Saudi Endodontic Journal

: 2019  |  Volume : 9  |  Issue : 1  |  Page : 27--33

Sodium hypochlorite use, storage, and delivery methods: A Survey

Sumaya O Basudan 
 Department of Restorative Sciences, College of Dentistry, King Saud University, Riyadh, Kingdom of Saudi Arabia

Correspondence Address:
Dr. Sumaya O Basudan
Department of Restorative Dental Sciences, College of Dentistry, King Saud University, P.O. Box 60169, Riyadh 11545
Kingdom of Saudi Arabia


Aim: The aim of this study is to investigate sodium hypochlorite (NaOCl) delivery and storage methods by general dental practitioners (GDPs) and specialists. Materials and Methods: A self-reporting questionnaire was distributed to academic, governmental, and private dental centers in Riyadh, Saudi Arabia. The survey consisted of questions related to the concentration, duration, volume, delivery methods of NaOCl irrigation, storage materials, and conditions. Results: Of the 261 dentists that responded, 63.2% were GDPs, 21.8% were endodontists, and 14.9% were advanced restorative specialists. A NaOCl concentration of 2.5%–5% was the most commonly selected (52.7%), 37.2% used 5–10 ml for irrigation of each canal and 44.8% performed irrigation for <1 min. Dentists who used higher concentrations reported longer irrigation durations. Irrigant delivery by needles and a syringe was reported by 83.9% of respondents, but only 5.7% applied irrigation activation methods. Regarding storage conditions, 40% used clear containers, and 75.5% stored it at room temperature. Endodontists used significantly higher concentrations, longer durations, and activated the irrigant more than GDPs. Conclusion: The most commonly used NaOCl concentration is 2.5%–5%. The storage conditions of NaOCl and use of activation methods need to be improved. In addition, practices of specialists differed from those of GDPs with regard to concentrations, duration of irrigation, storage of NaOCl, and use of irrigation adjuncts.

How to cite this article:
Basudan SO. Sodium hypochlorite use, storage, and delivery methods: A Survey.Saudi Endod J 2019;9:27-33

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Basudan SO. Sodium hypochlorite use, storage, and delivery methods: A Survey. Saudi Endod J [serial online] 2019 [cited 2019 Jan 20 ];9:27-33
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The role of irrigation is pivotal to the success of root canal treatment.[1],[2],[3] Many types of root canal irrigants have been used in endodontics, yet sodium hypochlorite (NaOCl) is the recommended main irrigant.[3],[4] NaOCl has strong antimicrobial effects against bacteria including those organized in biofilms, fungi, and viruses. It is fast-acting, can dissolve organic compounds including pulpal tissue, inexpensive, and readily available.[3],[4]

NaOCl is commonly used in concentrations ranging from 0.5% to 6%,[5],[6],[7],[8],[9] which is achieved by purchasing it at the desired concentration or by diluting a full-strength solution. Its properties originate from the availability of the chlorine ion,[10] which directly depends on the concentration of the solution.[10],[11] Thus, higher concentrations possess stronger tissue dissolution capabilities and effectivity on biofilms.[10],[12] However, they can cause weakening of the tooth structure and severe irritations if exposed to the oral tissues.[13],[14] Clinical studies have demonstrated that low concentrations are effective against bacteria.[2] Nevertheless, the chlorine ion, especially in lower concentrations, can rapidly become ineffective. Accordingly, a minimum contact time with the tissue is necessary for NaOCl to exert its action. It has been demonstrated that prolonging working times and replenishing with higher volumes may increase the effectiveness of lower concentrations.[10],[15] In addition, ultrasonic activation can aid in tissue dissolution and improve irrigant delivery compared to the use of a needle and syringe alone.[10]

Moreover, the stability of NaOCl solution is strongly affected by its source, type of solvent, time since dilution, storage material, and storage conditions including light, high temperatures, and presence of contaminants.[11],[16],[17],[18],[19] Despite this, literature on dental practices regarding these issues is scarce. Therefore, this study aimed to investigate the practices used by dentists in Riyadh, Saudi Arabia, regarding the use, delivery, application, and storage of NaOCl in endodontics.

 Materials and Methods

The study design was approved by the Research Center and Ethics Committee of the College of Dentistry, King Saud University (NF 2333). A two-part questionnaire was designed, piloted, and modified [Appendix 1]. The first part was related to the participants' demographic data including age, gender, specialty, place of work, and number of cases treated per month. The second part inquired about the NaOCl concentration and volume used, delivery methods, and storage conditions, and finally, on the irrigant delivery systems used. Questions included multiple selections with the option of write-in answers. The survey included questions on irrigant selection and preference according to case diagnosis. The responses to these questions were analyzed and published in a previous paper.[20][SUPPORTING:1]

Participants were dentists who routinely perform endodontic treatment, including general dentists, advanced restorative specialists (i.e., specialists who received advanced endodontic training as part of their specialty training), and endodontists, working in Riyadh, Saudi Arabia. Riyadh was stratified by region, and one major governmental dental center or dental department at a governmental hospital, and two private dental clinics were included from each region. Two academic institutions, one governmental and one private, were included too.

Permission to distribute the questionnaire to the doctors was obtained from the administration from each institution. A paper-copy was presented to the administration, who then distributed it to the dentists. One month later, completed questionnaires were collected. Due to the low number of questionnaires completed by endodontists, a web-based format of the questionnaire was E-mailed to members of the Saudi Endodontic Society in Riyadh.

All data from returned questionnaires were entered and analyzed using the Statistical Package for Social Sciences (SPSS), version 22.0 (IBM Corp., New York, USA). Descriptive statistics (means, frequencies, and percentages) were computed. The relationship between NaOCl concentration and the volume and duration of irrigation in addition to comparisons between general dental practitioners (GDPs) and specialists were analyzed with Chi-square tests followed by Bonferroni post hoc tests. Statistical significance was set at 0.05 (P < 0.05).



Of the 275 dentists who responded to the questionnaire, 14 did not meet the selection criteria (e.g., they stated that they are not dentists, or they do not perform root canal treatment routinely) and were excluded from the study. Of the remaining 261 respondents, 63.2% were GDPs, 21.8% endodontists, and 14.9% advanced restorative specialists. More than half (61.3%) of the dentists surveyed were younger than 30 years, 26.8% were aged 31–40 years old, and 11.9% were above 40. There were 43.7% males compared to 56.3% females. Nearly half (44.8%) had been practicing dentistry for 1–5 years, 16% had been practicing for over 10 years, 39.9% treated fewer than 5 endodontic cases per month while 22.2% treated >20. The nationality of the majority (83.5%) was Saudi. Regarding workplace, 46.9% worked in academic institutions, 40% in governmental centers and 13% worked primarily in a private practice.

Irrigant use

[Table 1] presents the participants' selections regarding NaOCl concentrations used, volume, and duration of irrigation. The most common NaOCl concentration was 2.5%–5%. More than one-third (37.2%) of the participants used a volume of 5–10 ml for irrigation, and nearly half of the respondents (44.8%) irrigated each canal for <1 min.{Table 1}

The NaOCl concentration used was significantly associated with the volume of irrigant (χ2(12) =30.151, P = 0.003), and duration of irrigation (χ2 (12) =33.471, P = 0.001). Dentists who used the highest concentrations (>5%) irrigated for the longest duration (>5 min) (P > 0.001). Participants who answered “I do not know” regarding the concentration answered the same regarding the volume used significantly more frequently than those that provided a concentration (χ2 (12) = 30.151, P = 0.003).

A significant relationship was found between the concentration of NaOCl used and age (χ2 (12) = 37.844, P < 0.001), number of cases treated per month (χ2 (12) = 46.569, P < 0.001), and the workplace (χ2 (12) = 35.024, P < 0.001). The highest concentrations (>5%) was used significantly more by participants who treat >20 cases/month than those who treat <5 (P < 0.001), and by the age group 31–40 (P < 0.001) and in governmental centers more than academic institutions (P < 0.001).

Preparation and storage

Seventy percent of the participants had dental assistants prepare and dilute the NaOCl solution for them. One-quarter of the dentists (25.4%) had the solution prepared just before treatment, 9.6% had it prepared once a week, and half of the dentists (50%) did not know when it was prepared.

NaOCl was stored at room temperature by 75.5% of dentists, and 8% stored it in the refrigerator. Regarding the storage containers, 41.4% reported the use of opaque containers, 39.5% clear containers, and 17.2% did not know how it was stored.

Sodium hypochlorite delivery

Most of the participants (86.6%) used regular stainless steel needles with syringes to deliver the irrigant. Nickel-titanium needles were used by 6.5% of the respondents. The most commonly used needle gauges (G) were 25 G or less (29.1%) followed by 27 G (26.8%), and 30 G (10%). Nearly one-third of the respondents (32.6%) did not know the needle size they used. Irrigation adjuncts, such as sonic, ultrasonic, and pressure devices, were used by only 5.7% of the respondents and five respondents added that they delivered their irrigants using pipettes.

General dental practitioners and specialists

[Figure 1] presents the preferred concentrations by the different types of practitioners. The differences between them were statistically significant (χ2 (8) =57.53, P < 0.001). Endodontists used full-strength concentrations (>5%) significantly more than the other participants (P < 0.001) and concentrations below 2.5% significantly less frequently than GDPs (P = 0.001). While GDPS significantly preferred the concentrations below 2.5% more than the other participants (P < 0.001). Endodontists significantly irrigated for longer durations (36.8% irrigated for >5 min) (P < 0.001), while most GDPs (53.3%) irrigated for <1 min (P < 0.001). Endodontists also used higher volumes of the irrigant, smaller needle gauges, and relied less on the dental assistants to prepare and mix the irrigant, although not statistically significant. Restorative specialists used higher concentrations of NaOCl, more volume, and longer duration of irrigation than GDPs; however, this difference was also not statistically significant. In addition, GDPs were significantly the highest to report storage of NaOCl in clear containers (χ2 (6) =30.81, P < 0.001). Regarding the use of activation methods, only 10.5% of the endodontists used irrigation adjuncts, compared to 7.7% of the restorative specialists and 3.7% of GDPs.{Figure 1}


NaOCl is the most commonly used endodontic irrigant by dentists in Saudi Arabia[20],[21] and worldwide.[7],[8],[9] However, the ideal concentration used in endodontics has been controversial. Studies have demonstrated the effectivity of the different concentrations of NaOCl,[1],[2] in addition to the adverse effects in relation to them.[13],[14] Which prompts the clinician to weigh the benefits versus the adverse effects when managing a case. Moreover, clinical situations arise in which altering the concentration maybe beneficial.[22] Surveys reflect this controversy and show that the preferred concentrations are different between countries and within the different regions of the same country too, which is possibly affected by their education trends.[6],[23] For instance, the most commonly used concentration in a report from Australia is 1%,[6] and 2.5%–4% is preferred by endodontists in India.[9] Higher concentrations (>5%) are commonly used in the United States[8] and Canada.[5] The majority of our participants used a concentration of 2.5%–5%, which is similar to previously published data.[21]

There is also no consensus regarding the minimum volume of irrigant needed to be effective. The respondents frequently irrigated with 5–10 ml, which is also similar to previous reports.[5],[9] In addition, the time needed for NaOCl to be effective in the root canal is unknown and can be affected by the surface area of the canal, amount of organic matter, and by the concentration of the solution; the higher the concentration, the faster its tissue dissolution actions.[10] Therefore, although in vitro studies demonstrate successful results with low concentrations of NaOCl,[15] clinically, higher concentrations and longer durations maybe required to reach the same results due to the presence of the organic materials in the root canal,[3],[24],[25] which can deactivate the chlorine ion within one minute.[10] Although the effectiveness of lower concentrations can be improved by using larger volumes of irrigant, replenishing the irrigant frequently and increasing the contact periods,[15] nearly half of the participants spent less than one minute on irrigation. Moreover, it was observed that clinicians who used the lower concentrations of NaOCl, irrigated for the least duration and vice versa, which strongly questions the effectiveness of the irrigation.

The chemical stability of NaOCl is also affected by its storing conditions. Exposure to high temperature, light, air, and the presence of organic and inorganic contaminants can affect its stability, which is also influenced by its concentration and length of storage.[17],[26] It has also been reported that the effective shelf life of NaOCl ranged from 1 day to 10 weeks in 5.25%, 2.62% and 1.0% solutions of NaOCl. The tissue-dissolving ability of the 2.62% and 1% concentrations remained relatively stable for 1 week after dilution then rapidly deteriorates, while the 5.25% solution remained stable for at least 10 weeks.[26] While most of the respondents (78.5%) used diluted NaOCl, half did not know when it was prepared. In addition, most of the storage conditions of our participants seem unfavorable. Clarkson et al.[16] demonstrated that the activity of NaOCl deteriorated rapidly with heat and that undiluted NaOCl was generally more stable than a diluted solution. They emphasized that NaOCl should be stored in closed, opaque containers, away from sunlight, which is not practiced by 40% of participants, and away from heat, which is practiced by the majority of participants and is accelerated in diluted solutions as used by 80% of the participants. Moreover, in examined samples, the average reduction of chlorine in irrigating solutions was calculated to be less by 27% than the dentist's estimation.[18] Thus studies have recommended that dentists raise their preferred concentration of NaOCl to at least 2% to account for the reduction and inactivation of chlorine to reach the desired 1% which is the minimum concentration that demonstrates the activity of NaOCl.[10],[18]

A 25 G needle measures 0.51 mm, while 27 G and 30 G correspond to 0.41 mm and 0.31 mm,[27] making smaller needle sizes preferable as they can reach deeper within the canal. Studies have shown that an irrigant is only effective one mm beyond the tip of the needle, consequently deeper placement of the irrigation needle close to the working length may improve the debridement and irrigant placement.[28] The most commonly selected needle gauge was size 25 G or less. These sizes can be relatively large and may not penetrate deep into the canal, thus preventing the action of the irrigant.

In complicated root canal systems, complete disinfection and debridement may require irrigation agitation techniques rather than conventional needle-syringe irrigation alone.[29] Only 11% of the endodontists in this report applied such techniques, while others reported numbers reaching 50%.[7],[8],[9]

Literature demonstrates that specialists and GDPs differ in their clinical decisions.[30] The endodontists in this report use higher concentrations, irrigate for longer durations and use larger quantities of NaOCl than GDPs. In addition, they activate their irrigants with adjuncts more than GDPs and store NaOCl in more favorable conditions. Other reports have also shown that endodontists use significantly higher concentration of NaOCl than GDPs.[6],[7] de Gregorio et al. argued that endodontists use higher concentrations probably for their action against biofilms, and for their faster and higher effectivity. Conversely, they are more careful in avoidance of accidents,[7] in addition to their preference to apply rubber dam more than GDPs.[31] Endodontists have also been reported to use ultrasonic activation more than GDPs.[7] These differences have also been observed in different aspects of management of cases,[20] and ultimately more favorable outcomes.[30],[32] However, it is GDPs who perform the majority of root canal treatments.[33]

Frequently, the respondents indicated that they were unaware of the materials or practices used in their clinics, which has been similarly reported too.[6] It could be that they are using what is available or provided in their place of work or that they rely on the dental assistant to prepare their irrigants. While it is strongly recommended that the respondents become more involved, it is also important that dental assistants acquire adequate knowledge and training and that dental centers provide all materials required to perform root canal treatment within the standard of care, since it has been reported that the unavailability of a material at the workplace was the main reason for not using it.[31]

To the best of our knowledge, this study is the first to address the delivery methods and storage conditions of NaOCl in Saudi Arabia. It is important to note that the numbers reported are only to the best of the respondents' estimations, considering that actual concentrations of NaOCl have been found to be less than the dentist's expectations in most cases.[18] The volume, duration of irrigation, concentration, and use of irrigant activation methods need to be improved, otherwise, the effectivity of the solutions used by a number of our participants is strongly questioned. In addition, dentists should overcome the limitations of low concentrations by increasing the duration and volumes of the solution and improve the storage conditions of NaOCl. It is strongly recommended that dentists' awareness is raised regarding these issues and on the characteristics and behavior of NaOCl in different situations and environments, to facilitate adequate irrigation, especially for GDPs, through emphasizing these roles during both undergraduate dental education and continuous professional education.


This report shows that the most commonly used NaOCl concentration by dentists in Riyadh is 2.5%–5%. The storage conditions of NaOCl and use of activation methods need to be improved. In addition, practices of specialists differed from those of GDPs with regard to concentrations, duration of irrigation, and storage of NaOCl.


The author expresses her gratitude to Dr. Sarah Alghamdi and Dr. Huriya Alsultan for their efforts in the distribution and collection of the questionnaire.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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