Elsevier

Journal of Endodontics

Volume 43, Issue 3, March 2017, Pages 472-476
Journal of Endodontics

Basic Research
Depletion Rate of Hydrogen Peroxide from Sodium Perborate Bleaching Agent

https://doi.org/10.1016/j.joen.2016.10.043Get rights and content

Highlights

  • Current recommendations concerning internal bleaching are based mainly on anecdotal clinical evidence and opinion and not scientific basis.

  • The chemistry of the reaction of sodium perborate and water releases H2O2 at a particular depletion rate.

  • The depletion of H2O2 showed a rapid rise peaking at 27 hours followed by a rapid decline and finally a plateau by 75 hours.

  • The implication of this research is that frequent replacement of the bleaching agent is probably unnecessary given the continued presence of low levels of H2O2, but this requires further ex vivo and in vivo investigation.

Abstract

Introduction

Internal bleaching of discolored teeth uses sodium perborate reacting with water to form the active agent, hydrogen peroxide (H2O2). Sodium perborate is replaced at varying time intervals depending on clinician preference and until esthetically acceptable results are achieved, but this is done without scientific basis. This study measured the depletion rate of hydrogen peroxide from sodium perborate as a bleaching agent.

Methods

Two sodium perborate bleaching products (Odontobleach [Australian Dental Manufacturing, Kenmore Hills, Queensland, Australia] and Endosure Perborate Micro [Dentalife, Ringwood, Victoria, Australia]) and distilled deionized water mixtures at ratios of 25 μg/mL, 50 μg/mL, and 100 μg/mL were placed into sealed microtubes and incubated at 37°C. H2O2 concentrations were measured at 23 time points over 4 weeks. Quantification of H2O2 concentrations was obtained using a ferrothiocyanate oxidation reduction reaction followed by spectrophotometry readings.

Results

The H2O2 concentration rapidly peaked within 27 hours and reached a plateau by about 3 days (75 hours). Low levels of H2O2 were evident beyond 3 days and for at least 28 days. No significant differences were found between the 2 sodium perborate products. There was also no significant difference in the depletion rate between the different ratios.

Conclusions

Based on the chemistry of H2O2 depletion, the minimum replacement interval for the bleaching agent is 3 days. Frequent replacements of the perborate clinically may be unnecessary because of the continued presence of low H2O2 levels for at least 28 days. Although these data cannot be extrapolated to the clinical situation, they set a baseline for further studies to address the many clinical variables influencing internal bleaching.

Section snippets

Preparation

Two brands of sodium perborate powders were used: Odontobleach (ODB) (Australian Dental Manufacturing, Kenmore Hills, Queensland, Australia) and Dentalife Endosure Perborate Micro (END) (Endosure Perborate Micro; Dentalife, Ringwood, Victoria, Australia). Initially, the intention was to include 2 g/mL as recommended for clinical use of sodium perborate (26), and a pilot study was developed to determine if this was feasible. Sodium perborate samples (ODB and END) were used at 1, 2, and 3 g/mL

Results

The first 27 hours showed a rapid increase in the concentration of H2O2, produced, which peaked at 27 hours before beginning to decline (Fig. 2). This rapid depletion continued until the concentration plateaued at about 3 days (75 hours); at this point, an equilibrium was reached in which the net production and depletion were equal (Fig. 3). Beyond 3 days, there remained a low level of H2O2 up to the last time point of 28 days. At 336 hours, ODB200 was not included in the analysis because it

Discussion

Despite the wide use of sodium perborate and water as an intracoronal bleaching agent, little is known about the dynamics of the reaction itself. Previous literature indicates that a pH change occurs over time after mixing sodium perborate with water (29). It is known that the addition of water to sodium perborate results in the release of H2O2, sodium metaborate (NaBO3), and nascent oxygen (20). The H2O2 decomposes into radicals and ions (20), and these radicals are responsible for oxidation,

Acknowledgments

The authors would like to thank Dr Samantha Byrne, Prof Stuart Daspher, Dr Harry Mohan, and Assoc Prof Menaka Abuzar for their support.

Supported by the Melbourne Dental School, The University of Melbourne.

The authors deny any conflicts of interest related to this study.

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