Bleaching at acidic and basic pH for enamel and dentin whitening using internal and external techniques

Area of Science:

• Dental Materials Science
• Biomaterials
• Oral Health Research

Background:

• Hydrogen peroxide gels are widely used for dental bleaching.
• The pH of bleaching agents can influence their efficacy and potential side effects.
• Understanding the in vitro effects of pH on whitening and enamel properties is crucial for clinical application.

Purpose of the Study:

• To compare the in vitro whitening effects of hydrogen peroxide gels at acidic and basic pH.
• To evaluate the impact of these gels on enamel and dentin physicochemical properties.
• To assess the diffusion and pH changes associated with different bleaching agents.

Main Methods:

• Forty bovine incisors were divided into four groups, with bleaching applied externally or internally using acidic or basic pH hydrogen peroxide gels.
• Evaluated CIELab color, microhardness, roughness, enamel demineralization (FT-Raman), and surface topography (SEM) at T0 and T7.
• Assessed bleaching agent diffusion and pH changes during application.

Main Results:

• Acidic pH gels promoted greater whitening and increased enamel roughness at 7 days post-bleaching.
• Both gel types reduced the mineral-matrix ratio and altered porosity.
• Basic pH gels exhibited higher pH decay and greater diffusion capacity into dentin.

Conclusions:

• Acidic pH hydrogen peroxide gels offer enhanced whitening but lead to increased enamel roughness.
• The 7-day saliva immersion period was insufficient to fully restore initial enamel roughness.
• pH significantly influences the whitening efficacy, enamel alterations, and diffusion characteristics of hydrogen peroxide bleaching agents.