Evaluation of the Bonding Performance of a New Universal Adhesive to Artificially Created Caries-Affected Dentin

This study aimed to evaluate the bonding performance of a newly developed universal adhesive, Scotchbond Universal Plus, to artificially created caries-affected dentin compared to sound dentin. Bovine teeth were used to prepare specimens with either sound dentin or caries-affected dentin, which was induced by 14 cycles of alternating demineralization and remineralization using a pH-cycling model. Forty specimens were randomly divided into four groups according to the dentin substrate condition and the type of adhesive used. The adhesives were applied according to the manufacturer’s instructions, followed by composite resin restoration. Shear bond strength was measured using a universal testing machine, and the resindentin interface was analyzed by scanning electron microscopy. The mean shear bond strength of Scotchbond Universal Plus was 37.32 ± 3.28 MPa on sound dentin and 31.21 ± 2.97 MPa on caries-affected dentin, while that of Single Bond Universal was 36.63 ± 3.93 MPa and 25.32 ± 4.67 MPa, respectively. There was no significant difference between the two adhesives on sound dentin (p = 0.621), but Scotchbond Universal Plus exhibited significantly higher bond strength than Single Bond Universal on caries-affected dentin (p = 0.008). Scanning electron microscopy and quantitative analysis revealed that Scotchbond Universal Plus produced longer and more abundant resin tags and a thinner adhesive layer compared to Single Bond Universal in caries-affected dentin. These outcomes may be attributed to the lower viscosity of the new adhesive, which facilitated improved infiltration. Within the limitations of this in vitro study, the new universal adhesive demonstrated enhanced bonding performance to caries-affected dentin and may offer clinical advantages for restorative procedures involving demineralized dentin. Further clinical investigations are necessary to validate its long-term effectiveness under natural caries conditions.