Evaluation of the tensile bond strength of 3D printed restorative resin and resincement

Objectives: This study aimed to evaluate the effects of mechanical surface roughness and chemical adhesives on the tensile bond strength between 3D printed resin (TC-80DP, Graphy, Seoul, Korea) and resin cement (RelyXTM Ultimate). Methods: Resin blocks were printed using DLP technology and subjected to mechanical surface treatment with 50 μm and 110 μm alumina abrasive particles at various pressures (0.05–0.3 MPa) and chemical surface treatment with Monobond N and Single Bond Universal. Surface roughness was measured using Ra, and tensile bond strength was tested using a universal testing machine. Results: The results showed that surface roughness values between 1–2 μm (Ra) were obtained at 0.2 MPa pressure, with the highest tensile bond strength (38.4 ± 7.0 MPa) observed in the 0.2 MPa-MB&SB group. Statistically significant differences in bond strength were found between groups (p < 0.05). Weibull analysis revealed a Weibull modulus of 5.948 in the 0.2 MPa-MB&SB group, indicating low variability in bond strength. SEM analysis of fracture surfaces revealed cohesive fractures in the resin matrix in the #600 SiC polished group, while mixed fractures (sandblasted interface and cohesive resin cement fractures) were observed in the 50 μm alumina-treated group. Conclusions: These findings suggest that the surface treatment strategy combining alumina sandblasting with Monobond N and Single Bond Universal may provide an effective approach for improving the bond strength of 3D printed resin restorations to resin cement, showing potential for clinical applications in restorative dentistry.