Effect of anodization on metal-ceramic bond strength of titanium manufactured by selective laser melting: an in vitro study

Titanium is used in metal-ceramic restorations due to its biocompatibility and cost-effectiveness, yet concerns persist regarding veneering ceramic debonding. This is largely attributed to titanium’s high elasticity and the formation of a thick, poorly adherent oxide layer. Anodization and additive manufacturing (SLM) have been proposed to improve titanium’s surface characteristics and bonding performance. This in vitro study aimed to evaluate the effect of anodization on the metal-ceramic bond strength of 3D-printed titanium compared to non-anodized titanium and cobalt–chromium (CoCr) alloy. Thirty metal plates (10 CoCr, 10 non-anodized titanium, 10 anodized titanium) were fabricated using selective laser melting (SLM). SEM-EDS analysis was performed on the metal plates to evaluate surface composition and morphology. Veneering process and the subsequent mechanical testing followed ISO 9693-1:2019 standards. Bond strength was measured using a universal testing machine, and data were statistically analyzed via one-way ANOVA and Tukey HSD post hoc test (α = 0.05). The anodized group showed higher bond strength (59.26 ± 4.19 MPa; 95% CI: 56.9–61.6) compared with non-anodized titanium (54.37 ± 4.13 MPa; 95% CI: 52.6–56.1; p = 0.034, mean difference 4.89 MPa, Cohen’s d = 1.18). Cobalt–chromium outperformed both titanium groups (86.81 ± 3.72 MPa; 95% CI: 84.8–88.8; p < 0.001). Although the anodization effect reached statistical significance, the ≈ 5 MPa difference is unlikely to be clinically meaningful according to ISO 9693 and prior clinical benchmarks. Anodization enhances the bonding performance of 3D-printed titanium but does not match the strength of conventional CoCr frameworks. When titanium is selected for metal-ceramic systems, especially in high-load cases, a bulkier framework design is recommended to minimize the risk of framework flexibility and failure.