Fracture resistance of mechanically compromised premolars restored with polyethylene fiber and adhesive materials

No previous study has tested the strength of teeth restored with a fiber post inside the root canal combined with a ribbon fiber in the crown surrounding the post. The aim of this study was to compare a new adhesive technique to other conventional techniques in the fracture resistance of endodontically treated premolars. Fifty superior premolars were divided into 5 groups (n=10), prepared as follows: intact teeth used in G1 as control; in the other experimental groups (G2, G3, G4 and G5), mesio-occlusal-distal cavities were prepared, extending toward the palatal cups (MODP), and root canal treatments were performed. Groups were restored by varying the restorative technique: G2 – only with composite resin (CR); G3 fiber post+CR; G4 – polyethylene fiber (Ribbond)+CR; and G5, fiber post+Ribbond+CR. The teeth were thermocycled 1000 times. After 24 h, the specimens were loaded in a universal testing machine until fracture, and the failure mode was checked. ANOVA and Tukey–Krammer tests were used for statistical analysis (α=0.05). Results: The fracture strength (N) of control (G1 – 410.7±106.9) was not significantly different (P>0.05) from Ribbond+CR (G4 – 300.7±80.2) and fiber post+Ribbond+CR (G5 – 377.5±107.7). Specimens restored only with CR (G2 – 177.7±52.1) and fiber post+CR (G3 – 264.6±88.5) were statistically similar (P>0.05), but both had their mean values differed from the control (P<0.05). Longitudinal and oblique crown fractures were predominant in all groups. Ribbon–fiber reinforced resin restorations provided superior fracture resistance of premolars with MODP and endodontic access cavities when compared to conventional direct techniques.