Abstract
Objective: To evaluate the effectiveness of different bonding protocols in enhancing the bond strength between 3D-printed titanium and 3D-printed denture base resin, compared with conventional cast titanium bonded to heat-polymerized denture base resin. Methods: Titanium discs (10 × 2.5 mm) and denture base resin cylinders (5 × 5 mm) were fabricated using both conventional and 3D-printing techniques. The control group comprised heat-polymerized resin bonded directly to cast titanium. Three bonding protocols were evaluated for 3D-printed titanium bonded to 3D-printed denture base resin (n = 20): The first protocol involved direct bonding with 3D-printed resin without surface pretreatment (Group N-ST). The second protocol consisted of airborne-particle abrasion with 50-μm aluminum oxide followed by application of a 10-MDP primer prior to bonding with 3D-printed resin (Group MP-ST). The third protocol included airborne-particle abrasion with 50-μm aluminum oxide followed by application of a silane-based primer and cementation (Group SP-ST). Half of the specimens from each group (n = 10) were subjected to thermocycling (10,000 cycles). All specimens were subjected to shear bond strength testing. Failure mode analysis and interfacial morphology evaluation were subsequently performed. Surface characterization of the titanium substrate, including surface roughness (Ra) and wettability (contact angle,°), was conducted on specimens treated according to the same bonding protocols (n = 10). Data were analyzed using binomial logistic regression and two-way ANOVA, followed by Tukey's post hoc test. Failure mode distribution was assessed using Fisher's exact test (α = 0.05). Results: SP-ST exhibited the highest bond strength (in MPa) both before and after thermocycling (p < 0.05). MP-ST showed bond strength values comparable to those of the control group, both without and with thermocycling. In contrast, N-ST demonstrated the lowest bond strength values before and after thermocycling, along with a higher incidence of mixed failures. N-ST showed greater surface roughness and lower wettability compared to cast titanium. MP-ST improved surface characteristics, while SP-ST resulted in values comparable to cast titanium. Conclusions: The combination of airborne-particle abrasion with 50-μm aluminum oxide, a silane-based primer, and resin cement was the most effective bonding protocol for enhancing the bond strength between 3D-printed titanium and denture base resin. Clinical relevance: For prosthodontic applications involving 3D-printed titanium frameworks, the use of airborne-particle abrasion with 50-μm aluminum oxide followed by a silane-based primer and resin cement provides a predictable bonding strategy that may enhance the longevity of denture base–titanium interfaces.