Optimizing adhesive protocols for CAD-CAM restorations: Is simplification a reliable alternative to conventional silane application?

PURPOSE: study compared the bond strength and surface morphology of CAD-CAM restorative materials treated with different silane-based strategies, evaluating the influence of material type and artificial aging. MATERIALS AND METHODS: Five CAD-CAM materials were evaluated: leucite-reinforced glass ceramic (LEU), lithium disilicate (LDS), zirconia-reinforced lithium silicate (ZLS), polymer-infiltrated ceramic network (PICN), and resin nanoceramic (RNC). A total of 315 specimens (63 per material) were assigned to five groups: conventional silane application (G1, positive control), silane-containing universal adhesive (G2), single-step cementation with silane-containing self-adhesive resin cement (G3), self-etching ceramic primer (G4), and no silane application (G5, negative control). Two resin cylinders were bonded to each specimen and tested either immediately or after 10,000 thermal cycles. Micro-shear bond strength testing was performed, failure modes were analyzed microscopically, and representative specimens were examined by scanning electron microscopy. Statistical analysis was conducted using linear mixed-effects models with post-hoc Tukey tests and planned contrasts (α = .05). RESULTS: < .001). The conventional protocol (G1) consistently yielded the highest values across all materials, while negative controls showed the lowest. Simplified strategies demonstrated intermediate values that were generally lower than G1 but remained within clinically acceptable ranges (15 - 25 MPa). Thermal cycling reduced bond strength in all groups, although the relative ranking of protocols was preserved. SEM analysis revealed material-dependent surface characteristics. CONCLUSION: The conventional three-step silane protocol remains the most reliable approach for durable bonding, while simplified strategies may represent acceptable alternatives depending on the material.