Effect of casein phosphopeptide-amorphous calcium phosphate on the stability of resin-dentin bonds against pH cycling

To investigate the effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on the stability of resin-dentin bonds against pH cycling. Resin-bonded dentin specimens were prepared following manufacturers' instructions, and randomly divided into 3 groups. Among them, 2 groups experienced pH cycling, in which specimens applied CPP-ACP or distilled and deionized water (DDW) on the bonding interface, respectively. Microtensile bond strength (muTBS) testing, failure mode analysis, micromorphological and nanoleakage evaluation of bonding interface and elemental analysis within hybrid layer were performed after 15 days pH cycling. The other group was tested immediately after specimens' preparation without pH cycling. No significant differences were found in muTBS between no pH cycling and pH cycling/CPP-ACP group. Their muTBS were both significantly higher than that of pH cycling/DDW group (P < 0.05). Mixed fractures were the most prevalent failure mode. The quality of hybrid layer in pH cycling/CPP-ACP