Enamel and Dentin Microhardness and Chemical Composition After Experimental Light-activated Bleaching

Area of Science:

• Dental Materials Science
• Biomaterials
• Surface Chemistry

Background:

• Dental bleaching agents are widely used for aesthetic purposes.
• The impact of these agents on tooth structure, specifically microhardness and chemical composition, requires thorough investigation.
• Understanding the remineralization potential of various agents is crucial for maintaining tooth integrity post-bleaching.

Purpose of the Study:

• To assess the effects of five bleaching agents, with and without light activation, on enamel and dentin microhardness and chemical composition.
• To evaluate the remineralizing efficacy of artificial saliva and amorphous calcium phosphate (ACP) on bleached tooth surfaces.

Main Methods:

• Human third molars were sectioned, and enamel and dentin microhardness was measured.
• Teeth were treated with hydrogen peroxide (HP) or carbamide peroxide (CP) gels, alone or with light activation (ZOOM2, LED, OLED, femtosecond laser).
• Chemical analysis was performed using energy-dispersive X-ray spectroscopy, followed by a two-week remineralization period with artificial saliva or ACP.

Main Results:

• Bleaching agents significantly reduced enamel and dentin microhardness, with higher peroxide concentrations (up to 40% reduction with 25% HP) causing more pronounced effects.
• Light activation showed negligible impact on microhardness changes.
• Remineralization treatment with ACP and artificial saliva resulted in minimal microhardness deviation (3%) and increased calcium, phosphorus, and fluorine concentrations.

Conclusions:

• Increased peroxide concentration and gel acidity in bleaching agents negatively impact the microhardness and mineral content of enamel and dentin.
• Amorphous calcium phosphate (ACP) and artificial saliva demonstrate significant potential to stimulate remineralization of dental hard tissues, counteracting bleaching-induced damage.