Abstract
We used the finite-element method (FEM) to investigate the effects of jawbone model integrity and the material properties of the periodontal ligament (PDL) on orthodontic tooth movement. Medical imaging software and computer-aided design software were used to create finite-element models of a partial and complete mandibles based on dental cone beam computed tomography images of the human skull. Additionally, we exerted an orthodontic force on the canine crown in the direction of an orthodontic miniscrew under a lower molar root to compare the von Mises strain on the canine PDL in three models: a partial mandible model under orthodontic force (Model 1), a complete mandible model under orthodontic force (Model 2), and a complete mandible model under orthodontic force with clench occlusion in the intercuspal position (ICP; Model 3). Additionally, in the complete mandible model under orthodontic force with ICP occlusion, we analyzed the effects of a PDL with a low (Model 4), moderate (Model 5), and high (Model 6) linear elastic modulus and a PDL a bilinear elastic modulus (Model 7). The simulation results for mandible integrity indicated that the maximum von Mises strains on the canine PDL for Models 1, 2, and 3 were 0.461, 0.394, and 1.811, respectively. Moreover, for the models with different PDL material properties, the maximum von Mises strains on the canine PDLs for Models 4, 5, 6, and 7 were 6.047, 2.594, 0.887, and 1.811, respectively. When the FEM was used to evaluate tooth movement caused by orthodontic force, the transformation of a complete mandible model into a partial mandible model or alteration of the elastic modulus of the PDL influenced the biomechanical responses of the PDL. Additionally, the incorporation of daily ICP occlusion resulted in a larger effect.
Highlights
Over the past 40 years, the finite-element method (FEM) has been widely used to study biomechanics in the fields of orthopedics and dentistry
The maximum von Mises strains on the canine periodontal ligament (PDL) in the partial mandible model under orthodontic force (Model 1), complete mandible model under orthodontic force (Model 2), and complete mandible model under orthodontic with intercuspal position (ICP) occlusal force (Model 3) were 0.461, 0.394, and 1.811, respectively (Figure 3)
The maximum von Mises strains on the canine PDL in the partial (Model 1) and complete (Model 2)
Summary
Over the past 40 years, the finite-element method (FEM) has been widely used to study biomechanics in the fields of orthopedics and dentistry. The FEM is widely used in dentistry for the research and development of artificial implants and surgical instruments, prediction of jawbone growth and developmental behaviors, orthodontic treatment or oral surgery, and preoperative and postoperative evaluations [1,2]. According to pressure–tension theory [3,4,5,6] in orthodontics, tooth movement is mainly caused by the biomechanical response of the periodontal ligament (PDL) surrounding the tooth. An orthodontic bracket exerts force on a tooth to compress or stretch the PDL. Previous studies have indicated that bone resorption and apposition are required in the compression and tension zones, respectively [3,4,5,6]
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