Physical, morphological, and micro-Raman chemical studies on bleaching strip effects on enamel, coronal dentin, and root dentin.

Objective: This study examined the effects of elevated-concentration hydrogen peroxide tooth whitening strips on the surface and subsurface integrity of enamel, coronal dentin, and root dentin.

Methodology: Sound human teeth were ground and polished to prepare a uniform substrate for bleaching. A cycling regimen included exposures to saliva, bleaching treatments, and fluoridated toothpaste. Bleaching was carried out with plastic strips containing hydrogen peroxide gel at 11.7 and 14% concentrations. A non-bleached group served as a control. Bleaching times measured up to 45 hours. Physical properties of tooth surfaces were assessed by microhardness, while surface morphological properties of teeth were examined by profilometry, surface Confocal Laser Scanning Microscopy (CLSM), and Variable Pressure Scanning Electron Microscopy (VP-SEM). Subsurface histomorphological effects on teeth were assessed by CLSM. Lastly, the influences of bleaching on tooth micro-chemical composition was studied by micro-Raman spectroscopy using a unique spectrometer in line, coupled to the CLSM via glass fiber.

Results: Surface microhardness, profilometry, CLSM, and VP-SEM measures showed enamel and root dentin surfaces were unchanged with bleaching. CLSM micromorphological assessments demonstrated normal histology for bleached teeth on surface and subsurface enamel, DEJ, and dentin. Raman spectroscopy demonstrated no effects of bleaching treatments on the microchemical mineral composition of enamel and dentin. Bleaching treatments were observed to reduce background luminescence of enamel, DEJ, and dentin.

Conclusion: These results confirm that whitening strips delivering controlled doses of hydrogen peroxide at 11.7 and 14% concentrations do not produce changes in surface/subsurface histomorphology, surface microhardness, or micro-chemical mineral composition of teeth. The effects of bleaches on tooth luminescence recorded in micro-Raman spectroscopy may serve as an internal signature to bleaching effects and warrant further study.