Objective: Durable adhesion under different conditions is one of key requirements for successful crown cementation. This study investigated the impact of thermal cycling on adhesion to dentin for various resin-modified glass-ionomer (RMGI) cements. We studied three commercial cements, RelyX Luting (RLC, 3M ESPE), RelyX Luting plus (RLP, 3M ESPE), FujiCEM Automix (FC-AM, GC), and one experimental auto-mix cement (ExpC-AM, 3M ESPE). RLC is powder/liquid system while others are paste/paste system. Method: Potted bovine teeth were ground to dentin using 320 grit SiC paper and Teflon molds were clamped onto them. Ten Molds were filled with each of cements and conditioned in 37oC 95% relative humidity chamber for 2 hrs followed by storage in 37oC de-ionized water for 22 hrs before testing. Thermal stressing was conducted for up to 6550 cycles. Each thermal cycle was carried out by immersing the cement/tooth in 5oC water for 20 s followed by a 20 s immersion at 55oC. Notch-Edged shear method was performed on an Instron tester. Results: Mean values including standard deviations are summarized below:
Cement | Format | Adhesion Initial (MPa) | Adhesion after 2500 cycles (MPa) | Adhesion after 6550 cycles (MPa) |
RLC | Powder/Liquid Hand mix | 6.5(2.8) | 8.5(3.1) | 6.7(5.4) |
FC-AM | Paste/Paste Auto-mix | 2.7(2.9) | 1.5(1.9) | 1.2(1.9) |
FC-AM with conditioner | Paste/Paste Auto-mix | 5.0(2.3) | 1.5(2.6) | 1.5(2.1) |
RLP | Paste/Paste Hand mix | 7.6(1.7) | 8.8(2.7) | 9.2(1.3) |
ExpC-AM | Paste/Paste Auto-mix | 5.8(1.4) | 6.4(1.7) | 7.2(2.5) |
Conclusions: This investigation observed 60% adhesion failures for FC-AM with or without Fuji Plus conditioner during thermal cycling while there was no failure for RLC, RLP, ExpC-AM cements. ANOVA analysis was performed at p < 0.05. There were significant differences between FC-AM (with or without the conditioner) and other cements after 2500 or 6550 thermal cycles. There were no significant adhesion difference among RLC (powder/liquid), RLP (paste/paste), and ExpC-AM (auto-mix) cements before and after thermal cycling.