Influence of Dentine Thickness and Intraradicular Reinforcement on Fracture Resistance of MTA-apexified Immature Anterior Teeth.

Introduction: The most common cause of failure of mineral trioxide aggregate (MTA)-apexified teeth is root fracture. This study aimed to identify the appropriate reinforcement materials following MTA apexification in immature teeth under simulated oral conditions.

Methods: Part 1: To investigate the effect of dentine thickness: twenty-four teeth (n = 8) were assigned to 3 groups; intact, simulated immature teeth with 2.0 mm, and 1.5 mm dentin thicknesses. Roots were prepared using Peeso reamers until the predetermined thickness was achieved. Part 2: To evaluate the effect of reinforcement materials: forty teeth were prepared as simulated immature roots with 1.5 mm dentin thickness and received MTA apexification. They were randomly assigned into 5 groups (n = 8): gutta-percha, MTA, DUAL-cure composite resin, fiber post, and anatomic post. All teeth underwent thermocycling and cyclic loading before compression testing. Fracture patterns and maximum load to fracture were recorded. Data were analyzed using one-way analysis of variance with Tukey's test and Weibull regression for survival probability.

Results: Teeth with 1.5 mm dentin thickness showed significantly lower fracture resistance than intact and 2.0 mm groups. An oblique horizontal root fracture was observed in all samples. In fiber postgroup, the most observed fracture was at the interface between MTA and post. The DUAL-cure composite resin group showed fracture resistance and survival probability comparable to intact group.

Conclusions: Within the limit of this study, MTA-apexified teeth could be reinforced with DUAL-cure composite resin.