Modeliranje iniciranja koštane pregradnje kod ortodontske terapije

Leder Horina, Jasna (2015) Modeliranje iniciranja koštane pregradnje kod ortodontske terapije. = Modelling of initiation of bone remodelling due to orthodontic treatment. Doctoral thesis , Sveučilište u Zagrebu, Fakultet strojarstva i brodogradnje, UNSPECIFIED. Mentor: Jurčević Lulić, Tanja and Rietbergen, Bert van.

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Abstract

Owing to its interesting properties, bone has always been an appealing area of research. In addition, bone reacts to daily life activities to which it is constantly exposed and its properties are in turn affected. Over the last century, many attempts have been made to describe the mechanical behavior of bone. Different analytical and experimental approaches and later numerical techniques have been exploited in order to explain and understand bone properties. Bone remodelling is the process of resorption of bone tissue material and formation of new bone. These processes are triggered by daily loading and it is constantly happening in the human organism and to all human bones. To explain the mechanical background of bone remodelling, many theories have been developed. First theories explained bone remodelling in the field of orthopedics, on the femur, where they admit to the existence of the mechanical stimulus. The mechanical stimulus represents the daily mechanical loading on bone. If the bone is in overloaded condition, then bone formation appears. On the other hand, if the bone is in underloaded condition, then bone resorption appears. Theories explaining bone remodelling in orthopedic biomechanics follow and confirm Wollf’s Law. In dental biomechanics, when orthodontic forces have been applied, bone remodelling appears in the alveolar bone. Since in orthodontics there are more tissues involved in bone remodelling in the alveolar bone, alternative theories have been made. These theories take into account the existence of the mechanical stimulus, but adjustments have been made because of the influence of the tooth and the periodontal ligament. Two approaches have been developed to explain bone remodelling in the alveolar bone. The first approach points out that the strains in the bone resulting from orthodontic force cause bone remodelling. The second approach points out that the deformities in PDL cause bone remodelling. Even though the present orthodontic treatment strategies generally lead to satisfactory results, the biomechanical mechanism which leads to tooth movement is still not fully understood. A better understanding of this mechanism could lead to further optimization of the treatment. The goal of this research was to test whether tooth movement resulting from orthodontic force application can be predicted using load adaptive bone remodelling theories developed in previous studies when applied to the alveolar bone. The hypothesis analyzed in this research is that the tooth is ‘hanging’ in the fibrous PDL when loaded by chewing forces, and that orthodontic forces would reduce the loading in the fibres on the side which the tooth is pushed towards and increase the loading in the fibres on the other side. To test this, patient-specific 3D models of tooth and the alveolar bone in combination with validated computational bone remodelling models were used. These models account for the cortical and cancellous bone, as well as the fibrous periodontal ligament. Chewing forces and orthodontic forces were applied as external forces and bone remodelling was predicted from changes in bone tissue loading, which was induced by the orthodontic forces. In the research that was carried out, bone remodelling initiation caused by wearing a fixed orthodontic appliance was numerically described. Furthermore, the goal was to develop a numerical model that is patient-specific, which would result in a personalized orthodontic treatment. In the research, a single root tooth, the incisor, was used, and the tooth was loaded with the vertical force that describes the chewing force, as well as with the transversal force that describes the influence of the orthodontic force. The research was carried out in four stages. The first stage was the development of a 2D model, and in this stage the focus was on the numerical description of the PDL and on quantifying the changes in bone loading due to the orthodontic and the chewing force. In the second stage of the research, the 3D geometry of the tooth, the PDL and the bone was defined. The geometry was based on 3D cone beam CT images of the patient. The geometry was obtained by using the Mimics software. In the third stage of the research analyses of the 3D model, obtained in the second stage, were made by using Marc Mentat, the software for finite element analysis. The finite element analysis was performed with three combinations of loads, so that the impact of the load on the model can be analyzed. The influence of the chewing force only, the influence of the orthodontic force only and the influence of both forces acting together was analyzed. The last stage of the research was the development of a bone remodelling algorithm in the Fortran programming language. The bone remodelling algorithm is implemented in Marc Mentat by using a special subroutine. This subroutine calculated the referent value of strain energy density, predicted bone formation, bone resorption and new apparent density as well. The results confirmed the hypothesis and showed stress distribution and changes in strain energy density during bone remodelling initiation, by showing the underloading side of the bone and the overloading side of the bone, and by initiating bone resorption on the underloading side and bone formation on the overloading side of the bone.

Item Type: Thesis (Doctoral thesis)
Uncontrolled Keywords: zubi, ortodontska terapija, koštana pregradnja, numerički model
Keywords (Croatian): tooth, orthodontic treatment, bone remodelling, numerical model
Subjects: TECHNICAL SCIENCE > Mechanical Engineering
Divisions: 200 Department of Engineering Mechanics > 240 Chair for Biomechanics and Ergonomy
Date Deposited: 20 Jul 2015 10:57
Last Modified: 16 Oct 2015 12:44
URI: http://repozitorij.fsb.hr/id/eprint/4652

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