Fractographic analyses of failed one-piece zirconia implant restorations

Promising results of initial clinical trials with yttria-stabilized zirconia have led to more extensive use of zirconia in dental implant superstructures. The applications have extended to abutments and complex individually designed crown-abutment one-piece structures. Little is known about their clinical success and the primary cause of failures.

The aim of this study was to identify the cause of fracture of retrieved implant-retained one-piece prostheses that failed during clinical use.

Nine fractured restorations were analyzed with fractographic methods and their fracture origins were identified.

All but two of the fractures originated in an area of tight contact between the implant or titanium screw and the abutment base. Results of the evaluation showed that zirconia-based implant restorations with very thin walls in the region connecting the prosthesis to the implant are vulnerable to damage from the screw retaining process and fracture from non-axial loads. Two restorations failed due to veneer fractures.

The findings suggest that large crowns on narrow implants or implants with internal fixation should preferably not be made with zirconia abutments, or that a new design approach should be considered.