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Modelling of mandibular functional deformation

Al-Sukhun, Jehad; (2003) Modelling of mandibular functional deformation. Doctoral thesis (Ph.D), UCL. Green open access

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Abstract

Functional jaw deformation is believed to be of significance in implant dentistry, particularly when using large implant-stabilised prostheses. This study investigated the hypothesis that such deformation could be modelled using finite element techniques. Mandibular surface strain and three patterns of mandibular deformation (medial convergence, corporal rotation and dorso-ventral shear) were studied. Both strain and deformation were studied in-vitro using a dried mandible mounted in a rig which simulated natural function. Surface strain was determined using resistance strain gauges mounted on the dried mandible, whilst deformation was measured using custom-fabricated displacement transducers mounted on endosseous implants in the premolar region. Functional jaw deformation was studied clinically using similar transducers in five patients who had been treated with endosseous implants. Both the dried mandible and the jaws of the patients who had been treated with implants were modelled using finite element techniques based on digitised CT scan images of the jaws. The contours of the bone sections were traced on an acetate overlay, and calibration bars on each image used to scale and reference the outlines to a common origin. Tracings were digitised by means of a computerised image analysis system, and the transcribed data were stored electronically. The contour data of the sections were transformed using translator software written by EMRC (Engineering Mechanics Research Corporation, Troy, Michigan, USA) to coordinate points, and then read by the finite element program. The finite element model (FEM) was found to closely replicate both the surface strains and patterns of observed mandibular deformation. Differences between the predicted and measured deformation values were expressed as a percentage of the measured value and ranged between 3 and 18 %. Medial convergence ranged between 9.0 and 57.8 μm. Dorso-ventral shear and corporal rotation ranged between 0.4 and 2.9 degrees. The predicted values of the antero-posterior shear ranged between 0.5 and 2.0 degrees. The close agreement between the predicted and measured deformation values provided a high level of confidence in the finite element model and its ability to provide a deeper understanding of functional mandibular deformation.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Modelling of mandibular functional deformation
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
URI: https://discovery.ucl.ac.uk/id/eprint/10100076
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