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
Rafat Sasany, Sultan Merve Uçar, Seyed Ali Mosaddad, Verónica Alonso
Abstract
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.