A Biomechanical Analysis of Muscle Force Changes After Bilateral Sagittal Split Osteotomy

Computational models and their applications in biomechanical analysis of mandibular reconstruction surgery

Advanced head and neck cancers involving the mandible often require surgical removal of the diseased parts and replacement with donor bone or prosthesis to recreate the form and function of the premorbid mandible. The degree to which this reconstruction successfully replicates key geometric features of the original bone critically affects the cosmetic and functional outcomes of speaking, chewing, and breathing. With advancements in computational power, biomechanical modeling has emerged as a prevalent tool for predicting the functional outcomes of the masticatory system and evaluating the effectiveness of reconstruction procedures in patients undergoing mandibular reconstruction surgery. These models offer cost-effective and patient-specific treatment tailored to the needs of individuals. To underscore the significance of biomechanical modeling, we conducted a review of 66 studies that utilized computational models in the biomechanical analysis of mandibular reconstruction surgery. The majority of these studies employed finite element method (FEM) in their approach; therefore, a detailed investigation of FEM has also been provided. Additionally, we categorized these studies based on the main components analyzed, including bone flaps, plates/screws, and prostheses, as well as their design and material composition.

Application of numerical simulation studies to determine dynamic loads acting on the human masticatory system during unilateral chewing of selected foods

Introduction: This paper presents its kinematic-dynamic computational model (3D) used for numerical simulations of the unilateral chewing of selected foods. The model consists of two temporomandibular joints, a mandible, and mandibular elevator muscles (the masseter, medial pterygoid, and temporalis muscles). The model load is the food characteristic (i), in the form of the function F_i = f(Δh_i)-force (F_i) vs change in specimen height (Δh_i). Functions were developed based on experimental tests in which five food products were tested (60 specimens per product). Methods: The numerical calculations aimed to determine: dynamic muscle patterns, maximum muscle force, total muscle contraction, muscle contraction corresponding to maximum force, muscle stiffness and intrinsic strength. The values of the parameters above were determined according to the mechanical properties of the food and according to the working and non-working sides. Results and Discussion: Based on the numerical simulations carried out, it can be concluded that: (1) muscle force patterns and maximum muscle forces depend on the food and, in addition, the values of maximum muscle forces on the non-working side are 14% lower than on the working side, irrespective of the muscle and the food; (2) the value of total muscle contraction on the working side is 17% lower than on the non-working side; (3) total muscle contraction depends on the initial height of the food; (4) muscle stiffness and intrinsic strength depend on the texture of the food, the muscle and the side analysed, i.e., the working and non-working sides.

The effect of lateral bone cut end on the patterns of the lingual split during BSSO in patients with skeletal class III malocclusion

This study examines the effect of the lateral bone cut end (LBCE) on the pattern of lingual split during bilateral sagittal split osteotomy (BSSO) in patients with skeletal class III malocclusion. A case-control study according to the pattern of the sagittal split osteotomy (SSO) lingual split line was conducted in patients who underwent BSSO. The primary predictor variable was the ratio of the LBCE. The primary outcome variable was the type of lingual fracture line classified according to the lingual split scale (LSS). Other variables included patients' weight, sex, age, left and right sides of the mandible, and experience of the surgeon. Logistic regression analysis or the chi-squared test was performed to determine the effect of these variables on various types of lingual fracture line. The significance level was 95% (p < 0.05). There were 271 patients enrolled in this study. The SSO lingual split lines were divided into LSS1 (329/542), LSS2 (82/542), LSS3 (93/542), and LSS4 (38/542) splits. Logistic regression analysis showed that the LSS3 split was more likely to appear when the LBCE was closer to the lingual side (p = 0.0017). The age of patients significantly affected the possibilities of LSS2 (p = 0.0008) and LSS3 (p = 0.0023) splits. A LBCE close to the lingual side was an inducer for the formation of a LSS3 split in patients with skeletal class III malocclusion during BSSO. The age of the patient also affected the possibility of LSS2 and LSS3 splits.