Effect of different intra-canal restorative techniques on the fracture resistance of endodontically treated anterior teeth: an in-vitro comparative study

Abstract Objective To evaluate the effect of different intra‑canal restorative techniques on the fracture resistance of endodontically treated anterior teeth and to assess the influence of marginal ridge loss on their mechanical behavior. Materials and methods Ninety extracted sound maxillary central and lateral incisors were selected and randomly divided into five groups. Ten teeth were left intact to serve as the control group, while the remaining teeth were endodontically treated, obturated, and randomly allocated into four groups according to different intra‑canal restorative techniques; (1) PS: packable short fiber‑reinforced composite, (2) FP: prefabricated glass fiber posts, (3) FS: flowable short fiber‑reinforced composite, (4) DC: dual‑cure composite core material, each group was further subdivided according to marginal ridge integrity into two subgroups ( n = 10), intact marginal ridges (I) and removed marginal ridge (R). All specimens were subjected to thermocycling for 10,000 cycles. Fracture resistance testing was carried out using a universal testing machine with a load applied at 135° to the long axis of the tooth until the fracture occurred. Fracture patterns were examined using a stereomicroscope and classified as favorable and unfavorable fractures. The data were statistically analyzed using two-way ANOVA, followed by Tukey’s post hoc test and fracture patterns were analyzed using Fisher’s exact test, with the significance level set at α = 0.05. Results Intra-canal restorative technique and marginal ridge integrity significantly affected fracture resistance ( p < 0.05), whereas no significant interaction was observed ( p = 0.564). Fiber post restorations demonstrated the highest fracture resistance values. No statistically significant differences were observed among fiber posts, packable short fiber-reinforced composite, and flowable short fiber-reinforced composite under either marginal ridge condition ( p > 0.05). Loss of one marginal ridge significantly reduced fracture resistance across all restorative techniques. The fracture pattern was significantly associated with the restorative technique ( p = 0.014), with flowable short fiber-reinforced composite showing the highest proportion of favorable fractures. Conclusions SFRC intra-canal restorations showed fracture resistance values that were not statistically different from those of fiber post restorations. Marginal ridge loss significantly compromised fracture resistance of endodontically treated anterior teeth. Clinical significance SFRC may represent a promising post-free restorative option for endodontically treated anterior teeth when sufficient coronal tooth structure remains, particularly in teeth with preserved marginal ridge integrity. However, long-term clinical studies and fatigue-loading investigations are required before definitive clinical recommendations can be made.