Fracture resistance of teeth restored with onlays of three contemporary tooth-colored resin-bonded restorative materials

Statement of problem. There are uncertainties regarding the use of large indirect composites and ceramics in the restoration of posterior teeth. Purpose. This study investigated the fracture resistance of teeth restored with restorations of 3 contemporary resin-bonded tooth-colored materials placed in a standardized onlay preparation. Material and methods. A random sample of preparations for tooth-colored onlays was obtained from a full service dental laboratory. A preparation was then duplicated in 30 natural teeth by copy milling. An additional 10 teeth were not prepared, and acted as a control. Ten onlays of each of the 3 materials (Belle Glass, SR Isosit, and Empress) were produced and resin bonded into place according to the manufacturers' instructions. The restorations were compressively loaded to fracture and the mode of failure recorded. Results. The fracture resistances obtained for the teeth restored with the composite material (mean 1.56 kN; SD 0.54) were greater than those obtained for the teeth restored with the ceramic material (mean 0.99 kN; SD 0.49) and the fiber-reinforced composite material (mean 0.99 kN; SD 0.56). Conclusion. Teeth restored with composite onlay restorations demonstrated a higher fracture resistance than equivalent sized onlay restorations produced from fiber-reinforced composite or a ceramic material. Failure under compressive loading may be found to be less catastrophic when a fiber-reinforced composite rather than a composite or ceramic material is used.