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Microhardness Recovery Kinetics, Surface Roughness Trajectories, and Erosive Wear Susceptibility of Enamel After
Berivan Laura Rebeca Buzatu1,2, Magda Mihaela Luca3, Roxana Buzatu4
1Faculty of Dental Medicine, Doctoral School, "Victor Babeș" University of Medicine and Pharmacy Timisoara, 300041 Timisoara, Romania.
Dentistry Journal
|July 27, 2026
Summary
In-office dental bleaching can reduce enamel microhardness and increase roughness, with recovery taking up to 28 days. Light-activated, higher-concentration hydrogen peroxide (H₂O₂) bleaching agents pose the greatest risk for delayed enamel recovery and increased erosive susceptibility.
Area of Science:
- Dental Biomaterials
- Enamel Microstructure
- Aesthetic Dentistry
Background:
- In-office dental bleaching is a popular aesthetic procedure.
- The biomechanical effects of bleaching on enamel, including microhardness, roughness, and erosive vulnerability, require further characterization.
- Understanding enamel's recovery trajectory post-bleaching is crucial for clinical practice.
Purpose of the Study:
- To quantify the 28-day mechanical recovery profile of human enamel following three common chairside bleaching protocols.
- To investigate the inter-relationships between mechanical, topographic, and erosive endpoints after bleaching.
- To assess the impact of different bleaching agents and activation methods on enamel's resilience.
Main Methods:
- Human molars and premolars were sectioned into matched control and experimental halves.
- Experimental halves were treated with Opalescence Quick (45% carbamide peroxide), Opalescence Boost (40% hydrogen peroxide, chemical activation), or BlancOne Ultra+ (35% hydrogen peroxide, light activation).
- Vickers microhardness (VHN), surface roughness (Ra), and erosive wear after citric acid challenge were measured at multiple time points up to 28 days.
Main Results:
- Immediate microhardness (VHN) decreased significantly across all groups, with light-activated BlancOne Ultra+ showing the largest drop (-29.6%).
- By 28 days, enamel microhardness recovered to over 91% of baseline values, but recovery rates varied significantly between protocols.
- Erosive wear increased 2.1x to 3.8x compared to controls, with light-activated systems exhibiting higher susceptibility. Immediate surface roughness change predicted incomplete recovery.
Conclusions:
- Higher-aggression bleaching protocols, particularly light-activated systems, delay enamel's mechanical recovery and increase its vulnerability to erosion.
- Enamel microhardness and roughness recovery trajectories are protocol-dependent.
- These findings underscore the need for careful patient selection and post-operative care following in-office bleaching, especially with more aggressive agents.
