Comparative Finite Element Analysis of the Biomechanical Stability of 2.0 Fixation Plates in Atrophic Mandibular Fractures
The objective of the present study was to conduct a computational, laboratory-based comparison of the biomechanical stability of 2.0 fixation locking plates with different profiles in Class III atrophic mandibular fractures using 3-dimensional finite element analysis.
Three-dimensional finite element models simulating Class III atrophic mandibular fractures were constructed. The models were divided into 4 groups according to plate thickness (1.0, 1.5, 2.0, and 2.5 mm). Fractures were simulated in left mandibular bodies, and 3 locking screws were used on each side of each fracture for fixation. Bite forces of approximately 63 N were simulated in the incisor and molar regions of the mandibles in finite element models.
The level of compressive strain on the bone around the screw was within the physiological limit. No significant difference was observed in the displacement of bone segments in the fracture region. Von Mises stress was higher during simulated bites in the molar region for plates with thicknesses of 1.0 mm. Plate tension values were below the level required for permanent deformation or fracture in all models. The 2.5-mm-thick plate presented better biomechanical performance than all other plates. The 2.0-mm-thick plate also showed satisfactory results and adequate safety limits.
Large-profile (2.0-mm-thick) locking plates showed better biomechanical performance than did 1.0- and 1.5-mm-thick plates and can be considered an alternative reconstruction plate for the treatment of Class III atrophic mandibular fractures.
Available from: Jinxing Huo
- "Some other studies have adopted an improved orthotropic bone material model  . Yet, these studies were not based on clinical cases. "
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ABSTRACT: In order to reconstruct a patient with a bone defect in the mandible, a porous scaffold attached to a plate, both in a titanium alloy, was designed and manufactured using additive manufacturing. Regrettably, the implant fractured in vivo several months after surgery. The aim of this study was to investigate the failure of the implant and show a way of predicting the mechanical properties of the implant before surgery. All computed tomography data of the patient were preprocessed to remove metallic artefacts with metal deletion technique before mandible geometry reconstruction. The three-dimensional geometry of the patient's mandible was also reconstructed, and the implant was fixed to the bone model with screws in Mimics medical imaging software. A finite element model was established from the assembly of the mandible and the implant to study stresses developed during mastication. The stress distribution in the load-bearing plate was computed, and the location of main stress concentration in the plate was determined. Comparison between the fracture region and the location of the stress concentration shows that finite element analysis could serve as a tool for optimizing the design of mandible implants.
Copyright © 2015 IPEM. Published by Elsevier Ltd. All rights reserved.
Available from: George K Sándor
- "A search of the prevalent literature did not provide information regarding muscle forces in mandible post-resection. To circumvent this lack of information, standard muscle forces (Korioth et al., 1992; Vajgel et al., 2013) were applied to determine the reaction force in the molars and then designated as chewing force. Subsequently, the boundary conditions were changed from muscle forces to zero displacement in all directions and molar chewing force applied. "
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ABSTRACT: Large mandibular continuity defects pose a significant challenge in oral maxillofacial surgery. One solution to this problem is to use computer-guided surgical planning and additive manufacturing technology to produce patient-specific reconstruction plates. However, when designing customized plates, it is important to assess potential biomechanical responses that may vary substantially depending on the size and geometry of the defect. The aim of this study was to assess the design of two customized plates using finite element method (FEM). These plates were designed for the reconstruction of the lower left mandibles of two ameloblastoma cases (patient 1/plate 1 and patient 2/plate 2) with large bone resections differing in both geometry and size. Simulations revealed maximum von Mises stresses of 63MPa and 108MPa in plates 1 and 2, and 65MPa and 190MPa in the fixation screws of patients 1 and 2. The equivalent strain induced in the bone at the screw-bone interface reached maximum values of 2739 micro-strain for patient 1 and 19,575 micro-strain for patient 2. The results demonstrate the influence of design on the stresses induced in the plate and screw bodies. Of particular note, however, are the differences in the induced strains. Unphysiologically high strains in bone adjacent to screws can cause micro-damage leading to bone resorption. This can adversely affect the anchoring capabilities of the screws. Thus, while custom plates offer optimal anatomical fit, attention should be paid to the expected physiological forces on the plates and the induced stresses and strains in the plate-screw-bone assembly.
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ABSTRACT: The aim of the presented work is compare a two different way of prescribing muscles and chewing force boundary condition. First variant of boundary condition consider muscle forces and their direction taken from literatures. Second variant of boundary condition consider muscles modeled as finite elements connecting lower jaw and skull together. At second variant a muscles material characteristic of Young ́s modulus was changed in range from 1e4 MPa to 2,1e5 MPa. Models of living tissues were created on base of CT images and modeled in 3D CAD software SolidWorks. Calculations were computed in the finite element software ANSYS. Material models were considered as homogenous, isotropic and linearly elastic for all parts. First, both variants of boundary condition were analyzed separately and after that, selected variables (as muscle forces and muscle direction scale factors) from both variant were compared together.
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