Biomechanical analysis of the behavior of cranial structures under conditions of pathological occlusion

Background. Asymmetric occlusion is considered one of the factors contributing to functional disorders of the cranio-mandibular system. Asymmetric forms of occlusion may be skeletal, dentoalveolar, or mixed. In clinical practice, dentoalveolar forms of asymmetry with functional displacement of the mandible are frequently observed. They develop as a result of unilateral occlusal contacts and adaptive changes in the dentoalveolar complex. However, the features of redistribution of mechanical stresses in cranial structures under conditions of transverse occlusal asymmetry remain insufficiently studied. Investigation of the stress-strain state of cranial struc- tures is important for substantiating modern orthodontic and gnathological approa- ches to treatment. Purpose – to investigate the characteristics of occlusal load transmission to cranial structures in conditions of unilateral asymmetric occlusion and to analyze changes in the stress-strain state of the cranial bones. Materials and methods. A three-dimensional computer model of the skull was created using the finite element method. The model included the mandible, articular cartilage, and the bones of the facial and cerebral parts of the skull connected by interosseous joints. Two geometric models were constructed: one with symmetric occlusion and one with unilateral asymmetric occlusion. The asymmetry was modeled as a dentoalveolar form with functional displacement of the mandible in the trans- verse direction, reproducing the clinical situation of unilateral occlusal contacts. A load of 100 newtons was applied to the model under conditions of symmetrical action of the masticatory muscles. The intensity of mechanical stresses and total dis- placements were evaluated. Results. In the model with unilateral asymmetric occlusion, a significant increase in mechanical stresses in the studied structures was observed. The stress intensity in the entire model increased from 191.58 to 317.93 megapascals. In the temporal bones, the values increased more than threefold, while in the articular cartilage they increased three to four times compared with the symmetric model. The total displace- ment of the entire model increased from 0.036 to 0.11 millimeters. Local overload zones were identified in the region of the temporomandibular joints and cranial sutures, along with changes in the direction of force vectors and an asymmetric pattern of occlusal load transmission. Conclusions. Unilateral asymmetric occlusion leads to an uneven distribution of mechanical stresses in the cranio-mandibular complex and may contribute to the development of functional disorders and degenerative changes in the temporoman- dibular joints. The obtained results confirm the effectiveness of the finite element method for studying biomechanical mechanisms of occlusal asymmetry and may be used to substantiate orthodontic and gnathological approaches to treatment.