Morphological effectiveness of platelet-rich plasma application in the experimental treatment of post immobilization extra-articular contractures of the mandible.

Objective: Aim: The purpose of the study was to prove the effectiveness of platelet-rich plasma (PRP) application in the treatment of post-immobilization extra-articular contractures of the mandible by modeling the specified pathology and conducting morphological analysis of experimental material.

Patients and methods: Materials and Methods: The study involved an experiment conducted on 60 male WAG rats aged 9-11 months. Four groups were formed. Group 1 included 6 intact rats that were not subjected to any interventions and were withdrawn from the experiment one month after its initiation. Group 2 included 18 rats with a mandibular fracture in the angle region which was treated over the course of one month using an immobilizing muzzle. After removal of the muzzle, extra-articular mandibular contracture was diagnosed. All rats were withdrawn from the experiment one month after its initiation. Group 3 included 18 rats with mandibular fractures that were treated over the course of one month using an immobilizing muzzle. After removal of the muzzle, post-immobilization extra-articular mandibular contracture was diagnosed. Following this diagnosis, 6 rats were withdrawn from the experiment. The other rats received PRP injections into the contracture area every three days for 15 days. After completion of the treatment, these rats were also withdrawn from the experiment. Group 4 included 18 rats with a mandibular fracture. After modeling a mandibular fracture, PRP was injected into the soft tissues surrounding the fracture through the available holes in the immobilizing muzzle every five days for one month. After a month, the immobilizing muzzle was removed from the rats, among which 6 rats were randomly selected and withdrawn from the experiment. The other rats continued to be injected with PRP every three days for 15 days, after which the animals were withdrawn from the experiment. The material for morphological examination consisted of masseter muscle samples. Histological, histochemical, immunohistochemical, morphometric and statistical methods were used.

Results: Results: The comprehensive morphological study showed that PRP in the masseter muscle had antifibrotic and anti-inflammatory effects, reduced the severity of alterative changes in muscle fibers and increased their regenerative potential, reduced the severity of hemodynamic disorders, and increased the number of vessels. The therapeutic effect of PRP was more pronounced in cases where it was applied both during the treatment of mandibular fracture using an immobilizing muzzle for one month and for an additional 15 days after its removal, compared to animals in which PRP was applied only during the 15 days following muzzle removal.

Conclusion: Conclusions: The comprehensive morphological study of experimental material conducted by the authors confirmed the effectiveness of platelet-rich plasma in the treatment of post-immobilization extra-articular contractures of the mandible, thereby expanding the available arsenal of treatment methods for this pathology.