Influence of Ferrule Height and Uniformity on Fracture Resistance of Post-core Crowns: An In Vitro Analysis

Objective To evaluate the effect of uniform versus non-uniform ferrule configurations on fracture resistance and failure mode in endodontically treated maxillary central incisors restored with cast dowel-core and metal-ceramic crowns. Methods In this in-vitro, controlled study, 50 extracted maxillary central incisors were equally allocated to five groups: intact crowned (CRN), root-canal-treated crowned (RCT/CRN), uniform 2-mm ferrule (2FRL), non-uniform ferrule (0.5/2FRL; 0.5 mm proximal/2 mm labial-lingual), and no ferrule (0FRL). Specimens were statically loaded at 45° to failure; peak load (N) was the primary outcome. Failures were classified as restorable or catastrophic, and reliability was summarized as P(load >400 N, >500 N) under a normal model fitted to each group. Results Groups differed significantly (analysis of variance (ANOVA), p