Effect of polydopamine surface treatment on the mechanical properties of zirconia and resin occlusal veneers fabricated using additive and subtractive manufacturing: An in vitro study.

OBJECTIVES

To evaluate the influence of polydopamine (PDA) treatment on bond strength, fracture, and wear resistance of occlusal veneers (OVs) fabricated using additive (AM) and subtractive manufacturing (SM) techniques.

METHODS

Three hundred twenty 0.5 mm-thick OVs were fabricated through AM and SM and from four groups of materials (n = 80): AM ceramic-filled resin (AM-C), AM zirconia (AM-Z), SM nano-ceramic resin (SM-C), and SM zirconia (SM-Z). Each group was further divided into PDA-treated and untreated subgroups (n = 40). Specimens were cemented onto resin dies using self-curing resin cement (Multilink N; Ivoclar Vivadent) and subjected to five million chewing cycles with thermal cycling. Fracture and wear resistance were assessed using a load-to-failure test and 3D surface analysis, respectively (n = 20). Additionally, bond strength was evaluated using a pull-out test (n = 20). Data were analyzed using three-way ANOVA to assess the main and interaction effects of material, manufacturing technique, and PDA treatment (α=0.05).

RESULTS

Significant main effects of manufacturing technique, material type, and PDA treatment were found for all outcomes (p<.001), along with significant manufacturing × PDA interactions. PDA notably improved fracture resistance and bond strength in AM-Z and AM-C (p<.05), but had minimal effect on SM groups. Wear was significantly reduced in AM groups following PDA (p<.001), while SM-C showed a slight increase (p=.021). Among all groups, untreated AM-C demonstrated the weakest overall mechanical performance.

CONCLUSIONS

PDA treatment enhanced fracture and bond strength in AM materials, with limited effect on SM ceramics. Milled zirconia showed the best overall performance, while untreated AM-C consistently performed the worst.

CLINICAL RELEVANCE: Polydopamine surface treatment enhances the mechanical performance of occlusal veneers fabricated by additive manufacturing, particularly improving bond strength and fracture resistance. This approach may increase the clinical reliability of 3D-printed restorations, especially in thin, conservative designs.