Repair strength of etched vs silica-coated metal-ceramic and all-ceramic restorations

The purpose of this in vitro study was to examine shear bond strengths of c omposite resin to metal-exposed porcelain-fused-to-metal (PFM) and all-cera mic restorations after silica coating or etching with 5% hydrofluoric acid (HF). Specimens were fabricated for each of the following groups: two all-ceramic materials [a feldspathic porcelain (Vita Mark II) and a leucite-reinforced glass-ceramic (IPS Empress)], and one noble metal-ceramic (Orplid Keramik I alloy; Vita VMK 68 N feldspathic veneer ceramic). These groups were repai red with resin composites after different pretreatment methods, In one meta l-ceramic subgroup the surface exhibited a 50% metal and 50% ceramic exposu re. In the silica-coating groups, the specimen surfaces were air abraded wi th silica acid-modified Al2O3 (CoJet Sand) and treated corresponding to the porcelain repair with resin composite. For control groups, the surfaces we re etched with 5% HF for 60 seconds and treated in the same way as the sili ca-coated groups. After 24 hours of storage (distilled water, 37 degrees C) and an additional 24 hours of thermocycling (1150 x 5 degrees C/55 degrees C) the specimens were debonded using a shear bond strength test (n=15). nIn all groups the silica coat repair achieved equal or significantly highe r bond strengths than did the etching technique (p<0.05, Mann-Whitney U tes t), In the metal-exposed group, the mean bond strength increased from 7.3 M Pa to 16.3 MPa following the silica-coat repair. Results indicated that sil ica coating represents a suitable treatment for the intraoral repair of the materials tested in the present study.