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Table of Contents
Year : 2021  |  Volume : 11  |  Issue : 2  |  Page : 68-72

Comparative evaluation of tissue dissolving capacity of sodium hypochlorite, peracetic acid and in combination: An In vitro study

Department of Conservative Dentistry and Endodontics, MGPGI, Puducherry, India

Date of Submission10-Sep-2020
Date of Acceptance14-Jun-2021
Date of Web Publication31-Aug-2021

Correspondence Address:
Dr. Prashanth Ponnusamy
No. 167, West Street, Gandhi Thirunallur, Mutharaiyarpalayam, Puducherry - 605 009
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jid.jid_74_20

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Background: The capacity of an irrigant to dissolve pulp tissue is of paramount importance as it can clean areas of the root canal that are inaccessible to instrumentation. Aim: To evaluate the tissue dissolving capacity of sodium hypochlorite (NaOCl) and peracetic acid (PAA) in combination. Materials and Methods: Forty maxillary central incisors were split longitudinally and grooved to mimic lateral canals. Pulp retrieved from freshly extracted impacted third molars were placed in grooves and repositioned in a putty index. All samples were irrigated with four different irrigants. 3% NaOCl; 1% PAA; 3% NaOCl and 1% PAA and Normal saline. Samples were irrigated for 5, 10 and 15 min weighed before and after each cycle with precision balance. Statistical analysis with ANOVA and post hoc Bonferroni was performed. Results: All groups showed tissue dissolution, except Group IV (Negative control). Complete dissolution did not occur in any sample. Group III showed statistically significant difference at 10 min. Conclusion: Results suggested that NaOCl and PAA in combination have better tissue dissolving capacity than used individually.

Keywords: Peracetic acid, pulp dissolution, sodium hypochlorite

How to cite this article:
Ponnusamy P, Borthakur BJ, Ganesan S, Swathika B. Comparative evaluation of tissue dissolving capacity of sodium hypochlorite, peracetic acid and in combination: An In vitro study. J Interdiscip Dentistry 2021;11:68-72

How to cite this URL:
Ponnusamy P, Borthakur BJ, Ganesan S, Swathika B. Comparative evaluation of tissue dissolving capacity of sodium hypochlorite, peracetic acid and in combination: An In vitro study. J Interdiscip Dentistry [serial online] 2021 [cited 2023 Apr 1];11:68-72. Available from: https://www.jidonline.com/text.asp?2021/11/2/68/325112

   Clinical Relevance to Interdisciplinary Dentistry Top

  • Currently, no single solution can fulfill all the requirements of an “ideal” root canal irrigant. Therefore, the combined, concomitant, or sequential use of two or more irrigating agents is required
  • It is desirable to have an irrigating solution with both tissue dissolution and smear layer removal capacity that can reduce substantial time during treatment
  • It is desirable to have an irrigating solution with both tissue dissolution and smear layer removal capacity that can reduce substantial time during treatment
  • The present study shows that the addition of peracetic acid (PAA) with sodium hypochlorite (NaOCl) enhances the tissue dissolution capacity in vitro.

   Introduction Top

Complete cleaning and shaping of the root canal is one of the important steps for the success of endodontic therapy. The capacity of an irrigant to dissolve pulp tissue is of paramount importance as the solution can clean areas of the root canal that are inaccessible to instrumentation.

Peters et al. assessed the effect of root canal instrumentation on root canal geometry using micro computed tomography scanning and demonstrated that proportionally large areas of the main root-canal wall remain untouched by the instruments,[1] highlighting the importance of chemical means of cleaning and disinfecting all areas of the root canal. Currently, there is no single irrigating solution that individually covers all of the functions required from an ideal irrigant. Optimal irrigation is based on the combined use of two or several irrigating solutions to predictably obtain the goals of safe and effective irrigation.

Various irrigants such as NaOCl, hydrogen peroxide, Ethylene diamine tetraacetic acid (EDTA), chlorhexidine (CHX) have been used individually and experimented in combinations.[2],[3] NaOCl is an excellent antimicrobial and tissue dissolving agent but has limited smear layer removing capacity. It is available in concentrations ranging from 0.5% and 6%. Among the root canal irrigants in general, NaOCl is the only irrigant that dissolves necrotic and vital organic tissues.

PAA is an oxidation agent and has been cited in the literature as a possible irrigant for root canals. PAA decomposes to oxygen and acetic acid. Acetic acid has the ability to dissolve inorganic contents, so it can free the canal system from smear layer during and after preparation with an advantage of antibacterial activity.[4],[5]

This study aimed to evaluate the in vitro tissue dissolving capacity of NaOCl, PAA and in combination.

   Materials and Methods Top

The root canals of 40 human maxillary central incisors were chemo-mechanically prepared and split. Teeth were collected from Department of Oral and Maxillofacial Surgery, MGPGI. Clearance from the ethical committee was obtained before performing the study. Specimen lengths were standardized to 16 mm by cutting the coronal part with a diamond disc.

A putty index was made before sectioning the teeth longitudinally, which will be used to re-approximate the sectioned root halves. With a fine-tipped marker two lines were created at one of the root halves at 2 mm from the apex till 6 mm from the apex. This was done to standardize the groove length to 4 mm. A groove was then created with a no. 2 round diamond bur to create a 2-mm-wide, 2-mm-deep, and 4-mm-long groove in one-half of all specimens. The root halves were then joined together and stored in distilled water to prevent dehydration [Figure 1].
Figure 1: Preparation of tooth specimen and pulp tissue placement

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For retrieving the pulp tissue, freshly extracted third molars were collected from the Department of Oral and Maxillofacial Surgery, MGPGI after obtaining consent from the patient. Teeth were split into two halves. Pulp specimens were removed and then washed in distilled water to remove any remnants of blood and refrigerated for 1 h at −20°C to assist in sectioning. Pulp tissue sample weights were standardized with a precision balance. BP blades are used to cut the tissue so that all the samples were within the range of 4 ± 1 mg[6] [Figure 2].
Figure 2: Sample weight measurement using a precision balance

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The pulp samples were then placed in the groove created in each half of the tooth.[7] The reassembled specimens in the putty index were randomly divided into experimental groups (n = 40) based on their irrigation protocol [Figure 1].

  • Group I – 3% NaOCl
  • Group II – 1% PAA
  • Group III – 3% NaOCl and 1% PAA at 1:1 ratio
  • Group IV – Normal saline (Negative control).

Samples were irrigated for 5 min and dried with paper points. The pulp tissue were then removed and weighed with a precision balance for weight change. Then the sample was again placed in the groove and irrigation is continued for the next 5 min. Every 10 s the irrigants were replenished. Weight change was measured after every 5 min for a total duration of 15 min (3 readings). The intergroup weight changes were statistically analyzed.

Statistical analysis

The mean and standard deviation of the percentage reduction of weight of the samples were calculated for all the groups. Two-way ANOVA was performed to compare the mean values of the variables. The level of statistical significance was set at P < 05. The statistical analysis was conducted by IBM SPSS statistics 20 software (SPSS for Windows: SPSS Inc., Chicago, IL, USA) software has been used for the statistical analysis. Post hoc analysis by Bonferroni was performed for intergroup comparisons.

   Results Top

The mean weight of pulp samples ranged from 3.2 to 4.7 mg. The mean percentage reduction of weight was calculated and computed for analysis. Both NaOCl and PAA and its combination (NaOCl + PAA) loss of weight of tissue compared to normal saline. In normal saline, there was gain in sample weight over time.

Comparison of four groups between initial and 5 min, initial and 10 min and initial and 15 min showed that there was no statistically significant difference observed among groups except in Group III (NaOCl + PAA) in the mean percentage reduction P < 0.001 [Table 1].
Table 1: Intergroup comparison for percentage reduction of pulp tissue using ANOVA

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Group III showed better mean percentage reduction compared to other groups in all three-time intervals.

Multiple comparison using Bonferroni showed statistical significant difference between Group III (NaOCl and PAA) with Group I (NaOCl) and Group II (PAA) at Initial and 10 min. All other groups showed no statistical significant difference [Table 2].
Table 2: Multiple comparisons using Bonferroni

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   Discussion Top

This study shows proof of principle for synergistic soft tissue dissolution ability for NaOCl + PAA mixtures, considering that this association performed better than the solutions separately. The mixture does not produce any observable precipitate.

The initial gain in sample weight at 5 min interval for all the groups can be attributed to the blotting procedure used in this study. The samples were blotted through the root canal using paper points and then the samples were removed and weighed separately. The residual irrigant might result in weight gain of samples at 5 min interval.

In this study, PAA was used at 1% concentration as it has showed to have efficacy similar to that of 2.5% NaOCl, 2% CHX and to 17% EDTA + 2.5% NaOCl against Enterococcus faecalis,[8] and a capacity for removing the smear layer when used as a final irrigant.[5]

In this study, during irrigation protocol, irrigants were replenished for every 10 s. This is of clinical importance, considering that the replacement of irrigating solutions is expected to occur regularly in routine clinical practice; thus, solutions are left in situ for a relatively short period.

Since the study had two independent variables (time intervals and irrigants), two-way analysis of variance was used to compare the means of the variables.

Different methods have been used to measure the dissolution process in vitro. Analysis of the hydroxyproline content in the residual tissue, analysis of hydroxyproline in the irrigant, measurement of available chlorine in the solution after dissolution process, assay of radioactive iodine in the irrigant, scanning electron microscopy, measurement of weight loss of tissue over a specified time, and assessment of the time needed for the complete dissolution of the specimen.

Kutty et al. reviewed the different methods used to assess the tissue dissolution in vitro and stated that measuring the weight change in a particular time interval is more relevant to the clinical scenario as compared to evaluating the time taken for complete dissolution.[9]

Human pulp tissue was used to assess and quantitatively compare the test solutions. Various other tissues have been used in previous studies such as bovine pulp, umbilical cord, pig palatal mucosa, rat dermal connective tissue. However, these tissues do not simulate the conditions present clinically within the human root canal. Hence, human pulp tissue was considered for this study.

PAA is one of the strongest disinfectants with antimicrobial property and smear layer removal effects, but a comprehensive quantitative study assessing its synergistic effect with NaOCl was missing.

In this study artificial grooves were created, to mimic those pathological defects found in intraradicular internal inflammatory root resorption and to some extent, isthmuses and cul-de-sacs found in canals[7] which were usually inaccessible to mechanical instrumentation. In this study, grooves were created so that the pulp specimen can be placed deep to the main prepared canal at the apical third of the sectioned root. So that when irrigation is performed, the pulp tissue will not be immersed by the irrigant rather it will be contacted from one side. This could be one of the reasons that there was no complete dissolution of samples in any of the groups.

In this study, the results showed no significant difference between 3% NaOCl and 1% PAA, suggesting PAA has similar pulp dissolving capacity. Moreover, the smear layer removal capacity of PAA adds to its advocating as a possible root canal irrigant.[10],[11]

The percentage of PAA tested in this study was within the safe limits as suggested by Viola et al.[12]

   Conclusion Top

Within the limitations of this study, it can be concluded that NaOCl and PAA in combination have better pulp tissue dissolving capacity than when used alone. Further studies are required to correlate the other variables such as antimicrobial efficacy, smear layer removal capacity, precipitate formation, and cytotoxicity of the combination.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   References Top

Peters OA, Schönenberger K, Laib A. Effects of four Ni-Ti preparation techniques on root canal geometry assessed by micro computed tomography. Int Endod J 2001;34:221-30.  Back to cited text no. 1
Dunavant TR, Regan JD, Glickman GN, Solomon ES, Honeyman AL. Comparative evaluation of endodontic irrigants against Enterococcus faecalis biofilms. J Endod 2006;32:527-31.  Back to cited text no. 2
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. 3
Taneja S, Kumari M, Anand S. Effect of QMix, peracetic acid and ethylenediaminetetraacetic acid on calcium loss and microhardness of root dentine. J Conserv Dent 2014;17:155-8.  Back to cited text no. 4
[PUBMED]  [Full text]  
De-Deus G, Souza EM, Marins JR, Reis C, Paciornik S, Zehnder M. Smear layer dissolution by peracetic acid of low concentration. Int Endod J 2011;44:485-90.  Back to cited text no. 5
Jain A, Shrivastava TV, Tabassum S, Bahuguna R. Comparison of human pulp tissue dissolution capacities of different irrigating solutions: An in vitro study. Eur J Gen Dent 2015;4:64.  Back to cited text no. 6
Estevez R, Conde AJ, de Pablo OV, de la Torre F, Rossi-Fedele G, Cisneros R. Effect of passive ultrasonic activation on organic tissue dissolution from simulated grooves in root canals using sodium hypochlorite with or without surfactants and EDTA. Int Endod J 2017;43:1161-5.  Back to cited text no. 7
Dornelles-Morgental R, Guerreiro-Tanomaru JM, de Faria-Júnior NB, Hungaro-Duarte MA, Kuga MC, Tanomaru-Filho M. Antibacterial efficacy of endodontic irrigating solutions and their combinations in root canals contaminated with Enterococcus faecalis. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011;112:396-400.  Back to cited text no. 8
Kutty SK, Lekshmi MS, Mohan A, Isaac L. Pulp tissue dissolution in endodontics – A review. Int J Appl Dent Sci 2017;3:193-6.  Back to cited text no. 9
Amato M, Pantaleo G, Abtellatif D, Blasi A, Gagliani M, Iandolo A. An in vitro evaluation of the degree of pulp tissue dissolution through different root canal irrigation protocols. J Conserv Dent 2018;21:175-9.  Back to cited text no. 10
[PUBMED]  [Full text]  
Grando CP, Martinez EF, Fontana CE, Rocha DG, Stringheta CP, da Silveira Bueno CE. Effectiveness of sodium hypochlorite plus EDTA compared with peracetic acid in removing smear layer and killing Enterococcus faecalis. Iran Endod J 2019;14:56-62.  Back to cited text no. 11
Viola KS, Rodrigues EM, Tanomaru-Filho M, Carlos IZ, Ramos SG, Guerreiro-Tanomaru JM, et al. Cytotoxicity of peracetic acid: Evaluation of effects on metabolism, structure and cell death. Int Endod J 2018;51 Suppl 4:e264-77.  Back to cited text no. 12


  [Figure 1], [Figure 2]

  [Table 1], [Table 2]


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