Biomechanical evaluation of chincup treatment with various force vectors.

INTRODUCTION: The aim of this study was to evaluate the biomechanical effects of chincup treatment by using a 3-dimensional finite element model. METHODS: Three-dimensional models of the mandible and the temporomandibular joint were modeled and analyzed. The final mesh consisted of 1572 solid elements with 5432 nodes. The chincup with 500 g of force was applied in a direction from the chin toward the mandibular condyle, the coronoid process, and a point anterior to the coronoid process. Then, the mechanical responses in terms of displacement and von Mises stresses are evaluated. RESULTS: The mandible was displaced backward and downward with the vector passing through the condyle. Forward and upward displacement was recorded with the force vector passing through or anterior to the coronoid process. The mandibular condyle and the coronoid process showed minimal displacement for all force vectors. The highest stress levels were observed in the condylar and posterior ramus regions and increased as the force vector was transferred away from the condyle. CONCLUSIONS: With the limitations of modeling, boundary conditions, and solution assumptions, chincups applied in various directions produce different force vectors, which induce different stress locations and displacements. The force vector is an important determinant of the orthopedic effects of the chincup and therefore should be carefully considered.

Comparative evaluation of different miniplates for internal fixation of mandible fractures using finite element analysis.

PURPOSE: In this computer-based study, finite element analysis (FEA) was performed to assess the most suitable shape and fixation technique for a certain type of mandible fracture at corpus. MATERIALS AND METHODS: A model of the mandible was prepared using computed tomography (CT) scans. The CT scans were transferred and converted to the finite element model by means of a procedure developed for this study. Simulated corpus fractures were fixed with 14 different fixation configurations of titanium miniplates. The FEA was performed with respect to displacement and stresses in the titanium miniplates for these configurations. RESULTS: The study results indicated that the use of 2 straight miniplates is more rigid than other fixation types. Fixation with only 1 miniplate at the inferior location resulted in mobility greater than the set limit of 150 microm. With "L" and "T" shaped miniplates and a straight miniplate at the middle location, fracture mobility was approximately equal to or less than the limit; however, displacement nearly reached to limit. Superior fixations with only 1 miniplate resulted in mobility lower than the limit. But these configurations exceed the yield limit of titanium miniplate. CONCLUSIONS: FEA may be useful in evaluation of other plate constructs, fracture types, and fracture sites, as confirmed by the agreement between our data and those in the literature and with clinical experience. This analysis should permit us to suggest and evaluate new miniplate designs and enable considerable savings to be made in terms of time, material, and animal experiments in the future development of osteosynthesis materials and techniques.

Evaluation of different miniplates in fixation of fractured human mandible with the finite element method.

The objective of this study was to develop a 3-dimensional finite element model (FEM) to formulate biomechanical justification of the positioning of different plates to achieve stable fixation of a fractured mandible. Miniplate systems that give acceptable levels of rigidity were investigated, and recommendations about miniplate location, orientation, and type selection are made. A fracture near the body region was bridged with a variety of commonly used plate configurations. Number, positioning and type of the plate system parameters. The results of this fracture model support the advantage of 2-plate systems. Using a longer plate in the superior position and a shorter one in the inferior position produced a more stable condition. Number of screws or length of the miniplate had no significant effect on the stability of fractured segments. The results obtained from this study offer the choice of a particular plate size, thickness, design, or configuration for application and thus provide information for clinical use.

Biomechanical evaluation of mandibular midline distraction osteogenesis by using the finite element method.

The aim of this study was to evaluate the biomechanical effects of mandibular midline distraction osteogenesis on the mandibular complex by using a 3-dimensional finite element model, whose construction was based on computer tomography scans of the mandible of a 22-year-old man. The computer tomography pictures were transferred and converted to the finite element model by means of a procedure developed for this study. The final mesh consisted of 1314 solid elements with 3076 nodes. The distraction was performed on the middle intersection point of the vertical and horizontal planes on the mandibular symphysis. The mechanical response in terms of displacement and von Mises stresses was determined by widening the mandible up to 5 mm on both sides. The results indicate that the mandible was separated almost in a parallel manner (4.45-5.0 mm separation from the mandibular incisors to the lower border of the mandibular symphysis and 4.09-4.92 mm from the mandibular canines to the symphyseal border at the canine region), superoanteriorly. Anteroposterior evaluation demonstrated that the greatest widening was achieved at the symphyseal region, and the widening effect gradually decreased from anterior to posterior. Viewed occlusally, the width of the mandibular bone at the symphyseal region increased remarkably, whereas the ramal and gonial regions of the mandible and the condyle had shown minimal displacement. Mandibular bone was displaced forward and slightly downward. The highest stress levels were observed bilaterally below the condylar areas. High stress levels were also observed in the ramal region of the mandible.