Sharanyadhevi, K T (2016) Three Dimensional Evaluation of Stress Distribution and Displacement by Miniscrew Implants Assisted Palatal Expander: A Finite Element study. Masters thesis, Ragas Dental College and Hospital, Chennai.
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Abstract
AIM OF THE STUDY: The aim of the present study is to assess the stress distribution and displacement of the maxilla and teeth in an average and constricted arch width models according to different designs of RME using miniscrew implants on a 3D FE model of the skull. MATERIALS AND METHODS: Two groups of FEM models, Group-A (average maxillary arch) and Group-B (constricted maxillary arch) were constructed. The maxilla including teeth and alveolar bone were sectioned into 1mm tetrahedrons and the skull sectioned into 5mm tetrahedrons. For the FE modelling a computed tomography scan of a skull is converted to STL file using MIMICS followed by meshing the geometric model. The final constructed FE model is then imported in to ANSYS version 15.0 software. There were 4 designs of rapid maxillary expanders. In type 1- four miniscrew implants were placed 3mm lateral to mid-palatal suture. In type 2-four mini screw implants were placed beneath the alveolar ridge at the palatal slope and connected to the expander through an acrylic resin cover. In type 3-two miniscrew implants placed 3mm lateral to mid-palatal suture between canine and first premolars and connected to the expander with conventional hyrax arms soldered on the first molar (Hybrid design). In type 4-Conventional tooth borne appliance assisted by perforations using miniscrew implants in mid-palatal suture at 3 points from the incisive papilla to the last molar. Expanders were activated transversely for 0.5 mm and force of 45 newtons (N) were applied to achieve sufficient separation of two halves of the maxillary segments. Geometric nonlinear theory was applied to evaluate Von-Mises stress distribution and displacement. RESULTS: More stresses were concentrated around the miniscrew implants in type1, 3 and 2. The mean stress distribution and depth of penetration were high in the type1. Type 2 had the least stress distribution around the anchorage and showed alveolar expansion without buccal inclination. The rotation of dentoalveolar unit was larger in type 4 and type3. Type 1 and type 2 exhibited downward displacement. Type 4 and type 3 exhibited downward and backward displacement. CONCLUSIONS: Miniscrew assisted RME showed more skeletal contribution in the net expansion result compared with conventional RME. Miniscrew assisted RME has the higher probability to elucidate the sutural response. Therefore, Customizing RME design (HYBRID) for every individual patients helps us to achieve the desired results with minimum relapse. Keywords: Rapid Maxillary Expansion, Bone-borne rapid maxillary expanders, tooth-borne rapid maxillary expanders, Finite Element Modelling. AIM OF THE STUDY: The aim of the present study is to assess the stress distribution and displacement of the maxilla and teeth in an average and constricted arch width models according to different designs of RME using miniscrew implants on a 3D FE model of the skull. MATERIALS AND METHODS: Two groups of FEM models, Group-A (average maxillary arch) and Group-B (constricted maxillary arch) were constructed. The maxilla including teeth and alveolar bone were sectioned into 1mm tetrahedrons and the skull sectioned into 5mm tetrahedrons. For the FE modelling a computed tomography scan of a skull is converted to STL file using MIMICS followed by meshing the geometric model. The final constructed FE model is then imported in to ANSYS version 15.0 software. There were 4 designs of rapid maxillary expanders. In type 1- four miniscrew implants were placed 3mm lateral to mid-palatal suture. In type 2-four mini screw implants were placed beneath the alveolar ridge at the palatal slope and connected to the expander through an acrylic resin cover. In type 3-two miniscrew implants placed 3mm lateral to mid-palatal suture between canine and first premolars and connected to the expander with conventional hyrax arms soldered on the first molar (Hybrid design). In type 4-Conventional tooth borne appliance assisted by perforations using miniscrew implants in mid-palatal suture at 3 points from the incisive papilla to the last molar. Expanders were activated transversely for 0.5 mm and force of 45 newtons (N) were applied to achieve sufficient separation of two halves of the maxillary segments. Geometric nonlinear theory was applied to evaluate Von-Mises stress distribution and displacement. RESULTS: More stresses were concentrated around the miniscrew implants in type1, 3 and 2. The mean stress distribution and depth of penetration were high in the type1. Type 2 had the least stress distribution around the anchorage and showed alveolar expansion without buccal inclination. The rotation of dentoalveolar unit was larger in type 4 and type3. Type 1 and type 2 exhibited downward displacement. Type 4 and type 3 exhibited downward and backward displacement. CONCLUSIONS: Miniscrew assisted RME showed more skeletal contribution in the net expansion result compared with conventional RME. Miniscrew assisted RME has the higher probability to elucidate the sutural response. Therefore, Customizing RME design (HYBRID) for every individual patients helps us to achieve the desired results with minimum relapse.
| Item Type: | Thesis (Masters) |
|---|---|
| Uncontrolled Keywords: | Rapid Maxillary Expansion, Bone-borne rapid maxillary expanders, tooth-borne rapid maxillary expanders, Finite Element Modelling. |
| Subjects: | DENTAL > Orthodontics and Dentofacial Orthopedics |
| Depositing User: | Subramani R |
| Date Deposited: | 22 Sep 2021 04:51 |
| Last Modified: | 22 Sep 2021 04:51 |
| URI: | http://repository-tnmgrmu.ac.in/id/eprint/18061 |
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