Impact Strength of Fractured-Teeth Submitted to Different Techniques of Fragment-Reattachment

Objectives: The aim of this study was to evaluate the effect of different materials and reattachment techniques on impact strength of 90 bovine incisors. Methods: Standardized fragments were obtained when 80 crowns was sectioned 12 mm from the incisal edge. Teeth were mounted in PVC rings, embedded in acrylic resin and distributed in 9 groups (n=10): G1– Direct bonding (DB) + Single Bond (SB) + Filtek Z350 Flow (FF); G2– DB + Clearfil SE Bond (CSE) + FF; G3- DB + SB + Rely X ARC (RX); G4– DB + CSE + RX; G5– Circumferential Chamfer (CC) + SB + FF; G6– CC + CSE + FF; G7– CC + SB + RX; G8– CC + CSE + RX and G control (sound teeth). Circumferential Chamfer was prepared after the bonding of the fragment by means of a spherical point and filled with the composite Filtek Z250. Impact strength was evaluated in a universal testing machine Instron. A compressive load was applied at a crosshead speed of 500mm/min on the buccal surface, 2 mm from the incisal edge. Data were submitted to ANOVA and Ryan-Einot-Gabriel-Welsch Multiple Range test (p<0.05). Results: The results (Kgf) were: G control– 64.8; G7– 43.36; G5– 37.82; G6– 37.44; G8– 26.68; G1– 26.48; G3– 23.59; G4– 17.55; G2– 12.42. The fragment reattachment using CC was significantly superior to DB. The use of SB significantly increased the impact strength when compared to the use of CSE. There was no significant difference among RX and FF. Conclusions: No technique or material, when individually considered, was capable of achieving the mechanical strength of the sound teeth. Only the association of reattachment technique CC with bonding system SB was capable of giving back to the restored teeth the impact strength shown by the sound teeth.