Novel method to measure enamel surface porosity with hydrogen peroxide bleaching.

Purpose: To establish methods to quantitate the physical surface change, not the chemical color bleaching change, of enamel occurring with hydrogen peroxide treatment in solution and commercially available plastic strips.

Methods: Bovine enamel was polished to a sound, uniform, optical flat, white subsurface that was used as the initial substrate for all substrate modification, treatment and instrumental measurement using digital photography-image analysis, SEM and profilometry. Sound enamel was treated with 10, 20 and 30% solutions of hydrogen peroxide. Plastic strips were used to treat both sound and acid modified enamel surfaces. Etched enamel, similar to a 10-second exposure to lemon juice, was treated with 0.5, 1, 3, 5, 10, and 15% hydrogen peroxide for 24-hour exposure at 37 degrees C to obtain a dose response curve to this modified enamel.

Results: The digital photography-image analysis system and scanning electron microscopy (SEM) were effective in detecting enamel surface porosity and structure disruptive changes, respectively. Plastic strip treatment of both sound and etched enamel produced little surface change. Measurable surface change of etched enamel was detected with as low as 1% hydrogen peroxide in solution. The surface change with 15% hydrogen peroxide was statistically significant. Dye uptake as measured by image analysis indicated an increase in surface porosity that was more evident with the acid modified surface. SEM studies were consistent with this observation.