An In Vitro Evaluation of Fracture Resistance of Endodontically Treated Maxillary Central Incisor Restored with Custom-Made Cast Post and Core with Uniform and Nonuniform Core Ferrule Heights

Aim: The aim of this study was to evaluate in vitro fracture resistance of endodontically treated teeth restored with custom-made cast post and core having uniform and nonuniform core ferrule heights. Materials and Methods: Thirty-five freshly extracted human maxillary central incisors were included in this study. All teeth were subjected to standard root canal treatment. The teeth were randomly divided into five groups-Group 1: uniform ferrule (2mm buccal, lingual, and proximal), Group 2: uniform ferrule (3mm buccal, lingual, and proximal), Group 3: nonuniform ferrule (2mm buccal, 3mm lingual), Group 4: nonuniform ferrule (2mm buccal, 4mm lingual), and Group 5: no ferrule. The teeth were sectioned horizontally 4mm above cementoenamel junction and post space preparation was performed maintaining 4mm of apical gutta-percha. Ferrule was prepared according to dimension designated for each group. Custom-made cast post and core were fabricated and luted using zinc phosphate cement. Testing was conducted using universal testing machine with application of static load (Newton), and failure load was recorded. Data were analyzed by one-way analysis of variance and Tukey test. The mode of fracture was noted by visual inspection for all specimens. Result: Significant differences (P < 0.001) were found among mean fracture forces of test groups. Group 1: 1181.66 +/- 68.29, Group 2: 1455.58 +/- 173.11, Group 3: 1019.00 +/- 52.55, Group 4: 971.58 +/- 66.52, and Group 5: 888.00 +/- 60.56. The presence of nonuniform ferrule height resulted in a significant decrease (P < 0.0001) in mean fracture strength compared to uniform 2- and 3-mm core ferrule height. Conclusion: The central incisors restored with cast post and core and crowns with 3-mm uniform core ferrule were more fracture resistant compared to central incisors with nonuniform core ferrule height. Both the uniform and nonuniform core ferrule groups were more fracture resistant than the group that lacked ferrule.