Subsurface microhardness of enamel and dentin after different external bleaching procedures

Area of Science:

• Dental materials science
• Biomaterials research
• Tooth whitening efficacy

Background:

• Tooth bleaching is a common cosmetic dental procedure.
• Concerns exist regarding the potential effects of bleaching agents on tooth structure.
• Assessing microhardness is crucial for evaluating structural integrity.

Purpose of the Study:

• To compare the effects of various dental bleaching systems on the microhardness of enamel and dentin.
• To determine the depth of microhardness reduction in enamel and dentin following bleaching treatments.

Main Methods:

• Sixty bovine crowns were divided into seven groups, each treated with a different bleaching system.
• Baseline Knoop microhardness of enamel and dentin was measured.
• Bleaching agents were applied according to manufacturer instructions over 10 days.
• Post-treatment microhardness was re-assessed, and data were statistically analyzed.

Main Results:

• One bleaching system (Rapid White) significantly reduced microhardness in both enamel and dentin.
• Other systems caused significant enamel microhardness reduction up to specific depths (e.g., Opalescence Quick up to 700µm).
• No significant changes in subsurface dentin microhardness were observed in most groups.

Conclusions:

• The choice of bleaching system can influence the microhardness of dental tissues.
• Some bleaching systems may pose a risk to enamel integrity, necessitating careful application.
• Further research is needed to fully understand long-term effects on dentin and clinical implications.