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Current Clinical Practices in Root Canal Irrigation Among Canadian Endodontists

May 11, 2016
by Isabel Mello, DDS, MSc, PhD, FRCD(C); Rodrigo Sanches Cunha, DDS, MSc, PhD, FRCD(C); Dieter J. Schönwetter, BTh, BA (Honors), MA, PhD


ABSTRACT
Purpose: Several aspects of irrigation have recently changed due to extensive research in the area. Research demonstrating preferences in irrigation practices among endodontists is limited, therefore, this study sought to assess current practices in root canal irrigation among endodontists using a web-based survey. Methods: Endodontists with a membership with the Canadian Academy of Endodontics (CAE) were invited to participate in a survey via email. Results: The number of endodontists that responded to the survey (48 percent of registered CAE members) is fairly reflective of the current distribution of population in each of the Canadian provinces. The participants seemed to have good understanding of the role of irrigation in cleaning and shaping and its importance in the treatment outcome. Five percent NaOCl is the preferred main irrigant regardless of the pulp and apical diagnoses. Most clinicians remove the smear layer and are concerned with the irrigation tip used as well as combination of irrigants, length of time spent and amount of irrigants. The use of an adjunct is popular among this group of endodontists.


The ultimate goal of root canal treatment is the elimination of the root canal space as a source of inflammation of the periodontium, so the tooth can be functional and free of symptoms and signs of apical pathosis.1 It is during cleaning and shaping that the root canal system is prepared to receive a tridimensional obturation with the aim of preventing its infection and/or reinfection. Shaping is usually accomplished with a combination of both hand and mechanized instruments that mainly remove dentin, physically preparing the root canal space. It is known though, that instruments leave approximately 35 percent of the root canal system untouched.2 Cleaning and disinfection is mostly achieved by irrigation, which removes dentin chips created by instrumentation, vital and necrotic tissues, including microorganisms. As the action of instruments within the root canal system is limited due to its complex anatomy, irrigants play an important role working not only in the main canals, but also in lateral canals, isthmuses and dentin tubules.3 The role of irrigants is two-fold: they react chemically with the tissues and also maintain the removed tissues in suspension so they can be flushed out from the root canal.4

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Irrigation is also critical after completion of cleaning and shaping. During instrumentation, the action of instruments create a smear layer, which is a 1-5-µm thick structure composed of organic and inorganic materials that is deposited on the canal walls.5 The removal of the smear layer has been advocated as it may hinder irrigants and medicaments from reaching deeper areas in the dentin and may pose an interface between the filling materials and the root canal walls. When the pulp is necrotic, the smear layer itself may contain microorganisms and yet protect microorganisms or biofilms underneath it.6

To date, there is no single irrigant that can remove both organic and inorganic tissues from the root canal system and a combination of chemicals in the correct sequence may contribute to a more effective cleaning and disinfection. Sodium hypochlorite (NaOCl) is the most widely used irrigant for cleaning and shaping as it dissolves organic tissue and kills microorganisms, but it has no activity on inorganic tissues.7 Chlorhexidine (CHX) has been recommended as an alternate irrigant for cleaning and shaping and, although it can kill microorganisms and has substantivity, it lacks tissue solvent ability. With regards to the inorganic matter, a number of irrigants have been suggested to remove them from the root canal walls such as ethylenediaminetetracetic acid (EDTA), MTAD, citric acid and QMix.5,8,9

The standard protocol to deliver irrigants into the root canal is the syringe and tip method. It is known that tips that reach the proximity of the working length are recommended so these irrigants can be delivered to the entire extent of the root canal system.10 It has also been shown that the amount of irrigant and the time spent during irrigation play an important role in successful irrigation.11 A few different methods of optimizing the action of irrigants have been suggested such as passive ultrasonic irrigation, sonic irrigation, negative pressure irrigation, or simply pumping the irrigants with a gutta-percha point.12-14

Some of the aspects of irrigation cited above have recently changed due to extensive research in the area. Surveys in different parts of the world have been carried out with the aim of assessing the understanding as well as clinical practice preferences regarding irrigation.15,16 The aim of this study was to assess current practices in root canal irrigation among Canadian endodontists, utilizing a web-based survey tool.

Methods
A team of two endodontists and a psychometricion developed a questionnaire. Some of the question items were chosen from previous studies15,16 and additonal questions were developed by the team. All questions were subjected to construct validity to ensure that the items were clearly assessing one-dimensional constructs and reflecting the research question for the current study. The survey consisted of a total of 15 questions, three focusing on demographics (i.e., current position; graduation from postgraduate endodontic training; and number of continuing education courses completed that focused on irrigation or irrigants), and 12 questions specifically regarding several aspects of irrigation, including irrigants and irrigation protocol. Questions included numeric rankings and multiple-choice items with an open-ended option. Crosstabs using contingency coefficient chi-squared-based statistical analysis was used to compare differences on the categorical data (i.e., different irrigants used or not used, etc.).
This study was approved by the Ethics Committee of the University of Manitoba (REB: HS:15810). The Canadian Academy of Endodontics (CAE) sent an invitation to all members in their database to complete the online questionnaire using SurveyMonkey©. Participants were sent reminders at two weeks and four weeks of the first invitation.

Results
Participant Demographics
A total of 103 members (48% of registered CAE members) responded to the survey. Data from six members were removed as they are not practicing in Canada. Out of the 97 members, 36% were from Ontario (n = 35), 26% were from British Columbia (n = 26), 9.28% were from Alberta (n = 9), 8.25% were from Nova Scotia (n = 8), 6.19% were from Quebec (n= 6), 5.15% were from Manitoba (n = 5), and 8.24% were from the other provinces (Saskatchewan, New Brunswick, Newfoundland and Labrador, and Prince Edward Island, n = 8).

Regarding the time of graduation, the distribution ranged from 1969 to 2014, indicating a range of 1 to 46 years since graduation (M = 18.19; SD = 12.23). In terms of continuing education courses, 85% of the participants completed some course on irrigation or irrigants (M= 5.04; SD = 4.77). Participants were divided into five cohorts for further analyses, according to their year of graduation (1969-1976, 1977-1986, 1987-1996, 1997-2007, and 2008-2014). A one-way ANOVA F (3, 93)=5.27, MSE=1-5.78, p<.01, demonstrated the most recent cohort of participants (2008-2014 graduants) as having statistically significantly lower number of continuing education courses than either the 1997-2007 tBonferoni (49) p< .001 (M=7.00, SD=5.45 vs. M=2.08, SD=2.45) or the 1987-1996 tBonferoni (49) p< .04 (M=5.67, SD=3.99 vs. M=2.08, SD=2.45) cohorts. There was no statistically significant difference between the 2008-2014 and the 1969-1976 or 1977-1986 cohorts.

Table 1. Answers (frequencies and percentages) provided by the participants collected in the web-survey.
Table 1. Answers (frequencies and percentages) provided by the participants collected in the web-survey.

Irrigation and Irrigant Usage in Private Practice
As seen in Table 1, participants provided various feedback concerning irrigation in private practice. NaOCl was overwhelmingly the most common irrigant used for cleaning and shaping and the concentration used ranged between 1% and 5%, with the latter being the most common concentration used (72%). The pulpal diagnosis does not seem to influence the choice of the concentration of NaOCl.

When asked about the concentration of CHX that they use, 61% of the participants responded that they do not use CHX, while 39% responded that they use either 0.12% (9% of respondents) or 2% (30% of respondents).

If a patient reported allergy to chlorine and the clinician’s common practice is to use NaOCl, 64% of ED would use chlorhexidine, while other clinicians would use either distilled water (8%) or saline (5%).

Fifty percent of the endodontists prefer to use 30 gauge irrigation tips. Thirty-two percent prefer to use 27 gauge and 15% use 25 gauge tips. Three clinicians did not know what tip gauge they used in practice. A crosstabs demonstrated a significant difference between the 2008-2014 cohort in using 30g as compared to all other groups X2 (12) = 20.83, p<.05.

Ninety-one percent of clinicians routinely remove the smear layer and EDTA is the preferred primary irrigant (80%), followed by QMix (30%) and NaOCl (18%). Sixty seconds per canal was the most common length of time spent for smear layer removal (41%), followed by 30 seconds (33%), and more than 60 seconds (17%). Regarding the volume of the primary irrigant per canal, approximately 1 mL per canal, more than 1 mL per canal and “I do not measure it” received similar response rates (approximately 30%).

Lastly, when asked about the use of an adjunct to final irrigation, 89% of the endodontists reported the use of some type of adjunct (EndoActivator = 50%; passive ultrasonics = 37%; gutta-percha point to pump the irrigant =18%; EndoVac = 5%, and “other” = 10% ). The 1969-76 graduation cohort of participants was less likely to use any adjuncts to irrigation than the other four cohorts, X2 (3) = 12.27, p<.007.

Discussion

A recent PubMed/Medline search on “root canal irrigants”, resulted in 2,877 articles. This is a substantial increase in publication on the topic, which had its initial dissemination in 1981 and a spike after 2007. It is evident that there is an increase in interest in studying different aspects of irrigants and/or irrigation. Based on the current literature, a successful endodontic treatment is based on thorough debridement with removal of vital and/or necrotic pulp tissue, dentin debris, and microorganisms. Irrigants are able to work in areas where instruments cannot reach and are key in the cleaning and disinfection process. There is currently no single irrigant that possesses all of the ideal properties of an endodontic irrigant. As a result, a combination of irrigants is advocated to reach maximum cleaning and disinfection of the root canal system.1-4

NaOCl seems to be the most popular irrigant in endodontics worldwide. Its unique antimicrobial and tissue solvent properties, at an expense of a low cytotoxicity, are what makes it the preferred irrigant for cleaning and shaping. Our results confirm this trend also among Canadian endodontists (91%). Other similar studies also found that the great majority of their participants prefer to use NaOCl as their primary irrigant.15,16 It is known that NaOCl can cause contact dermatitis and even trigger an asthmatic attack. Topic chloramine has shown to cause a true anaphylactic reaction when applied topically.17 The medical history of the patient must be thoroughly collected and recorded to avoid unexpected situations. The choice of using CHX when the patient reports allergy to chlorine should be revisited (64%). Chlorhexidine is a synthetic cationic bisguanide that contains two cholorophenyl rings. Mohammadi and Abbot showed that various allergic reactions to CHX have been reported including contact dermatitis, contact urticaria and asthma attack, and suggest that practitioners should be aware of this potential risk when using CHX.18 As a whole, sensitivity to chlorine is rare, however complications should be kept in mind during the use of irrigants that contain this substance. Alternate irrigants include saline, distilled water, iodine potassium iodide and hydrogen peroxide. Saline and distilled water will simply cleanse the root canal by being flushed out and replenished. Iodine potassium iodide is antibacterial but it stains the dentin and allergy to iodine must be ruled out prior to use. Although much less potent than NaOCl, hydrogen peroxide possesses some antibacterial and tissue dissolving activity. In cases where NaOCl or even CHX cannot be used, intracanal interappointment medication with calcium hydroxide must be used as it dissolves vital and necrotic tissue and it is bactericidal.19

The pulp and apical diagnoses seem to minimally influence the choice of the concentration of NaOCl and 72% of the participants prefer to use 5% NaOCl. This concentration of NaOCl is capable of killing microorganisms and dissolving organic tissue very rapidly but clinicians must be mindful that NaOCl is more cytotoxic at this concentration.7

The smear layer was first identified in root canal walls in the 1970’s but only a decade later it became a topic of concern for clinicians.5 The subject was debated for years until some consensus was reached that it is advisable to remove it after cleaning and shaping is complete.6 Removal of the smear layer is widely practiced among Canadian endodontists (91%). A survey with American endodontists found that 77% of them remove the smear layer.16 Although their numbers are lower than the numbers in this study, it is still a high percentage. Differences in teaching philosophies and techniques could be the cause of this difference as well as the lack of randomized controlled studies confirming that the removal of the smear layer may improve treatment outcome.
Several details account for effective cleaning and disinfection of the root canal system, including the proper irrigants and sequence, the needle gauge used to deliver the irrigants, the length of time and the amount of irrigants used and if an adjunct to irrigation is used.4 EDTA is the preferred primary irrigant for smear layer removal (80%). EDTA is a chelating agent capable of binding calcium ions present in the dentin, thus aiding in removal of inorganic components of debris and smear layer created during cleaning and shaping procedures.7 The combined irrigation with EDTA and NaOCl will approach both inorganic and organic matters in the root canal system (5,11,14). Although other irrigants are available for smear layer removal they tend to be more costly or may contain antibiotics.7,10

The choice of irrigation tip size (25, 27, 30g or unknown) used for irrigation was spread out and it does not seem to be linked to year of graduation. It is known that the irrigant travels only about 2 mm passed the needle tip and a needle that reaches closer to the working length will deliver the irrigants closer to the ideal horizontal dimension previously established.10 Some clinicians may think that larger needles are safer and may reduce the chance of pushing irrigants to the periodontium causing a dramatic accident. However, this may prevent irrigants from working in deeper areas of the root canal system. Side-vented needles are recommended as they deliver the irrigant towards the root canal wall and not towards the foramen.3

Most of this study’s respondents who remove the smear layer spend about 60 seconds per canal to perform the procedure. The length of time spent is important as it allows adequate working time for irrigants to go through their chemical reactions and reach their maximum potential.7 Regarding the amount of irrigant used, the choices of approximately 1 mL per canal, more than 1 mL per canal and “I do not measure it” received similar response rates (approximately 30% each). The amount of irrigant is also influential11 for the same reasons as for length of time.

The use of adjuncts to aid in improved cleaning and disinfection has gained more attention in the last few years. Research has suggested that their use is advantageous since they encourage movement and refreshment of the irrigant when compared to manual irrigation alone.3,14,20 A survey with American endodontists found that 48% of the endodontists are using an adjunct.18 In this present study, the majority of Canadian endodontists uses some sort of adjunct to irrigation (89%). The 1969-76 graduation cohort of participants is less likely to use any adjuncts to irrigation than the four cohorts. Teaching philosophies regarding irrigation have evolved especially in the last two decades and clinicians who graduated between 1969 and 1976 likely did not have access to the equipment that is now available and part of the daily training in post-graduate endodontic programs.

The numbers of endodontists that responded to the survey are fairly reflective of the current distribution of population in each of the Canadian provinces and it is believed that the data collected in this study are representative of the current practices in root canal irrigation among Canadian endodontists. This study may benefit undergraduate and graduate programs in guiding them to develop their curricula as well as Continuing Education Departments in planning courses in the area. Although the present study provides critical information, future research utilizing broader cohorts comparing practices globally would provide more meaningful information.

Conclusions
This study provides important information regarding irrigation practiced by endodontists in Canada. In general, the participants have an understanding of the role of irrigation in cleaning and shaping and its importance in the treatment outcome. Five percent NaOCl is the preferred main irrigant regardless of the pulp and apical diagnoses. Most clinicians remove the smear layer and are concerned with the irrigation tip used as well as combination of irrigants, length of time spent and amount of irrigants. The use of an adjunct is popular among this group of endodontists. Further studies looking at larger populations, comparing practices among endodontists globally and also between general dentists and endodontists will provide useful information in what areas in irrigation consistency is lacking among endodontists and between general dentists and endodontists.

Acknowledgments
:
The authors would like to thank the Canadian Academy of Endodontics for their assistance with contacting the endodontists and inviting them to participate in the study, and Dr. Wayne Maillet for reviewing the manuscript. OH


Isabel Mello, DDS, MSc, PhD, FRCD(C), Associate Professor, Department of Dental Clinical Sciences, Faculty of Dentistry, Dalhousie University, Halifax, NS, Canada. Adjunct Professor,
Department of Restorative Dentistry, Faculty of Dentistry, University of Manitoba, Winnipeg, MB, Canada.

Rodrigo Sanches Cunha, DDS, MSc, PhD, FRCD(C), Associate Professor, Department of Restorative Dentistry, College of Dentistry, Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada.


Dieter J. Schönwetter, BTh, BA (Honors), MA, PhD, Professor and Director of Educational Resources and Faculty Development, College of Dentistry, Faculty of Health Sciences, University of Manitoba, Winnipeg, Manitoba, Canada.


Disclaimer: The authors deny any conflict of interest.

Oral Health welcomes this original article.

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