Effect of Post Material and Length on Fracture Resistance of Endodontically Treated Premolars: An In-Vitro Study

Endodontically treated teeth with posts are more prone to fracture. Hence, the purpose of this study was to investigate the in-vitro fracture resistance of devitalized teeth and mode of failure restored with posts of different materials and different lengths. Sixty freshly extracted human mandibular premolars were endodontically treated and then restored with 1 of 2 prefabricated posts: Stainless-steel (SS) and glass-fiber (fiber posts [FP]) with intraradicular lengths of 4, 5 or 10 mm (n = 10). Following core restoration, a static compressive load was applied perpendicular to the long-axis of the teeth. Initial failure of each specimen was recorded in Newton. The mode of failure was also determined radiographically. The data were analyzed using two-way ANOVA and Tukey's post-hoc analysis with Bonferroni adjustment. Analysis indicated significant differences (P < 0.001) among the groups. Among the SS posts, SS/7 (246 N) exhibited the highest failure load and SS/4 (122 N) the lowest. FP/10 (140.5 N) exhibited the highest failure load among the FP and FP/4 (68.5 N) the lowest. SS posts showed post pull out, followed by core fracture while FP showed core debonding, followed by core fracture as the primary mode of failure. Fracture resistance of the teeth proportionately increased with increase in the length of FP while it decreased with that of metal post. SS posts showed greater fracture resistance than FP when 90° load was applied.