Effect of different bonding agents and airborne-particle abrasion on shear bond strength and mode of failure between 3D-printed denture tooth-colored specimens and 3D-printed denture bases

Background In conventionally fabricated dentures, debonding between the denture teeth and the denture base accounts for 22 to 30% of all denture repairs, with failures predominantly occurring in the anterior region. Various surface treatments and bonding protocols have been proposed to enhance adhesion between denture teeth and denture base; however, reliable bonding between three-dimensional (3D)-printed denture teeth and denture bases remains a challenge, and evidence regarding the influence of bonding strategies and surface treatment protocols is limited. Methods 3D-printed tooth-colored and denture base specimens ( n = 72) were fabricated and allocated into 3 bonding agent groups ( n = 24); in each group, the tooth-colored specimens were subdivided into two subgroups. In subgroup A, the undersurface of the tooth-colored specimens was air-abraded, while in subgroup B, it remained untreated. The bonding agent in the first group was 3D printing denture base liquid resin; in the second group, a universal adhesive; and in the third group, a resin cement. All the specimens were subjected to thermocycling for 5000 cycles, after which shear bond strength was evaluated using a universal testing machine. The mode of failure was evaluated under a stereomicroscope. Two-way analysis of variance was used to assess the effect of the bonding agents, surface treatment, and their interactions. Pairwise comparisons were performed utilizing pairwise t-tests with Bonferroni correction. Failure mode distributions were evaluated using the Fisher’s exact test. Results The null hypothesis was partially rejected. Two-way ANOVA revealed significant main effects of bonding agent ( P < 0.001); neither surface treatment ( P = 0.881) nor the bonding agent-surface treatment interaction ( P = 0.146) reached statistical significance. The highest shear bond strength was reported in the liquid resin subgroups 9.04 ± 2.27 and 8.39 ± 2.12, and the lowest shear bond strength was in the resin cement subgroups 5.12 ± 1.75 and 4.27 ± 1.46. Airborne-particle abrasion had no significant effect within any individual bonding agent ( P = 0.438, P = 0.130, P = 0.315, respectively). Failure mode distribution differed significantly among the bonding protocols with and without air abrasion ( P < 0.001). Airborne-particle abrasion significantly altered failure mode distributions for liquid resin ( P < 0.001) and universal adhesive ( P = 0.001), but not for resin cement. Conclusions Under the tested conditions, liquid resin showed higher mean shear bond strength than universal adhesive and resin cement for bonding 3D-printed denture tooth-colored specimens and denture base, with a predominant cohesive failure mode. The effect of airborne-particle abrasion of the tooth-colored specimen-bonding surface did not significantly change shear bond strength within any individual group, but, resulted in a statistically significant change in failure mode for both the liquid resin and universal adhesive bonding protocols.