From porcelain-fused-to-metal to zirconia: clinical and experimental considerations.

OBJECTIVE The interest of dental research in metal-free restorations has been rising in the last 20 years following the introduction of innovative all-ceramic materials in the daily practice. In particular, high strength ceramics and related CAD/CAM techniques have widely increased the clinical indications of metal-free prostheses, showing more favourable mechanical characteristics compared to the early ceramic materials. The purpose of the present paper is providing a brief review on the all-ceramic dental materials, evaluating pros and cons in the light of the most recent scientific results and of the authors' clinical experience. MATERIALS A structured review of the literature was given on the basis of medical and engineering papers published in the last decades on the use of dental ceramics and zirconia in particular. The experimental and clinical findings of the most relevant researches were reported. RESULTS Zirconia is one of the most promising restorative materials, because it yields very favourable mechanical properties and reasonable esthetic. Several in vitro and in vivo investigations reported suitable strength and mechanical performances of zirconia, compatible with clinical serviceability as a framework material for both single crowns and short-span fixed partial dentures. However, clinical results are not comparable, at the moment, with conventional metal-ceramic restorations, neither is there sufficient long-term data for validating the clinical potential of zirconia in the long run. SIGNIFICANCE The use of zirconia frameworks for long-span fixed partial dentures or for implant-supported restorations is currently under evaluation and further in vivo, long-term clinical studies will be needed to provide scientific evidence for drawing solid guidelines.