Fatigue resistance of composite resins and glass-ceramics on dentin and enamel

Statement of problem: Composite resins and glass-ceramics are both used to restore worn teeth. Which restoration material is more durable is unclear. Purpose: The purpose of this in vitro study was to evaluate the load to failure of thin composite resins and glass-ceramic restorations on enamel and dentin under increasing repetitive loads. Material and methods: Glass-ceramic blocks (IPS e.max CAD; Ivoclar Vivadent AG) were shaped into cylinders (Ø4.0×1.0 mm), crystallized, and adhesively luted to bovine dentin and enamel substrates that were embedded in polymethyl methacrylate (n=20). Identical direct composite resin restorations (Clearfil AP-X; Kuraray Noritake Dental Inc) were made and directly applied on the same substrates (n=20). All specimens were tested in a pneumatic device with a stainless steel ball that provided a stepwise increase of the load (N) starting at 250 N and increasing by 50 N after every 10 000 cycles to a maximum of 1150 N. Failures were detected by a displacement sensor and defined by chipping of restorative material or catastrophic failure. Results: On dentin, composite resin showed a significantly higher fatigue resistance than glass-ceramic. On enamel, no significant difference was found between the 2 materials. Conclusions: When bonded to dentin, thin direct composite resin restorations were more durable than glass-ceramics. When bonded to enamel, no difference was found.