Effects of Crest Whitestrips bleaching on subsurface microhardness and ultrastructure of tooth enamel and coronal dentin

Purpose : To describe the complementary subsurface analysis of structural and ultrastructural effects of bleaching with Crest Whitestrips on enamel and coronal dentin Methods: Human tooth enamel specimens were cycled through a daily regimen including salivary immersions and treatments with commercial tooth whitening gels containing hydrogen peroxide or carbamide peroxide. Treatments with hydrogen peroxide in Crest Whitestrips gel base were carried out for up to 70 hours bleaching (some five fold to the clinical exposure required to produce satisfactory whitening in bleaching strip systems) as established by double blind placebo controlled clinical studies. Following in vitro laboratory cycling, the teeth were cross sectioned and remounted for observation of microhardness and ultrastructural characteristics in subsurface regions. Ultrastructure was assessed by application of confocal laser scanning microscopy (reflection mode). Results: Peroxide whitening compositions had no effects on subsurface microhardness of enamel or dentin, even under conditions of five fold overbleaching. Crest Whitestrips gel containing up to 6.5% hydrogen peroxide applied for periods up to 70 hours (five kit) overbleaching was found to produce no changes (at a lateral resolution of 200-300 mn) in observed subsurface enamel and dentin ultrastructure or architecture.