Dynamics of regeneration following transplantation of octacalcium phosphate into an experimental defect in the rabbit mandibular bone: electron microscopic and morphometric study

The relevance of this research lies in the in-depth exploration of bone tissue remodeling dynamics following the creation of a defect and its filling with osteoplastic material. Despite the known results of osteoplastic materials application in clinical practice, complete and high-quality regeneration of the maxillofacial bone, its mechanisms and dynamics remain incompletely understood, requiring further clarification and detailed study. Aim. The aim of this study is to determine the dynamics of histoarchitectural changes in the bone-ceramic regenerate after transplantation of octacalcium phosphate into an experimental defect in the rabbit mandible. Materials and methods. Adult male rabbits aged 6–7 months and weighing 2.5–3.0 kg were used for the study. The control group consisted of animals with a bone defect that healed under a blood clot. The experimental group consisted of rabbits in which the bone defect was filled with an osteotropic material containing octacalcium phosphate. Post-traumatic bone tissue status within the defect area was monitored for 84 days. Ultrastructural changes were studied using transmission and scanning electron microscopy. To determine changes in the regenerate composition, three parameters were counted. The data was analyzed using the Student’s t-test, and a difference at p < 0.05 was considered statistically significant. Results. Studying the surface relief characteristics of the experimental bone defect in the lower jaw after implantation of the octacalcium phosphate material revealed numerous regenerative changes that occurred after the injury and correlated with the dynamics of changes in the relative area of bone tissue, osteoplastic material, and connective tissue in the regenerate. Morphometric analysis of the relative area of the regenerative components of the experimental defect established a phased nature of the dynamics of the studied changes. It was established that the osteocytic lacunar-canalicular system formed after implantation of the material acquired features of typical structure. Foci of incomplete osteogenesis were not visualized. Unlike control animals, in the zone of the outer bone plate after application of the octacalcium phosphate material, the osteons of the regenerate in their structure and geometry did not differ from the typical structure of the maternal bone. Conclusions. It was established that in the experimental group of animals where the defect was filled with octacalcium phosphate material, a regular increase in the relative area of bone tissue in the regenerate was observed, which in terms of dynamics was similar to that in the control group, however, in terms of intensity of changes it significantly differed from the control, approaching the norm in terms of the studied indicators.