Fracture resistance of regenerated immature teeth in different simulated stages of root development: an <i>in vitro</i> cyclic loading study

Objectives: This in vitro study aimed to assess the fracture resistance of simulated stages of root maturation following regenerative endodontic treatment using a cyclic loading method. Methods: Ninety extracted maxillary central incisors were randomly allocated into three experimental groups representing different stages of root development, following revitalization: Group A for completely immature teeth immediately after treatment; Group B for teeth with apical closure, and Group C for teeth with apical closure and wall thickening. Two control groups were also included: Group D for intact teeth and Group E for simulated immature teeth without the bioceramic material. Following simulation of immature apices and treatment with a bioceramic material, all specimens were subjected to cyclic loading using a step-stress fatigue protocol until failure. The number of cycles to fracture and the peak load were recorded and statistically analyzed. Results: Statistically significant differences in loading forces were observed between the negative control group (Group D) and Groups A, B, and E (p < 0.05). However, no statistically significant differences were detected among the experimental groups. These results indicate that apical closure and dentinal wall thickening alone did not substantially improve mechanical reinforcement under cyclic loading conditions. Conclusions: Although intact teeth exhibited superior mechanical performance, apical closure and wall thickening alone were insufficient to enhance reinforcement under cyclic loading.