Effects of carbamide peroxide whitening agents on enamel surfaces and caries-like lesion formation: an SEM and polarized light microscopic in vitro study.

Whitening enamel with carbamide peroxide (CP) to remove cosmetically displeasing stains has become common-place in dental practice. This in vitro study evaluated CP treatment effects on enamel surface morphology and caries-like lesion susceptibility. Tooth quarters were prepared from 10 caries-free human molars following a fluoride-free prophylaxis. The tooth quarters were assigned to the following treatment groups: 1) Distobuccal-10 percent NW gel (Nite White, Discus Dental); 2) Distolingual-10 percent PL paste (Platinum, Colgate); 3) Mesiobuccal-16 percent NW gel; and 4) Mesiolingual-Control. Following the manufacturers' recommended treatment, each quarter was sectioned with one portion prepared for SEM and the other portion for caries-like lesion formation. Intact enamel surfaces were present with all treatments. Enamel prism markings with exaggerated prism peripheries and mild to moderate prism core loss were seen with both 10 percent NW and 16 percent NW gels, but was more prominent with 16 percent NW gel. Amorphous surface layers with occasional exposure of indistinct prism markings occurred with 10 percent PL paste. Body of lesion mean depths were 135 microns control, 159 microns 16 percent NW, 144 microns 10 percent NW, and 122 microns 10 percent PL. Lesion depths were significantly different (p < 0.05 DMR paired design) between 10 percent PL and 16 percent NW, and between control and 16 percent NW. Whitening enamel surfaces in vitro with 10 percent carbamide peroxide paste containing dicalcium phosphate dihydrate (Colgate-Platinum) produced an amorphous surface layer and reduced caries susceptibility when compared with 16 percent carbamide peroxide gel (Nite White).