Fracture resistance of different characteristics posts: material, configurations and lengths

Objective:The purpose of this study was to evaluate the in vitro fracture resistance of roots with glass-fiber and metallic cast post varying the lengths and the geometric configuration, using the compression test. Methods:Eighty caries-free maxillary canines had their crowns sectioned and the radicular canals endodontically treated. The roots were embedded in acrylic resin, except for the 4 mm of cervical area. The specimens were divided into four groups: I - conical metallic cast posts (n= 20); II - cylindrical metallic cast posts (n= 20) III - glass-fiber tapered posts (n= 20) and IV - glass-fiber cylindrical posts (n= 20). Each group was divided into 2 subgroups according to the post length: A - 10 mm (n= 10) and B - 8 mm (n= 10) and the post spaces were opened with cylindrical and conical burs at low speed attached to a surveyor. Metallic cast crowns were made and cemented with zinc phosphate. The resin/dentin blocks were positioned in the Instron 4444 Universal Machine and using a rectangular tip with round edge, in an angle of 135o in relation to the root long axis, the specimens were subjected to increasing compressive load at a speed of 1 mm/min until fracture. Results:The ANOVA analysis indicated significant differences (p<.05) between post types: metal cast (0.66kN) and fiberglass (0.77kN) between the geometric configurations: cylindrical (0.80kN) and conical (0.62kN) and between the lengths: 10 mm (0.77kN) and 8 mm(0.65N. Conclusion:It was concluded that the different materials used in the composition of the posts and the different lengths and geometric configurations may interfere with the fracture resistance of roots.