All-ceramic multi-unit implant-supported fixed dental prostheses : A prospective clinical study

The development of high-strength oxide ceramic materials has led to increased interest in all-ceramic fixed dental prostheses (FDPs). Success rates reported in clinical studies on such reconstructions are close to those of porcelain fused to metal (PFM) FDPs. These reconstructions however, are still of limited size and have so far only concerned FDPs supported by natural teeth. Objectives: The purpose of this study was to evaluate the clinical performance of mutli-unit all-ceramic FDPs supported by dental implants. Methods: Ten patients received all-ceramic FDPs designed according to the Cercon® technique and supported by four AstraTech implants in the lower jaw. Nine patients received ten-unit prostheses and one patient received a nine-unit FDP. The FDPs were cemented with Panavia F2.0 onto preparable titanium abutments. The FDPs were evaluated at baseline, twelve, twenty-four and thirty-six months. The surface and marginal integrity were rated according to the California Dental Association (CDA) quality assessment system. Results: At the three-year follow up all FDPs were in use and all patients reported that they were fully satisfied with the treatment. None of the reconstructions had fractured. Superficial cohesive, chip-off, fractures of the veneering porcelain were, however, observed in nine patients. A total of 34 of 99 units (34%) showed such chip-off fractures. Corresponding results for the twelve-month and twenty-four month follow-ups were 14% and 19% respectively. Most patients were unaware of the fractures, some fractures were adjusted by polishing but no FDPs were in need of replacement. Conclusion: Results from this three-year study suggest that multi-unit all-ceramic implant-supported FDPs designed according to the Cercon® technique may be considered a treatment alternative. Better understanding of the factors behind chip-off fractures is necessary togehter with long-term follow-up studies before the material and technique can be recommended for general use