Resin Bonding to Dentine After Casein Phosphopeptide-Amorphous Calcium Phosphate (CPP-ACP) Treatments

Casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) has the ability to enhance enamel and dentine remineralisation and thus has been incorporated in new medicaments for such clinical problems as tooth hypersensitivity and early carious lesions. The current study investigated whether the application of CPP-ACP in the proprietary paste, Tooth MousseTM, would influence the subsequent resin adhesion to dentine. Bonding effectiveness was assessed by microtensile bond strength test and scanning electron microscopy. A three-step etch-and-rinse adhesive (OptiBond FL) or a two-step self-etch adhesive (Clearfil SE Bond) was bonded to three groups of dentine surfaces: no treatment; 5 min or 5 days CPP-ACP application. The microtensile test was performed and bond strength data were analysed using ANOVA and Tukey-Kramer post hoc test. Etching characteristics on respective dentine surfaces and resin-dentine interface were observed under SEM. Bond strengths of Clearfil SE Bond to dentine appeared to be similar for all tested groups. OptiBond FL, however, showed lower bond strengths following the application of CPP-ACP for both time periods. Under SEM observations, the CPP-ACP treated dentine displayed a layer of residue or precipitate attached to the surface after the phosphoric acid treatment. The sectioned specimens also showed the resin-dentine interface with less intertubular linking of resin tags, which could mean mineralisation of these channels, hence preventing resin infiltration. The presence of CPP-ACP on the dentine surface, therefore, may compromise bonding effectiveness of etch-and-rinse adhesive system. However, CPP-ACP application may be beneficial to the dentine bonding of self-etch adhesive system, as the chemical interactions between calcium and functional monomers of the adhesives might be enhanced to some degree.