engleski

Modelling of Initiation of Bone Remodelling due to Orthodontic 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 xii CHAPTER . SUMMARY 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.

tooth, orthodontic treatment, bone remodelling, numerical model

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