An In-Vitro Assessment Of Apical Sealing Ability Of Resin Based Endodontic Sealer At Various Time Intervals

by

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

ABSTRACT:

Primary objective of root canal therapy is to eradicate microorganisms followed by perfect seal obtained by obturation of the root canal. The purpose of doing this study was to find out quality of apical seal of root canal obturated by cold  lateral technique. For obturation, epoxy resin  based sealer was used and tested at various interval of time period of at 1 week,4 weeks and 8 weeks.

METHODOLOGY: We selected 180 permanent extracted teeth with single root. x.smart protaper were used for canal instrumentation, obturation was done by lateral cold condensation. Samples were stored for 24 hours in an incubator .Finally, prepared tooth sample were divided into two major group.  Control gp [n=30] and experimental group[n=150]. We sub divided the experimental group into further three sub group, containing fifty teeth each, representing the immersion period of 1 week, 4weeks and 8 weeks in methylene blue 5% dye, at a constant temperature of 37º. After storage the samples were sectioned and observed under stereomicroscope. Linear dye leakage was evaluated in millimeters. Statistical analyses was done by using SPSS of  Windows V. 16.0 .Descriptive statistics were shown as Mean±SD in millimeters (mm).One Way ANOVA were used to evaluate the  mean dye leakage value differences. The significance level was set at 0.05.

RESULT: Group A exhibited minimum leakage (2.53mm,SD ±0.87) followed by, Group B (2.69mm,SD±1.01) and Group C (2.77mm, SD±1.02) respectively. The difference amongst all three groups was statistically insignificant. (p=0.468). However 50% teeth in Group C showed grade 3 dye penetration with comparison to 40% and 30% in Group A and Group B.

CONCLUSION: Every samples leakage.. A gradual increase in mean leakage value was observed as the storage time increases. The differences amongst the groups remain insignificant (p=0.468).

KEY WORDS: Apical seal, Apical microleakage, Resin based sealer.

HOW TO CITE: Sardar PK, Abidi SYA, Iqbal W, Meo AA, Jawaed NA, Khan RSM. An In-vitro Assessment of Apical Sealing Ability of Resinbased Endodontic Sealer at Various Time Intervals. J Pak Dent Assoc 2015; 24(2): 75-80.

INTRODUCTION

The cleaning and shaping of root canal followed by its filling in all three dimensions is the primary objective of contemporary endodontics1,2. 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 failure1,6.

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 compared6,10. 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-chemical15-17. 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.

Table.1 Grading system that was used to evaluate penetration of Methylene blue dye 19

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

Table.2 Mean depth of dye penetration in millimeters (mm) and Standard Deviation (±S.D)
Table.3 Proportion of teeth with various Grades of dye penetration in the experimental groups.

IMMERSION TIME PERIOD

Figure.1 The bar graph explains, mean values (mm) of the leakage of dye for the three experimental groups.
Figure.2 leakage of dye value measured in millimeter with the use of Stereomicroscope(D) Indicate Dentine, (M) Indicate Methylene blue penetration.

(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 market20,21. 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 files7,8.

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 chromatography25-27. 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).

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  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 >