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Objective To establish the implant-mandible model with different design parameters, observe stress distributions on the implant and surrounding bone, and analyze the influence of different design parameters on dental implant of the mandible. Methods Eight implant models were designed based on structural characteristic parameters (implant diameter, thread depth, height of abutment through gingiva, thread shape), and assembly of the mandibular model was performed respectively. The models were applied with static 150 N vertical and oblique 45° loads, so as to analyze peak von Mises stress of the implant and bone tissues and explore the structural parameter variables of implant most sensitive to peak von Mises stress. Results The peak stress of the mandible was larger under inclined load than that under vertical load. Implant diameter was the key factor affecting the peak von Mises stress of cortical bone, while thread depth was the key factor affecting the peak von Mises stress of cancellous bone. The peak von Mises stress was also affected by the height of abutment through gingiva, but the effect was not as significant as thread depth and implant diameter. Thread shape had little effect on the peak von Mises stress of the mandible. Conclusions Different implant design parameters can affect the peak stress of different tissues of the mandible, so it is necessary to carefully consider the selection of implant parameters for personalized implants. This study can provide theoretical guidance for structural parameter design of oral implants and provide references for accurate prediction of oral implants.
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Objective To analyze stress distributions on mandible bone and periodontal ligaments during acceleration of orthodontic tooth movement by mechanical vibration, and investigate the mechanism of static-vibration coupled loading to accelerate orthodontic tooth movement. MethodsThe finite element model including tooth, periodontal ligament, cancellous bone and cortical bone was established by Mimics，SolidWorks，Geomagic and ANSYS Workbench software. Conventional static orthodontic force and low-magnitude high-frequency mechanical vibration loads were applied to the finite element model for dynamic analysis. ResultsThe compression and tension zones of alveolar bone and periodontal tissues were identified based on Y-normal stress distribution of alveolar bone and periodontal tissues, which was periodic with the same frequency as the applied low-magnitude high-frequency vibration. The von Mises stress of alveolar bone and periodontal tissues also showed periodic changes, but the compression and tension zones of alveolar bone and periodontal tissues could not be identified based on von Mises stress distribution of alveolar bone and periodontal tissues. Conclusions In the field of orthodontics, Y-normal stress is a reasonable mechanical stimulus, and static-vibration coupled loading is an effective method for accelerating orthodontic treatment. The research findings can provide guidance for low-magnitude high-frequency mechanical vibration to accelerate orthodontic tooth movement.
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BACKGROUND:Mechanotransduction is an issue of concern in the study on the relationship between stress and growth. Mechano-growth factor (MGF) holds stress sensitivity, and exerts similar effect with stress in bone metabolism regulation. OBJECTIVE: To explore the mechanotransduction during bone remodeling, and investigate the relationship between stress and growth at molecular level. METHODS: The governing equations about the relationship between MGF and mechanical stimulation, regulation of MGF on osteoblasts and osteoclasts, regulation of MGF on RANK-RANKL-OPG signaling axis were established, and then the MGF-mediated bone reconstruction model was established to simulate the bone remodeling process under mechanical stimulation. RESULTS AND CONCLUSION:Under the condition of disuse, there was a decrease in osteoblasts/osteoclasts ratio, bone mass and bone volume fraction, and bone resorption was more than bone formation. Under the condition of overload, there was an increase in osteoblasts/osteoclasts ratio, bone mass and bone volume fraction, and bone formation was more than bone resorption. The simulation results were in accordance with Frost mechanostat theory. These findings show that the mechanobiological model of bone remodeling based on MGF can simulate the bone remodeling process under mechanical stimuli, and achieve mechanotransduction.
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Glycosides are the active ingredients (AIs) of many Chinese herbs and have become hot spots along with the findings of their new functions,such as anti-inflammatory,antivirus,enhanced immunity and anti-cancer.It has been found that glycosides exert their effects by converting to aglycons or other AIs in vivo.Therefore,the transformation of glycosides to the corresponding AIs in vitro becomes very important to enhance their bioavailabilities.The microbial transformation has an unparalleled advantage in the transformation of Chinese herbs in vitro for its reaction specificity,less by-products,mild reaction conditions and environmental protection.This paper summarized and prospected researches of glycosides' microbial transformation.
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Abstract The processs of female Osteoporosis and its prevention by Physical activity were simulated using anisotropic bone remodelling model with mechanostat combining with finite element method. The results show that bone mass declines slowly at the beginning, bone loss accelerates in postmenopause and bone mass declines 25. 84%-28.63% at the age of 60 and 38.50%-40.44% at the age of 80. Bone mass increases 3.05%-10.26% by an increase of 10%-20% in physical activity. The above results are consistent with clinical observations,which proves that declination of mechanical usage is the primary factor leading to osteoporosis, menopause quickens the process of female osteoporosis, physical activity can decelerate it.
Subject(s)
Aged , Female , Humans , Middle Aged , Biomechanical Phenomena , Bone Remodeling , Computer Simulation , Exercise , Physiology , Models, Biological , Osteoporosis, PostmenopausalABSTRACT
At present, the numerical model of bone remodeling is inadequate to copy the physiological process of bone remodeling. According to the physiological mechanism of bone remodeling and the anisotropy of bone mechanics properties, an anisotropic bone modeling model with mechanostat was developed, and then was applied to a study on the remodeling evolution of 2D squareplate model. Good results were obtained. The model can be used in the study of implant, osteoporosis and other bone diseases.