A study of the Rapid Maxillary Expansion with the use of the finite element method

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Biomechanics and Remodelling for Design and Optimisation in Oral Prosthesis and Therapeutical Procedure

The purpose of dental prostheses is to restore the oral function for edentulous patients. Introducing any dental prosthesis into mouth will alter biomechanical status of the oral environment, consequently inducing bone remodelling. Despite the advantageous benefits brought by dental prostheses, the attendant clinical complications and challenges, such as pain, discomfort, tooth root resorption, and residual ridge reduction, remain to be addressed. This thesis aims to explore several different dental prostheses by understanding the biomechanics associated with the potential tissue responses and adaptation, and thereby applying the new knowledge gained from these studies to dental prosthetic design and optimisation. Within its biomechanics focus, this thesis is presented in three major clinical areas, namely prosthodontics, orthodontics and dental implantology. In prosthodontics, the oral mucosa plays a critical role in distributing occlusal forces a denture to the underlying bony structure, and its response is found in a complex, dynamic and nonlinear manner. It is discovered that interstitial fluid pressure in mocosa is the most important indicator to the potential resorption induced by prosthetic denture insertion, and based on this finding, patient-specific analysis is performed to investigate the effects caused by various types of dentures and prediction of the bone remodelling activities. In orthodontic treatments, a dynamic algorithm is developed to analyse and predict potential bone remodelling around the target tooth during orthodontic treatment, thereby providing a numerical approach for treatment planning. In dental implantology, a graded surface morphology of an implant is designed to improve osseointegration over that of a smooth uniform surface in both the short and long term. The graded surface can be optimised to achieve the best possible balance between the bone-implant contact and the peak Tresca stress for the specific clinical application need

Assessment of the stresses produced on the bone implant/tissue interface to the different insertion angulations of the implant - a three-dimensional analysis by the finite elements method

The present study aimed to assess the stresses produced on the surface of the bone tissue around dental implants with three different insertion angulations subjected to axial and oblique loading. The study was created according to the recommendations of the Checklist for Reporting In-vitro Studies (CRIS). The Straumann? bone level RC (4.1 x 10 mm) implant, Cone Morse connection (CM), RC Straumann Variobase? with abutment (3.5 mm) was placed in the region of element 16, with the platform positioned at the height of the bone crest. Three assessment models were produced: model M1 or control - implant perpendicular to the bone crest; model M2 - implant angulated at 17° relative to the bone crest; and model M3 - implant angulated at 30° relative to the bone crest. The masticatory loads were simulated with 100 N of intensity and two loading patterns (axial and oblique) were applied to each model. Then, the models were exported to the finite elements simulation software Ansys Workbench V19.2 (Ansys Inc., Canonsburg, PA, USA). To assess the finite elements, qualitative and quantitative analyses were performed. It was observed that, under axial loading, qualitatively, the peaks occurred in the cavosurface region, palatal aspect in M1 and M2, and buccal aspect in M3. Quantitatively, the greatest angulation resulted in a low stress peak. Under oblique loading, qualitatively, the peaks occurred in the cavosurface region, buccal aspect in the three groups. Quantitatively, the greatest angulation of the implant resulted in an increase in stress peaks on the buccal aspect. Under axial loading, the three insertion angulations of the implant - M1, M2, and M3 - were clinically viable. When subjected to oblique loading, the 30° angulation (M3) suggested a significant risk of bone loss and it was contraindicated

Three Dimensional Evaluation of Stress Distribution and Displacement by Miniscrew Implants Assisted Palatal Expander: A Finite Element study

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

Management of bone defects with Bio-oss

Introduction: The defects in the alveolar bone might appear as a result of congenital malformations, traumatic injuries, periodontal disease, surgical traumas, chronic periapical changes and tumors from benign or malignant origin. The aim of this study was to provide solid and healthy area with application of Bio-Oss in the defect. Materials and methods: Based on the clinical diagnosisestablished by previously taken history, clinical examination and radiographic images oral-surgery interventions was made. To realize the aim of this work, augmentative material was implicated in the bone defects made in the patients after removal of follicular cyst, chronic periapical lesion, and parodontopathia. During the first and seventh day of the interventions, the patients have been followed through from aspect of possible development of local and general complications after the oral-surgery intervention. After period of one, three and six mount control x-ray was made. Results: Obtained results confirmed that: volume of the socket and defect of the bone was kept, fast revascularization was achieved, bone formation and slow resorption of the augmentative material was achieved, and period of normal healing without infection was also achieved. Conclusions: The augmentative materials used for treatment of bone defects besides their basic chemical and physical characteristics referring to their solubility in the body fluids, the transformation, modulation and resorption must be completely safe or secure, i.e. not to bring any risk of infection, immunological risk, physiological intolerance or inhibition of the process of restitutio ad integrum. In our study Bio-Oss was confirmed as augmentative material who had this characteristics. Keywords: bone defect, resorption of the bone, augmentative material, Bio-Os

Application of polyetheretherketone (PEEK) posts: evaluation of fracture resistance and stress distribution in the root: in vitro and finite element analyses

Abstract To evaluate the feasibility of using a milled polyetheretherketone (PEEK) post and core in endodontically treated teeth with or without a ferrule. Sixty bovine tooth roots were endodontically treated followed by cementation of intraradicular retainers (IR), according to each experimental group: a) non-ferrule glass fiber post (f0FP); b) 2-mm-ferrule glass fiber post (f2FP); c) non-ferrule resized glass fiber post (f0PR); d) 2-mm-ferrule resized glass fiber post (f2PR); e) non-ferrule PEEK post and core (f0PPC); and f) 2-mm-ferrule PEEK post and core (f2PPC). Metal crowns were made and cemented. A periodontal ligament was simulated using polyether. A force was applied to the palatine portion of each sample at 45°, until fracture. Fracture resistance data were submitted to two-way ANOVA and Tukey’s test (α = 0.05). Three-dimensional digital models were developed to calculate the tensions formed in the root using finite element analysis. Models of glass fiber posts and PEEK posts and cores were evaluated with or without a ferrule. The results were analyzed by the Mohr-Coulomb criterion. The type of IR was not influenced by fracture strength (p = 0.243). There were significant statistical differences among the remaining factors. Ferrule groups had greater fracture resistance, and the failure mode of teeth with a ferrule was more catastrophic than the non-ferrule group. A ferrule increases fracture resistance and influences failure mode; the PEEK post and core did not modify the biomechanics of endodontically treated teeth, and resembled the glass fiber post results. The crack initiation point differed between the ferrule and non-ferrule groups