Comparison of three internal fixation techniques in mandibular sagittal split osteotomy, a finite element analysis
Citation:HASSAN, MUHAMMAD KAMIL, Comparison of three internal fixation techniques in mandibular sagittal split osteotomy, a finite element analysis, Trinity College Dublin.School of Dental Sciences.ORAL BIOSCIENCES, 2018
MSc Thesis Kamil Hassan.pdf (Research thesis, final approved version) 5.985Mb
Various internal fixation techniques are used in orthognathic surgery. The aim of this study was to analyse and compare the biomechanical properties of three internal fixation techniques (2.0mm bi-cortical screws, 2.0mm miniplate and 1.7mm miniplate) in mandibular sagittal split osteotomy. A peri-operative CT of patient?s skull was used to develop a dentate hemi-mandible using computer software. The hemi-mandible model underwent sagittal split osteotomy virtually, and was reproduced. A total of 9 models consisting of the 3 fixation techniques with mandibular movements of 3mm setback, 3mm advancement and 7mm advancement were developed. Bite forces applied were 50, 75, and 100N for incisors, and 100, 200 and 300N for molars. The finite element analyses were carried out in Simulation Solidworks?. Stresses and displacement readings in fixations and bone were recorded. The bi-cortical screws with an inverted-L orientation was the most rigid fixation technique in all mandibular movements. It had the least displacement and stress in the models. Stress is mostly concentrated in the inferior-distal screw for the bi-cortical screws fixation, whereas the stresses in miniplates are generally dissipated in the connector region of the plate. Not surprisingly, the 1.7mm miniplate was the least rigid fixation. The stresses in surrounding bone of the fixations were variable for each technique. Miniplate fixations had higher bone stresses in the setback movement and lower with mandibular advancements, whilst bi-cortical screws showed higher stress in bone with mandibular advancements. The application of bi-cortical screws has shown to be the most rigid fixation, although with increased stresses in surrounding bone in mandibular advancements. The 1.7mm and 2.0mm miniplates are less rigid than the bi-cortical screws but importantly handled stresses within the ultimate yield strength. The amount of displacement of the mandible segment in the 1.7mm miniplate group is less than 1mm for all mandibular movements. The 1.7mm miniplate can be considered as an alternative fixation technique for setbacks and advancements of 3 mm, and although probably satisfactory, we need more clinical follow up for advancements of 7mm or more.
Author: HASSAN, MUHAMMAD KAMIL
Publisher:Trinity College Dublin. School of Dental Sciences. Discipline of Dental Science
Type of material:Thesis
Availability:Full text available