Effects of Luting Cements and Surface Conditioning on Composite Bonding Performance to Zirconia.

Abstract

This study compared bond strength, durability, and mechanical properties of luting cements for bonding zirconia: a resin-modified glass ionomer cement (RMGIC), a conventional composite cement, and two self-adhesive composite cements. The air-abraded zirconia specimens were assigned to 12 groups (n = 30) to prepare bonded specimens. Classification was based on the pre-conditioning selection: none; primers containing 10-methacryloyloxydecyl dihydrogen phosphate (MDP); universal adhesives containing MDP. Further classification was done according to the type of luting cement: RMGIC; conventional composite cement; MDP-free self-adhesive composite cement; MDP-containing self-adhesive composite cement. The shear bond strength (SBS) was measured after 24 h of water storage or aging with 20,000 thermocycles plus an additional 60 days of water storage at 37°C. The elastic modulus and three-point bending strength were determined, and a related Weibull analysis of the four luting cements was performed. The choice of luting cement and aging significantly affected the SBS. Aging decreased the SBS in most groups, except for those that used MDP-containing primers plus conventional composite cements. RMGIC had SBS (before and after aging) that were similar to the MDP-free self-adhesive composite cement. Use of MDP-containing products prior to conventional composite cements provided the highest initial SBS. However, pre-conditioning with MDP-containing products failed to increase the SBS of RMGIC. RMGIC showed lower elastic modulus and three-point bending strength than did the three composite cements. RMGIC is an alternative to composite cements for luting zirconia restorations. Conditioning with a primer containing MDP combined with conventional composite cement is more reliable.