Does repeated autoclave sterilization cause changes in the color and fragility of fiberglass reinforced resin crowns?

BACKGROUND: Since the effects of sterilization on the Fiberglass Reinforced Resin Crowns (FRRCs) is not well-known the aim of current study was to evaluate the effects of autoclave sterilization on the fracture resistance, color stability, and surface composition of FRRCs. METHODS: A total of 48 crowns were used. The crowns were divided into three groups according to the sterilization number: no sterilization (Control Group), one sterilization (Group 1), and four sterilizations (Group 2). The microstructure of the three crowns from each group was evaluated using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) spectroscopy. Thirteen FRRCs from each group were first used for color stability testing and then for the fracture resistance analysis. One-way analysis of variance (ANOVA), one-way repeated measures ANOVA, and paired t-tests were used in the statistical analysis. RESULTS: EDX results revealed that the weight% of surface silicon atoms in group 2 was significantly higher. Some crack lines could be observed on the SEM images. Statistically significant differences were found in color stability following the first and fourth sterilization cycles (p < .01). The increase in the sterilization cycle did not statistically decrease the fracture resistance of the FRRCs (p = .055); however, overall, a decreasing trend was observed in fracture resistance as the sterilization cycle increased. CONCLUSIONS: Autoclave sterilization caused some changes in the surface elemental composition and surface morphology of FRRCs. Avoiding unnecessary FRRC trials is important to reduce the number of sterilizations.