Microtensile bond strength testing of resin cements

To investigate the microtensile bond strength (μTBS) and failure mode of resin cements bonded to ceramic blocks following various surface treatments. Seventy-two Ceramco II (Ceramco lnc., Burlington, NJ) ceramic discs 10 mm in diameter and 4 mm thick were prepared. The ceramic specimens received 8 different surface conditions treatments before the application of resin cement. These surface treatments were sanding with 600-grit silicon carbide paper, microetching with aluminum oxide, sanding followed by silane application, microetching followed by silane application, hydrofluoric acid etching, hydrofluoric acid etching followed by silane application, application of adhesive resin, and combination of the previous two treatments (HF+S+Adh). Seventy-two extracted molars were ground flat at 90° to the long axis of the tooth until a sufficient circular area of dentin was exposed (at least 5 mm in diameter). Three resin cements were applied to these surfaces. After 24 h storage at 37 °C, the non-trimming version of μTBS test was used to produce 1 mm ² microbars. The microbars were subjected to a tensile load using a modified testing device. Data were analyzed with 2-way analysis of variance. The interaction between the substrate surface treatment and cement type is significant ( p<0.001). The results of this in vitro study suggest that when the tested ceramic restoration is cemented with a resin cement system, the ceramic should be etched with hydrofluoric acid, silane and adhesive should be applied prior to cementation. The results also suggest that an auto- or light-polymerizing cement should be considered instead of a dual-polymerizing cement.