RESUMO
STATEMENT OF PROBLEM: Whether direct coronal restorations of endodontically treated teeth with short fiber-reinforced composite combined with polyethylene fibers provide adequate mechanical strength is unclear. PURPOSE: The purpose of this in vitro study was to compare the fracture strength of endodontically treated premolars with standardized mesio-occluso-distal (MOD) preparations restored with short fiber-reinforced composite (SFRC) combined with polyethylene Ribbond fibers (PRFs). MATERIAL AND METHODS: A total of 40 premolars were selected and distributed into 4 groups (n=10) as follows: group restored with SFRC (EverX Posterior), group restored with PRF (Ribbond fibers), and group restored with the combination PRF+SFRC, all followed by a conventional composite resin (IPS Empress Direct). MOD preparations and endodontic treatments were prepared except in the control group (intact teeth). MOD preparations and endodontic treatments were prepared except in the control group (intact teeth). Specimens were loaded using a universal testing machine until fracture occurred at a crosshead speed of 0.5 mm/min, and the failure type and fracture patterns was reported descriptively. The mean values of the groups were analyzed by using the Shapiro-Wilk test and 1-way ANOVA tests (α=.05). RESULTS: Restoration with PRF+SFRC provided the highest mean ±standard deviation fracture resistance (288.2 ±73.5 N). Restoration with just PRF had the lowest values (192.4 ±25.4 N), which were statistically different from those of SFRC and PRF+SFRC (P<.05). The predominant mode of failure was mixed, and all fracture patterns were favorable. CONCLUSIONS: Reinforcing endodontically treated premolars with MOD cavities with Ribbond fibers followed by a conventional composite resin enhanced fracture resistance and may be suitable for the direct coronal restoration of large posterior cavities in stress-bearing areas.