This research identified the existing gaps regarding the current endodontic irrigation practices among GDPs in Malaysia, as well as measured if the practitioners' years of experience had any effect on their knowledge.

Based on the outcome of our survey, NaOCl was the most preferred irrigant among Malaysian GDPs, owing to its excellent tissue-dissolving capabilities and superior antimicrobial action, as was shown in earlier surveys conducted in Saudi Arabia, India and the UK.1,2,6,7Additionally, our research portrayed that the majority of GDPs used a concentration ranging from 1.6-2.5%. Although higher concentrations of NaOCl are more efficacious compared to lower concentrations in similar clinical situations, the ideal concentration of NaOCl is still debatable as clinicians need to weigh the risk-to-benefit ratio of using higher concentrations of NaOCl and the associated potential risks, such as reduction in the fracture strength of dentin, as well as the greater toxicity.9,10Concentrations ranging from 0.5-5.25% are clinically recommended for endodontic use. However, higher concentrations like 5.25% require particular care due to its toxicity, so are majorly used by endodontists and less used by general dentists.1,5,8

Clorox is almost eponymous with household bleach, owing to its largest retail share value in Malaysia, hence, its brand name was used in the questionnaire.11 It is notable that most respondents used Clorox instead of dental-grade NaOCl, likely due to the higher cost of the latter. The level of free, available chlorine is the main factor affecting the antimicrobial and proteolytic activity of NaOCl solutions, followed by pH, time and concentration.12 Studies have shown that household bleach may contain differing concentrations, thus causing difficulty in determining the actual concentration used for irrigation.13,14There are also health concerns with household bleach as it is unclear if the various products may be contaminated with unregulated amounts of heavy metals or other non-biocompatible products. The production for domestic use is much less stringent than that for healthcare use.15 Hence, it is recommended to use NaOCl products manufactured for the sole purpose of endodontic treatment.

Unexpectedly, 11% of the respondents selected saline as the primary choice of irrigant. Saline is mainly used to flush out chemical irrigant residue and debris. However, it has neither antimicrobial nor tissue-dissolution potential. It is recommended that intermittent saline rinse should always accompany any switches in the irrigant to prevent interaction between the two irrigants.3,4Also, after completion of shaping and cleaning, saline may be used as a last rinse to flush out any leftover chemical irrigant which may interact with the sealer.3

The GDPs had suitable knowledge pertaining to the use of saline as the first choice of irrigant in cases with active pus drainage from canals. Saline is recommended to be used to maintain the apical patency until pus is actively draining through the canal. NaOCl in such cases may clump exudates, causing the plugging of apical constriction and thus disrupting pus drainage.3,16CHX possesses a broad spectrum of antimicrobial activity, provides sustained action and has little toxicity. Also, 2% CHX has similar antimicrobial action of 5.25% NaOCl and is more effective against Enterococcus faecalis.9 However, the majority of GDPs participating in our studies did not choose CHX as an irrigant. Most of the research conducted in endodontics regarding the effectiveness of CHX as an antimicrobial agent has focused on E. faecalis.4 Therefore, it is possible that the results of these studies have provided an overly optimistic view of CHX's usefulness in endodontics as an antimicrobial agent.4 Despite being an excellent antimicrobial, CHX cannot replace NaOCl as it lacks tissue-dissolving capability. A 2% concentration of CHX may be incorporated into the final irrigation protocol to maximise the antibacterial effect of the final rinse.17

Any mechanical root canal instrumentation produces a smear layer over the prepared dentin walls that comprises of organic and inorganic material, possibly including bacteria and their byproducts. The smear layer reduces the penetration of intracanal medication into the dentinal tubules and may interfere with the adhesiveness of sealers to the root canal walls, resulting in microleakage over a period of time.18,19Chelating agents like EDTA, citric acid and MTAD (a mixture of doxycycline, citric acid and a detergent) are recommended to be used in conjunction with NaOCl to remove the smear layer. The results of our survey showed that GDPs had adequate knowledge regarding the use of EDTA for the removal of the smear layer from root canal walls.

Although there is no consensus regarding the most effective sequence of irrigant use, the authors would recommend the following irrigation protocol based on the existing evidence, the common irrigants available in Malaysia and their personal clinical experience. For all root canal treatment, regardless of diagnosis or clinical condition, copious amounts of NaOCl, followed by saline, EDTA, saline and finally NaOCl, would be used in that sequence. For canals with draining pus, the authors would use saline as the first irrigant. The clinician would also take into account the type of root filling sealer and the subsequent coronal restoration used, as this would play a role in choosing the final irrigant. EDTA is recommended to be used before resin and to remove the smear layer before the use of dental adhesives for the final restoration, while NaOCl is suggested to be used before bioceramic materials.20

The volume of irrigant and contact time are among the most crucial factors in achieving satisfactory intracanal disinfection owing to the limited fluid dynamics achieved by syringe irrigation within narrow and complex root canal systems. A substantial volume of irrigant should be delivered to root canals to achieve optimal cleaning effectiveness because fresh irrigant comes into contact with tissue.21 Similarly, an increased contact time between irrigant and root canal walls is directly related to greater antimicrobial and antibiofilm activity, which is especially important in necrotic cases.3 Based on the results of our survey, GDPs had adequate knowledge about the volume of irrigant employed during the final wash. However, the usage time substantially varied ranging from less than five minutes to ten minutes per canal after the shaping procedure. NaOCl solutions are suggested to be volume- and time-dependent, especially in lower concentrations. It is suggested that only fresh NaOCl has enough freely available chlorine as the amount of chlorine rapidly declines in the root canal as it is consumed during interaction with tissues and microorganisms.13 However, ex vivo studies have shown that too much volume of irrigant, or too long contact time of irrigant, induces a reduction in fracture strength of root dentine in higher concentrations.22 Although a consensus guideline is lacking, it is recommended to perform copious irrigation of more than 5 ml per canal and increase the irrigation time to achieve adequate canal disinfection.14

Guerreiro-Tanomaru et al. suggested that a gauge 30 needle (0.31 mm) has a smaller diameter that can improve the efficacy of irrigant flow up to the working length. Nonetheless, canal disinfection might be compromised with the usage of a gauge 23 needle (0.60 mm) as it is too large for penetration of the needle into the root canal.23 Usage of a larger diameter needle is related to a greater diameter of the prepared canal; however, the reason for choice of needle size was not included in this survey. Around one-quarter of the respondents from our research still practised the use of needle gauge 25 (0.53 mm) for endodontic irrigation. Within the closed confinements of the root canal space, irrigants only manage to reach 1-3 mm beyond their openings, hence it is imperative that the irrigation needle should be of an appropriate size which is able to deliver irrigants up to working length.24,25 The appropriate sizes of endodontic irrigation needles are 27 G needles (0.42 mm) for larger diameter root canals, as in the case of anterior and premolar teeth, while comparatively narrower canals in molar teeth should be irrigated with needle size 30 G (0.31 mm) or smaller.26

In our questionnaire, all types of needles were acceptable answers, with the exception of the open-ended flat needle. Closed-ended needles with side vents are recommended to reduce the risk of extrusion of irrigant beyond the apical foramen and prevent the incidence of hypochlorite incidents. However, there is controversy, as open-ended needles are considered more efficacious than closed-ended needles in terms of irrigant penetration and exchange.27 Hence, the suggested optimum position for open-ended needles is 2-3 mm short of the working length, while closed-ended needles need to be placed within 1 mm of the working length.28

Activating devices are proven vital in enhancing the efficacy of root canal irrigants. They aim to activate irrigants chemically and mechanically, thereby improving their antimicrobial and tissue-dissolving efficiency and enhancing the irrigant's penetration into the complex root canal anatomy, including lateral fins by displacing the apical ‘vapour lock' effect.3,14,29In total, 40.1% of the respondents from our study used manual dynamic agitation, which is encouraging as it is a simple and cost-effective method proven to be more effective than static needle-and-syringe irrigation.30 In the absence of more advanced adjunct techniques, it is strongly recommended that clinicians incorporate this technique into their final irrigation protocol. The utilisation of sonic activation by 48.3% of GDPs is a notable finding. Studies have demonstrated that sonic activation and passive ultrasonic irrigation are effective in enhancing dentinal tubular infiltration as compared to conventional needle irrigation.14,29Therefore, practitioners are advised to consider the use of these techniques for the activation of irrigant solutions.

Unlike studies conducted in Saudi Arabia and the USA,5,30our analysis of 19 knowledge questions (marked * in results tables) shows that years of experience was not a significant predictor for the level of knowledge. Overall, the practitioners had a mean score of 12.9 out of 19 knowledge questions, which is above average. However, as this knowledge is applicable to daily practice, a higher score closer to the full score was expected, showing a gap in knowledge that needs to be addressed. It is encouraging that 62.2% of the respondents have attended at least one further education activity on endodontic irrigation. As the field of endodontics is ever-evolving, clinicians of all levels of experience are encouraged to participate in continuous professional development (CPD) courses to keep their clinical endodontic practice up to date based on the latest scientific evidence. CPD includes training courses, workshops, conferences and online learning, which helps practitioners stay informed of the latest advances in their field and improve their abilities to provide high-quality care to patients.31 It is recommended that CPD for dentists should also include peer review and self-assessment which can be helpful in identifying gaps in knowledge, as well as reflecting on one's own practice which can help to improve clinical skills and knowledge.31,32

This study used a mixed-mode method for data collection, distributing the survey both through online methods (email and social media messaging application) and physically in order to increase the response rate, as well as to reach a wider number of respondents. There are several limitations to this method, one being that although the study accessed the vast majority of Malaysian GDPs, it likely missed out some GDPs who are not members of the Malaysian Dental Association and those that do not check their emails. Moreover, the researchers experienced difficulty in getting a satisfactory number of responses despite a reminder being sent, a participation incentive being offered and multiple methods of circulation.33 This could be due to the length of the questionnaire as abridged questionnaires have been found to increase response rates in general dentists.34 The lower-than-expected response rate, which fell short of the calculated minimum required sample size, limits the generalisability of the results. As with other survey-based studies, this study has a non-response bias, as GDPs who participated in the survey are more likely to be interested in endodontics and hence would be more up to date on this topic.35 Respondent bias in which the respondents misrepresent their answers was less likely to be present due to the anonymous nature of the responses as assured by the authors in the survey introduction page. Close-ended questions were used for irrigation protocol for ease of coding; however, it comes with the limitation of biasing the respondents to select one out of the many options, especially on the topic of irrigation protocol for different pulpal and periapical diagnoses, which may vary from one practitioner to another.36 Bearing in mind the limitations and biases of the survey, the results of this study should be interpreted with caution. Despite the limited generalisability of the study, the results indicate that there is still a variety of irrigation protocols among Malaysian GDPs. This study can serve as a preliminary study for future research in the effort to develop comprehensive and evidence-based guidelines for irrigation during endodontic treatment.

Future surveys may include questions on types of practice, whether public or private, to see if there is any difference in irrigation practices among different practice settings. A future study on the storage practices of NaOCl and other irrigants may be beneficial for future guidelines in pre-operative irrigant handling. The number of years of practice can be compared with the number of CPD events attended. Future, similar cross-sectional studies can be conducted to observe the change in irrigation protocols among Malaysian GDPs over a longer time period.