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Micro-dissection of Enamel Organ from Mandibular Incisor of Rats Exposed to Environmental Toxicants
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Enamel damage from tooth-whitening- a systematic review and meta-analysis
Péter Márton1, Melinda Antal1, Szilvia Kiss-Dala2
1Centre for Translational Medicine, Semmelweis University, Budapest, Hungary; Department of Prosthodontics, Semmelweis University, Budapest, Hungary.
Journal of Dentistry
|May 23, 2026
Summary
Hydrogen- or carbamide-peroxide bleaching causes small, statistically detectable reductions in human enamel microhardness. These changes are unlikely to be clinically significant, supporting continued use of peroxide bleaching agents.
Area of Science:
- Dental materials science
- Biomaterials engineering
- Oral health research
Background:
- Dental bleaching with hydrogen peroxide or carbamide peroxide is a common cosmetic procedure.
- Concerns exist regarding potential alterations to tooth enamel's physical properties, specifically microhardness.
- Standardized in vitro testing is crucial for evaluating the safety and efficacy of bleaching agents.
Purpose of the Study:
- To systematically evaluate the impact of hydrogen- and carbamide-peroxide bleaching on human enamel microhardness.
- To adhere to ISO 28399 standards for in vitro dental material testing.
- To perform a meta-analysis and meta-regression to identify factors influencing microhardness changes.
Main Methods:
- Systematic literature search following PRISMA 2020 and Cochrane guidelines.
- Inclusion of in vitro studies measuring enamel microhardness (Vickers or Knoop) before and after bleaching.
- Multilevel random-effects meta-analysis of log-transformed ratios of means (ROM) with meta-regression for moderators (peroxide concentration, time, load, dwell time).
Main Results:
- Pooled analysis of nine studies revealed a small, statistically significant reduction in enamel microhardness (ROM = 0.89).
- Exposure time was a significant moderator, with longer exposure correlating to decreased microhardness, though this was sensitive to outliers.
- Heterogeneity remained moderate (I² = 50.8%), and time-course analyses suggested concentration-dependent effects.
Conclusions:
- Peroxide bleaching results in statistically detectable but small enamel microhardness reductions, generally not exceeding 10% (clinically meaningful threshold).
- Current evidence does not strongly support strict regulatory limits on peroxide concentrations based on microhardness.
- Further ISO 28399-compliant studies with standardized, clinically relevant outcome measures are needed to confirm safety and efficacy.
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