Bond Performance of Four Universal Adhesive Systems on Sound and Biomimetically Remineralized Artificially Caries-Affected Dentin Before and After Artificial Aging

Background: This study evaluated the bonding performance of four universal adhesive systems applied to sound dentin (SD) and artificially caries-affected dentin subjected to biomimetic remineralization with casein phosphopeptide–amorphous calcium phosphate (CPP–ACP), before and after artificial aging. Methods: One hundred and four human molars were allocated according to dentin substrate (SD or biomimetically remineralized [BRD]), adhesive system (FuturaBond® M+, Scotchbond™ Universal, Prime&Bond Active®, and One Coat7 Universal®), and aging (24 h or 10,000 thermocycles). Artificially caries-affected dentin was produced by pH cycling and subsequently remineralized with CPP–ACP. Adhesive interface morphology was assessed by FEG-ESEM, while shear bond strength (SBS) and failure modes were also evaluated. Statistical significance was set at p ≤ 0.05. Results: Adhesive layer thickness was significantly affected by the adhesive system, dentin substrate, and aging (p < 0.001), with a significant adhesive × substrate interaction (p < 0.001). Resin tag length was affected by the adhesive system (p = 0.03), substrate (p < 0.001), and aging (p < 0.001), with significant adhesive × substrate (p = 0.03) and adhesive × substrate × aging interactions (p = 0.001). SBS was significantly higher on SD than on BRD (p < 0.001) and decreased after thermocycling (p < 0.001). Conclusions: Universal adhesives exhibited substrate- and aging-dependent behaviour. BRD showed lower SBS than SD, while morphological differences did not consistently correspond to higher bond strength. Further studies including untreated artificially caries-affected dentin are needed to determine the specific contribution of CPP–ACP remineralization.