Browsing by Author "Hsu, Yung-Ting"

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    Modeling Progressive Damage Accumulation in Bone Remodeling Explains the Thermodynamic Basis of Bone Resorption by Overloading
    (Springer, 2020-10-10) Sego, T. J.; Hsu, Yung-Ting; Chu, Tien-Min; Tovar, Andres; Cariology, Operative Dentistry and Dental Public Health, School of Dentistry
    Computational modeling of skeletal tissue seeks to predict the structural adaptation of bone in response to mechanical loading. The theory of continuum damage-repair, a mathematical description of structural adaptation based on principles of damage mechanics, continues to be developed and utilized for the prediction of long-term peri-implant outcomes. Despite its technical soundness, CDR does not account for the accumulation of mechanical damage and irreversible deformation. In this work, a nonlinear mathematical model of independent damage accumulation and plastic deformation is developed in terms of the CDR formulation. The proposed model incorporates empirical correlations from uniaxial experiments. Supporting elements of the model are derived, including damage and yielding criteria, corresponding consistency conditions, and the basic, necessary forms for integration during loading. Positivity of mechanical dissipation due to damage is proved, while strain-based, associative plastic flow and linear hardening describe post-yield behavior. Calibration of model parameters to the empirical correlations from which the model was derived is then accomplished. Results of numerical experiments on a point-wise specimen show that damage and plasticity inhibit bone formation by dissipation of energy available to biological processes, leading to material failure that would otherwise be predicted to experience a net gain of bone.
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    On the Significance and Predicted Functional Effects of the Crown-to-Implant Ratio: a Finite Element Study of Long-Term Implant Stability Using High-Resolution, Nonlinear Numerical Analysis
    (Office of the Vice Chancellor for Research, 2016-04-08) Sego, T.J.; Hsu, Yung-Ting; Chu, Tien-Min Gabriel; Tovar, Andres
    Background. As the use of short dental implants becomes increasingly popular, the effects of the crown-to-implant (C/I) ratio on stress and strain distributions remain controversial. Previous studies in literature disagree on results of interest and level of necessary technical detail. Purpose. The present study sought to evaluate the strain distribution and assess its functional implications in a single implant-supported crown with various C/I ratios placed in the maxillary molar region. Materials and Methods. A high-fidelity, nonlinear finite-element model was developed to simulate multiple clinical scenarios by laterally loading a set of single implants with various implant lengths and crown heights. Strain distribution and maximum equivalent strain were analyzed to evaluate the effects and significance of the crown height, implant length and C/I ratio. The consistency of predicted functional responses to resulting strain at the implant interface were analyzed by interface surface area. Results. Results were evaluated according to the mechanostat hypothesis to predict functional response to strain. Overloading and effects of strain concentrations were more prevalent with increasing C/I ratios. Overloading was predicted for all configurations to varying degrees, and increased with decreasing implant lengths. Fracture in trabecular bone was predicted for at least one C/I ratio and all implant lengths of 10 mm or less. Conclusions. Higher C/I ratios and lower implant lengths increase the biomechanical risks of overloading and fracture. Increasing C/I ratios augment the functional effects of other implant design factors, particularly implant interface features. Greater C/I ratios may be achieved with implant designs that induce less significant strain concentrations.
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    On the Significance and Predicted Functional Effects of the Crown-to-Implant Ratio: A Finite Element Study of Long-Term Implant Stability Using High-Resolution, Nonlinear Numerical Analysis
    (ASME, 2016-04) Sego, T. J.; Hsu, Yung-Ting; Chu, Tien-Min Gabriel; Tovar, Andres; Mechanical Engineering, School of Engineering and Technology
    With the rising popularity of short dental implants, the effects of the crown-to-implant (C/I) ratio on stress and strain distributions remain controversial. Previous research disagrees on results of interest and level of necessary technical detail. The present study aimed to evaluate the strain distribution and its functional implications in a single implant-supported crown with various C/I ratios placed in the maxillary molar region. A high-fidelity, nonlinear finite-element model was generated to simulate multiple clinical scenarios by laterally loading a set of single implants with various implant lengths (IL) and crown heights (CH). Strain distribution and maximum equivalent strain (MES) were analyzed to evaluate the effects and significance of the CH, IL and C/I. Predicted functional response to strain at the implant interface was analyzed by interface surface area. Results. Results were evaluated according to the mechanostat hypothesis to predict functional response. Overloading and effects of strain concentrations were more prevalent with increasing C/I. Overloading was predicted for all configurations to varying degrees, and increased with decreasing IL. Fracture in trabecular bone was predicted for at least one C/I and all IL of 10 mm or less. Higher C/I ratios and lower IL increase the risk of overloading and fracture. Increasing C/I augments the functional effects of other implant design factors. Greater C/I ratios may be achieved with implant designs that induce less significant strain concentrations.