Assessing Bone Healing in Mandibular Segmental Repair: A Simulation Study
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University of Toledo / OhioLINK
2016
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ndltd-OhioLink-oai-etd.ohiolink.edu-toledo14703550392021-08-03T06:38:03Z Assessing Bone Healing in Mandibular Segmental Repair: A Simulation Study Raad, Bahram, Raad Mechanical Engineering Mandibular defects may result from trauma, tumor resection, or inflammation. The goals for mandibular reconstruction surgeries are to retrieve mandible functions, applications, and appearance. To this end, surgeons use a combination of bone grafts and metallic implants. Implants mechanical properties are drastically different from the surrounding bone. So, the density and stress distribution in the mandible changes after the surgery. In addition, the long-term abnormal stress/strain distribution may lead to graft failure due to bone resorption as a result of stress shielding and hardware failure due to stress concentrations. During the healing period of six to nine months, it is important to achieve complete immobilization and changing mandibular micro-motion down to the level of 200-500 µm while chewing. After this period, it is desired that bone retrieve its normal density distribution as the success of the treatment. Although current stiff fixation hardware accomplishes the immobilization during the healing period, over the long-term, the immobilized and stress-shielded engrafted bone tends to resorb. On the other hand, screw loosening or/and hardware fracturing is observed as the stress concentration at certain hardware locations. The first stage of this research is to investigate the problems encountered following a mandible reconstructive surgery. In this respect, we designed a finite element model of a healthy mandible, which includes cancellous and cortical bone, the periodontal ligament and teeth. Using this model, we studied a healthy adult mandible under maximum bite force for stress, strain, reaction force distribution, and bone density distribution. Stress distribution of the healthy mandible was then used as the criteria to show the problems of the current standard of care.For mandibular segmental reconstruction surgery, the current standard of care includes the use of Surgical Grade 5 titanium also known as Ti-6Al-4V hardware and a single/double fibula barrel vascularized bone graft. Our model which is designed for this study includes double barrel fibular bone graft containing a section of the mandible, metallic fixation hardware and screws. We found out that the stiffness mismatch between the bone and the fixation hardware causes stress concentration at the fixation hardware and screws and stress shielding on the bone graft and the host mandible. To improve the long-term outcome of using metallic implants, it is essential to recreate the normal density distribution and the stress pattern to achieve a faster bone healing period. To this end, we investigated the use of porous superelastic nitinol (NiTi) as a substitute for the currently used high stiffness titanium hardware. While nitinol has a lower stiffness than titanium, it is possible to add porosity to reduce its stiffness, even more, to be closer to the stiffness of cortical bone. The ultimate goal is to design a fixation hardware that has proper stiffness for immobilization during remodeling the normal bone density distribution. Using an FE model of devices fabricated from titanium and nitinol, we have found that using porous superelastic nitinol hardware with conventional geometries leads to the recreation of normal density distribution, stress-strain trajectories, and finally better treatment outcome. 2016 English text University of Toledo / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=toledo1470355039 http://rave.ohiolink.edu/etdc/view?acc_num=toledo1470355039 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws. |
| collection |
NDLTD |
| language |
English |
| sources |
NDLTD |
| topic |
Mechanical Engineering |
| spellingShingle |
Mechanical Engineering Raad, Bahram, Raad Assessing Bone Healing in Mandibular Segmental Repair: A Simulation Study |
| author |
Raad, Bahram, Raad |
| author_facet |
Raad, Bahram, Raad |
| author_sort |
Raad, Bahram, Raad |
| title |
Assessing Bone Healing in Mandibular Segmental Repair: A Simulation Study |
| title_short |
Assessing Bone Healing in Mandibular Segmental Repair: A Simulation Study |
| title_full |
Assessing Bone Healing in Mandibular Segmental Repair: A Simulation Study |
| title_fullStr |
Assessing Bone Healing in Mandibular Segmental Repair: A Simulation Study |
| title_full_unstemmed |
Assessing Bone Healing in Mandibular Segmental Repair: A Simulation Study |
| title_sort |
assessing bone healing in mandibular segmental repair: a simulation study |
| publisher |
University of Toledo / OhioLINK |
| publishDate |
2016 |
| url |
http://rave.ohiolink.edu/etdc/view?acc_num=toledo1470355039 |
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AT raadbahramraad assessingbonehealinginmandibularsegmentalrepairasimulationstudy |
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