1 (benign:malignant)⁷ to as much as 29:1⁶, it is difficult to compare studies in this area as most of them included salivary gland tumors, hard tissue tumors and odontogenic tumors. Rhabdomyosarcoma (especially the embryonal variant)is a malignant tumor often encountered in pediatric patients.All three cases in this study were embryonal. Squamous cell carcinoma of the dorsal tongue is very rare in comparison to ventral and lateral tongue in all studies on adult populations. The single case in an unusual site seen in this study probably underlines a relative difference in the etiologic source from cases commonly seen in the adult population. Generally in the adult population, majority of oral squamous cell carcinoma are related to tobacco and alcohol use.

In the very few previous studies that  classify salivary gland lesions as a separate entity^8,15 the findings were generally similar to the present study. Mucous extravasation cyst and chronic sialadenitis appear to be the two most common lesions. Tumors of salivary glands are rather uncommon but when diagnosed, are more likely to be pleomorphic adenoma if benign,and mucoepidermoid carcinoma when malignant.

In conclusion, this study reviewed the range of lesions seen in biopsies obtained from pediatric patients in a Saudi teaching hospital. Although it cannot claim to represent the actual prevalence of the diagnostic entities making up the soft tissue lesions because the setting is auniversity teaching hospital, it has shown the range of lesions that should be expected by the clinician when sending a biopsy from pediatric patients for histopathology. As in most previous studies, most lesions in pediatric patients are reactive and benign but the clinician ought to be aware that malignant lesions maybe sometimes encountered. In addition, based on this study, it appears that lymphangioma may be relatively more common in Saudi patients.

REFERENCES

1. 1. Wang YL, Chang HH, Chang JY, Huang GF, Guo MK. Retrospective survey of biopsied oral lesions in pediatric patients. J Formos Med Assoc. 2009;108:862871.
   2. Rachidi S, Sood AJ, Patel KG, et al. Melanotic Neuroectodermal Tumor of Infancy: A Systematic Review. J Oral Maxillofac Surg. 2015.
   3. Conrad R, Perez MC. Congenital granular cell epulis. Arch Pathol Lab Med. 2014;138:128-131.
   4. Chen YK, Lin LM, Huang HC, Lin CC, Yan YH. A retrospective study of oral and maxillofacial biopsy lesions in a pediatric population from southern Taiwan. Pediatr Dent. 1998;20:404-410.
   5. Das S, Das AK. A review of pediatric oral biopsies from a surgical pathology service in a dental school. Pediatr Dent. 1993;15:208-211.
   6. Dhanuthai K, Banrai M, Limpanaputtajak S. A retrospective study of paediatric oral lesions from Thailand. Int J Paediatr Dent. 2007;17:248-253.
   7. Gultelkin SE, Tokman B, Turkseven MR. A review of paediatric oral biopsies in Turkey. Int Dent J. 2003;53:26-32.
   8. Jones AV, Franklin CD. An analysis of oral and maxillofacial pathology found in children over a 30-year period. Int J Paediatr Dent. 2006;16:19-30.
   9. Lawoyin JO. Paediatric oral surgical pathology service in an African population group: a 10 year review. Odontostomatol Trop. 2000;23:27-30.
   10. Lima Gda S, Fontes ST, de Araujo LM, Etges A, Tarquinio SB, Gomes AP. A survey of oral and maxillofacial biopsies in children: a single-center retrospective study of 20 years in Pelotas-Brazil. J Appl Oral Sci. 2008;16:397-402.
   11. Shah SK, Le MC, Carpenter WM. Retrospective review of pediatric oral lesions from a dental school biopsy service. Pediatr Dent. 2009;31:14-19.
   12. Skinner RL, Davenport WD, Jr., Weir JC, Carr RF. A survey of biopsied oral lesions in pediatric dental patients. Pediatr Dent. 1986;8:163-167.
   13. Sousa FB, Etges A, Correa L, Mesquita RA, de Araujo NS. Pediatric oral lesions: a 15-year review from Sao Paulo, Brazil. J Clin Pediatr Dent. 2002;26:413-418.
   14. Zuniga MD, Mendez CR, Kauterich RR, Paniagua DC. Paediatric oral pathology in a Chilean population: a 15-year review. Int J Paediatr Dent. 2013;23:346-351.
   15. Krolls SO, Trodahl JN, Boyers RC. Salivary gland lesions in children. A survey of 430 cases. Cancer. 1972;30:459-469.
   16. Blackwood HJ. Odontogenic tumours in the child. Br Dent J. 1965;119:431-438.
   17. Qannam A. Odontogenic tumors in children and adolescents: a 25 year’s retrospective study in Saudi population. Egypt Dent J. 2010;56:191-196.
   18. Jones JH. Non-odontogenic oral tumours in children. Br Dent J. 1965;119:439-447.
   19. Majorana A, Bardellini E, Flocchini P, Amadori F, Conti G, Campus G. Oral mucosal lesions in children from 0 to 12 years old: ten years’ experience. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2010;110:e1318.
   20. Bessa CF, Santos PJ, Aguiar MC, do Carmo MA. Prevalence of oral mucosal alterations in children from 0 to 12 years old. J Oral Pathol Med. 2004;33:17-22.
   21. Gianelly AA. Crowding: timing of treatment. Angle Orthod. 1994;64:415-418.
   22. Walusansa V, Okuku F, Orem J. Burkitt lymphoma in Uganda, the legacy of Denis Burkitt and an update on the disease status. Br J Haematol. 2012;156:757-760.
   23. Jafarzadeh H, Sanatkhani M, Mohtasham N. Oral pyogenic granuloma: a review. J Oral Sci. 2006;48:167175.
   24. Lei F, Chen JY, Lin LM, et al. Retrospective study of biopsied oral and maxillofacial lesions in pediatric patients from southern Taiwan. J Dent Sci. 2013. 25. Redondo P. Vascular malformations (I). Concept, classification, pathogenesis and clinical features. Actas Dermosifiliogr. 2007;98:141-158.

1.Assistant Professor, Department of Oral Medicine and Diagnostic Sciences.

2.King Saud University College of Dentistry

Corresponding author: “Dr Ahmed Qannam ”  < : dr.qannam@hotmail.com  >

Faiza Amin ¹                                    

Sidra Akram ²                                    

Amir Akbar Shaikh ³                                    

INTRODUCTION

Acrylic resins were introduced in 1936 as denture base material¹.Amongst their characteristics, are good thermal conductivity, low permeability to oral fluids, easy handling and colour stability¹. One of the major disadvantage of these materials is that they can be deeply  colonized by microorganisms.

Like  cadida albicans, Streptococcus sanguis, Streptococcus salivarius, Streptococcus mutans, Fusobacterium nucleatum and Actinomyces viscosus² These microorganisms transmitted from the contaminated devices between dental personnel and patients³. Most common opportunistic infection that is seen in denture wearers is denture-related stomatitis which is causedby the accumulation of  denture plaque on prosthesis⁴. In the elderly patients there is a major risk of developing respiratory tract infection because of these microorganisms⁵.To prevent cross infection of microorganisms from contaminated prosthesis to dentists, dental assistant and patients, disinfection of theses prosthesis has been recommended as an vital procedure. For denture disinfection many procedures have been suggested. They are immersion in solutions^6-15 and irradiation^16-20. A study established an effective infection control protocol for denture disinfection by immersing the prosthesis in 3.78% solution of sodium perborate after scrubbing with 4% chlorhexidine¹⁰.In a preliminary study, the researchers immersed the specimens in water and then disinfection was carried out with  microwave irradiation of 3 hard reline resins and they found that this regimen was effective against both pathogenic and nonpathogenic microorganisms¹⁷. Many chemical cleansers that contain sodium hypochlorite, acid solutions, enzymes,  and alkaline peroxide, are available to remove the residual biofilm attached to denture surfaces^15,21-23. Many studies demonstrated that denture cleansing solutions have antimicrobial properties^22-27; however, none of these methods seem to effectively prevent recolonization on the denture surface and to remove the biofilm^21-22. There is a wide variation in the literature  regarding the use of denture cleansers as a study has shown that for reducing microorganisms the most effective denture cleanser is  0.5% sodium hypochlorite solution²⁸. On the other hand in an another study researchers evaluate the maxillary dentures by usingalkaline peroxide tablets that there is significant decrease in  Candida albicans colonyforming units as well as other²⁹ microbial bioburden³⁰. Surface hardness of the denture base polymers can be affected by dentifrice toothbrush/ abrasion,³¹ denture cleansers³², polymerization cycles,³³ different systems used for polymerization of denture base³⁴ and thermal cycling³⁵. When acrylic resins were disinfected by chlorhexidine gluconate, sodium hypochlorite or sodium perborate, lower hardness values were observed³⁶. According to Previous studies the hardness of the resins was not affected by immersing the conventional denture base polymer in 1% sodium hypochlorite, 4%

chlorhexidine solutions or in sodium perborate^14,37.  On the other hand the hardness can be altered by solutions of  2% glutaraldehyde , 4% chlorhexidine or  1% sodium hypochlorite³⁸. Therefore the aim of this  study is to assess the surface hardness of acrylic resins after immersed in different denture cleansers solution.  The hypothesis of this in vitrostudy was that thesurface hardness of denture base resins was decreased after disinfection with denture cleansers.

METHODOLOGY

Table I presented the material used in this study. For the fabrication of samples Vertex™ Rapid Simplified Holland was used that represent the conventional denture base acrylic resins. Fabrication and testing of specimens was conducted at Dr IshratulEbad Khan institute of Oral Health Sciences (Department of Science of Dental Materials and Department of Prosthodontics). Test specimens were fabricatedby the investment of material in stainless steel mold 13 x 4 mm. The American society for testing and material standard D 256-O6a was used for the dimension of specimens. The material was mixed accordingto the instructions by the manufacturer and after dough stage achieved, material was inserted into the molds. Specimens were inspected visually for any defects or porosities. Only those specimens were

included in the studywhich were free of voids or porosity and having smooth surfaces. Excess material (flash) was removed immediately after polymerization and then polishing was done using progressively finer grades by silicon carbide paper (3M of Brazil; São Paulo, Brazil) for smooth, flat surface. Sample size was estimated by considering;Neppelenbroek KH et al¹⁷ work.  A total of 108 specimens were fabricated. These specimens were divided randomly 06 groups (n=18). These groups were: at baseline (0 day dry specimens), artificial saliva (control) group. The experimental solutions of the study were: fittydent denture cleanser tablets, corega denture cleansers tablets, polidentdenture cleansers tablets and fixodent Denture Cleanser for 10 minutes according to manufacturer recommendations (Table 2). The samples were distributed

through non probability convenience sampling. All specimens were placed in their respective containers and filled with distilled water except the specimens of baseline group.  The specimens in the baseline group were measure at 0 day. The distilled water was discarded after 24 hours. The containers were then filled with their respective denture cleansers and artificial saliva.  The specimens were washed and stored in distilled water.  This disinfection regime was repeated twice a day for total of 60 days.

When no disinfection was carried out during storage specimens were placed in distilled water. The artificial saliva consisted of NaCl (0.40 g), KCl (0.4 g), NaOH (0.05 g), CaCl2·2H2O(0.22 g), NaH2PO4 (0.12 g), urea (1 g) in 1 dm3 of distilled water, adjusted to pH⁷. After 60 days, microhardness was evaluated using Vickers microhardness tester (Wolpert W group micro Vickers hardness tester digital auto-turret model number 402 MVD Figure 1,2 and 3). Data analysis was performed by using Statistical Package for Social Sciences (SPSS) version-16. The data was analyzed by using one way analysis of variance-one way (ANOVA)  which was followed by Tuckey’s HSD (Honestly significant difference) was used at 0.05 significance level.

RESULTS

The mean values of the specimensat baseline, artificial saliva (control) and when immersed in experimental solutions were shown in Table 3. The corega denture

cleanser tablets showed lowest value of hardness as compared to baseline and artificial saliva(control) specimens. One way ANOVA showed that significant difference was observed among all the groups (p < 0.001). It was further confirmed by post-Hoc Tukey test (Dunnett test) which stated that significant difference was found when baseline and artificial saliva (control) was compared with Fittydent, corega and poildent denture cleanser tablets (p < 0.001).

DISCUSSION

The effect of exposure of disinfection methods on the properties of denture base materials is of prime importance Vickers microhardness of denture base resins after immersed in denture cleansers were evaluated in this study. One sodium hypochlorite based, two sodium perborate based, and one tetraacetylethylenediamine based denture cleansers in effervescent tablet form which are commonly used on the local market were included in the study.  The hypothesis that denture cleansers may decrease the micro hardness of denture base resins was accepted. The results showed that there was a significant decrease in Vickers micro hardness when specimens were immersed in denture cleansers solution when compared with the specimens who were not immersed in control group. The denture cleansers are chemical soak-type products. Sodium-perborate decomposed to form nascent oxygen, sodium metaborate and hydrogen peroxide and transforms to an alkaline peroxide solution⁴¹.This peroxide solution has  chemical as well as mechanical cleansing mechanism by  releasing oxygen³⁹.

The decrease in Vickers hardness observed in this study might because of active oxygen released by hydrogen peroxide and oxygen liberating solution at a certain soaking temperature in the present study³⁹ in perborate containing denture cleansers tablets that is Fixodent and fittydent denture cleanser tablets.A similar study conducted by Machado et al³⁹ in which author used sodium perborate as an immersion media and found that hardness of denture base  was decreased significantly after seven days of immersion as compared to the control group which was distilled water. In the present study, instead of distilled water, artificial saliva was used and found that hardness was not affected significantly after immersion into artificial saliva.

Other important factor might be due to the plasticizing effect of chemicals. lowering the hardness of the acrylic resin denture base resins as compared with artificial saliva might be due to the plasticizing effects of  chemicals present in denture cleansers. These chemicals ingredients diffused in between the  polymer chains causing relaxation of these chains  and subsequently  affected the hardness of denture base resins^18,40,12,41. The duration of immersion and the type of denture cleanser play an important role in affecting the properties of denture base. Consistent with previous research,⁴¹ the hardness of heat cure resins  decreased after immersion in denture cleansers. When acrylic resins are immersed in cleansers, residual monomers release⁴² and water absorption occur simultaneously. These processes are diffusion controlled and time-dependent⁴³. It has been demonstrated that both water⁴¹ and residual monomer^42,44 molecules act as plasticizers, thus affecting the strength of polymerized resins. As stated by Takahashi et al⁴⁵ if the constituents that leach out exert a lesser plasticizing effect than ingredients in the denture cleansers, the strength of polymers will decrease.

To evaluate the effect of chemical immersion on denture bases,in vivo studies should be carried out. Evaluation of the efficacy of chemical disinfection through long term clinical trials should be carried out in the future.As the material is subjected to compressive, thermal, tensile and shear stresses unfavorable oral environment should be probed in future studies.one of the most important limitations of the study is due to the availability of limited technical resources available Vickers microhardnesswas evaluated.

CONCLUSION

Within the limitations of this in vitro study, it was concluded that:

• Surface hardness of denture base resins decreased after immersion in denture cleansers.
• The most significant decrease in the surface hardness of heat cure acrylic resins was with corega denture cleanser tablets when compared to the specimens at baseline (dry) and control group. This was followed by Fixodent denture cleanser tablets.
• The least change in hardness was observed with Fittydent denture cleanser tablets and poildent denture cleansers tablets respectively after immersing the specimens for 60 days.

REFERENCES

1. Kurtulmus H, et al. Effects of saliva and nasal secretion on some physical properties of four different resin materials. Med Oral Patol Oral Cir Bucal, 2010;15:969975.
2. Glass RT, Bullard JW, Hadley CS, Mix EW, Conrad RS. Partial spectrum of microorganisms found in dentures and possible disease implications. J Am Osteopath Assoc 2001;101:92-49.
3. Jafari AA, Tafti AF, Falahzada H, Yavari MT. Evaluation of presence and levels of contamination in pumice powder and slurry used in clinical dental laboratories. Middle East J Sci Res 2006;1:50-53.
4. Barbeau J, Séguin J, Goulet JP, de Koninck L, Avon SL, Lalonde B, et al. Reassessing the presence of Candida albicans in denture-related stomatitis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2003;95:51-59.
5. Sumi Y, Miura H, Sunakawa M, Michiwaki Y,Sakagami N. Colonization of denture plaque by respiratory pathogens in dependent elderly. Gerodontology 2002;19:25-29.
6. Abelson DC. Denture plaque and denture cleansers: review of the literature. Gerodontics 1985;1:202-206.
7. Crawford CA, Lloyd CH, Newton JP, Yemm R.Denture bleaching: a laboratory simulation of patients’ cleaning procedures. J Dent 1986;14:258-261.
8. Shen C, Javid NS, Colaizzi FA. The effect of glutaraldehyde base disinfectants on denture base resins. J Prosthet Dent 1989;61:583-9.
9. Asad T, Wattkinson AC, Huggett R. The effects of various disinfectant solutions on the surface hardness of an acrylic resin denture base material. Int J Prosthodont 1993;6:9-12.
10. Pavarina AC, Pizzolitto AC, Machado AL, Vergani CE, Giampaolo ET. An infection control protocol: effectiveness of immersion solutions to reduce the microbial growth on dental prostheses. J Oral Rehabil 2003;30:532-536
11. Haywood J, Wood DJ, Gilchrist A, Basker RM, Watson CJ. A comparison of three hard chairside denture reline materials. Part II. Changes in colour and hardness following immersion in three commonly used denture cleansers. Eur J Prosthodont Restor Dent 2003;11:165.
12. Rodrigues Garcia RC, Joane Augusto de S Jr, Rached RN, Del Bel Cury AA. Effect of denture cleansers on the surface roughness and hardness of a microwave-cured acrylic resin and dental alloys. J Prosthodont 2004;13:173178.
13. Devlin H, Kaushik P. The effect of water absorption on acrylic surface properties. J Prosthodont 2005;14:233238.
14. Azevedo A, Machado AL, Vergani CE, Giampaolo ET, Pavarina AC, Magnani R. Effect of disinfectants on the hardness and roughness of reline acrylic resins. J Prosthodont 2006;15:235-242.
15. Paranhos HF, Silva-Lovato CH, Souza RF, Cruz PC, Freitas KM, Peracini A. Effects of mechanical and chemical methods on denture biofilm accumulation. J Oral Rehabil 2007;34:606-612.
16. Dixon DL, Breeding LC, Faler TA. Microwave disinfection of denture base materials colonized with Candida albicans. J Prosthet Dent 1999;81:207-214.
17. Neppelenbroek KH, Pavarina AC, Spolidorio DM, Vergani CE, Mima EG, Machado AL. Effectiveness of microwave sterilization on three hard chairside reline resins. Int J Prosthodont 2003;16:616-620.
18. Campanha NH, Pavarina AC, Vergani CE, Machado AL. Effect of microwave sterilization and water storage on the Vickers hardness of acrylic resin denture teeth. J Prosthet Dent 2005;93:483-487.
19. Sartori EA, Schmidt CB, Walber LF, Shinkai RS. Effect of microwave disinfection on denture base adaptation and resin surface roughness. Braz Dent J 2006;17:195-200.
20. Sartori EA, Schmidt CB, Mota EG, Hirakata LM, Shinkai RS. Cumulative effect of disinfection procedures on the microhardness and tridimensional stability of a poly(methyl methacrylate) denture base resin. J Biomed Mater Res B ApplBiomater 2008;86B:360-364.
21. De Souza RF: de Freitas Oliveira Paranhos H, Lovato da Silva CH, Abu-Naba’a L, Fedorowicz Z, Gurgan CA. Interventions for cleaning dentures in adults. Cochrane Database Syst Rev 2009, 7.
22. Vieira AP, Senna PM, Silva WJ, Del Bel Cury AA: Long-term efficacy of denture cleansers in preventing Candida spp. biofilm recolonization on liner surface. Braz Oral Res 2010, 24:342-348.
23. Dhamande MM, Pakhan AJ, Thombare RU, Ghodpage SL: Evaluation of efficacy of commercial denture cleansing agents to reduce the fungal biofilm activity from heat polymerized denture acrylic resin: An in vitro study. ContempClin Dent 2012;3:168-172.
24. De Freitas Fernandes FS, Pereira-Cenci T, da Silva WJ, Filho AP, StraiotoFG,Del Bel Cury AA: Efficacy of denture cleansers on Candida spp. Biofilm formed on polyamide and polymethyl methacrylate resins. J Prosthet Dent 2011;105:51-58.
25. Da Silva PM, Acosta EJ, Pinto Lde R, Graeff M, Spolidorio DM, Almeida RS, Porto VC: Microscopical analysis of Candida albicans biofilms on heat-polymerised acrylic resin after chlorhexidine gluconate and sodium hypochlorite treatments. Mycoses 2011, 54:e712-717.
26. De Andrade IM, Cruz PC, da Silva CH, de Souza RF, ParanhosHde F, Candido RC, Marin JM, de SouzaGugelmin MC: Effervescent tablets and ultrasonic devices against Candida and mutans streptococci in denture biofilm. Gerodontology 2011, 28:264-270.
27. Sousa FA, Paradella TC, Koga-Ito CY, Jorge AO: Effect of sodium bicarbonate on Candida albicans adherence to thermally activated acrylic resin. Braz Oral Res 2009, 23:381-385.
28. Sousa-Porta, S. R., Lucena-Ferreira, S. C., Silva, W. J. & Del Bel Cury, A. A. Evaluation of Sodium Hypochlorite as a Denture Cleanser: A Clinical Study,” Gerodontology, 2013.
29. Uludamar, A., Ozkan, Y. K., Kadir, T. & Ceyhan, I. “In Vivo Efficacy of Alkaline Peroxide Tablets and Mouthwashes on Candida Albicans in Patients with Denture Stomatitis,” J Appl Oral Sci, 2010;18:291-296.
30. Rossato, M. B., Unfer, B., May, L. G. & Braun, K. O. “Analysis of the Effectiveness of Different Hygiene Procedures Used in Dental Prostheses,” Oral Health Preventive Dent, 2011;9: 221-227
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32. Durkan, R., Ayaz, E. A., Bagis, B., Gurbuz, A., Ozturk, N. &Korkmaz, F. M. “Comparative Effects of Denture Cleansers on Physical Properties of Polyamide and Polymethyl Methacrylate Base Polymers,” Dent Mat J, 2013;32; 367-375.
33. Lira, A. F., Consani, R. L. X., Mesquita, M. F., Nobilo, M. A. A. &Henriques, G. E. P. “Effect of Toothbrushing, Chemical Disinfection and Thermocycling Procedures on the Surface Microroughness of Denture Base Acrylic Resins,” Gerodontology 2012:29 E891-E897.
34. Ali, I. L., Yunus, N. & Abu-Assan, M. I. “Hardness, Flexural Strength, and Flexural Modulus Comparisons of Three Differently Cured Denture Base Systems,” J Prostho, 2008;17:(7) 545-549.
35. Goiato, M. C., Dos Santos, D. M., Baptista, G. T., Moreno, A., Andreotti, A. M. &Dekon, S. F”Effect of Thermal Cycling and Disinfection on Microhardness of Acrylic Resin Denture Base,”J Med Eng Technol. 2013 Apr;37:203-207.
36. Neppelenbroek, K. H., Pavarina, A. C., Vergani, C. E. &Giampaolo, E. T. “Hardness of Heat-Polymerized Acrylic Resins after Disinfection and Long-Term Water Immersion,” J Prosth Dent,2005;93:171-176.
37. Machado, A. L., Breeding, L. C., Vergani, C. E. Perez, L. E. C. “Hardness and Surface Roughness of Reline and Denture Base Acrylic Resins after Repeated Disinfection Procedures,” J Prosth Dent, 2009;102:115-122.
38. Carvalho, C. F., Vanderlei, A. D., Marocho, S. M., Pereira, S. M., Nogueira, L. &Paes- Junior, T. J. “Effect of Disinfectant Solutions on a Denture Base Acrylic Resin,” Acta Odontol Latinoam, 2012;25:(3) 255-260.
39. Yatabe M, Seki H, Shirasu N, Sone M. Effect of the reducing agent on the oxygen inhibited layer of the crosslinked reline material. J Oral Rehabil 2001; 28: 180-185.
40. Azevido A, Machado AL, Pavarina AC, Vergani CE, Giampaolo ET. Hardness of denture base and hard chair side reline acrylic resins. J Appl Oral Sci.2005;13:291295.
41. Pavarina AC, Vergani CE, Giampaolo ET, Machado AL, Teraoka MT. The effect of disinfectant solutions on the hardness of acrylic resin denture teeth. J Oral Rehabil.2003; 30:749-752
42. Lee SY, Lai YL, Hsu TS. Influence of polymerization conditionson monomer elution and microhardness of autopolymerizedpolymethyl methacrylate resin. Eur J Oral Sci. 2002;110:179-183.
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1.Assistant Professor, Dow Dental College Dow University of Health Sciences.Science of Dental Materials.

2.Assistant Professor, Dental section, Dow International Medical College, Dow University of Health Sciences.

3.Assistant Professor, Ziauddin University.

Corresponding author: “Dr Faiza Amin ”  < drdentist2004@hotmail.com  >

Nazish Fawad ¹                                     BDS, MDS

INTRODUCTION

In dentistry, light cured resin composite have been widely used as esthetic restorative material for anterior and posterior teeth¹. Light-cured resins contain photoinitiators, which are activated by blue light to begin the polymerization process. The light must have sufficient intensity and must be of the correct wave length to activate the photo-initiator. It has been documented that the rapid development of light-curing units (LCUs) has found to be parallel with the advancement in dental resins^2,3.

The minimum light intensity required to adequately cure 1.5 to 2 mm of composite resin is reportedly between 280 and 300 mw/cm² as both the physical and biological properties of resin composites are affected by the degree of polymerization^4,5. Inadequate curing of the composite may cause problems such as premature breakdown at the margins and staining of the   restoration, dimensional instability, decreased biocompatibility of the resin and increased cytotoxicity^6,8.

Dental clinics must maintain a high level of infection control, in order to protect both patients and the dentist. According to the guidelines of Centers for Disease Control and Prevention (CDC) for Infection Control in Dental Health-Care Settings, patient-care items are divided as critical, semi-critical, or non-critical depending upon the possible risk for infection related with their intentional use⁹. Caughman and others had reported that after clinical use contamination of light guides and LCU handles were found to be common³. Presently the most common method of maintaining sterility of the light guide are wiping the guide with a disinfectant, such as glutaraldehyde, after each patient; using autoclavable guides; using presterilized, single-use plastic guides; and translucent disposable barriers to cover the guide^10-12. Unfortunately, when light guide tips are autoclaved it increases boiler scale from vaporized water and need repeated polishing to keep optimal intensity of light. Chemical sterilization necessitate up to 10 hours of immersion which is not always possible, and not all clinics have facility for vapor sterilization¹³.

Disposable barriers are suitable, non invasive and cost-effective way of avoiding contamination of the light guide as it prevents direct contact between the oral tissues and the light guide¹⁴. These barriers also reduce the risk of damaging the light guide during autoclaving or disinfection^15,16. Among various infection control barriers, the plastic wrap (food wrap) is commonly used as it has the little effect on the LCU power density¹⁷. But, a thin single-layer of wrap have a tendency to tear easily while the handling of LCU, or by the sharp edges of the prepared cavity¹⁸. As a result, more than one layer of wrap for infection control barrier is used which could reduce the risk of cross infection¹⁹. Conversely, a multi-layer infection control barrier wrap reduced the light output of the LCUs and accordingly it affects the polymerization resulted in reduced micro-hardness of the composite restoration¹⁸.

However, earlier studies have concluded that the light intensity may reduce up to 35% when barriers are used. Warren and others found that four different types of barrier used on each of four different light guides all reduced light output. One barrier reduced the power density from the curing light up to110 mW/cm^{2 19,20}. Cellophane wrapped around the light guide has been caused the least reduction in power density from the curing light¹². Although these studies were useful, they may have produced deceptive results because a dental radiometer was used to measure light intensity. Many dental radiometers do not provide reliable measurements, they do not report wavelength, and they may not accurately measure light intensity^3,21.

Leonard and others had found that the accuracy of dental radiometers varies by as much as 80% and were dependent on the diameter of the light guide. Unlike a dental radiometer, a laboratory-grade spectrometer connected to an integrating sphere that can capture and measure all light output from an LCU and provides a visual display of the spectral output. For these reasons, a laboratory-grade spectrometer or photo spectrometer should be used to measure power output from dental curing lights as well as to record their spectral outputs²¹.

As Barry and colleagues claimed that radiometric evaluation of LED light units tested did not satisfy manufacturers claims for minimum intensities however the spectral emission from the light source did meet manufacturer requirements; most of the studies had used radiometer while  there are only few studies have been documented that  used spectrometer, thus this lacking of usage helped in setting the objectives of  current study. ²².

The objective of this study was to evaluate the effect of a multi-layer barrier on the micro-hardness of different composite resin cured with a light emitting diode (LED)unit (Mectron Starlight Pro-LED, intensity 1.200 mW/cm², Italy) and also estimated the intensity of LED lights with different protective layers.

The hypothesis tested was that multi layers of infection control barriers would have a significant effect on the intensities of LED light and micro-hardness of the different composite resin.

METHODOLOGY

This experimental study was conducted at Department of Operative Dentistry, Dr. Ishrat-ul-Ebad Khan Institute of Oral Health Sciences, Dow University of Health Sciences, Karachi. Microhardness evaluation was carried out at the Department of Material Sciences, NED University, Karachi, from August 2014 to January 2015.

Materials used in the study included a Hybrid composite ValuxTM Plus (3M Dental Products, St. Paul, MN, USA) , Nano resin composite Filtek_Z350 (3M Dental Products, St. Paul, MN, USA) and nano ceramic composite CeramoX (Dentsply Caulk, Milford, DE, USA). Detailed descriptions of the material are given in Table I.

Specimen preparation

A polytetrafluoroethylene mold of 10 mm in diameter and 2 mm thick was placed on a substrate consisting of a polyethylene sheet covered glass slide. The mold was filled with the uncured paste of dental composite and enclosed with a mylar strip and glass slide and light pressure was applied. This method provided specimens with smooth top and bottom surfaces. The restoration material was cured using an LED curing lamp (Mectron Starlight Pro-LED, intensity 1000 mW/cm², Italy) for 20 seconds. LED curing lamp was covered with one, two, f o u r , Table 1: Materials used in the present study and

eight layers of a disposable wrap barrier (Cleanwrap,Gimhae, Korea). The thickness of single wrap barrier sheet is about 0.5 mils. The barrier was cut to an enough size and was used to cover the light guide without air entrapment; the specimens were matured in an incubator at 37 ^oC for 24 hours. Groups A1/B1/C1 (control) cured with LED covered with single wrap barrier, Groups A2/B2/C2 cured LED covered with two wrap barriers, Groups A3/B3/C3 cured LED covered  with four wrap barriers led lamp, and Groups A4/B4/C4 cured Led covered with eight wrap barrier .

Micro hardness testing

Micro hardness of every specimen was determined using a micro-hardness tester (Micro-vickers hardness tester, Wolpert group, China) equipped with a diamond Vickers indenter. The indentation load was 100gm and the dwell time was 10 s. Three indentations spaced equally over the surface of each specimen.

Spectrophotometric Analysis

The spectral distribution generated by LCU with different number of plastic wrap was calculated by passing the light through a spectrophotometer model (Data color; SF 600; Plus-CT; USA). The unit was calibrated prior to wrapping. The tip of the light guide was placed over the aperture of an integrating sphere, which captured all light from the guide. The following 3 measurements were recorded: total power (mW), peak wavelength (nm) and irradiance at the peak value (mW/nm).The light output was measured with no barrier (control) and with each barrier.

The power recordings obtained from the spectrometer were converted into power density values (mW/cm²) by dividing the total power by the area of the tip of the light guide, since this is the unit in which values are commonly reported when LCUs are assessed.

Data were entered in IBM SPSS v. 21 (Chicago, Illinois, Inc.). Microhardness of different materials was presented in terms of mean and standard deviation. Two way Analysis of Variance (ANOVA) was used to compare micro hardness between groups and subgroups. Bonferroni (LSD) test was used to detect mean difference in each pair of groups. Tukey’s HSD test was used to observe significant difference between subgroups. Level of examining significant difference was kept atmost 0.05.

RESULTS

The data was analyzed for normal distribution prior to the use of multiple comparisons. The Q-Q plot analysis revealed a normal distribution of data, thus a parametric test ANOVA was utilized for statistical analysis. The mean micro hardness of micro hybrid composite (71.58 ± 3.51) was significantly less (p= .0000000051) than micro hardness of nano composite (82.63± 2.488) and nano ceram X (82.53±2.470). (Table 2 & 3).

Multiple comparisons between the control (single wrap) and multiple barrier method revealed statistically

significant difference. Micro hardness of eight wrap micro-hybrid composite (A4) was significantly low than its other 3 counterparts (A1, A2, A3) (P < 0.0001). Similar

results were observed for eight wrap subgroups of Nano composite (B4) and Nano Ceram (C4). (P Value = .0000015599 for B4, p= .0000290233 for C4) as shown in table III and graph no 1.

Spectrophotometric Analysis

The mean values for the light intensity records for the control (single wrap) and Two Wrap, four wrap and eight wrap were 570 mW/cm², 565.52 mW/cm², 535.4mW/cm², and 497.0mW/cm², respectively.

DISCUSSION

It is important that curing tips used for curing resin composites in the mouth must be sterile as well as it is also an essential aspect to ensure that the resin receives sufficient power density and appropriate spectral output for adequate curing. The current study has revealed that usage of eight layers for infection-control barriers reduces the intensity of LCU as evaluated by spectrophotometer, as well as micro-hardness of composites was also reduced. On the contrary, covering curing tip with up to four layers wrap did not show any considerable effect on power density and microhardness. It might be due to the fact that distance from the tip of the light guide to the resin has a much greater effect on power density. It has been reported that 1-mm space between the light guide and the resin may cause a reduction in power density of between 8% to 16%²³.   With increasing number of layers the distance of curing unit from restoration is also increased, thus decreasing the light intensity and adversely affect the cure and hardness of the composite resin²⁴.

Light produced by light curing unit has a direct effect on the polymerization of restoration by the virtue of spectral emission and power intensity²⁵. Diameter of a curing tip as well as shade of material altogether exert direct effect on light penetrance and eventually the hardness of restoration. In the present study we overcame this limitation by choosing single material of same shade and same light diameter in order to achieve uniform experimental conditions. Furthermore, hand held portable light meters have been used to check intensity of lights as they are relatively inexpensive and easy to use, however its consistency and accuracy has been challenged²⁶. According to Barry and Rodriguez, evaluation of LED units tested by radiometer did not satisfy manufactures claim but spectral emission by Spectrophotometer did meet the manufacturer’s requirement. Thus, in this study we used spectrophotometer to overcome this

limitation^22,27.Micro-hardness testing has been used in many previous researches, because surface hardness has been commonly correlated with physical properties of material like mechanical strength and shown to be an indicator of the degree of polymerization^28,29. The null hypothesis of the current study was partially accepted and demonstrated that eight wrap has significantly reduced the micro-hardness of all type of tested composite. On the contrary, one, two and four wrap barrier did not significantly affect the hardness. These findings are in accordance to the study reported by Scott et al¹⁷.

Results of present study corroborate with the results of Chong et al. They concluded that increase in thickness of infection control barrier reduced the light output. In our study significant reduction in hardness were seen in all three materials when eight layer wrap were used because each layer thickness was about 0.5 mils and 8 wrap thickness was about  0.1016 mm.30

Al Marzok observed a reduction in light intensity on radio meter on using barriers of different thicknesses; however the hardness values were not affected. These results were not in concordance our findings because they had used knoop hardness test whereas, in our study Vicker’s hardness test was used, which is considered as better indicator of the degree of polymerization²⁸.

When choosing a procedure to disinfect curing tips, dentist should consider numerous aspects. If the curing tips are to be autoclaved between patients, then it is necessary to purchase additional tips. Disposable Cure Sleeve barriers and Cure Elastic barriers are available and are expensive; but plastic wrap is the most cost effective and about 10 cm of plastic wrap is enough to cover a curing tip.

According to the results of this in vitro study, four layers rather than two layer of an infection control barrier should be used in order to decrease the possibility of cross infection and chance of  easy tear with single or two layers. It is also recommended that several manufacturers have provided disposable, plastic infection control barriers as an effective mean of protection for both the unit as well as the curing tips. Although these barriers do not significantly affect spectral distribution, the irradiance is reduced, especially if the beam of the barrier lies across the light tip³¹.

This present study has some limitations as it could not completely replicate the complex oral environment.

The role of artificial saliva, thermo cycler and all versions of materials were not taken into consideration.

CONCLUSION

Within the limitations of this in vitro study, we conclude that wrapping the light-cure tip with one, two or four wrap has no significant effect on the micro hardness of the all types of cured composite resin. While the eight warp barrier significantly reduced the micro hardness of composite resin.

REFERENCES

1. Kawaguchi M, Fukushima T, Miyazaki K. The relationship between cure depth and transmission coefficient of visible-light-activated resin composites. J Dent Res 1994;73:516-21.
2. Anusavice KJ. Phillips’ science of dental materials.11th ed. St. Louis: Elsevier Science; 2003. p. 411.
3. Rueggeberg FA. Precision of hand-held dental radiometers. Quintessence Int 1993;24:391-6.
4. Forss H, Widstrom E. From amalgam to composite: selection of restorative materials and restoration longevity in Finland. Acta   Odontol Scand 2001;59:57-62.
5. Fan PL, Schumacher RM, Azzolin K, Geary R, Eichmiller FC. Curinglight intensity and depth of cure of resin-based composites tested according to international standards. J Am Dent Assoc 2002;133:429-34.
6. Pearson GJ, Longman CM. Water sorption and solubility of resinbased materials following inadequate polymerization by a visible-light curing system. J Oral Rehab 1989; 16:57-61.
7. Ferracane JL. Correlation between hardness and degree of conversion during the setting reaction of unfilled dental restorative resins. Dent Mater 1985; 1:11-14.
8. Chen RS, Liuiw CC, Tseng WY, Hong CY, Hsieh CC, Jeng JH. The effect of curing light intensity on the cytotoxicity of a dentin-bonding agent. Oper Dent 2001; 26:505-510.
9. Kohn WG, Collins AS, Cleveland JL, Harte JA, Eklund KJ, Malvitz DM. Guidelines for infection control in dental health-caresettings. MMWR Recomm Rep 2003;52:161.
10. Rueggeberg FA, Caughman WF, Comer RW. The effect of autoclaving on energy transmission through light-curing tips. J Am Dent Assoc 1996; 127(8):11831187.
11. Rueggeberg FA, Caughman WF. Factors affecting light transmission of single-use, plastic light-curing tips. Oper Dent 1998; 23:179-184.
12. Chong SL, Lam YK, Lee FK, Ramalingam L, YeoAC, Lim CC. Effect of various infection-control methods for light-cure units on the cure of  composite resins. Oper Dent 1998; 23(3):150-154.
13. Kakaboura A, Tzoutzas J, Pitsinigos D, Vougiouklakis G. The effect of sterilization methods on the light transmissioncharacteristics and structure of light-curing tips. J Oral Rehabil. 2004;31:918-923.
14. Chang HS. Infection control of light curing units. J Korean Acad Conserv Dent 2010;35:235-237.
15. McAndrew R, Lynch CD, Pavli M, Bannon A, Milward P. The effect of disposable infection control barriers and physical damage on the power output of light curing units and light curing tips. Br Dent J 2011;210:E12.
16. Pollington S, Kahakachchi N, van Noort R. The influence of plastic light cure sheaths on the hardness of composite resin. Oper Dent. 2009;34:741-745.
17. Scott BA, Felix CA, Price RB. Effect of disposable infection control barriers on light output from dental curing lights. J CanDent Assoc 2004;70:105-110.
18. Chang HS, Lee SR, Hong SO, Ryu HW, Song CK, Min KS. Effect of infection control barrier thickness on light curing units. J Korean Acad Conserv Dent 2010;35:368-373.
19. Miller CH, Palenik CJ. Infection control and management of hazardous materials. St. Louis: Mosby Pub. Co.; 1994.
20. Warren DP, Rice HC, Powers JM. Intensity of curing lights affected by barriers. J Dent Hyg 2000;74:20-23.
21. Leonard DL, Charlton DG, Roberts HW, Cohen ME. Polymerization efficiency of LED curing lights. J Esthet Restore Dent 2002;14:286-295.
22. Owens BM, Rodriguez KH. Radiometeric and spectrophotometric analysis of third generation lightemitting diod (LED) of light curing unit. J Contemp Dent Prac 2007:8;43-51.
23. Price RB, Dérand T, Sedarous M, Andreou P, Loney RW. Effect of distance on the power density from two light guides. J Esthet Dent 2000;12:320-327.
24. Knobloch L, Kerby RE, Clelland N, Lee J. Hardness and degree of conversion of  posterior packable composites. Oper Dent 2004;29:642-649.
25. Mills RW, Uhl A, Black well GB. High power light emmiting diod (LED) arrays versus halogen light polymerization of oral bio materials: Bascol hardness, compressive strength  and radiometric properties. Biomat 2002; 23: 2955-2963
26. Uhl A, Mills RW, andt KD. Polymerization and light induced heat of dental composite cured with LED and halogene technology. Biomet 2003;24:1809-1820.
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28. Al Mazrok MI. The effect of wrapping of light-cure tips on the cure of composite resin. Eur J Gen Dent 2012; 1:83-86.
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30. Chong SL, Lam YK, Lee FK, Ramalingam L, Yeo AC, Lim CC. Effect of various infection-control methods for light-cure units on the cure of composite resins. Oper Dent 1998;23:150-154
31. McAndrew R, Lynch CD, Pavli M, Bannon A, Milward P. The effect of disposable infection control barriers and physical damage on the power output of light curing units and light curing tips. Br Dent J 2011;210:E12.

1. Assistant professor Ziauddin University.

Corresponding author: “Dr Nazish Fawad ”  < Nazish_fawad@yahoo.com  >

Khurram Parvez Sardar ¹                                     BDS, MDS

Syed Yawar Ali Abidi ²                                          BDS, FCPS

Wasif Iqbal ³                                                             BDS, MSc

Ashraf Ali Meo ⁴                                                       B.E (Met.), PhD (UK)

Noor-ul-Ain Jawaed ⁵                                            BDS, FCPS

Rao Subhan Mustafa Khan ⁶                              DMD,DDS, MDS

INTRODUCTION

The cleaning and shaping of root canal followed by its filling in all three dimensions is the primary objective of contemporary endodontics^1,2. If apical seal is inadequate, it can cause  apical leakage and will allow the microorganisms and their toxins to enter and  disturb periradicular  tissues and can nnegatively effect the endodontic prognosis³.

The Root canal treatment fails if doesn’t meet adequate standard⁴. Endodontic treatment may fail due to procedural errors such as broken instruments, over or under fillings, perforations, ledges⁵. Presence of viable bacteria in the canal and its improper obturation is one of the major cause of endodontic failure^1,6.

Canal preparation technique may also influence the endodontic outcome. Literature is replete with reports of superiority of Nickel-titanium rotary (NiTi) files over hand files of stainless steel (ss)^7,8. Von Fraunhofer reported that irrespective of obturating technique used, the canal preparation technique influenced apical leakage with canals prepared with NiTi files exhibiting less leakage⁹. Amongst the obturation techniques used nowadays, cold lateral condensation is most widely taught and a gold standard against which newer techniques are compared^6,10. The root canal sealer plays an important role for the achievement of an impermeable tight seal. It fills the canal irregularities and discrepencies between the filling material and canal wall¹¹. It may also lubricate the core material during obturation¹². The  canals devoid  of smear layer, may not only allow adhesion to dentine walls, sealer may also penetrate the patent tubules¹³.A sealer should be well tolerated and non toxic to the peri-radicular tissues, the majority of the sealers show toxicity however their toxicity is very much reduced during  setting and the majority of the sealers are absorbable when they are in contact  with tissue fluids¹⁴.

The sealers utilized in root canal system are generally divided into groups depending on their components, for example sealers based on calcium hydroxide, sealers based on Zinc oxide-eugenol , glass ionomer cement (GIC) sealers, chloropercha, formaldehyde containing sealers as well as resin based sealers¹⁴. In this study we used Epoxy resin based sealer.

Various methods of dye leakage have been reported in the literature (linear measurement),e.g. methylene blue, eosin aqueous solutions,  ink India , bacteria, radioisotopes as well as electro-chemical^15-17. Other  technique for evaluating the apical leakage consist of a vacuum environment technique, air bubble movement  technique and fluid filtration¹⁷. The initial acceptable seal of the canal may be challenged by length of time, solubility of sealer, negative pH in periapex, presence of periapical fluids, residual smear layer as well as by residual intracanal medicament. All of these factors have been extensively studied except for extended time duration. The physical deterioration of dental materials is time dependent. It was therefore, the aim of this study to study the effect of extended storage of upto 8 weeks on apical seal of  root canals obturated with an epoxy resin sealer.

METHODOLOGY

This in vitro study was carried out at Operative Dentistry Department  and in the Department of Dental Materials at DIKIOHS,(DowUniversity of Health Sciences). Microscopic evaluation of samples  was done in the Department of Materials at NED University Karachi, Pakistan. The study was conducted over a duration of one year.

A total of 180 single rooted  human teeth with no caries or restoration present and extracted due to advanced periodontitis were selected for the study. We excluded teeth that were cracked, broken down or has internal or external resorption.

ISO/TS 11405 standard were followed to Store and handle the extracted teeth. Ultrasonic scalers were used to remove all deposits and cleaned thoroughly.. The teeth were decoronated 1mm coronal to the CEJ and placed in normal saline. PA view X-ray (Kodak) was taken to assess the approximate working length and patency of the root canal.A size K file ISO # 15 (MANI) was used for calculating working lengths.

The canals were prepared protaper rotary NiTi instruments (Dentsply/Maillefer) using the standard sequence. Sx was introduced first to widen the orifice, followed by S1 and S2 to prepare the coronal and middle third. Apical third was gauged and prepared by F1, F2 or F3 according to manufacturers’ instructions.  The irrigation was accomplished with a 27 gauge needle and sodium hypochlorite (Sultan Healthcare Inc, USA) was used. 17% EDTA (Prime Dental Products of India) was used to smear layer management followed by drying of canals with paper points. Cold lateral condensation technique was used for obturating the canals. An appropriate size ISO standardized master gp was prefitted in the canal. If the gp point exhibited tug back at 0.5 to 1 mm from the working length it was selected. The epoxy resin sealer was mixed according to the manufacturers’ instructions. The master gp was coated with sealer and inserted in the canal. The gp was laterally condensed with a finger spreader. Accessory gp’s were subsequently filled until the whole of canal was obturated. The top protion of gp’s were seared off using a hot instrument and condensed with a no. 4 hand plugger.  Quality of the fill was assessed with a radiograph and those deemed unsatisfactory were refilled.. The cavity of access of all teeth were filled by using  Ketac Molar to make certain of a coronal seal. Samples were placed in distilled water and store up in an incubator for one day in the environment of 100% humid environment and at 37ºC to allow setting of a sealent.

The tooth samples (n=180) thus prepared were divided into an experimental group (n=150) and control group (n=30). We divided the experimental group into three suggroups (n=50 each) that were kept in 5% methylene blue (MERCK) at 37°C for 1week (group 1) , 4weeks (group 2) and 8 weeks (group 3) respectively. The control group was divided further into a positive (group D) (n=15) and negative (Group E)(n=15) group.

Two coats of varnish/ nail polish were used to paint the external surfaces of root samples in the experimental groups (A,B,C) and in positive control group (D), up to the apical 2mm area , and completely in the negative group (E). As mentioned earlier, the sample belonging to group A, B & C were kept in methylene blue dye for a period of 1, 4 & 8 weeks respectively. While the positive and negative control (Group D & E) samples were further subdivided into smaller groups comprising of 5 samples each. Each sub group from group D 7 D were also kept in methylene blue for 1, 4 & 8 weeks.

After the prescribed incubation period the samples were washed, dried and varnish removed with a scalpel. The samples were subsequently sectioned horizontally with the help of a sectioning disc (Noritake Dental Supply Co. Ltd).

DATA COLLECTION PROCEDURE

Apical leakage was assessed by computing linear extention of the methylene blue dye infiltration in millimeters in apico-coronal direction.

To eliminate bias, two evaluators made independent assessments and a mean of their readings was considered as the final value. A stereo-microscope (Motic, Hong Kong) was used for visual analysis of sectioned specimens. Motic Image Plus 2.0 ML (Motic, Hong Kong) software was used for measurement of linear dye leakage in all study groups.

DATA MANAGEMENT

A 3mm dye penetration was considered as an adequate seal, as reported earlier¹⁸. The gradin method used in this study was modified from the one reported byKytridou and is presented in table no 1¹⁹.

STATISTICAL ANALYSIS

SPSS version 16 was used for statistical analysis. Descriptive statistics was used to calculate mean and standard deviation of dye leakage, whereas frequency of leakage was calculated from the grading system. The difference in mean of various groups was calculated using the ANOVA at a level of significance of 0.05.

RESULTS

There was no leakage in negative control group, whereas every sample in positive control group leaked Group A demonstrated the least leakage value (2.53mm, SD ±0.87) followed by group B (2.69mm SD±1.01) and Group C (2.77mm, SD±1.02). However, this difference was statistically insignificant (p=0.468).  (Table 2, Figure 1). Table 3 represents the dye leakage in terms of our grading criteria mentioned in table 1. Almost half samples of group C exhibited grade 3 leakage, whereas worst

IMMERSION TIME PERIOD

(a) After 7 days of Storage  (b) 4 Weeks of Storage

(c) 8 Weeks of Storage

DISCUSSION

We used an epoxy resin sealer (AH-26) in our study since it is one of the most commonly used sealer in the market^20,21. This sealer is cost-effective and has a proven efficiency²².

AH plus may form a better adhesion with the redicular dentin due to its hypothesized formation of covalent bond with amines of collagen²³. In our study the samples that leaked upto 3mm or less were considered as hermetically sealed as reported by Freymann¹⁸. Majority of our samples (70% of group A and C and 62% of group B ) leaked 3mm or less thus fulfilling the criteria for hermetic sealing. Thus an impervious seal was achieved in our samples for an extended period, however since we didn’t compare AH plus with other sealers a generalization cannot be made and it is one of the limitation of our study and a possible future direction. We kept group C specimens in dye for 8 weeks to assess the claim of De Munck that the bond of resin to radicular dentin deteriorates over an extended exposure to dye. However, the results of our study disagreed with these observations. This difference might result from a different methodology or types of sealer used in the previous study. On the other hand when individual leakage values are considered instead of group mean, a trend of an increasing leakage with time can be observed¹⁷.

In Group A, 30% of samples leaked more than 3mm, out of which 6% leaked more than 4mm. Whereas in Group b, 40%  samples leaked more than 3mm and only 4% more than 4mm. Interestingly in this group 2%samples showed dye penetration of more than 5mm. In Group C, 30% of samples leaked for more than 3mm while 12% leaked more than 4mm. Out of this 12% sample, 2% leaked more than 5mm and another 2% leaked more than 6mm.

In spite of our insignificant findings, our results suggests that future researches may be planned keeping these limitation in mind. We recommend using either a different methodology or a longer exposure time to dye.

We used a crown down technique to shape canals with NiTi instruments. Numerous in-vitro and in-vivo studies have reported the superiority of NiTi over stainless steel files^7,8.

Another limitation of the study is that a comparison among instrument type, technique and methodology was not performed.

We used cold lateral condensation technique in our study since it is considered to be a gold standard²⁴. A variety of root canal obturation techniques and materials have been reported in literature²⁴. Similarly, a variety of in-vitro studies have been conducted including but not limited to coloured dye penetration, bacterial penetration, radiolabelled tracer penetration, dissolution of hard tissue, clearing of teeth, spectrometry of radioisotopes, electrochemical methods and gas chromatography^25-27. It must however be noted that an ideal method of leakage detection doesn’t exist²⁶.

Despite of the inaccuracy in dye penetration method, this technique is more commonly used in the analysis of  coronal or apical leakage²⁶ perhaps due to its simplicity of laboratory procedure and measurements. Literature demonstrate that 82% of leakage studies in root canal system used dye or radioisotope penetration technique²⁷. Starkey²⁸ concluded that methylene blue dye generally demonstrate accurate apical leakage. According to Ahlberg²⁹ methylene blue dye is a satisfactory indicator of leakage of microorganisms, large size endotoxins and toxic agents with low molecular weight.

Methylene blue was used in the study because it showed accurate results in previous studies²⁸. It is easily available, less expensive and simple. Our results suggest that none of the samples had an impervious seal since some leakage was present in each group with a statistically insignificant difference between the groups. According to Hovland and Dumsha, leakage is present in most if not all the sealers in-vivo. It only becomes pathological or symptomatic if it reaches a certain critical limit resulting in apical periodontitis. The exact dynamics of the leakage is complicated by the presence of many interfaces between canal wall, solid core and sealer. Dissolution of the sealer itself may enhance leakage³⁰. Similarly, De Moor has reported that the use of a tracing mechanism and its observation by splitting a root may be a simple and efficient method to study leakage³¹.

In our study, in spite of non-significant findings there is still a need for further work to compare different canal preparation techniques, sealers and obturation techniques since all of these variables may influence the final seal of the canal. It is also important not to overlook the bio-compatibility and cyto-toxicity and one should strive to strike a balance. Other reasons of leakage in our study might be attributed to the presence of entrapped air or aberrant anatomy which was not studied in our work and hence the results of our study must be interpreted with caution and may be topic of research in future studies.

CONCLUSION

We draw following conclusions on the basis of our results. . Leakage was present in all the samples . A gradual increase in mean leakage value was observed as the storage time increases. The differences amongst the groups remain insignificant (p=0.468).

REFERENCES

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4. Sundqvist G, Figdor D, Persson S, Sjögren U. Microbiologic analysis of teeth with failed endodontic treatment and the outcome of conservative re-treatment. Oral Surg Oral Med Oral Pathol Oral Radiol Endod1998; 85: 86-93.
5. Ingle JI, Simon JH, Machtou P, Bogaerts P. Outcome of endodontic treatment and retreatment In: Ingle JI, Bakland LK: Endodontics, 5th Edition. London: BC Decker Inc 2002; p. 753.
6. Orstavik D. Materials used for root canal obturation: technical, biological and clinical testing. Endodontic Topics 2005; 12: 25-38.
7. Schäfer E, Vlassis M. Comparative investigation of two rotary nickel titanium instruments: ProTaper versus RaCe. Part 1. Shaping ability in simulated canals. Int Endod J 2004; 37:229-238.
8. Tasdemir T, Aydemir H, Inan U, Unal O. Canal preparation with Hero 642 rotary Ni-Ti instruments compared with stainless steel hand K-file assessed using computed tomography. Int Endod J 2005; 38:402-408.
9. Von Fraunhofer JA, Fagundes DK, McDonald NJ, Dumsha TC. The effect of root canal preparation on microleakage within endodontically treated teeth: an in vitro study.Int Endod J 2000; 33: 355-360.
10. Ugur I, Hikmet A, Tamer T. Leakage evaluation of three different root canal obturation techniques using electrochemical evaluation and dye penetration evaluation methods. Aus Endod J 2007; 33:18-22.
11. Schafer E, Olthoff G. Effect of three different sealers on the sealing ability of both Thermafil obturators and cold laterally compacted gutta-percha. J Endod 2002; 28: 638-642
12. Baumgartner G, Zehnder M, Paqué F. Enterococcus faecalis type strain leakage through root canals filled with Gutta-Percha/AH plus or Resilon/Epiphany. J Endod. 2007;33:45-47.
13. ANSI/ADA Specification No. 57-Endodontic Sealing Material: 2000 (Reaffirmed 2006).
14. Dahl JE. Toxicity of endodontic filling materials. Endod Topics 2005; 12:39-43.
15. Cobankara FK et al. The quantitative evaluation of apical sealing of four endodontic sealers. J Endod 2006; 32:66-68.
16. Perdigao J. Lopes MM, Gomes G. Interfacial adaptation of adhesive materials to root canal dentin. J Endod 2007; 33: 259-263.
17. De Munck J, Van Landuyt K, Peumans M, et al. A critical review of the durability of adhesion to tooth tissue: methods and results. J Dent Res 2005; 84: 118-132.
18. Freymann M, Fanti V, Claisse A, Poumier F, Watson M. Apical Microleakage of Radiolabeled Lysozyme over Time in Three Techniques of Root Canal Obturation. J Endod 2000; 26: 148-152.
19. Kytridou V, Gutmann JL, Nunn MH. Adaptation and sealability of two contemporary obturation techniques in the absence of the dentinal smear layer. Inter Endod J 1999; 32: 464-474.
20. Zmener O, Spielberg C, Lamberghini F, Rucci M. Sealing properties of a new epoxy resin based root canal sealer. Int Endod J 1997; 30:332-334.
21. Onay EO, Ungor M, Unver S, Ari H, Belli S. An in vitro evaluation of the apical sealing ability of new polymeric endodontic filling systems. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2009; 108: 49-54.
22. Sevimay S, Kalayci A. Evaluation of apical sealing ability and adaptation of two resin-based sealers. J Oral Rehabil 2005; 32: 105-10.
23. Bouillaguet S, Shaw L, Barthelemy J, Krejci I, Wataha JC. Longterm sealing ability of Pulp Canal Sealer, AHPlus, GuttaFlow and Epiphany. Int Endod J 2008; 41: 219226.
24. Cohen S, Hargreaves KM. Pathways of the pulp. 9th ed. St.Louis: Mosby Elsevier; 2006; p. 358-392.
25. Gernhardt CR, Kruger T, Bekes K, et al. Apical sealing ability of 2 epoxy resin-based sealers used with root canal obturation techniques based on warm gutta-percha compared to cold lateral condensation. Quintessence Int 2007; 38:229-234.
26. Peak JD, Hayes SJ, Bryant ST, Dummer PM. The outcome of root canal treatment. A retrospective study within the armed forces (Royal Air Force). Br Dent J 2001; 190: 140-144.
27. Brosco VH, Bernardineli N, Torres SA, Consolaro A, Bramante CM, de Moraes IG, et al. Bacterial leakage in obturated root canals-part 2: a comparative histologic and microbiologic analyses. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2010; 109: 788-794.
28. Starkey DL, Anderson RW, Pashley DH. An evaluation of the effects of methylene blue dye pH on apical leakage. J Endod 1993; 19: 435-439.
29. Ahlberg KM, Assavanop P, Tay WM. A comparision of apical dye penetration patterns shown by methylene blue and india ink in root-filled teeth. Int Endod J 1995; 28:30-34.
30. Hovland EJ, Dumsha TC. Leakage evaluation in vitro of the root canal sealer cement Sealapex. Int Endod J 1985; 18:179-182.
31. De Moor RJ, Hommez GM. The long-term sealing ability of an epoxy resin root canal sealer used with five gutta percha obturation techniques. Int Endod J 2002; 35: 275-282.

1. Assistant Professor MDS Supervisor & Subject Coordinator. Department of Science of Dental Materials. Dr.Ishrat-ul-Ebad Khan Institute of Oral Health Sciences. Dow University of Health Sciences.
2. Program Director MDS Program. Associate Professor, Incharge, Department of Operative Dentistry, Supervisor MDS (Science of Dental Materials), Supervisor FCPS (Operative Dentistry), Dr.Ishrat-ul-Ebad Khan Institute of Oral Health Sciences. Dow University of Health Sciences.
3. Assistant Professor, HOD Department of Science of Dental Materials. Ishrat-ulEbad Khan Institute of Oral Health Sciences. Dow University of Health Sciences
4. Chairman, Department of Materials Engineering, NED University of Engineering and Technology, Karachi.
5. Department of Operative Dentistry. Dr.Ishrat-ul-Ebad Khan Institute of Oral Health Sciences. Dow University of Health Sciences
6. Department of Science of Dental Materials.Dow International Dental College Dow University of Health Sciences Consultant Dental surgeon Aga Khan Hospital.Corresponding author: “Dr Khurrum Parvez Sardar” <dr_khurramparvez@hotmail.com >

Behzad A.Zai ¹                                              MSc

Abdul S. Khan ²                                           BDS, MSc, PhD

Hassan Mehboob ³                                     MSc

INTRODUCTION

Recently number of patients who have been suffering from dentofacial disharmony is increasing1. Among these patients quite a few of them suffer from maxillary transverse deficiency needing correctional treatment for transverse disharmony between upper and lower jaw bones and malocclusions2. Among correctional treatments, surgically assisted rapid maxillary expansion is a treatment of choice3-6.

To help transverse expansion of palatine bones various methods of osteotomy for upper jaw bone has been suggested. Hyrax (Hyrax Orthodontic Expander, ExpoOrtho) device is used to expand the maxilla and the stresses are generated in the maxilla due to the applied force⁷. For stress and displacement analysis of maxillary expansion, different material properties can be incorporated in Finite Element Method (FEM) analysis according to patient’s sex and age. With the conditions using FEM, distributions of stress and displacements developed on maxilla have been analyzed for osteotomy and without clinical procedure the locations can be determined where patient can feels pain^8-9. In this paper, FEM was used to predict and analyze the developed stresses by maxillary expansion which can help to improve the surgical methods. To develop simulated conditions the same force was exerted on maxilla through Hyrax and same conditions for different methods of osteotomy were employed in commercially available FEM software ANSYS V14.0.

Method

2.1- Development of FEM model

A Three-Dimensional (3-D) prototype of maxillary model was produced by taking the impression on a plaster of a volunteer patient. The model was also scanned with a KCI 3D scanner (Korea Computer Information Co., Ltd, South Korea). The data generated of 353,230 nodes by the scanning was incorporated in commercial software for 3-D reverse engineering called RAPIDFORM V6000 (Rapidform, Inc. Sunnyvale, CA). RAPIDFORM converted the 353,230 nodes into 3-D volume of 117703 elements for FEM analysis. The model generated by RAPIDFORM was used to create a virtual 3-D structure as shown on Figure 1.

A device Hyrax (Hyrax Orthodontic Expander Stainless Steel made) was fabricated for the application of rapid maxillary expansion as shown in Figure 2. The device was activated with central

expansion screw. Each 1/4 turns of screw caused transverse expansion of 0.25mm. With intermittent turning of the screw in a time sequence an expansion was made to left and right in due turns. Actual operation of Hyrax was applied by assuming one full turn (4 of 1/4 turn) corresponding to 1mm expansion. Reaction forces were computed with these conditions using commercially available finite element software ANSYS V14.0.

The hyrax is generally made of stainless steel. The material properties of tooth, bones and AISI Type 403 stainless steel Hyrax were used in 3-D finite element model as listed in Table 1-2. Based on the analysis of stress distribution and displacement using FEM, the optimum surgical methods were determined. One control

group and four test groups (as shown in Figure 3) were formed and the experimental material properties provided to software as tabulated in Table 2.

Control group: No surgery

Test group: With surgery

1. Test 1: Le-fort I Osteotomy
2. Test 2: Le-fort I Osteotomy + Para-median Osteotomy
3. Test 3: Le-fort I Osteotomy + Pterygomaxillary separation
4. Test 4: Le-fort I Osteotomy + Para-median Osteotomy + Pterygomaxillary separation

Stresses and strains induced at the maxilla under each condition listed above were evaluated for the comparative analysis. Also the stresses generated in the Hyrax are shown in Figure 4. In the control group no

surgical operation was applied, simple induced stress and strain distributions by Hyrax were analyzed with FEM. Appropriate boundary conditions were applied in FEM analysis to properly represent the three surgical methods. Von-Mises theory was adopted to analyze the stress distribution ⁷. In addition to analysis of maxilla model the displacements of the first molar and premolar were also considered along y and z-axis.

Results

The average displacement value (both left and right sides) at first molar and premolar was 0.326×10^-2mm.

In Figure 5, results of induced stress were shown. The

largest stress around this area was 268.66×10^-3kgf /mm². For Test 1, upon the applications of Le-fort I osteotomy the displacements at first molar and premolar on right and left sides were similar which were 0.723×10^-2 mm for each as shown in Figure 6(a). Stresses developed on the right and left sides at first molar and premolar were 233.38×10-3kgf/mm² which was lower compared to the values for control group as shown in Figure 6(b).

However, a stress concentration of 700×10^-2kgf/mm²

was found at the area where pterygomaxillary separation was not applied.  Similar analysis was performed for all the other three cases, the displacement and stress values are shown in Table 3 and Table 4 respectively. It was observed from the results mentioned in Table 3,

4 and Figure 7 that the maximum strain was substantially

increased from Test 1 to Test 4 which was due to the application of pterygomaxillary separation. The maximum strain or displacement at first molar and premolar was observed for Test 4 which was 1.88x102mm on average. A stress level of 200.11×10^-3kgf/mm² was developed at first molar and premolar on right and left sides. Whereas, in Test 1 where pterygomaxillary

separation was not performed a stress concentration of 900×10^-3 kgf/mm² was observed. Le-fort I osteotomy and pterygomaxillary separation greatly relieved the level of stress to 153.03×10^-3 kgf/mm² at first molar, premolar and hard palate. The observed stress concentration was reduced to the level of 0.0014×10^-3kgf/mm² at the area where pterygomaxillary separation was applied.

DISCUSSION

In control group, without an application of the surgery simply the stresses and strains developed by the Hyrax were evaluated. The study model’s left and right maxillaries were not symmetric leading to development of asymmetrical displacements. However, considering the left and right side of maxilla from control y-axis the general trend was that largest displacement was developed at premolar and first molar on both left and right sides, at which Hyrax exerted forces. It was observed that the distributions of largest values were at hard palate area, first molar and premolar where the Hyrax was attached. The results already indicated that pterygomaxillary separation was the most effective surgical method for rapid maxillary expansion. Since all the surgical methods including Le-fort I osteotomy, pterygomaxillary separation and para-median osteotomy were applied, larger displacement was achieved compared to control and other test groups. Moreover the stress level was continuously decreased because of simultaneous surgical operation of Le-fort I osteotomy, pterygomaxillary separation and para-median osteotomy a stress level of 136.08×10^-3 kgf/mm² was developed at first molar and premolar, also reduced stress concentration of 0.0012×10^-3 kgf/mm² was observed. It is suggested that 3-D FEM analysis technique along with Hyrax can be used to determine the stresses and displacement developed on the maxilla without actually performing surgical operations.  Using 3-D FEM analysis, stresses and strains can be theoretically evaluated. Moreover, by supplying different bone properties for different patients, various analyses can be customized for a specific patient revealing all the characteristic nature of the problems. The results of the analysis can be visually confirmed in detail.

CONCLUSION

This study analyzed the strains developed at the maxilla, the stresses and the reactions which were generated during rapid maxillary expansion, for which a small stress applying device, Hyrax, was used and also the four different surgical methods were employed. When all the results were combined and analyzed the Test 4, where the three surgical methods were jointly applied showed the largest strains and the smallest stress compared with the control and other test group. The combined surgical method (Test 4) was the most desirable method which can minimize patient’s pains and maximize the expansion during rapid maxillary expansion. The application of pterygomaxillary separation had great effect on strains and stress.

ACKNOWLEDGMENTS

The authors would like to acknowledge Higher Education Commission of Pakistan to provide scholarship for higher studies.

REFERENCES

1. Parrello D, Bolamperti L, Caprioglio A. Interdisciplinary treatment of Class III malocclusion: a case report. Prog Orthodont, 2011; 12: 169-179.
2. Yang CY, Min SK, Oh SH, Kwon KH, Lee J, Cha JW. Clinical study of surgically assisted rapid maxillary expansion. J Kor Assoc Oral Maxillofac Surg, 2005; 31: 60-69.
3. Stromberg C, Holm J. Surgically assisted rapid maxillary expansion in adults. A retrospective longterm follow-up study. J Craniomaxillofac Surg, 1995; 23: 222-227.
4. Lines PA. Adult rapid maxillary expansion with corticotomy. Am J Orthodont, 1975; 67: 44-56.
5. Moss JP. Rapid expansion of the maxillary arch I.  J Pract Orthodont, 1986; 2: 165-171.
6. Progrel MA, Kaban LB, Vargervik K, Baumrind Surgically assisted rapid maxillary expansion in adults. Int J Adult Orthodont Orthodont Surg, 1992; 7: 37-41.
7. Jafari A, Shetty KS, Kumar M. Study of stress distribution and displacement of various craniofacial structures following application of transverse orthopedic forces–a three-dimensional FEM study. Angle Orthodont, 2003; 3: 12-20.
8. Holberg C. Effects of rapid maxillary expansion on the cranial base an FEM analysis. J Orofac Orthoped, 2005; 66: 54-66.
9. Kennedy JW, Bell WH, Kimbrough OL, James WB. Osteotomy as an adjunct to rapid maxillary expansion. Am J Orthodont, 1976; 70: 123-137.
10. Harvey PD (ed). Engineering Properties of Steels, American Society for Metals, Metals Park, OH, USA, 1982.
11. Peckner D, Bernstein IM (eds). Handbook of Stainless Steels, McGraw-Hill Book Company, New York, USA, 1977.
    

    ---

1.Department of Mechanical Engineering, Myongji University, South Korea.
2.Associate Professor Interdisciplinary Research Centre in Biomedical Materials COMSATS Institute of Information Technology, M.A. Jinnah Campus Defence Road, Off Raiwind Road, Lahore, Pakistan
2.School of Mechanical Engineering, Chung-Ang University, South Korea
3.Interdisciplinary Research Centre in Biomedical Materials, COMSATS Institute of Information Technology, Lahore, Pakistan
Corresponding author: “Dr. Abdul Samad Khan ” < draskhan@ciitlahore.edu.pk >

Haroon Rashid ¹                                              BDS, MDSc

Ayesha Hanif ²                                                 BDS

Fahim Vohra ³                                                 BDS, MFDS, M.Clin.Dent, MRDRCS

Zeeshan Sheikh ⁴                                            BDS, MSc, PhD

INTRODUCTION

Over-dentures are defined as,”removable dental prosthesis that cover and rests on one or more remaining natural teeth, the roots of natural teeth, and/or dental implants”^[1]. It may also be termed as an overlay denture, overlay prosthesis, superimposed prosthesis, hybrid prosthesis, a crown and sleeve prosthesis, superimposing denture and a biological denture¹.

The concept of retaining teeth/roots of the terminal dentition for the provision of an overdenture dates back to more than 100 years^[2],[3]. It was first described in 1950’s that the residual alveolar bone undergoes resorption which continues to progress after tooth extraction compromising support for a conventional dentures to be provided. The analysis of several longitudinal studies confirmed that the resorption was progressive, irrevocable and

continuous^[4],5. The rate of resorption is the greatest in the first six months after tooth extraction however; it slows down due to several biological and mechanical factors⁴. Overdenture abutments, whether a retained root or an implant, have shown to preserve alveolar bone height^7,8 and stabilize dentures, particularly the mandibular ones⁹. Retained roots are cost effective than implants, with no requisite of an invasive therapy, and therefore should be considered by general practitioners as a useful platform for over dentures, particularly for older individuals¹⁰. From physiological viewpoint, the roots provide not only a periodontal ligament to support the teeth, but also directional sensitivity, tactile sensitivity to load, dimensional discrimination,^7,11,12 and gives an individual a sense of not being edentulous¹³. Dental implants provide adequate retention and stability for overlying prosthesis however; the individual is deprived of tactile sensitivity¹⁴.

Dental implant therapy is considered the treatment of choice for edentulous patients¹⁰. IODs have gained worldwide acceptance and improve the quality of life for edentulous patients. IODs although retentive and stable,require good maintenance of the prosthesis and implant retentive components⁶.  Continued research related to IODs has resulted in multiple options and combinations for IOD attachment systems with varying success. The aim of the current paper is to briefly review the attachment systems used for IODs and the factors influencing their selection. Chair-side pickup Impression technique for mandibular implant over-denture is also briefly described. The treatment of the patient described in the current paper was carried out at the department of prosthodontics, college of dentistry,Ziauddin University, Karachi.

OVERDENTURE ABUTMENTS

In the early days, only bare teeth with questionable prognosis as a whole were used as abutments for over dentures. Recently, the use of implant abutments for overdenture use has increased. The use of sub-mucosal roots with magnets is also still in use ^15,16.

When using naturally retained bare teeth, it is aimed that canines and second premolars are preserved on both sides of the arches. Teeth are prepared in a dome shape, 2-3 mm above the gingival level, with the dome converging occlusally. To cope up with certain disadvantages of bare teeth such as caries progression, attrition of the abutment teeth, metal copings (short and long) were used over the dome shaped prepared teeth. Sub-mucosal root retention helps to reduce the possible oral hygiene obligations for the patients but delays residual ridge resorption. Being submerged, they escape the sequelae of poor oral hygiene by being isolated from the oral cavity.

With advancements in implant dentistry, implant supported over-dentures are gaining wide popularity. Along with implant abutments, sub-mucosal vital tooth retention and use of magnets are also commonly used. For many years, osseointegrated implant-supported overdentures have been used in the rehabilitation of the edentulous jaws particularly the lower ones, offering promising results ^17,18,19.

Literature states that the IODs should become the first choice of care for the edentate mandibles^20,21. This is a lucrative option but simultaneously, has been questioned for the fact that wide number of the edentate patients are poor and cannot afford the cost of implant therapy 22,23.

ATTACHMENT SYSTEMS FOR IODs

IODs come with a variety of attachment systems including the bar and clip attachment systems or a range of individual, abutment-based attachments called stud attachments (ball, magnets, and resilient stud attachments such as Locators [Zest Anchors], ERA [Sterngold], and non resilient stud attachments such as Ankylos Syncone [DENTSPLY Implants])^{24,25,26,27,28}. Fabrication of an IOD over these systems is costly; require clinical expertise and signification chair-side time¹⁸.

FACTORS INFLUENCING SELECTION OF THE ATTACHMENT SYSTEMS

Selecting the most apposite system for an individual is dependent on a variety of factors²⁹. These factors are identified during the treatment and planning phase of the therapy. Following are the factors that influence the selection:

a) Implant site:

The location of the placed implant in reference to the bone and the pontics will guide the selection of the type of attachments. However; the selection should ideally be decided during the phase of treatment planning. For ample retention, it is highly recommended that the implants are placed as parallel as possible^30,31,32.  Where parallelism cannot be achieved, a bar designed is favored. Bar design is also preferred in cases where the unfavorable location of the anatomic structures such as, prominent mental foramen or the knife-edge ridge, precludes the ideal placement of the implants^33,34,35,36.

b) Cross arch stabilization:

Bars are indicated in patients with shallow vestibules and resorbed ridges. The bar helps to resist the lateral loading and provides stabilization³⁷. The stability of the prosthesis is also improved and cantilever design may be provided with one to two teeth distal to the most posteriorly placed implant³⁸. The cases where denture stability is not a concern and retention is the only requirement, individual attachments should be used which offer promising results.

c) Prosthesis extent:

When the patient demands the prosthesis to be of the minimal size, custom designed milled bars is the attachment system of choice³⁹.  These types of restorations require ideal implant placement. The size of the prosthesis may be limited while keeping in mind the principles of anterior-posterior spread and cross arch stabilization. This also minimizes the lateral loads on the implants³⁸. Fabricating a denture using the neutral zone technique will also determine the horizontal space availability for the prosthesis³⁹. Neutral zone is the area of the minimal conflict i.e. the potential denture space; “that space in the edentulous mouth vacated by the natural dentition and dental supporting tissues and bound by the tongue medially, and the lips and cheeks laterally”^40,41,42 .

d) Sore spots:

It is established that the patients who are prone to soft-tissue sore spots, for instance xerostomic patients, are reportedly more comfortable with a bar, since the denture can rest entirely on the bar without impingement of the soft tissues⁴³. With individual attachments, the denture is supported by the mucosa and the compressive forces acting on the mucosa cause may cause soreness in patients who are prone to it⁴⁴.

e) Patient’s Oral Hygiene:

Dentures retained over bars are capable of gathering more debris and hence make such patients more susceptible to mucosal inflammation and peri-implantitis 44,45,46,47,48,49,50,51. Unless the patient commits to the meticulous oral hygiene measures⁵², the bar attachments should be denied in patients with poor oral hygiene.

f) Treatment Costs:

Bar attachments are costly as compared to the stud abutments in most of the scenarios^35,53. Cost is one of the major decisive factors in the selection of the attachment system. Patients may be upgraded to the bars and a new over denture may be fabricated if the financial condition of the patient has improved and other factors are considered. Yet, in every case, the selective treatment option must follow the appropriate guidelines maximizing the welfare of the patient and the options should never be merely dependent on patient’s finances.

g) The Restorative Space:

Restorative space is the space which is available for prosthesis restoration. In general, this space is bounded by the planned occlusal plane, the denture bearing tissues, facial tissues i.e. the lips, cheeks and the tongue⁵⁴. When planning an implant overdenture, considerations should be given to the adequate space available for the denture base, denture teeth, and the attachment system of the implant. The freeway space, phonetics and aesthetics must also be considered. The minimum space requirement for implant supported over-dentures with Locator attachment system is 8.5mm of vertical space and 9 mm of horizontal space⁵⁵. Ideally, for maxillary implant over-dentures, 13-14mm of vertical space is required for dentures which are supported by bars and 10-12mm for the over-dentures supported with individual attachments⁵⁶.

h) The Aesthetic Space:

This is defined as “the space between the ridge crest and the corresponding lips at rest”²⁹. Prosthesis supported by the individual attachment systems will require less aesthetic space compared o the bar counterparts. The measurement of the aesthetic space helps the dentist in determining the space allowed for a particular type of the attachment system of an over-denture.

i) Ease of Fabrication and Repair:

Bar supported removable prosthesis require manual dexterity for the fabrication and repair compared with the removable prosthesis supported by individual studs ^{24,57,58,59,60}. Many a times, the attachment systems are chosen without the proper consideration given to the aforementioned factors. This eventually leads to a failed prosthesis with patient dissatisfaction.

j) Resilience Difference:

Another factor documented that influences the selection of the attachment system for implant-retained over-dentures, is the difference of resilience between the implant and the oral mucosa^61,62. Furthermore, this difference should be considered while taking the impression of the implant and tissue retained over-dentures.

k) The Attachment System:

IODs supported with bars or balls offer good survival rates and patient’s appreciation levels with a denture retained with implants are better as compared to a conventional complete denture⁶³. The use of magnets for retaining over-dentures is also described in the literature however; their success rates have been limited⁶⁴. The limited success of magnets is mainly due to corrosion of the magnets caused by saliva and partly because of less retentive forces achieved as compared to other attachment systems. Bar and ball attachment systems offer better mechanical retention and have many differences between them. Table 1 outlines the differences between

the attributes of bar and ball attachment systems ^{65,45,66,49,67}.

CHAIR SIDE “PICK-UP” IMPRESSION TECHNIQUE FOR IODs

The selected attachment can be incorporated into the denture either chair-side or in the laboratory. Chair-side pick-up technique allows for passive in-vivo pick up of the attachment, furthermore, attachments are picked-up under mucosal compression allowing for even load distribution during function^68,69. The technique requires manual dexterity but simultaneously provides the incorporation of the attachments into a pre-fabricated denture. Direct chair-side attachment incorporation also avoids laboratory cost and a further denture delivery visit. Usually resilient, non-splinted, prefabricated attachments are utilized.

Abutments are selected with an appropriate gingival height (Figure 1), which is obtained by measuring the vertical distance from the implant collar to the highest

point of soft tissue circumferentially. Another important factor for abutment selection is the available space in occlusion in the denture. The suitable abutments are torqued at 25Ncm and housings are placed over the overdenture abutments after placing a spacer to avoid acrylic block-out (Figure 2, Figure 3). The prefabricated complete denture prosthesis is hollowed at the location of abutments for the housing to be incorporated, (Figure 4) and is checked intra-orally.  The denture preparation results in two open windows lingual to the mandibular anterior denture teeth. The abutment housings are placed on to verify and check the full seating of the final prosthesis and ensure there is not interference either from the

attachments or the housings. Auto-cure denture base acrylic resin is mixed and placed into the housing space and the denture is seated in position. The patient is made to bite in centric occlusion and the acrylic resin excess

on the polished surface of the denture is cleared. On complete setting of acrylic resin, the prosthesis is removed and any defect in the reline/pick up, is filled extra-orally using the auto cure acrylic (Figure 5). The prosthesis after the final finishing and polishing is ready to be delivered (Figure 6).

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    1.Assistant Professor, Department of Prosthodontics,Ziauddin College of Dentistry, Karachi, Pakistan.

    2.Clinical Lecturer, Department of Prosthodontics, Ziauddin College of Dentistry, Karachi, Pakistan.

    3.Assistant Professor, Department of Prosthetic Dental Science, King Saud University, Riyadh, Saudi Arabia.

    4.Post-doctoral Fellow, Faculty of Dentistry, University of Toronto, Ontario, Canada.

    Corresponding author: “Dr Haroon Rashid ” < drh.rashid@hotmail.com >

Fazal Ghani ¹                                      PhD, FDSRCPSGlasg, FRSM, MSc , BDS, BSc

These days everyone loudly speaks that dental education needs a shakeup. Many also cite gaps between how dental students are trained and how dental healthcare is delivered¹. In response much investment has been made by all stakeholders. To a great extent, this effort has facilitated the creative ways for better preparing dental practitioners for their careers². However much is still needed to be done by the dental schools to reduce the apparent gap between training of dental graduates and the way they are required to deliver the dental healthcare.

In the past, the training and education of dental students was traditionally structured to do their basic science education in the so called pre-clinical years and then to move them into the clinical science years with very little focus in the science of dental healthcare delivery. Dental schools, now, must revise the way they teach fundamentals like basic medical and dental sciences. In fact, the three core elements in which dental students need grounding are “basic science”, “clinical science”, and the “science of dental healthcare delivery”, To achieve this objective, now rather than waiting until the “clinical years” to put students into clinical settings, they are to be placed into clinical environments starting from the very first year of induction in training³. This will require the adoption of a new curriculum having the “Trunk and Branch” architecture. The “Trunk” is about laying the core for all three mentioned sciences in the beginning years. All students will thus get a really important foundation in those, and then they will ‘Branch Off’ where they will differentiate themselves, based on their professional trajectory,” That trajectory may be a focus on managing patients with dental  diseases, or it may be procedurally based specialized dental care, or a focus on hospital-based dental care.

In this proposed training approach, student will not mentored by the faculty. Thus they will have a very different orientation than the traditional beginning years in the classroom, the remaining last years in the clinical setting, and then figuring out what to specialize in.

When teaching them the basic medical and dental sciences, the dental schools should not try to cram everything in. Instead, students should be taught each basic science throughout their training years in the dental school in a clinically relevant context that is most meaningful to them. Students will begin their core clinical rotations in their early years, with the last years being the “immersion phase” during which they will have the chance to build a very individualized curriculum and figure out what they need more help with. For example, if a student needs help with chair-side presentation, he or she can ask for additional feedback to improve that particular skill. During their entire training, students are to be self-directed, self-motivated to become lifelong learners and empowered to be always analyzing what the gaps in their knowledge are” and thus seeking to fill them.

Dental schools should facilitate their students in learning the evolving and changing pattern of dental diseases and consequent changes in the dental healthcare delivery system. It is important that the “Tomorrow’s Dental Practitioners” are educated and informed how to make better use of oral and dental health data so they not only improve community-wide orodental health but to also make a difference for their individual patients. For this purpose, dental students should be informed how to access the health related data bases of the concerned international, regional and their own federal and local governments. Of specific importance in this context is to inculcate in them the skills of accessing the data about the healthcare delivered by dentists and dental care settings. With the changes happening in healthcare and the changing role of technology and data, teaching them data analysis skills seems more important than ever. It is very important for the “Tomorrow Dental Practitioner” to be knowledgeable about the trends of dental disease procedures and treatments provided as well as of the quality of care provided and variations in treatment charges and expenditures involved. It is very important for our dental practitioners to have good understanding

of what the data mean and how to improve quality of dental care as these are the critical skills for them even down to the practice level. As the healthcare system is rapidly evolving, the dental practitioner is required to know the latest trends. Knowledge and information obtained 5 or 10 years ago is surely different than what is available today. Thus in addition to the knowledge of basic science and clinical science, the knowledge of the “science of healthcare delivery” is also very important for them. Dental students must be trained in biostatistics and epidemiology and information technology as well as they are to be fully made aware of healthy disparities and social determinants of orodental health⁴ Contemporary dental practitioners are not just those who know everything clinically, but they are those who also know how to answer questions and find information that’s out there and are able to adeptly use that information and those skills to help their patients lead healthier living.

The primary responsibility of dental schools is to produce dental graduates who are capable of improving the orodental health of communities and reduce the burden of suffering from orodental diseases⁵. It is vital that our dental students upon graduation possess the important skills, competencies, and attitudes. They must be prepared to work with public health peers so as to design environments where people are less likely to get dental diseases of modern society through different strategies of prevention. This means that they will work in teams and across boundaries to advance the science governing dental health. They are also willing to measure the outcomes of their care. Dental student, during their education in the dental schools, need to be educated about, the safety, cost and quality of care, team-based care and leadership skills of  a leading dental practitioner and a leading servant leader of the community. They are also trained to provide person-centered care so as to treat patients holistically rather than considering only disease management. The objective of dental education and training is to not only help students heal the sick and provide excellent patient care, but to also have the tools to heal the ailing healthcare system. They are trained to understand the journey that the patient takes through the dental healthcare system and they know the challenges they have and the things that work for them.

In conclusion, “Tomorrow’s Dentist” is a person who has been educated and trained in a dental school setting that follows an “Integrated Truck and Branch Model Curriculum”. He is well prepared for using and applying the basic medical and dental science and clinical dental science knowledge for preventing and managing orodental problems, He / she is also current in knowledge about dental health policy, dental health economics, the role of community agencies, the importance of electronic dental health information, the importance of teamwork, leadership, evidence-based dental care, dental healthcare financing and affordable dental care.

REFERENCES

1. Mossey P. The changing face of dental education. Birt Dent J. 197, 3 – 4 (2004). doi:10.1038/sj.bdj. 4811678.
2. Ryder MI, Morio I. Current challenges for dental education in Japan and the United States. Japanese Dent Sci Rev2011; 47: 23-30. DOI: http://dx.doi.org/10. 1016/j.jdsr.2010.05.001.
3. Frieden J. The Changing Face of Medical Education: Part I, II & III. MedPage Today series August 2015. http://www.medpagetoday.com/ accessed on 18-08-2015.
4. Tedesco LA. Issues in dental curriculum development and change. J Dent Educ 1995;59:97-147.
5. Vargas CM, Crall JJ, Schneider DA. Sociodemographic distribution of pediatric dental caries: NHANES III, 1988 1994. J Am Dent Assoc 1998;129:1229-38.
6. Newacheck PW, Stoddard JJ, Hughes DC, Pearl M. Children’s access to health care: role of social and economic factors. In: Ruth E.K. Stein, ed. Health care for children. New York: United Hospital Fund, 1997:55-57.

Professor / Head of Department of Prosthodontics, Dean Postgraduate Dental Studies & Coordinator International, Peshawar Dental College , Warsak Road, Peshawar, Khyber Pakhtunkhwa (Pakistan).

Corresponding author: “Dr Fazal Ghani ” < fazalg55@hotmail.com >