Fracture Resistance of Monolithic High Translucency Zirconia Implant-Supported Crowns

Aim: To evaluate the resistance to axial forces of screw-retained monolithic high translucency zirconia ( mHTZr) crowns compared with high translucency zirconia + feldspathic ceramic ( HTZrC) crowns, low translucency zirconia + feldspathic ceramic ( LTZrC) crowns, and metal-ceramic ( MC) crowns, and also to observe the different fracture patterns between all groups. Methods: Twenty-four crowns were fabricated ( 6 of each group) and loaded until failure, using a testing machine with a 5.0-kN load cell. Results: Mean fracture results varied between 1092.7 N ( LTZrC group) and 3439.7 N ( mHTZr group). No statistically significant differences were found between the HTZrC, LTZrC, and MC groups. However, statistically significant differences ( P < 0.05) were found between mHTZr and the other 3 groups. In the MC group, only chipping of the ceramic veneering occurred. In the mHTZr group, when fracturing occurred, it was of the whole structure. Finally, the LTZrC and HTZrC groups suffered both chipping and core fractures. Conclusion: High translucency monolithic zirconia implant-supported crowns proved to be the toughest group studied when an axial force was applied. Fracture patterns varied between different materials, chipping being the most common occurrence.