Review of the effects of peroxide on enamel and dentine properties

Abstract

Objectives

To review the available literature investigating the effects of peroxide-based products and solutions on enamel and dentine properties.

Sources

All original scientific full papers listed in ISI Web of Science and Medline were included in this review using the search terms peroxide AND (enamel OR dentin*) up to the end of 2006.

Conclusions

The majority of studies indicate that peroxide containing products and solutions have no significant deleterious effects on enamel and dentine surface morphology and chemistry, surface microhardness, subsurface enamel and dentine microhardness or ultrastructure. In addition, in vitro studies indicate that they have no significant clinically relevant effects on subsequent enamel and dentine loss caused by acidic erosive challenges, toothpaste abrasion or caries lesion formation. The contrasting studies that do show an effect on some of the above properties, in general, have some limitations in the in vitro methods used which do not accurately reflect the in vivo situation or use products/solutions that have a particularly low pH where acidic erosive processes are likely to dominate and explain the observed changes in enamel and dentine.

Introduction

There are a number of methods and approaches that have been described in the literature for the bleaching of vital teeth. For examples, methods utilising different bleach agents, concentrations, times of application, product format, application mode and light activation.¹ Contemporary bleaching agents are typically either hydrogen peroxide (HP) or carbamide peroxide (CP). HP is capable of oxidizing a wide range of coloured organic and inorganic compounds, causing decolourisation and hence bleaching of the substrate. CP is a chemical adduct of urea and HP, which upon dissolving in water or saliva disassociates back into HP and urea. Thus, CP can be considered as a precursor of the active bleach species HP.

Three fundamental vital tooth bleaching approaches exist, namely, dentist-supervised nightguard bleaching, in-office or power bleaching and over the counter (OTC) bleaching products. Nightguard bleaching typically uses a relatively low level of whitening agent applied to the teeth via a custom fabricated mouth guard and is worn at night for at least 2 weeks. In-office bleaching generally uses relatively high levels of whitening agents, for examples 25–35% HP or 35% CP containing products, for shorter time periods. The whitening gel is applied to the teeth after protection of the soft tissues and the peroxide may be further activated by heat or light. OTC products typically contain low levels of whitening agent (e.g. 3–6% hydrogen peroxide) that are self-applied to the teeth via gum shields, strips or paint-on product formats and typically require twice daily application for up to 2 weeks.¹

The purpose of the current review is to summarise the available literature concerning the effects of peroxide containing bleaching agents on enamel and dentine. All English language original scientific full papers listed in ISI Web of Science and Medline were included in this review using the search terms peroxide AND (enamel OR dentin*) up to the end of 2006. A total of 88 papers were included and 278 papers excluded in this review. Papers that were relevant to the dental material science field were excluded since this topic has recently been extensively reviewed.² In addition, the following were not included in the current review: abstracts; peroxide delivered via toothpaste formats; papers where the level of peroxide was not stated; formulations directed towards intra-coronal bleaching methods, and papers not relevant to the current review.

The influence of hydrogen peroxide (HP) and carbamide peroxide (CP) treatments on enamel and dentine properties have been extensively investigated in the literature, primarily using in vitro studies and the levels of HP and CP used ranged from 5.3 to 38% and 10 to 37%, respectively. The current review has collated these studies into investigations on the surface morphology and chemistry, surface microhardness, subsurface properties such as microhardness and ultrastructure, and the subsequent effects of acid challenges and abrasion on enamel and dentine, and these are summarised in Table 1.