Effect of different partial ferrule locations on the fracture resistance of endodontically treated teeth restored with fiber posts and complete crowns

Abstract

Purpose. The purpose of this in vitro study was to evaluate the effect of partial ferrule locations on the fracture resistance of endodontically treated maxillary canines restored with complete crowns. Material and Methods. Fifty extracted maxillary canines were sectioned 18 mm from their apices, endodontically treated, and divided into 5 groups of 10 teeth each. All groups were prepared with full shoulder crown preparations. the first group having axial wall heights of 2 mm around the preparation circumferences, the axial walls were circumferential, 360 degrees around the preparations (Complete group), the second, third, and forth groups the axial walls were continuous for 180 degrees (one half of the axial tooth structure) of Palatal, Labial, and Proximal groups, and the fifth group all axial tooth structure was sectioned to the level of the preparation shoulder (Level group). All prepared teeth were then restored with quartz fiber posts (RTD), composite resin (Multicore) cores, and complete metal crowns. The fracture resistance was measured in a universal testing machine at 135 degrees to the long axis of the tooth until failure. Data were analyzed by ANOVA and then by Least Significance Difference test (LSD). The mode of failure was determined by visual inspection of all specimens. Results. Significant differences (P<0.05) were found among the mean fracture loads of the test groups, and was 803.7 N, 747.7N, 347.3 N, 386.6 N, and 186.7N for the Complete, Palatal, Labial, Proximal, and Level groups, respectively. When the mode of failure was evaluated, all failure was an oblique palatal to facial root fracture for the groups with remaining coronal tooth structure. In the Level group, post debonding was the predominant mode of failure. Conclusion. The palatal axial wall was more effective than the labial or proximal axial wall in providing fracture resistance to force applied to the palatal aspect in endodontically treated teeth.