Experimental silane primers improve adhesion to 3D-printed resin-based composite materials for definitive dental restorations

This study aimed to characterize 3D-printed resin-based composites (3D-RBCs) for definitive restorations, and to evaluate the effect of experimental γ-methacryloxypropyltrimethoxysilane (γMPTS) primers on the adhesion strength of 3D-RBCs. The microstructure, elemental composition, degree of conversion (DC), and Vickers microhardness (HV) of Ceramic Crown, SprintRay, LA, USA and VarseoSmile Crown plus, Bego, Bremen, Germany were determined. Two experimental primers were prepared by mixing a 10 wt% γMPTS solution with either 2 wt% acetic acid (AA), Exp-1 (γMPTS + AA) or 3 wt% 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP), Exp-2 (γMPTS + 10-MDP). The hydrolysis of γMPTS was validated by FTIR analysis. The tensile bond strength (TBS) of a dual-cure resin cement to Ceramic Crown and VarseoSmile Crown plus was evaluated after priming with Exp-1 or Exp-2, while 3M™ RelyX™ Ceramic Primer, Solventum, St. Paul, MN, USA was used as the positive control, and no priming was the negative control. The 3D-RBCs exhibited a heterogeneous microstructure, particularly in filler content and particle size. The DC (Ceramic Crown, 75.58 ± 7.2%; VarseoSmile Crown plus, 83.21 ± 9.22%) and HV (Ceramic Crown, 40.60 ± 2.74; VarseoSmile Crown plus, 42.72 ± 3.28) did not differ significantly between the two 3D-RBCs. γMPTS hydrolysis after mixing with AA or 10-MDP was confirmed by a reduction in the peak intensity at 2840 cm −1 and 1079 cm −1 . The two experimental primers yielded significantly higher TBS than 3M™ RelyX™ Ceramic Primer, indicating their superior priming efficiency for 3D-RBCs. The TBS of Ceramic Crown and VarseoSmile Crown plus did not significantly differ. The 3D-RBCs tested showed adequate DC; however, their HV was suboptimal.