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Year : 2018  |  Volume : 8  |  Issue : 3  |  Page : 208-211

Comparative evaluation of temperature changes on tissue-dissolution ability of sodium hypochlorite, calcium hypochlorite, and chlorine dioxide

Department of Conservative Dentistry and Endodontics, Manipal College of Dental Sciences, Mangalore, Karnataka, India

Date of Web Publication25-Jul-2018

Correspondence Address:
Dr. Karthik Shetty
Department of Conservative Dentistry and Endodontics, Manipal College of Dental Sciences, Mangalore (Manipal Academy of Higher Education), Light House Hill Road, Mangalore - 575 001, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/sej.sej_99_17

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Aim: The present study evaluated the tissue-dissolution ability of 3% sodium hypochlorite (NaOCl) and two other irrigants, namely, 10% calcium hypochlorite and 13.8% chlorine dioxide (ClO2) at different temperatures, keeping isotonic saline as control.
Materials and Methods: The bovine muscle tissue specimens which were prepared for the study, were weight adjusted (50 ± 5 mg). One hundred and twenty frozen tissue samples were distributed equitably between the four groups. The experiments were conducted at three different temperature slabs, that is, room temperature, 37°C and 45°C, respectively. The 30 tissue samples in each group were immersed in 5 mL of the allocated test solution at the desired temperature for a total of 20 min, with change of solution done every 2 min. At the end of the 20-min experiment period, the tissues were carefully removed, blotted dry on absorbent paper, and weighed on a precision balance. The percentage weight loss of the specimens was then recorded for the experiment period.
Results: The results of this study showed that at room temperature, the 3% NaOCl solution presented maximum tissue dissolution, whereas at 37°C, 13.8% ClO2solution was most effective in dissolving the tissue. However, when the temperature was raised to 45°C, all the three test solutions were equally effective in their tissue-dissolving capacity.
Conclusion: The present study showed that heating the solutions enhances their ability to dissolve organic material.

Keywords: Calcium hypochlorite, chlorine dioxide, root canal irrigants, sodium hypochlorite

How to cite this article:
Basaiwala AK, Shetty K, Nath KS. Comparative evaluation of temperature changes on tissue-dissolution ability of sodium hypochlorite, calcium hypochlorite, and chlorine dioxide. Saudi Endod J 2018;8:208-11

How to cite this URL:
Basaiwala AK, Shetty K, Nath KS. Comparative evaluation of temperature changes on tissue-dissolution ability of sodium hypochlorite, calcium hypochlorite, and chlorine dioxide. Saudi Endod J [serial online] 2018 [cited 2023 Feb 1];8:208-11. Available from: https://www.saudiendodj.com/text.asp?2018/8/3/208/237568

  Introduction Top

Disinfecting and cleaning the root canal system to ensure complete elimination of microbial flora and pulpal tissue are prerequisites for successful root canal treatment.[1] It has been reported that mechanical instrumentation of the canals alone without antimicrobial intervention reduces the bacterial count.[2] Recent studies have shown that even after thorough mechanical preparation of the root canal space, approximately 35% to 50% of the pulp space still remains uninstrumented.[3] The persistence of residual pulp tissue, infected dentin, or bacteria in the root canal system is known to be responsible for the failure of root canal treatment.[4] Irrigation is one of the most important aspects of root canal treatment because it can help clean those areas of the root canal system which are not within the reach of the mechanical instrumentation.[5] Some of the most favorable features of irrigants are their flushing action, tissue-dissolving ability, antimicrobial effect, and low toxicity.[6],[7] Dissolution of pulp tissue, in particular, is a highly desirable property in any irrigating solution because it greatly enhances root canal cleaning.

A number of options are available for consideration to the clinician while choosing the endodontic irrigants. Many times a combination of irrigants are applied to enhance the effectiveness of the irrigation regimen. From the perspective of getting better clearance of the pulp tissue, several irrigants have been studied for their ability to dissolve pulp tissue quickly and efficiently. Some of the recent studies have shown that sodium hypochlorite (NaOCl), calcium hypochlorite, and chlorine dioxide (ClO2) are the most effective options available nowadays.[2],[8],[9]

Increasing the temperature has been found to improve the effectiveness of irrigants in the root canal system during their use. Over the years, this approach has been popular with NaOCl solutions as this has shown to improve their immediate tissue-dissolution capacity.[9],[10] Preheating allows for the usage of less concentrated dilution/formulations to bring about the desired effects from the irrigants. However, there is only little-documented data available on features of heated irrigated solutions relevant to the endodontist. Furthermore, the effect of temperature on the tissue-dissolving capacity of calcium hypochlorite and ClO2 has not been studied till now.

In the present study, the tissue-dissolution ability of 3% NaOCl, 10% calcium hypochlorite, and 13.8% ClO2 at different temperatures was evaluated. Isotonic saline was used as control.

  Materials and Methods Top

A commercially available 3% concentration solution of NaOCl (Vishal Dentocare Pvt. Ltd., Ahmedabad, India) was obtained. The solution was stored in an opaque, airtight polyethylene bottle and used on the day of experiment.

A 10% solution of calcium hypochlorite was freshly prepared from the granule formulation (Loba Chemie Pvt. Ltd, Mumbai, India) at the time of each experiment using distilled water (weight/volume ratio). Mixing was done with a magnetic stirrer for 10 min.

A 13.8% ClO2 solution was prepared just before use, by mixing equal parts of solutions A and B according to the manufacturer's (BioClenz; Frontier Pharmaceutical, Melville, New York, USA) instructions. After mixing, the pH of this original ClO2 solution was adjusted from 4.7 as measured by a pH meter to 12 by adding NaOH solution.

The bovine muscle tissue once harvested was cut to produce tissue samples approximately 8–10 mm long and 1–2 mm thick with a standardized weight of 50 ± 5 mg. Each sample was then transferred in a 10 mL plastic vial and stored at −20°C until used in the study.

The frozen tissue samples were distributed equitably into four groups of 30 samples each. The experiments were conducted at three different temperature slabs, that is, room temperature, 37°C and 45°C, respectively. A water bath (Water Bath Digital 10 L; INDLAB, Chennai, India) was used for the experiments at 37°C and 45° C. The temperature of the solutions was confirmed using a thermometer (Fisher Scientific). Each sample was then immersed in 5 mL of the allocated test solution at the desired temperature, for a total of 20 min, with change of solution done every 2 min. At the end of the 20 min experiment period, the tissues were carefully removed, blotted dry on absorbent paper, and weighed on a precision balance (Essae Teraoka Ltd, Bengaluru, India). The difference in weight of the tissue sample before and after exposure to the test solution was divided by the original tissue weight and multiplied by 100 to obtain the percentage of tissue weight loss or gain. The resulting data were analyzed statistically using one-way analysis of variance and post hoc Tukey test.

  Results Top

The mean percentage reduction in weight of samples after 20 min in different test solutions at three different temperatures is shown in [Figure 1]. According to the results of this study, 3% NaOCl solution caused maximum tissue dissolution at room temperature. At the next higher temperature band of 37°C, 13.8% ClO2 solution was most effective in dissolving the tissue among the three test solutions. However, when the temperature was raised to 45°C all the three test solutions showed similar results.
Figure 1: Mean percentage reduction in weight of samples

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The statistical analysis showed that at room temperature and at 37°C, all the three test solutions showed significant differences in their ability to dissolve the tissue, while all the three groups were more effective than the saline control group (P< 0.05). At 45°C, no statistically significant difference was found between the tissue-dissolving properties of the three test solutions, while all of them were significantly more effective than saline (P > 0.05). There was an increased weight loss associated with a raise in the temperature in all the three experimental groups.

  Discussion Top

The dissolution of pulp tissue is an ideal requirement of an endodontic irrigant. The available literature on the tissue-dissolution abilities of endodontic irrigants has covered all the conventionally used irrigants over the last few decades. However, there has been recent interest in some newer agents for irrigation such as ClO2 and calcium hypochlorite and their potential as tissue solvents has not yet been fully explored. In particular, the effect of temperature change on these irrigants has not yet been documented. Our study aims to eliminate these lacunae in endodontic scientific data.

NaOCl is one of the most commonly used irrigants in endodontic therapy, and its antimicrobial and organic tissue-dissolving properties have been widely reported in literature.[4],[11] The effect of NaOCl on the pulp tissue has been studied extensively and its ability to dissolve pulp tissue is well documented. NaOCl ionizes to liberate hypochlorous acid (HOCl) and hydroxyl ions in an aqueous environment. Saponification, amino acid neutralization, and chloramination reactions contribute to its tissue-dissolution ability. In addition, it is inexpensive, has a long shelf life, and is readily available. Calcium hypochlorite (Ca[OCl]2) is used for industrial sterilization, bleaching, and water purification treatment.[12] It is relatively stable and has greater available chlorine than NaOCl, up to 65% available chlorine as compared to 45% in NaOCl.[8] Ca (OCl)2 is available as granules and in a freshly prepared aqueous solution the following reaction occurs: Ca(OCl)2 +2 H2O/2 HOCl + Ca(OH)2. Available data with Ca(OCl)2 as an endodontic irrigant are very scarce. ClO2 is chemically similar to chlorine hypochlorite, the familiar household bleach. ClO2 is currently used in food processing, water treatment, veterinary care, surface disinfection, dental waterline treatment, and some commercially available mouth rinses.[13],[14],[15] Its powerful oxidizing properties enable it to kill bacteria by disrupting the transport of nutrients across the cell wall.[16] ClO2 has recently come under consideration as a possible root canal irrigant because of its reported antibacterial activity and compatibility with living tissue.[17],[18],[19] In addition, the recent detection of cytomegalovirus and Epstein–Barr virus associated with periradicular lesions might promote the use of ClO2, which kills both enveloped and nonenveloped viruses.[20]

Tissues from a number of different sources have been used in earlier studies on the tissue-dissolving ability of NaOCl.[21] Porcine muscle tissue, rabbit liver, rat connective tissue, pig palatal mucosa, bovine muscle tissue, and bovine pulp have been used to simulate pulpal tissue while determining the tissue-dissolution ability of different irrigants. The reasons for using different tissue instead of dental pulp have been their easy availability and easier standardization.[6] In the present study, bovine muscle tissue was used with a standardized weight of 50 ± 5 mg. During pilot experiments, it was observed that it is difficult to determine the endpoint of complete dissolution of the tissue because of a great number of bubbles resulting from the saponification reaction; therefore, a fixed time period was used and the samples were weighed before and after exposure.

There has been research which has documented that highly concentrated solutions of the irrigants are more toxic than their preheated counterparts of lower concentrations when administered to the periodontal tissues.[22] Furthermore, according to the current literature, irrigating solutions which are used clinically, reach temperature equilibrium relatively quickly.[10] The thermal conductivity of human dentin is low.[23] This factor combined with the presence of an intact vasculature of the tooth-supporting tissues provides a thermal dissipation effect [24] and can help us conclude that heated irrigating solutions can be used within the root canal spaces safely.

The present study showed that heating the test solutions enhanced their ability to dissolve organic material. These results are in accordance with other studies done earlier using NaOCl.[9],[25] Furthermore, heated hypochlorite solutions demonstrate more available chlorine and remove organic debris from dentin shavings more efficiently than unheated counterparts.[26],[27] Results of this experiment cannot be directly extrapolated to the clinical situation, as the current experiment was performed in an ideal in vitro environment. Furthermore, further studies can be pursued to find the ideal temperature/concentration combination for different irrigating solutions to be used in vivo.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

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Oliver SP, Lewis MJ, Ingle TL, Gillespie BE, Matthews KR. Prevention of bovine mastitis by a premilking teat disinfectant containing chlorous acid and chlorine dioxide. J Dairy Sci 1993;76:287-92.  Back to cited text no. 13
Frascella J, Gilbert RD, Fernandez P, Hendler J. Efficacy of a chlorine dioxide-containing mouthrinse in oral malodor. Compend Contin Educ Dent 2000;21:241-4.  Back to cited text no. 14
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EPA 2002c. Chlorine Dioxide. U.S. Environmental Protection Agency, Office of Pesticide Programs. Available from: http://www.epa.gov/pesticides/factsheets/chlorinedioxidefactsheet.htm. [Last accessed on 2002 Apr 24].  Back to cited text no. 16
Eddy RS, Joyce AP, Roberts S, Buxton TB, Liewehr F. An in vitro evaluation of the antibacterial efficacy of chlorine dioxide on E. faecalis in bovine incisors. J Endod 2005;31:672-5.  Back to cited text no. 17
Barnhart BD, Chuang A, Lucca JJ, Roberts S, Liewehr F, Joyce AP, et al. An in vitro evaluation of the cytotoxicity of various endodontic irrigants on human gingival fibroblasts. J Endod 2005;31:613-5.  Back to cited text no. 18
Nishikiori R, Nomura Y, Sawajiri M, Masuki K, Hirata I, Okazaki M, et al. Influence of chlorine dioxide on cell death and cell cycle of human gingival fibroblasts. J Dent 2008;36:993-8.  Back to cited text no. 19
Sabeti M, Simon JH, Nowzari H, Slots J. Cytomegalovirus and Epstein-Barr virus active infection in periapical lesions of teeth with intact crowns. J Endod 2003;29:321-3.  Back to cited text no. 20
Clarkson RM, Moule AJ, Podlich H, Kellaway R, Macfarlane R, Lewis D, et al. Dissolution of porcine incisor pulps in sodium hypochlorite solutions of varying compositions and concentrations. Aust Dent J 2006;51:245-51.  Back to cited text no. 21
Spangberg L, Engström B, Langeland K. Biologic effects of dental materials 3. Toxicity and antimicrobial effect of endodontic antiseptics in vitro. Oral Surg Oral Med Oral Pathol 1973;36:856-71.  Back to cited text no. 22
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Sirtes G, Waltimo T, Schaetzle M, Zehnder M. The effects of temperature on sodium hypochlorite short-term stability, pulp dissolution capacity, and antimicrobial efficacy. J Endod 2005;31:669-71.  Back to cited text no. 25
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