Department of Mechanical and Mechatronic Engineering

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    Development and validation of a parametric mandible plate design method
    (Stellenbosch : Stellenbosch University, 2021-03) Giddy, Brett Ian; Vander Merwe, J.; Stellenbosch University. Faculty of Engineering. Dept. of Mechanical and Mechatronic Engineering.
    ENGLISH ABSTRACT: This study investigated the feasibility and attempted to develop a parametric mandible reconstruction plate design method in order to reduce surgical lead time, improve fit and structural performances. This method includes a CAD template that accepts a range of realistic mandible dimensions as the input. The output is a 3-dimensional mandible reconstruction plate. A reconstruction plate/mandible comparison test was performed on several combinations in order to determine whether the parametric plate provided a suitable alternative to conventional reconstruction plates in terms of fit and structural performance. 37 male and 37 female random mandibles were generated and measured. These measurements were used to create the corresponding parametric plates. The plates were aligned with their mandibles and the Hausdorff distances were recorded. A Finite Element Analysis was performed on the male and female mandibles which exhibited the most curvature, with three common plate configurations in literature. All boundary conditions such as the displacements, supports, muscle force vectors and magnitudes, as well as mandible and plate material properties were taken from literature. The comparison test indicated that the parametric plate provides a reasonable approximation of mandible geometry. The mean mandible plate deviation for lateral short and symphyseal plates was less than 2 mm for the male and female configurations. The mean hemimandible plate deviation was less than 2.6 mm for both the male and female plates. Some bending may be required due to the irregularities in mandible geometry, however significantly less than what is required to shape the commercial straight mandible reconstruction plate. The Finite Element Analysis results indicate that the maximum Von-mises stresses in parametric plate were noticeably lower in all three plate configurations when compared to the commercial straight reconstruction plates. The lowest recorded maximum stress recorded in the parametric plates was in the male symphyseal plate at 102.31 MPa. The highest maximum stress recorded in the parametric plates was in the female hemimandible plate at 623.38 MPa. Whereas the respective stresses in the commercial straight plates were 223.09 MPa in the male symphyseal and 652.25 MPa in the female hemimandible plates. Reaction values were compared with hand calculations as a means of model validation.