Fracture toughness of a ceramic–resin interface

Objectives The purpose of this study was to compare the interfacial fracture toughness of smooth and roughened ceramic surfaces bonded with a luting resin using an optimized method of silane treatment. Methods Ceramic discs were prepared with four different surface preparations (n = 20) consisting of (1) polished, (2) gritblasted, (3) hydrofluoric acid etched and (4) gritblasted and etched. The ceramic discs were then covered by a PTFE tape with a chevron shaped circular hole. The exposed surfaces were treated by an optimized silane treatment followed by an unfilled resin and then a luting resin. Specimens were then stored in distilled water at 37 °C for (A) 24 h and (B) 30 days. The interfacial fracture toughness was measured, the mode of failure and fracture surfaces were also examined under a stereo-zoom microscope and a scanning electron microscope. Results One-way ANOVA showed that there was no statistically significant difference in the mean interfacial fracture toughness for groups A1–A4 (P > 0.05). However, the mean interfacial fracture toughness for group B1 was significantly different from that for groups B2, B3 and B4 (P < 0.05). Independent-samples t-test results showed that there was a significant increase in the GIc mean value for groups B2 and B3 after 30 days water storage (P < 0.05). The modes of failure were predominantly interfacial or cohesive within the resin. Significance It can be concluded that micro-mechanical retention by gritblasting the ceramic surfaces could be sufficient with no need for HF acid etching the ceramic surfaces when an appropriate silane application procedure is used.