RESUMO
OBJECTIVES: To assess the influence of ferrule and core type on the fracture strength of endodontically treated anterior teeth (ETAT) and identify the failure mode type and distribution across different core types and ferrule conditions. METHODS: Sixty extracted human central incisors were endodontically treated, decoronated and divided into two main groups (F=with ferrule, NF=no ferrule). Each main group was further subdivided into three subgroups according to the core material used: direct composite cores (DC), Ribbond fibre-reinforced composite cores (RIB-DC), and glass fibre post (GFP) with direct composite cores (GFP-DC). All specimens received E.max crowns and underwent thermal cycling and cyclic loading. Subsequently, the fracture resistance was tested with static loads applied to the crown restoration. Two-Way ANOVA and Chi square tests identified significant differences among the groups (p < 0.05). RESULTS: The means and standard deviations (SD) of fracture loads in Newtons (N) for specimens in the F subgroups were RIB-DC: 465.0 (104.20), GFP-DC: 367.6 (79.59), DC: 275.8 (68.48), and in NF subgroups were RIB-DC: 110.8 (24.33), GFP-DC: 95.6 (25.47), DC: 67.4 (7.46). Specimens with ferrule yielded significantly higher fracture loads than those without ferrule (p = 0.0054). In the F groups, fracture loads of specimens with RIB-DC cores were significantly higher than those with GFP-DC (p = 0.0019) and those with DC (p = 0.0001). Moreover, fracture loads for the GFP-DC were significantly higher than those for the DC (p = 0.0026). The GFP-DC specimens showed the highest incidence of catastrophic failures (p = 0.0420). CONCLUSIONS: Using fibre-reinforced composite (FRC) cores significantly increased fracture resistance in ETAT with ferrule. The failure modes repairable and possibly repairable were dominant in most specimens. CLINICAL SIGNIFICANCE: When restoring ETAT with insufficient coronal tooth structure, preserving 2 mm of tooth structure ferrule and preparing cores with FRC can increase fracture resistance and reduce the incidence of non-repairable catastrophic fractures of teeth.