Document Detail

The modular endoprosthesis for mandibular body replacement. Part 2: Finite element analysis of endoprosthesis reconstruction of the mandible.
MedLine Citation:
PMID:  22516866     Owner:  NLM     Status:  Publisher    
INTRODUCTION: Problems with loosening of the modules for the modular endoprosthesis were encountered in animal studies for mandibular body replacement. We performed a finite element analysis to look at the stress distribution and areas of stress concentration in a human sized mandible. Variations were made to the stem and defect length to look at how the forces changed. The hypothesis was: (1) reconstruction with a modular endoprosthesis did not lead to areas of stress concentration beyond the material strength of cortical bone and titanium alloy; (2) changes in dimensions of the endoprosthesis did not cause a corresponding linear increase to the stresses. MATERIALS AND METHODS: The endoprosthesis was modelled to create a male, female part with stems and a connection screw (Case I). The stem length was halved (Case II) and defect length doubled (Case III). Geometric data of a human sized mandible were obtained, a continuity defect created digitally at the right molar area and the models combined. Boundary conditions were set and the model loaded to get a bite force of 300 N at the incisor region. An intact mandible was used as a control. RESULTS: The right side of the reconstructed mandible became less rigid and flexed more. The highest stresses were within the endoprosthesis at two areas of stress concentration: (1) shear stress at the superior surface of the stems close to the junction of the stem and the module body; (2) compressive stresses at the bottom bevel of the dove-tailed connection. The stress distribution for Case I and II did not differ much except for the magnitude which was slightly higher for Case II. There was a tendency for outward bending at the module connection for Case III which potentially might cause loosening of the module connection. Displacements of the mandible were less than 1 mm throughout. CONCLUSION: The endoprosthesis with its present dimensions would be expected to perform adequately at a bite force of 300 N. An increase in defect length caused a tendency for bending at the stem and the module connection. With a decrease in stem length, there were little differences except a slight increase in magnitude.
Raymond C W Wong; Henk Tideman; Matthias A W Merkx; John Jansen; Suk Ming Goh
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-4-17
Journal Detail:
Title:  Journal of cranio-maxillo-facial surgery : official publication of the European Association for Cranio-Maxillo-Facial Surgery     Volume:  -     ISSN:  1878-4119     ISO Abbreviation:  -     Publication Date:  2012 Apr 
Date Detail:
Created Date:  2012-4-20     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8704309     Medline TA:  J Craniomaxillofac Surg     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2012 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Department of Oral and Maxillofacial Surgery, National Dental Centre, Singapore.
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