Effect of ER:YAG Laser Irradiation on the Load-Bearing Capacity and Reliability of All-Ceramic Zirconia Crowns

Background: This study evaluated the effect of Erbium:Yttrium–Aluminum–Garnet (Er:YAG) laser irradiation on the fracture load, failure mode, and reliability of monolithic and porcelain-veneered zirconia crowns. Methods: Monolithic ultra-translucent zirconia crowns (5YZ-M, n = 30) and porcelain-veneered zirconia crowns (3YZ-V, n = 30) were divided into control (Ctrl-no surface treatment) and Er:YAG laser irradiation (Las) groups (n = 15). Las was performed on the cementation surface (250 mJ, 10 Hz, 2.5 W for 30 s). Crowns were adhesively cemented onto dentin-analog abutments and subjected to compressive load-to-failure testing. Data were analyzed by two-way ANOVA, Tukey’s post hoc test, and Weibull analysis (α = 0.05). Fractographic analysis was performed. Results: Laser irradiation did not affect the fracture load (p = 0.183). Monolithic crowns (5YZ-M) showed significantly higher fracture load than veneered crowns (3YZ-V) (p < 0.001). There was no effect of the interaction between factors (p = 0.150). The m-values were similar among groups, while the L0 of 3YZ-V-Ctrl was significantly lower than that of 5YZ-M. Veneered restorations predominantly showed chipping and delamination; whereas, monolithic crowns mainly exhibited catastrophic failures. Fracture origins were mostly located at the occlusal loading area. Conclusions: Er:YAG laser irradiation of the cementation surface did not affect the load-bearing capacity or structural reliability of zirconia crowns.