A survey of sterilisation and disinfection practices for new endodontic files and gutta-percha in US dental offices

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1 CASE REPORT 1 Jeffrey A Banas, Ryan Lubinsky, Fang Qian, M Margaret Vickerman A survey of sterilisation and disinfection practices for new endodontic files and gutta-percha in US dental offices Key words disinfection, endodontic files, gutta-percha, sterilisation, survey Jeffrey A Banas, PhD University of Iowa College of Dentistry, Iowa City, Iowa 52242, USA Aim: The aim of this survey was to assess US dentists practice for sterilising or disinfecting new endodontic files and gutta-percha. Materials and methods: A random sample of general dentists and endodontists from all 50 US states were contacted either by (Survey Monkey) or by post, and asked to complete a questionnaire on sterilisation and disinfection practices for new endodontic files and gutta-percha. Results: A total of 105 questionnaires were returned, with a response rate of 4.2% and 25% for and post, respectively. Sixty-one percent of endodontists and 56% of general dentists answered yes or sometimes to the query regarding sterilisation of new endodontic files prior to use. The difference in the responses of specialists and general dentists was not statistically significant, despite the fact that general dentists were statistically more likely to answer that they were very or somewhat concerned about the effects of sterilisation on the structural integrity of endodontic files. Half of the general dentists responded yes or sometimes to disinfection of new gutta-percha cones, with endodontists (59%) statistically more likely to do so than general dentists (32%). Equal percentages (84% each) of endodontists and general dentists responded that they place endodontic files and gutta-percha on a sterile work surface in the dental operatory. Conclusions: The results indicate that a majority of the respondents use endodontic files and/or gutta-percha straight out of the manufacturers packaging. There is a need to reinforce education about existing recommendations and rationale for sterilisation/disinfection of endodontic instruments and materials before use as part of the infection control process. Ryan Lubinsky, BS University of Iowa College of Dentistry, Iowa City, Iowa 52242, USA Fang Qian, MA, MPhil, PhD University of Iowa College of Dentistry, Iowa City, Iowa 52242, USA M Margaret Vickerman, DMD, PhD School of Dental Medicine, University at Buffalo, Buffalo, New York 14214, USA Corresponding Author: M. Margaret Vickerman, DMD, PhD Department of Periodontics and Endodontics Department of Oral Biology 223 Foster Hall University at Buffalo School of Dental Medicine Buffalo, New York USA Phone: Fax: mmv4@buffalo.edu Introduction New endodontic files and gutta-percha often, if not usually, arrive in packaging that may not necessarily be guaranteed to be sterile. Many studies have tested the sterility of new, unused files and guttapercha 1-8. Van Eldik et al 1 failed to detect bacterial growth from any of the 30 files placed on blood agar plates. However, Roth et al 2 tested 150 files and found that 13% were contaminated based on turbidity following incubation in Brain-Heart Infusion broth. Gnau et al 3 found that 6% of the 100 new files incubated in Thioglycollate broth were contaminated. As for gutta-percha, Seabra Pereira & Siqueira Jr 4 failed to detect contamination of those from newly opened packages when incubated in Thioglycollate broth. Pang et al 5 also failed to detect contamination among 30 gutta-percha cones tested, from newly opened boxes, but reported a 19.4% contamination rate for those in opened boxes stored for more than 3 months in hospital-based endodontic clinics. Montgomery 6, Namazikhah et al 7,

2 2 Banas et al Survey of sterilisation and disinfection practices and Gomes et al 8 reported that gutta-percha cones from newly opened boxes were contaminated at rates varying from 8 to 25%. These studies not only confirmed the expected contamination of products that are not guaranteed to be sterile, but the variable levels represent minimum rates of contamination as the various sterility tests were only appropriate for the detection of a subset of potential microbes. Although contaminants isolated in these studies may be non-oral species and may not be considered pathogenic, it is important to recognise that most are capable of being opportunistic infections if conditions are right. Studies on the microbiology of endodontic infections have documented the breadth and complexity of potential pathogens, including bacterial, archaeal and fungal species that may normally be unassociated with the human oral cavity 9,10. Since one of the aims of endodontic treatment is to decontaminate the root canal system, the introduction of microbial contaminants via non-sterile instruments and materials is counterproductive and may influence treatment outcome. In addition, intentional or unintentional placement of non-sterile instruments beyond the tooth apex, for example if apical patency is practised, may result in inoculation of contaminants into the surrounding periapical tissues. Although antimicrobial irrigants are used during endodontic treatment, the use of non-sterile instruments and materials results in an unnecessary microbial burden and decontamination load. In this study, the results of a survey of US dentists for the purpose of determining the consistency of sterilisation practices involving new, previously unused endodontic files and gutta-percha are presented. Materials and methods Human Subjects Approval. The University of Iowa Human Subjects Institutional Review Board (HSIRB) approval was sought and obtained for this study. All participants who responded to the survey consented to participating, in accordance with the HSIRB requirements. Survey. A questionnaire consisting of 11 questions was prepared. This included questions about the sterilisation of new, unused endodontic files, disinfection of gutta-percha cones, the placement of endodontic files and gutta-percha on sterile working surfaces during treatment and demographic information (Table 1). Participants could also elect to write the name of the US state in which their practice is located. Random lists of general practitioners and endodontists within the US were obtained from Hippo Direct (Solon, Ohio, USA). The lists were used to manually search the internet for addresses of practices. Survey requests were sent electronically to 1284 practices, evenly split between general dentists and endodontists, using Survey Monkey ( in order to protect the anonymity of the respondents. A follow-up request was sent 2 weeks after the initial request. Due to an initial low response rate of less than 5%, the survey was sent by post, in paper form, to an additional 200 practices (100 general dentists and 100 endodontists) accompanied by a stamped, self-addressed envelope. Respondents wishing to remain anonymous were given the option to omit providing a return address when returning the questionnaire. Statistical Analyses. Descriptive statistics were conducted for all of the variables in the survey. Bivariate analyses were performed to explore the significant factors related to the sterilisation practices using standard chi-square test and Fisher s exact test. A P-value of less than 0.05 was used as a criterion for statistical significance, and 0.05 P < 0.10 was used as a criterion for marginal significance. SAS for Windows (v9.3, SAS Institute, Cary, North Carolina, USA) was used for the data analysis. Results A total of 105 questionnaires from 26 different states were returned, 55 via (response rate of 4.2%) and 50 via post (25% response rate) giving a combined response rate of 7.1%. The breakdown of questionnaire responses is shown in Table 1. Sixty percent of respondents reported sterilising or sometimes sterilising new, unused endodontic files, 88.5% of the time by autoclaving. Therefore nearly half of the respondents did not report sterilising new endodontic files prior to use in patients, at least some of the time. There was no statistical difference between endodontists (61% answered yes or sometimes ) and general dentists (56% answered

3 Banas et al Survey of sterilisation and disinfection practices 3 yes or sometimes ) in response to this question, even though general dentists were statistically more likely than endodontists (78% vs 48% respectively; P = ) to be concerned or very concerned about the effects of autoclaving on endodontic file integrity (Table 2). The response to sterilising new endodontic files did not correlate with the number of years in practice, the location, gender or the disinfection of gutta-percha cones, but did correlate with placing endodontic files or gutta-percha on a sterile surface in the operatory (P = ). About half of the respondents disinfected guttapercha cones at least sometimes, with endodontists statistically more likely than general dentists (59% vs 32% respectively; P = ) to do so (Table 2). The number of years in practice showed a marginal statistical association (P = ), with those in practice for fewer years, more likely to answer yes or sometimes. Equal percentages (84% each) of endodontists and general dentists answered yes or sometimes to placing endodontic files and gutta-percha on a sterile surface in the operatory (Table 2). Answers to this question did not correlate significantly with any of the demographic data. Discussion The results of this study reveal that a substantial proportion of practitioners do not routinely sterilise new files or disinfect gutta-percha prior to use; however, the questionnaire did not explicitly delve into their reasons. One potential reason for not autoclaving files prior to use may be that practitioners may be concerned about the effects of heat sterilisation on file flexibility, breakage potential, or cutting ability; this was addressed indirectly in the questionnaire. A majority of practitioners (57.7%) were somewhat or very concerned about file integrity being altered by autoclaving. Although the level of concern did not correlate with whether or not new files were sterilised, a review of the literature reveals that most studies offer little basis for concern that initial autoclaving alters file properties Another potential explanation for failure to autoclave new files may be due to the interpretation of recommendations and failure to recognise what may be considered critical Table 1 Survey questions and answers Questions Answers (%) 1. Please indicate your dental profession. a. General Dentist 30.5 b c. Other What type of endodontic file do you use for root canal treatment most often? a. Brasseler 21.0 b. Dentsply 52.4 c. Sybron 9.5 d. Kerr 7.6 e. Other Do you sterilize new, unused endodontic files prior to use? a. Yes 52.4 b. No 40.0 c. Sometimes If you sterilize or sometimes sterilize new, unused endodontic files, what method do you use? a. Autoclaving 88.5 b. Other Do you disinfect gutta-percha cones? a. Yes 44.7 b. No 48.2 c. Sometimes 5.9 d. Don t use gutta-percha If you disinfect or sometimes disinfect gutta-percha, what method do you use? a. Chairside chemical disinfection 63.9 b. Other 4.8 c. Not applicable In the operatory, are endodontic files and gutta-percha placed on a sterile surface during treatment? a. Yes 81.7 b. No 15.4 c. Sometimes 1.9 d. Not sure How concerned are you that endodontic file autoclaving will lead to the deterioration of an endodontic file over time? a. Not concerned 42.3 b. Somewhat concerned 40.4 c. Very concerned Number of years in practice a. 1 to 5 years 14.5 b. 6 to 10 years 13.6 c. 11 to 20 years 24.3 d. Greater than 20 years Current location of practice a. Urban/suburban (metropolitan population > 100,000) 71.8 b. Small town/rural (population < 100,000) Gender a. Female 21.6 b. Male 78.4

4 4 Banas et al Survey of sterilisation and disinfection practices Table 2 Results of bivariate analysis of factors associated with sterilization practices General dentist Disinfect gutta-percha cones Yes and Sometimes No and Don t use gutta-percha Place endodontic files and gutta-percha on a sterile surface Yes and Sometimes No General Dentist Number of years in practice 1 to 5 years 6 to 10 years 11 to 20 years Greater than 20 years Current Location Urban/Suburban Small town/rural General Dentist General Dentist Sterilizing new, unused endodontic files prior to use Yes & Sometimes (n = 63) No (n = 42) (56%) 44 (61%) 35 (81%) 28 (67%) 56 (64%) 6 (38%) Yes & Sometimes (n = 43) 9 (32%) 33 (59%) 8 (67%) 8 (80%) 11 (58%) 16 (38%) 34 (58%) 9 (38%) 14 (44%) 28 (39%) 8 (19%) 14 (33%) 31 (36%) 10 (63%) Disinfecting gutta-percha cones No & Don t use (n = 42) 19 (68%) 23 (41%) 4 (33%) 2 (20%) 8 (42%) 26 (62%) 25 (42%) 15 (62%) * * ** ** Placing endodontic files and gutta-percha on a sterile surface Yes & Sometimes (n = 87) No (n = 16) (84%) 59 (84%) 5 (16%) 11 (16%) Concerns about endodontic file autoclaving Not concerned (n = 44) Very & Somewhat concerned (n = 60) * 7 (22%) 37 (52%) 25 (78%) 34 (48%) *Statistically significant (P < 0.05) using chi-square test. **Marginally statistically significant (0.05 P < 0.10) using chi-square test or Fisher s exact test. instruments. According to the Centers for Disease Control and Prevention (CDC) 21 and the American Dental Association (ADA) 22 guidelines, critical items [that] penetrate soft tissue or bone have the greatest risk of transmitting infection and should be sterilised by heat. Endodontic files and gutta-percha qualify as critical items since they may extend to tissue beyond the apex of the tooth. However, when heat sterilisation is not practical, as in the case of gutta-percha, disinfection is appropriate. An additional reason for using items directly from the manufacturers packaging may simply be because of ease and convenience. Indeed, the recent appearance of pre-packaged individually-sterilised files in the dental marketplace may reflect manufacturers perceived need for pre-sterilised files. The data from this survey support the idea that in some cases such packaging would increase compliance with sterilisation recommendations. In this survey, there does not appear to be a strong correlation or consistency amongst practition-

5 Banas et al Survey of sterilisation and disinfection practices 5 ers regarding the various infection control practices; that is, practitioners may be concerned about sterility in one instance but not another. While there was a statistical correlation between sterilisation of new endodontic files and placing endodontic files and gutta-percha on a sterile working surface, this did not extend to disinfecting gutta-percha prior to use. Of those practitioners who answered yes or sometimes to sterilisation of new endodontic files, only 56% answered yes or sometimes to disinfecting gutta-percha while 90% answered yes or sometimes to placing files and gutta-percha on a sterile working surface. Demographic differences were not a major factor. There was a marginal statistical correlation between disinfection of gutta-percha and the number of years in practice, with those who have been in practice longer less likely to disinfect gutta-percha cones, possibly reflecting a generational influence. There was also a marginal statistical correlation between disinfection of gutta-percha and the urban or rural location of a practice, with those in small towns less likely to practice disinfection. This may reflect a community influence on the perceived threat of microbial contamination or may merely be a consequence of the relatively low numbers of respondents in small town/rural practices. Limitations of this survey include those associated with self-reported information and the potential for respondents to interpret questions differently. It is possible that practitioners that answered no to placing endodontic files and gutta-percha on a sterile working surface nonetheless routinely use a disinfected surface. In retrospect, this question should have been worded more precisely to include both possibilities. Although the wording of the survey was chosen to avoid advocacy of sterilisation/ disinfection practices, it is nevertheless possible that those who routinely sterilise new files and/or disinfect gutta-percha were more likely to participate. For this reason, the relatively low overall response rate is not a significant limitation for interpreting results; the responses from 105 dentists reveal that a lack of sterilising new, unused endodontic materials is not an isolated occurrence. Additionally, since 26 US states were represented among respondents, outof-the-ordinary, localised practices were unlikely to account for the results. In general, a higher response rate would be expected to improve the accuracy of the proportion of practitioners engaging in the various infection control practices. However, there was no discrepancy in the distribution of answers between questionnaires returned electronically (lower response rate) and those returned by post (higher response rate). For example, the answers to the question on sterilising new, unused files was 30, 20, and 5 (yes, no, and sometimes respectively) for respondents and 25, 22, and 3 (yes, no, and sometimes respectively) for regular post respondents. Consequently, it is very unlikely that an overall higher response rate would alter the conclusion that there are inconsistent approaches among practitioners with respect to sterilisation of new, unused endodontic materials. Instruments and materials used in endodontic procedures including brand new files in non-sterile manufacturers packaging are potential sources of contamination 2,24. Although antimicrobial irrigants may be used during endodontic treatment, they may not always be sufficient to eliminate all microorganisms including those that might be present on new files 25. Gutta-percha cones are often stored in the original box with individual cones removed as needed during treatment. Only 44.7% of respondents reported that they routinely disinfect gutta-percha cones before using them to fill prepared root canals. Some studies found that unopened packages of gutta-percha do not harbour cultivable bacteria perhaps due to the antimicrobial properties of the zinc oxide in the cones 4,26. However, once a box is opened, the likelihood of contamination upon repeated use increases 5,8. These studies support the recommendation that gutta-percha cones should be disinfected before use. The role of environmental and secondary contaminants in packaged instruments and filling materials on endodontic treatment has not been investigated sufficiently. Nevertheless, the potential for iatrogenically-introduced microorganisms to flourish in the root canal system or periapical tissues does exist. There are reports of endodontic infections that include microorganisms that are not usually members of the oral microbiota 10,23. Such microbes may be of increasing clinical relevance in patients with compromised medical conditions. Since the goal of endodontic treatment is to eliminate microorganisms from the root canal, the use of potentially contami-

6 6 Banas et al Survey of sterilisation and disinfection practices nated treatment instruments and materials should be avoided. The results of this survey of US dental practitioners indicate that following removal from the manufacturers packaging and before use, both endodontists and general dentists failed to routinely sterilise or disinfect endodontic files and gutta-percha. The findings provide initial insights into possible reasons for these practices and highlight the need to maintain and reinforce infection control practices. Acknowledgments We thank the Dows Institute for Research at the University of Iowa for financial support and Ms Mary Lynn Eckert for help in administering the version of the survey. References 1. Van Eldik DA, Zilm PS, Rogers AH, Marin PD. Microbiological evaluation of endodontic files after cleaning and steam sterilization procedures. Aust Dent J 2004;49: Roth TP, Whitney SI, Walker SG, Friedman S. Microbial contamination of endodontic files received from the manufacturer. J Endod 2006;32: Gnau HL, Goodell GG, Imamura GM. Rapid chairside sterilization of endodontic files using 6% sodium hypochlorite. J Endod 2009;35: Seabra Pereira OL, Siqueira JF Jr. Contamination of guttapercha and Resilon cones taken directly from the manufacturer. Clin Oral Investig 2010;14: Pang NS, Jung IY, Bae KS, Baek SH, Lee WC, Kum KY. Effects of short-term chemical disinfection of gutta-percha cones: identification of affected microbes and alterations in surface texture and physical properties. J Endod 2007;33: Montgomery S. Chemical decontamination of gutta-percha cones with polyvinylpyrrolidone-iodine. Oral Surg Oral Med Oral Pathol 1971;31: Namazikhah MS, Sullivan DM, Trnavsky GL. Gutta-percha: a look at the need for sterilization. J Calif Dent Assoc 2000;28: Gomes BP, Vianna ME, Matsumoto CU, Rossi Vde P, Zaia AA, Ferraz CC et al. Disinfection of gutta-percha cones with chlorhexidine and sodium hypochlorite. Oral Surg Oral Med Oral Path Oral Radiol Endod 2005;100: Vianna ME, Conrads G, Gomes BP, Horz HP. Identification and quantification of archaea involved in primary endodontic infections. J Clin Microbiol 2006;44: Siqueira JF Jr, Rôças IN. Diversity of endodontic microbiota revisited. J Dent Res 2009;88: Mitchell BF, James GA, Nelson RC. The effect of autoclave sterilization on endodontic files. Oral Surg Oral Med Oral Pathol 1983;55: Iverson GW, von Fraunhofer JA, Herrmann JW. The effects of various sterilization methods on the torsional strength of endodontic files. J Endod 1985;11: Morrison SW, Newton CW, Brown CE Jr. The effects of steam sterilization and usage on cutting efficiency of endodontic instruments. J Endod 1989;15: Silvaggio J, Hicks ML. Effect of heat sterilization on the torsional properties of rotary nickel-titanium endodontic files. J Endod 1997;23: Rapisarda E, Bonaccorso A, Tripi TR, Condorelli GG. Effect of sterilization on the cutting efficiency of rotary nickeltitanium endodontic files. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1999;88: Hilt BR, Cunningham CJ, Shen C, Richards N. Torsional properties of stainless-steel and nickel-titanium files after multiple autoclave sterilizations. J Endod 2000;26: Casper RB, Roberts HW, Roberts MD, Himel VT, Bergeron BE. Comparison of autoclaving effects on torsional deformation and fracture resistance of three innovative endodontic file systems. J Endod 2011;37: Plotino G, Costanzo A, Grande NM, Petrovic R, Testarelli L, Gambarini G. Experimental evaluation on the influence of autoclave sterilization on the cyclic fatigue of new nickeltitanium rotary instruments. J Endod 2012;38: King JB, Roberts HW, Bergeron BE, Mayerchak MJ. The effect of autoclaving on torsional moment of two nickeltitanium endodontic files. Int Endod J 2012;45: Bulem UK, Kececi AD, Guldas HE. Experimental evaluation of cyclic fatigue resistance of four different nickel-titanium instruments after immersion in sodium hypochlorite and/or sterilization. J Appl Oral Sci 2013;21: Centers for Disease Control and Prevention. Guideline for disinfection and sterilization in healthcare facilities, Available at: Sterilization/13_0sterilization.html. Accessed 1 July Centers for Disease Control and Prevention. Guidelines for infection control in dental health care settings Available at: mmwrhtml/rr5217a1.htm. Accessed 1 July Fujii R, Saito Y, Tokura Y, Nakagawa KI, Okuda K, Ishihara K. Characterization of bacterial flora in persistent apical periodontitis lesions. Oral Microbiol Immunol 2009;24: Morrison A, Conrod S. Dental Burs and Endodontic Files: are routine sterilization procedures effective? J Can Dent Assoc 2009;75: American Association of s Root canal irrigants and disinfectants. Available at: Accessed 1 July Moorer WR, Genet JM. Antibacterial activity of guttapercha cones attributed to the zinc oxide component. Oral Surg Oral Med Oral Pathol 1982;53: