Fiber-reinforced composite substructure: load-bearing capacity of an onlay restoration.

OBJECTIVE To determine the static load-bearing capacity of composite resin onlay restorations made of particulate filler composite (PFC) with two different types of fiber-reinforced composite (FRC) substructures. MATERIAL AND METHODS Specimens were prepared to simulate an onlay restoration, composed of a 2 to 3 mm FRC layer as the substructure (short random and continuous bidirectional fiber orientation) and a 1 mm surface layer of PFC. Control specimens were prepared from plain PFC. The specimens were incrementally polymerized with a hand-light curing unit for 40 s and then post-cured in a light-curing oven for 15 min. The specimens were cemented on dentin substrate of extracted human molars using a standard adhesive resin cementation technique. The specimens (n=8/group) were water stored either for 24 h at room temperature or for 4 weeks at 37 degrees C before they were statically loaded until fracture using a universal testing machine. Failure modes were visually examined. RESULTS ANOVA revealed that all specimens with FRC substructures had higher values of static load-bearing capacity than those obtained with plain PFC (p<0.001). The load-bearing capacity of all the specimens decreased after water storage (p<0.001). CONCLUSIONS Restorations made from a combination of FRC and PFC showed better load-bearing capacity than those obtained with PFC alone.