Effect of Thermocycling on Dentin-Resin Cement-CAD/CAM Bond Durability
Objectives: This study evaluated the dentin-resin cement CAD/CAM composite resin block (Katana Avencia, Kuraray) micro-tensile bond strength (uTBS) of four resin cements: RelyX Unicem 2 (3M ESPE), Panavia V5 (Kuraray), RelyX Ultimate Adhesive Resin Cement (3M ESPE) and Multilink (Ivoclar) subjected or not to PCR thermocycling. Methods: Human third molars were mounted indental stone, then the occlusal surface was reduced to expose superficial to middle dentin using a 55 carbide bur under copious air-water spray using an electric hand-piece at 200,000 rpm in a CNC Specimen Former. Resin cement systems were applied according to manufacturer’s instructions with their respective bonding system to the dentin surface. The bonded tooth was stored benchtop for 10-minutes before placing in neutral artificial saliva at 37°C. Each tooth was sectioned to obtain eight 1mmx1mm specimens using a water-cooled, low-speed diamond saw. Specimens were then equally and randomly distributed to 30-days water storage and a 100,000 cycles of 15°C to 45°C. Thermal treatments were continuously monitored using a data acquisition system. A crosshead speed of 1mm/min in a testing machine (Zwick/Roell) was used to obtain uTBS. Results: Statistical analysis consisted of descriptive statistics and one- and two-way ANOVA with the post-hoc Tukey-Kramer test and a two-sample t-test (alpha=0.05). The interaction between materials and thermocycling proved significant (p=0.0036). Subsequent analyses demonstrated that there was no significant difference among four types of materials with cycling (p=0.7769). For non-cycling, mean uTBS observed in Multilink was significantly lower than that observed in other three materials, while no significant difference was found between Panavia V5 and Ultimate or between Unicem2 and Ultimate. Moreover, for each resin cement, the mean uTBS observed in non-cycling group consistently displayed greater mean uTBS than the cycling group (p<0.05 in each instance). Conclusions: A simple and efficient simulated environmental challenge, using PCR thermocycling significantly lowered the uTBS for all resin cements.