Fatigue Resistance of Defective Teeth restored with fiber-post-core crowns

Objective: To study effects of different defects in root-canal wall and three types of resin cements on fatigue resistance of anterior teeth reconstructed with prefabricated fiber-post-and-core crowns. Methods: Thirty extracted maxillary central incisors were removed crowns. Roots were created intracanal wall defects and divided into 5 groups (n=6), G1: slight canal wall defect (control group), G2: moderate canal wall defect, G3, G4 and G5: severe canal wall defect. Specimens were restored with prefabricated fiber-posts, composite core material and PFM crowns without ferrule effect. Prefabricated fiber-posts were cemented with Rely X Unicem in G1, G2, and G3, with Panavia F in G4, and with Super-Bond C&B in G5 respectively. All specimens were underwent thermocycling and dynamic mechanical loading for simulating 5-year service. And then survival specimens were further loaded to fracture using a universal testing machine. Two specimens of G3, 4, and 5 were randomly selected for observations with SEM. The data of load times in nonnormal distribution was statistically analyzed with Kruskal-Wallis test. Results: There were significant differences in load times among G1, G2 and G3 (P<0.05). Four specimens of G1 withstood 5-year load, one in G3, but none in G2. The mean residual fracture strength of G1 was 383.80N. Comparing the specimens with severe canal wall defect, the load times of G5 was significantly more than those of G3 and G4 (P<0.05), being 1.2 million times. The mean residual fracture strength of G5 was 657.51N. SEM analysis indicated that there were more resin tags observed in intracanal wall of G5 than those in G3 and G4. Conclusions: The defective teeth restored by prefabricated fiber posts cemented with Super-Bond C&B presented significantly high fatigue resistance. The restored teeth with moderate canal wall defect showed lower fatigue resistance than those with slight and severe canal wall defects.