Effect of Ferrule Height on the Fracture Resistance of Endodontically Treated Teeth Restored With Glass Fiber Posts: An In Vitro Study

Abstract

Introduction: Restoration of endodontically treated teeth (ETT) presents a significant challenge due to compromised structural integrity. The ferrule effect is crucial in reinforcing teeth and improving fracture resistance. This study aimed to compare and evaluate the effect of different crown ferrules on the fracture resistance of ETT restored with a glass fiber post and to evaluate the failure pattern.

Materials and methods: Fifty-six extracted human maxillary central incisors were selected and randomly divided into four groups (n = 14 per group) based on ferrule height: Group 1 (control, no ferrule with a metal post), Group 2 (0 mm ferrule with a glass fiber post), Group 3 (2 mm ferrule with a glass fiber post), and Group 4 (3 mm ferrule with a glass fiber post). After endodontic treatment and post-space preparation, the teeth were restored using composite cores and full metal crowns. A universal testing machine was used to apply a compressive load at a 45° angle until fracture occurred. The fracture resistance was recorded in Newtons (N), and the failure modes were analyzed under a stereomicroscope. Statistical analysis was performed using analysis of variance (ANOVA) and post-hoc Tukey test (p < 0.05).

Results: The mean fracture resistance values were highest in Group 1 (559.68 ± 92.52 N) and lowest in Group 2 (215.60 ± 70.79 N). Group 3 (428.53 ± 154.27 N) and Group 4 (439.06 ± 118.83 N) exhibited significantly higher fracture resistance than Group 2 (p = 0.001) but were not significantly different from each other (p = 0.950). Unfavorable root fractures were predominant in Group 1 and Group 2, whereas Group 3 and Group 4 showed repairable core-debonding failures.

Conclusions: Ferrules play a significant role in the fracture resistance of glass fiber post-restored teeth. Increasing the ferrule length significantly increases fracture resistance. Although metal posts provide higher fracture resistance, they are associated with a greater incidence of non-repairable failures. Glass fiber posts combined with an adequate ferrule are a more favorable option for restoring structurally compromised teeth.

Keywords: endodontically treated teeth; fracture; glass fiber; post; resistance.

Figure 1. Methodology of post and core: (A) root canal preparation, (B) post-space preparation by micromotor, (C) post space for glass fiber post, (D) selected incisor tooth for post and core, (E) obturated canal with sealer, (F) post space visible on radiograph, and (G) fiber post cemented in canal

Figure is derived from the study data.

Figure 2. Ferrule preparation in samples: (A) no ferrule at CEJ, (B) 2 mm of ferrule at CEJ, and (C) 3 mm ferrule at CEJ

CEJ: cementoenamel junction Figure is the author's original work.

Figure 3. Types of fracture in ETT: (A) core fracture, (B) core and post fracture, (C) coronal third root fracture, and (D) vertical root fracture

The fracture line is represented as a red arrow, and the load applied is represented as a blue arrow. ETT: endodontically treated teeth Figure is the author's original work.