Objective: The aim of this study was to compare diode laser-activated bleaching effect versus chemical bleaching on enamel surface and subsurface of human mandibular incisors concerning morphology and chemical profile.
Materials and Methods: Forty extracted human, caries and defect-free mandibular incisors were divided into four groups by dividing their labial surface longitudinally into two halves. The distal halves of 20 teeth were assigned for chemical bleaching protocol using 38% hydrogen peroxide, their mesial halves represented their control. The other 20 teeth were assigned by the same method into laser-activated bleaching group and its control. The morphology and chemical profile of the surface and subsurface of the labial enamel were investigated, chemical profile of the subsurface was investigated at 50 and 100 μm depth.
Results: The enamel surface of chemically bleached group showed surface irregularities, porosities and erosive areas, ternary diagram of its chemical profile presented a slight shift to an area of less mineralized enamel. Morphology of the subsurface of chemically bleached enamel showed structural defects in prisms configuration and channels extending from surface defects through the enamel, its ternary diagram presented a shift to a demineralized area at both depths examined. Enamel surface of laser-bleached teeth appeared as a molten glazed surface and presented almost no shift in the ternary diagram. Subsurface of laser-bleached teeth showed loss of prismatic enamel integrity and presented a shift to a more mineralized area at 50μm depth and to a demineralized area at 100μm depth.
Conclusion: Laser-activated bleaching caused less enamel surface irregularities than chemical bleaching, but its effect was more deleterious on the morphology of the enamel subsurface. Concerning enamel chemical profile, subsurface enamel of chemically bleached teeth was more affected than that of the laser-bleached teeth.