Influence of varying ferrule heights and configurations on the fracture resistance of endodontically treated mandibular first molars- An in vitro study

Purpose: To evaluate the influence of varying ferrule heights and configurations on the fracture resistance of endodontically treated teeth restored with custom cast post and cores and full metal crowns. Method: Fifty extracted human mandibular first premolars were randomly divided into 5 groups: I, no root canal treatment (RCT), crown; II, no post and core, crown; III, 2-mm ferrule, cast post and core and crown; IV, non-uniform ferrule (2 mm buccal and lingual, 0.5 mm proximal), cast post and core and crown; and V, no ferrule, cast post and core and crown. Samples were subjected to a static load on the buccal cusp, 150° to the long axis of the tooth, and failure load was recorded. Statistical analysis was carried out with a 1-way analysis of variance and the Bonferroni pairwise comparison. The mode of fracture was noted by visual inspection. Results: Absence of ferrule resulted in significantly lower fracture resistance (V: 308.27 +/- 75.567 N) as compared to all other groups. Group I: 714.69 +/- 89.37 N, and Group II: 656.90 +/- 133.15 N were significantly more resistant as compared to Group IV: 471.98 +/- 115.99 N (p < 0.01). However, there was no significant difference between non-uniform ferrule and the uniform 2-mm vertical ferrule. Conclusion: The premolars with a ferrule were more fracture resistant as compared to the teeth with no ferrule preparation.