Investigation of the Stability of Maxillary Posterior Downward and Forward Movement by Using Finite Element Analysis: Methodological Study

Abstract

The maxillomandibular complex's counterclockwise movement with maxillary advancement and posterior downward repositioning was considered as one of the most unstable movements in orthognathic surgery. This study examines the reliability of fixation of different plate-screw systems in grafted and nongrafted models in the counterclockwise rotation where the maxilla is positioned anteriorly with posterior downward movement. Material and Methods: Stress distribution has been examined in four maxilla models. The transportable segment was moved 5 mm forward and posteriorly 4 mm downward in all models. Two scenarios with and without graft applied to the posterior region were created. These two scenarios were fixed with 2.0-and 1.5-mm diameter osteosynthesis systems. Four forces were applied separately to these models (45 and 125 N to the incisive tooth, 110 and 250 N to the molar tooth). Stress distribution on the bone and osteosynthesis screw plate system were examined in all models. Results: The application of graft decreased the load distribution on the bone and osteosynthesis systems. The stress distribution of both plate systems in the grafted models was similar in bone and osteosynthesis systems. The highest stress was measured in the non-grafted model using the 1.5 osteosynthesis system (Screw-F, 249.81 N/mm 2 ), while the lowest stress was measured in the 2.0 system (Screw-G, 0.49 N/mm 2 ) with the graft-applied model. Conclusion: The study results support the view that it is predicted that the necessity of graft application in surgeries where the maxilla is downward posteriorly with advancement. The 1.5 mm diameter system can be used safely if a graft-applied to the posterior gap.