Biomechanical comparison of stability of resorbable plate-screw fixation systems in different configurations after sagittal split ramus osteotomy

Sagittal split ramus osteotomy (SSRO) has been successfully and widely applied in the treatment of specific dentofacial deformities. Many techniques and materials have been used by surgeons like wire osteosynthesis miniplates and screws used for fixation and stabilization after SSRO. While most post surgical complications related to titanium mini plates and/or screws requring second surgery to remove and disadvantages of metalic fixations have been developed and employed in studies focusing on evaluation of resorbable metarials in mandibular sagittal split osteotomy fixation and stabilization. Recently more surgeons have prefered to use resorbable materials in upregulation, stil the reliability of resorbable materials at different jaw sites after osteotomies or fractures remains a matter of concern for surgeons which limits to use resorbable materials systems by such surgeons. In literature, number of studies about analysis and comparison of clinical results of sagittal split ramus osteotomy performed with the use of resorbable plate/screw systems have not been satisfactory enough yet. In this study, 8 polyurethane synthetic mandibular replicas (Synbone 8598, Switzerland) were used and totally 2 groups were comprised. Afer employed SSRO on samples, fixations of bone segments were achieved using resorbable plate/screw systems (Inion CPS sistem, Tampere, Finland) in different configurations. Next, stabilities of fixation conducted by different systems were compared with together applying biomechanical loading tests. Then, stabilities of fixations which were applied with various systems were compared by applying biomechanical load tests. For this aim, 20N, 60N, 120N, 140N and 200N compressive loads were performed to each tooth on models by using of servohydrolic universal axial test machine. Experiments were carried out in biological test cabin which was full with continuously circulating physiological saline solution (PBS) at constant 37°C to mimic in vivo successfully. Compressive load behaviors of madibles which were in posterior and anterior region were recorded by using of non-contact video extensometer. According to the results, mandible group fixed by using screw was found more stabile than the group fixed by plate. Moreover, less strain accumulation was observed in neighborhood of the cut zone in posterior part of osteotomy applied mandible in comparison with further areas. In conclusion resorbable screw-plate systems provide sufficient stability in the fixation process. Only the fixation with screws is safer than plate+screw fixation.