Secondary caries inhibition promoted by adhesive systems and bleaching agents with fluoride

To evaluate the initial caries development at adhesive/enamel interface after 10% carbamide peroxide bleaching (CP) with or without fluoride (F) under dynamic pH-cycling.

Standard cavities were prepared on the bucal surface of 60 bovine incisors, which were restored with two fluoride-containing adhesives: Optibond FL (FL) and Optibond Solo Plus (SP). The restored teeth were submitted to thermal cycling process in order to age the adhesive/enamel interface. Both SP and FL adhesive-restored teeth were divided into groups (n= 10) and bleached with 10% CP (CP) and 10% CP + F (CPF) or remained unbleached (Control). Bleaching was performed for 14 days simultaneously with pH-cycling. The specimens were prepared for cross-section microhardness evaluation and polarized light microscopy analysis to evaluate caries lesions at different depths around the bonded interface.

Group FL (not bleached) presented the lowest mineral loss rate among groups, but secondary caries formation was observed for all groups around the bonded interface. An inhibition zone was observed for all groups, with caries lesion detected at 5 microm from the cavity wall.