bonding between layering materials and zirconia frameworks

The availability of zirconium dioxide (zirconia) ceramics in dentistry has expanded the range of designs and applications for all-ceramic restorations and increased its popularity. This article reviews the literature on the bond strength between layering materials and zirconia frameworks used in dental restorations. Database searches were conducted for in vitro studies of bond strength between layering materials and zirconia frameworks. The search was carried out in different electronic databases, supplemented by handsearch in dental journals and by examination of the bibliographies of the retrieved articles. A variety of studies on bond strength was identified, including comparisons with metal–ceramic systems and studies on mismatched coefficients of thermal expansion, the use of press-on ceramics or liner materials, and the effect of cooling time after firing. The available data provide considerable information on achieving stable layering of material/zirconia composites. However, only a few in vitro studies on bond strength between indirect composites and zirconia were identified. Such studies and additional controlled clinical trials are needed.