Influence of Different Multilayer Zirconia Materials on the In Vitro Load‐Bearing Capacity of Resin‐Bonded Fixed Partial Dentures in the Posterior Region

ABSTRACT Objective Comparison of the load‐bearing capacity and failure pattern of posterior resin‐bonded fixed partial dentures (RBFPDs) differing in retainer design, zirconia material, and vertical nesting position. Materials and Methods RBFPDs replacing a maxillary first molar were fabricated with 2 retainer designs (inlay‐retained, IR; wing‐retained, WR) and of 2 multilayer zirconia materials (3Y‐TZP and 5Y‐PSZ, 3Y/5Y; 5Y‐PSZ, 5Y). For 3Y/5Y blanks, 2 vertical nesting positions (center; top) were evaluated. For each group, 16 monolithic RBFPDs were fabricated. Half of the RBFPDs underwent artificial aging. Load‐bearing capacity (F u ) was tested under oblique loading. The data were statistically analyzed using Welch ANOVA and Dunnett‐T3 post hoc tests ( α = 0.05). Results No decementations or defects were observed after aging. Mean F u ranged between 684 and 1216 N for IR‐RBFPDs and 1025–1617 N for WR‐RBFPDs. There was a clear hierarchy between the subgroups, with the lowest F u recorded for restorations made of 5Y zirconia and the highest F u for restorations fabricated from a centric position in 3Y/5Y blanks. Aging had no influence ( p ≥ 0.526). Conclusions Posterior RBFPDs made of multilayer 3Y‐TZP/5Y‐PSZ zirconia can be recommended for clinical trials. Vertical positioning in the blank influences the safety margin of the load‐bearing capacity. The use of 5Y‐PSZ should be critically scrutinized for this indication. Clinical Significance Posterior resin‐bonded fixed partial dentures made of monolithic zirconia (3Y‐TZP) are a valuable treatment option. The opacity of the restorations limits their esthetics. Multilayer zirconia materials with color and/or material gradient can further improve the esthetics of monolithic zirconia restorations. Resin‐bonded fixed partial dentures made of multilayer zirconia materials differing in color and/or material gradient might be a viable alternative to restorations made of 3Y‐TZP zirconia in the posterior region.