In vitro fracture resistance of fiber reinforced cusp-replacing composite restorations

摘要

Objectives. To assess the fracture resistance and failure mode of fiber reinforced composite (FRC) cusp-replacing restorations in premolars. Methods. Forty-five extracted sound upper premolars were randomly divided into three groups. Identical MOD cavities with simulated buccal cusp fracture and height reduction of the palatal cusp were prepared. In Group A two layers of resin impregnated woven continuous FRC (EverStick Net) were applied. In Group B one-layer of unidirectional continuous FRC (EverStick) was used. In Group C no fibers were applied (control). Subsequently, all teeth were restored with resin composite (Clearfil Photo Posterior), subjected to thermocycling (6000x5-55℃) and static load tests. Load until fracture was registered for each tooth. Simultaneously, fracture propagation was monitored using acoustic emission analysis (AE). Failure modes were visually assessed. Results: Weibull analysis revealed a characteristic strength and Weibull modulus (m) at 2364.8 N for Group A (m = 8.9), 2437.9 NforGroup B (m = 5.9) and 2160.3 N for Group C (m = 13.6). Fracture loads were not significantly different (ANOVA, p > 0.05). Teeth with FRC showed less fractures,below the cemento-enamel junction (CEJ) (38% and 23% for Groups A and B, respectively) than teeth without FRC (93%) (chi-square, p < 0.05). The control group showed the least AE energy signals. Significance. The results suggest that glass FRC does not increase fracture load of premolars with cusp-replacing restorations. However, FRC has a beneficial effect on the failure mode. Woven fibers give more consistent results than unidirectional fibers.