Impact of different surface conditioning protocols on fracture resistance of monolithic zirconia vonlay restorations

Background The purpose of this study was to evaluate and compare the influence of three different surface conditioning protocols on the fracture resistance of maxillary premolars restored with monolithic multilayer zirconia vonlay restorations fabricated from two zirconia materials. Methods Forty-eight maxillary premolars were prepared for zirconia vonlay restorations and allocated to two groups ( n = 24) according to zirconia type: Group I (C): Cercon xt ML, and Group II (K): KATANA YML. Each group was further divided into three subgroups ( n = 8) based on surface treatment: subgroup (A): airborne particle abrasion; subgroup (L): Er: YAG laser; and subgroup (E): hot chemical etching. Following cementation, all specimens were subjected to 10,000 thermocycles. Axial loading was applied using a universal testing machine. Data were analyzed using two-way ANOVA and Bonferroni’s post-hoc test, with one-way ANOVA conducted for each factor. Results Two-way ANOVA demonstrated that the surface treatment had a significant effect on fracture resistance ( P < 0.0001), whereas the main effect of zirconia material was not statistically significant ( P = 0.229). The hot chemical etching KATANA YML subgroup recorded the highest mean values, 1476.25 (177.33) N, while the airborne particle abrasion and Cercon xt ML subgroup showed the lowest mean values, 1053.33 (172.78) N. Conclusion The fracture resistance values of both zirconia materials were within the accepted range for clinical application. Hot chemical etching resulted in significantly higher fracture resistance than airborne particle abrasion and Er: YAG laser treatment, while no significant difference was found between the two zirconia materials.