Effect of Silane Incorporation on the Bonding Performance of Universal Adhesives to Dentin

ABSTRACT Purpose The effect of silane in universal adhesives (UAs) on dentin adhesion remains unclear. Therefore, this study evaluated the dentin bonding of UAs with and without silane immediately and after thermocycling. Materials and Methods Sixty‐four sound human molars were randomly assigned to eight groups according to silane incorporation (UAs without silane: Scotchbond Universal [SBU] and Ambar Universal APS [AUA]; and UAs with silane: Scotchbond Universal Plus [SUP] and Ambar Universal APS Plus [AUP]), bonding strategy (etch‐and‐rinse [ER] or self‐etch [SE]), and evaluation time (immediate or after thermocycling). Adhesives were applied to occlusal dentin and restored with composite resin. Resin–dentin sticks (0.8 mm 2 ) were prepared for microtensile bond strength (μTBS), nanoleakage (NL), and degree of conversion (DC). Data were statistically analyzed ( α = 0.05). Results Thermocycling significantly reduced μTBS for all adhesives ( p < 0.001), while silane incorporation had no effect ( p = 0.31). ER showed higher μTBS than SE ( p < 0.001). After thermocycling, NL was similar among adhesives in ER but differed in SE, particularly between SBU and SUP ( p < 0.001). DC was unaffected by adhesive type or bonding strategy. Conclusions Dentin bonding of UAs was mainly influenced by bonding strategy and aging, whereas silane incorporation showed a limited effect.