Enzymatically Driven Mineralization of a Calcium-Polyphosphate Bleaching Gel

Area of Science:

• Biochemistry
• Dental Materials Science
• Enzyme Kinetics

Background:

• Hydrogen peroxide-based bleaching gels are widely used in dentistry.
• Alkaline phosphatase (ALP) is an enzyme with potential applications in biomaterials.
• Calcium polyphosphate (CaPP) is a component in some dental formulations.

Purpose of the Study:

• To investigate the activity of ALP in hydrogen peroxide bleaching gel formulations.
• To assess the impact of incorporating ALP and CaPP into bleaching gels on orthophosphate levels, bleaching efficacy, and enamel microhardness.
• To determine the stability of ALP in different gel mediums.

Main Methods:

• ALP activity was measured across various pH levels and hydrogen peroxide concentrations.
• Circular dichroism (CD) analyzed ALP's secondary structure in different mediums (water, Tris, H2O2).
• Enamel/dentin specimens were subjected to different bleaching treatments, and color changes (ΔE/ΔE00, ΔWID) and microhardness (SMH, CSMH) were assessed.

Main Results:

• ALP activity was optimal at pH 9 but reduced in H2O2 mediums, causing enzyme denaturation.
• Incorporating ALP increased orthophosphate (PO43-) levels in the thickener solutions.
• Bleaching effectiveness (ΔE/ΔE00, ΔWID) was comparable across groups; surface microhardness decreased in H2O2-based gels, while cross-sectional microhardness was highest in the ALP-T group.

Conclusions:

• ALP activity is sensitive to the alkaline pH and hydrogen peroxide concentration in bleaching gels.
• While ALP incorporation elevates orthophosphate levels, it does not compromise bleaching effectiveness.
• The addition of ALP to CaPP-thickened gels may preserve or enhance enamel microhardness, particularly in cross-section.