Initial Bonding Performance to CAD/CAM Restorative Materials: The Impact of Stepwise Concentration Variation in 8-Methacryloxyoctyl Trimethoxy Silane and 3-Methacryloxypropyl Trimethoxy Silane on Feldspathic Ceramic, Lithium Disilicate Glass-Ceramic, and Polymer-Infiltrated Ceramic

This study investigated the effects of varying concentrations of two distinct silane agents, 8-methacryloxyoctyl trimethoxy silane (8-MOTS) and 3-methacryloxypropyl trimethoxy silane (γ-MPTS), on their initial bonding efficacy to feldspathic ceramic (FC), lithium disilicate glass-ceramic (LD) and polymer-infiltrated ceramic (PIC) specimens, in 10% increments for concentrations ranging from 10% to 40%. Shear bond strengths between the ceramic substrates and the luting material were assessed following 24 h incubation in distilled water. For FC, the median value of shear bond strength peaked at 20% of γ-MPTS (7.4 MPa), while 8-MOTS exhibited a concentration-dependent increase, reaching its highest value at 40% (13.1 MPa). For LD, γ-MPTS above 10% yielded similar strength median values (10.2 MPa), whereas 8-MOTS at 30% (15.8 MPa) and 40% (13.4 MPa) yielded higher strength values than at 10% (2.9 MPa) and 20% (4.1 MPa), with the highest median value exhibited at 30%. For PIC, both γ-MPTS and 8-MOTS demonstrated similarly low bond strength values which were not significantly different from the non-silane-treated specimens. When applied on silica-based FC and LD, silane revealed a concentration-dependent bonding effect, with 8-MOTS exhibiting superior bond strength to γ-MPTS. However, PIC, characterized by a high inorganic filler content, demonstrated limited bondability with both silanes.