Effect of Restorative Cavity Designs and Restoration Techniques on Fracture Resistance and Fracture Patterns in Simulated Immature Teeth: An In Vitro Study

Objectives: This study evaluated the effects of different restorative techniques—direct composite, fiber post, and the Bioblock technique—on the fracture resistance and fracture patterns of simulated immature teeth with mesio-occlusal (MO) and single buccal cusp (SBC) cavity designs.Materials and Methods: Seventy single-rooted mandibular premolars were selected. Ten teeth served as the control group, while the remaining specimens were randomly allocated into six experimental groups (n=10) according to cavity design (MO or SBC) and restorative technique (direct composite, fiber post, or Bioblock). To simulate immature apices, root canals were enlarged using Gates Glidden drills, followed by apexification with a 3-mm-thick MTA layer. All specimens then underwent fracture resistance testing. Fracture resistance data were analyzed using one-way analysis of variance (ANOVA), while fracture pattern data were evaluated with the chi-square test. The level of statistical significance was set at α = 0.05.Results: The lowest fracture resistance was observed in the SBC fiber post group, while the control group exhibited the highest values. All MO subgroups demonstrated significantly higher fracture resistance than the SBC subgroups (p0.05); however, both exhibited significantly greater fracture resistance than the fiber post groups (p0.05).Conclusion: MO cavity designs provided greater fracture resistance compared with SBC designs. Fiber post restorations yielded the lowest resistance values, whereas direct composite and Bioblock techniques performed significantly better.