Fracture resistance of glass-fiber and cast posts with different lengths

Objective: In this study, it was evaluated, in vitro, the resistance of fracture roots with glass-fiber and metallic intraradicular retainers with different lengths, using the compression test. Methods: Sixty caries-free superior canines had their crowns sectioned and radicular canals endodontically treated. The roots were embedded in acrylic resin, except for the 4 mm of cervical area. The prosthetic space was performed with cylindrical bur in low speed attached to a parallelometer, obtaining prepares with length of 6 mm (GI), 8 mm (GII) and 10 mm (GIII). Each group was divided into 2 subgroups according to the post material: glass-fiber posts and metallic cast posts, which were luted with Panavia F cement. Metallic cast crowns made done and cemented with zinc phosphate. The resin/dentin blocks were positioned in the Instron 4444 Universal Machine, using a rectangular tip with round edge, in an angle of 135 in relation to the root long axis and at a speed of 1 mm/min. Results: The Dunn test showed no significant difference (p>0.05) among the metallic posts of different length (6 mm – 0.91 kN, 8 mm – 0.87 kN and 10 mm – 0.74 kN). Besides in the glass-fiber post group, there weren't significant difference among posts of 8 mm (0.58 kN) length, when compared to the 6 mm (0.43 kN) and 10 mm (1.00 kN). However, the post of 6 mm were statistically different (p<0.01) when compared with the 10 mm length. Conclusion: It was concluded that the post length influenced on the fracture resistance depending on the post type.