Prevailing Knowledge And Practices About Dental Impressions Disinfection


Faiza Amin1                                  BDS, MDS

Amir Akbar Sheikh2                  BDS, MSc

Ambrina Quershi3                     MPhil ,BDS, MDS

Muhammad Abbas4                   BDS, FCPS


BACKGROUND: Dentistry may play its role in transmission of infection through dental impressions. Instructing dentists about infection control may decrease the odds of infection transmission.

OBJECTIVE: This study investigated to determine the knowledge of dentists regarding the disinfection of impression materials.

METHODOLOGY: A Cross sectional descriptive study was conducted on 51 dentists from 09 dental colleges of Karachi. A self-administered questionnaire having 30 open and closed ended questions on knowledge related to disinfection of impression materials was used to collect data by convenient sampling technique. Variables included type of disinfectant they used, its concentration, duration of disinfection for particular impression materials, importance of disinfecting impressions prior to handling and they were observed about their actual practices. Statistical analysis was done using SPSS 16 version. The collected data was analyzed by descriptive statistics and presented in frequency tables.

RESULTS: : There were 17 (33.3%) male and 34 (66.7%) female dentists. Seniority wise, there were 27 (52.9%) house officers, 3 (5.9%) lecturers, 11 (21.6%) demonstrators, 6 (11.9%) senior registrars and 4 (7.8%) assistant professors. Almost 55% participants had an experience of less than a year, 20% of 1-3 years, 12% of more than 3 years and 14% of working 5 years in the prosthodontic department. Qualification wise, 88.2% were BDS. 5.9% MSC and only 2% were postgraduates. (MDS, MCPS or FCPS). Forty one (41%) of the participants washed impression trays before taking dental impressions. Moreover, only 1/3rd of the practitioners disinfected impression material and more than 1/3rd never practiced impression scrubbing after taking impression. It was also interesting to find out that majority of the study group stored dental impressions in tissue papers and only few in disinfectant soaked paper towels It was observed that almost half of the total participants did not know about the methods and type of disinfectants used to disinfect dental impressions.

Out of 51 dentists, 19 (38 %) did not have knowledge on the method used for the disinfection of alginate impression material while 32 (62%) had knowledge. When inquired about the type of disinfectant used 22 (43.1%) did not know while 29 (56.9%) knew it.

CONCLUSIONS: Dentists practicing in the Prosthodontic department had insufficient knowledge on disinfection of impression materials.

KEY WORDS: Disinfection, Chemical Disinfectants, Impression Materials, Prosthodontics department, Cross Infection control.

HOW TO CITE: Amin F, Sheikh AA, Qureshi A, Abbas M. Prevailing knowledge and practices about Dental impressions disinfection. J Pak Dent Assoc 2014; 23(4):164-169


Transmissions of pathogens to Health Care Workers (HCW) is often due to their exposure to blood, tissue or other body fluids1. For dentists crosscontamination from contaminated working atmosphere or from patients is the major risk factors[1],[2]. Blood or saliva is considered as a direct carrier of infection, whereas contaminated equipment’s, surfaces and airway carry infection indirectly. AIDS, Hepatitis, Herpes and

Tuberculosis are very frequently passed to the HCW through patients and health care departments and this issue is of grave concern in dentistry[1],5.

Dental impressions contaminated with patients’ blood and saliva cause contamination of the stone cast models.

Moreover, microbiological examination of these casts in many studies have shown pathogenic

microorganisms3,4,6,7. A survey done on 400 Dental laboratories in USA found that that besides lack of knowledge about disinfecting procedures for impressions, dentists and labs disinfect impressions for longer than recommended durations because of the lack of awareness.

Moreover same scenario is observed in many developing countries. In a study conducted by Marya CM  et al8 the authors concluded that there is lack of commitment to high standards of infection control practice in dental colleges in India. On the other hand, a study conducted among the students and house officers in Pakistan by A. Saad at al9 in Lahore Pakistan reported that infection control protocols for the disinfection of do have knowledge and are following cross infection protocols for impression disinfection.

Considering the variability of data about cross infection control procedures of dental impressions performed in developing countries the aim of this was to assess the current practice  of cross infection control of dental impressions, also  to evaluate how dentists are communicating with lab personnel about impression disinfection, and finally to  detect the awareness about infection control practices in dental institutes of Karachi in prosthodontics department.


A cross sectional study was conducted among registered practitioners working in the department of Prosthodontics in dental colleges of Karachi metropolitan city. Our target was to include all prosthodontics practitioners, including house officers, residents, faculty and consultants.  For the purpose all nine colleges were visited and ethical standards, in accordance with the guidelines provided by the World Medical Association Declaration of Helsinki were followed. Prior permission was taken from administrative heads of each dental institute after explaining the study objectives and methodology. A validated self-administrated questionnaire was used as data collection tool. The questionnaire assessed the information on duration of experience of the participant in their field, education and any additional courses in their field, their knowledge about the impression procedures and disinfection of these materials. The questions were both open and closed ended type and no grading system was used to quantify their knowledge.  For Statistical analysis, SPSS 16 was used. The collected data was analyzed by descriptive statistics and presented as frequency tables.


Sixty registered practitioner were identified at the data collection sites who were giving the selfadministrated questionnaire. Out of 60 questionnaires that were distributed, only 51 were returned, giving a response rate of 85%.  Out of 51 dentists 17 (33.3%) were males and 34 (66.7%) females.  The years of experience of the dentists is shown in Figure 1 where

Figure 1: Work experience in dentistry among study participants

almost more than half of the total participants had experience of less than 1 year. Majority of the respondents had basic registered degree of BDS, only few of them an added postgraduation degree.  Table 1 portrays the knowledge about Dental Impressions Disinfection among the study participants.

Table II shows the description of knowledge and practices of the study participants regarding disinfection protocols of dental impressions. Almost half of the total study participants working in the prosthodontics department reported of using antimicrobial soap for hand washing as their daily practice. It was interesting to find that 41% of the study group washed impression trays

before taking dental impressions. Moreover, only 1/3rd of the practitioners disinfected impression material and more than 1/3rd never practiced impression scrubbing after taking impression. It was also interesting to find out that majority of the study group stored dental impressions in tissue papers and only few in disinfectant soaked paper towels.

Tables III and Table 1V display the participants’ responses regarding the knowledge about appropriate

Table 1: Knowledge and practices about Dental Impressions Disinfection

Table II: Knowledge of respondents regarding methods of disinfection to disinfect impression materials.

Table III: Knowledge of respondents regarding type of disinfectants used for disinfecting impression materials.

methods and type of disinfectants used for different impression materials. It was observed that almost half of the total participants did not know about the methods and type of disinfectants used to disinfect dental impressions.


Dental Impressions, a prerequisite for all dental procedures have direct contact with saliva and blood and thus is a potential source of cross -infection. According to the British Dental Association (BDA) “infection control is a core element of dental practice”10. An impression, if not disinfected, can cross-contaminate the entire laboratory area, allowing microorganisms to travel back and forth from the laboratory to the clinical area. Although almost all of the respondents realized the importance of hand washing before and after the impression making, only half of them used the appropriate method of hand washing. The respondents are so entheustsic about washing protocols that majority of them besides washing their hands before and after impression making, washed impression trays before impression making. These results showed that majority of respondents were unaware of the correct protocol that should be followed for cross infection control. As washing trays before impression making will further decontaminate the impression trays through water contamination. Once trays are autoclaved then they should be directly insert in patient mouth with the gloves.

American dental association guidelines states that impression should be rinsed to removed saliva, blood and debris and then disinfect before being sent to the laboratory. When considering methods of disinfection for impression in the current study, majority of the respondents were unaware about the appropriate method of disinfection for different impression materials. A questionnaire based survey on contamination of alginate impression material revealed that only 50% clinics implement disinfection protocols for the impression materials, while others rinse impression material in running water only11. A survey in Taiwanese dentists revealed improved adherence to crossinfection control practices, however the handling of impressions was still a concern12. In our study, almost half of the respondents did not know the method for disinfection of Polyether impression material. Similar observations were made in another study13 where 42% dental health care providers knew about disinfection of dental impressions and use of different dilutions of the same product. Before disinfection only 2.6% brushed debris away where as 37.2% rinsed the impressions with water only. Almost a quarter (24.7%) of dentists did not inform the laboratory staff about disinfection and 95% paramedical staff received blood-contaminated impressions13. Similar results were reported in another study where 76% respondents used tap water only to clean the impressions.8 In another study, the knowledge about disinfection of impression materials among professors and students of public and private dental school was compared and they reported that most professors (66%) and students (81%) performed disinfection of the dental impressions14. In our study 43.2% respondents were ignorant of the method for disinfection of Alginate impression material. In another questionnaire based study authors reported that 30% laboratories receive known undisinfected work from dental surgery16 which included dental impressions (77%) and dentures (51%). Knowledge of laboratory directors about disinfection used and length
of time involved was assessed in another study and they reported that 23% had deficient knowledge of former and 47% of later and 45% confessed that they received inadequate instructions in disinfection techniques16. In the current study similar results were found that despite the fact that alginate is most commonly used material, 43% health care workers did not know which disinfectants can be used to disinfect alginate impression material. Shah R et al17 conducted a study on cross infection control within UK orthodontics departments in which they found that the majority of departments had policy in place to decontaminate impressions and at the chairside. Of those who decontaminated at the chairside, majority of departments informed the laboratory in writing that the impression had been decontaminated, whereas the remainder did not have policy in place to ensure this was done. ADA recommends disinfectants are chlorine compounds such as sodium hypochlorite solutions (1:10 dilution).

This study therefore strongly recommends that that is need to raise awareness and implement disinfection of impression materials in dental settings, which needs to be incorporated in the curriculum of Universities and dental schools.


From our findings, following conclusions can be drawn:

The results of this study showed that the majority of dentists in Karachi hospital have poor knowledge about the use of disinfecting agents, necessitating continuous educational programs in this respect. Majority of the participants did not have knowledge regarding the methods used for the disinfection of various impression materials. After the survey, authors concluded that disinfection techniques are still little practiced in prosthetic departments where most of the impressions are recorded, so there is an urgent need of implementing concepts of bio security in dental schools in Karachi Pakistan. This will absolutely decrease the risks of future complications related with contaminated impressions and will improves the quality of life of dentists, paramedical staff and patients.


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  1. Assistant Professor, Dow Dental College Dow University of Health Sciences. Science of Dental Materials.
  2. Assistant Professor, Ziauddin University. Department of Community Dentistry.
  3. Associate Professor, Department of Community & Preventive Dentistry. Dr Ishrat ul- Ebad Khan Institute of Oral Health Sciences, Dow University of Health Sciences.
  4. Ziauddin University, Karachi.Corresponding author: “Dr Faiza Amin ” < >