Safe and effective vital tooth bleaching requires the development of formulations which produce aesthetic improvements in tooth appearance while maintaining the surface and subsurface integrity of hard tissues and restorative materials. Objectives: This study examined the effects of bleaching gels on the micro-chemical composition of enamel and dentin in vitro. Methods: Human molars were mounted in methacrylate blocks. Color determinations (CIELAB) of standardized areas on surface enamel were taken by image analysis. Teeth were bleached with Crestâ Whitestripsä commercial gel base containing either 6.0 % H2O2 (14 hours) or 6.5 % H2O2 (70 hour). Placebo gel treated molars served as controls. In a prototype experiment a series of subsurface CLSM-microtomographic images combined with simultaneous Micro-Raman spectra were recorded on transverse sectioned teeth permitting subsurface evaluation of ultrastructural and micro chemical effects on enamel and dentin. Results: Micro-Raman spectral properties were compared for test and control specimens as subsurface line scans in defined intervals. Particular attention was paid to the mineral PO4 (954 cm-1), CO3 (1071 cm-1) and non-apatite HPO4 (1002 cm-1) vibrations characteristic of hard tissue integrity. The CLSM and Micro-Raman tomographic and spectral properties of bleached enamel were unchanged from control enamel specimens. Conclusions: The CLSM and Raman spectroscopic properties of enamel and dentin appear unchanged in bleaching processes representative of those encountered in vital tooth bleaching. These chemical observations support the safety of vital tooth bleaching to the hard tissues.