Review of biomechanical models used in studying the biomechanics of reconstructed mandibles

Abstract

This study looked at computer and physical biomodels used to study the biomechanical performance of mandibular reconstruction, reviews the literature and explains the strengths and limitations of the models. Electronic databases (Pubmed, Medline) were searched. 17 articles were selected. Computer biomodels can be divided into virtual biomodels (mainly used for clinical diagnosis and treatment planning) and computational models (e.g. finite element analysis), they can predict areas most likely to fail based on internal stress distribution and areas of maximum stress concentration. Physical biomodels include: rapid prototyping, animal bone, human cadaveric bone, and bone substitute models. Physical models allow testing on a gross level to give fatigue performance and fracture strength. The use of bone substitutes allows a more consistent specimen size and a reduction in sample size. Some commercially available products can replicate the material properties of bone. The use of any biomodel depends on the question being asked: the bending strength of a reconstruction plate would necessitate a three point bending test; the biomechanical performance of a new method of reconstruction (e.g. the mandibular modular endoprosthesis) would necessitate finite element analysis to predict areas of likely failure and also a physical biomodel to look at fatigue failure.

Surgeons dealing with mandibular resection have been seeking the ideal method of mandibular reconstruction for centuries . The mandible is the only movable stress bearing bone of the face. Methods of mandibular reconstruction that disregard the various forces acting on it, led to early screw loosening, plate fracture, bone loss and failure of the reconstruction. There have been various studies on the forces acting on the mandible and its reconstruction including clinical observations, animal studies that need to be extrapolated to humans, and experimental analysis on models created to simulate mandibular function. Rules on the ethical treatment of animals have minimized the use of animal models. Biomechanical models that replicate the form and function of the mandible, either physically or on a computer, have reduced the need for animal experimentation.

Biomodelling describes the ability to replicate the morphology of a biological structure. Numerical (computer) and physical models are used by researchers to design, analyze objects and understand physical phenomena. Computer modelling has allowed work to be done in a virtual environment, where complex numerical models can be handled with relative ease. Such methods allow simulation of the forces acting on the mandible and approximate calculations of these forces at various points throughout the mandible. Physical models range from simple bone models mounted on a testing jig to more complex biomodels rendered in solid form that can be produced by engineering technologies such as rapid prototyping techniques, which replicate the morphology of the mandible .

The objective of this study was to look at the available knowledge on the use of biomodels for studying mandibular reconstruction, the technical processes involved, possible future directions for research and to review the literature. The authors aim to help the surgeon without a technical background evaluate and understand these papers, which use technical (engineering) terms and methods, and point out the deficiencies of each method.

Method

A computer database search was performed, through the use of Medline (Pubmed) for all the years available. The following subject headings were used individually and in combination: ‘Biomechanics’ [Mesh] AND ‘Mandible’ [Mesh]; ‘Models, computer’ [Mesh] OR ‘Models, computational’ [Mesh] OR ‘Computer simulation’ [Mesh] OR ‘Finite element analysis’ [Mesh] AND ‘Mandible’ [Mesh]; ‘Models, Anatomic’ [Mesh] OR ‘Models, Structural’ [Mesh] OR ‘Models, Theoretical’ [Mesh] OR ‘Models, Animal’ [Mesh] AND ‘Mandible’ [Mesh]. A keyword search was also performed: bone biomodels, mandible biomodels, computer models, computer simulation, finite element analysis, physical biomodels, biomechanics, mechanical testing and mandible reconstruction. Terms were limited to studies that were published in the English language, core clinical and dental journals.

Studies were included if models were used for looking at the biomechanics of any method of mandibular reconstruction either alone or in combination with clinical studies. Studies were excluded if they reported on models used for fracture fixation, orthognathic surgery, distraction osteogenesis, dental implants and dental prosthesis. Any papers reporting only clinical outcomes were also excluded.

Articles that met the inclusion criteria based on their abstract information were selected and collated. Articles were also obtained when there was not enough information in the abstracts or if a citation had no abstract. Reference lists of the selected articles were also searched for any publications that had been missed by the search engines.

Results

447 papers were found using the search terms ‘Biomechanics’ [Mesh] AND ‘Mandible’ [Mesh]; 333 papers with the terms ‘Models, computer’ [Mesh] OR ‘Models, computational’ [Mesh] OR ‘Computer simulation’ [Mesh] OR ‘Finite element analysis’ [Mesh] AND ‘Mandible’ [Mesh]; 1371 papers with ‘Models, Anatomic’ [Mesh] OR ‘Models, Structural’ [Mesh] OR ‘Models, Theoretical’ [Mesh] OR ‘Models, Animal’ [Mesh] AND ‘Mandible’ [Mesh]. Combinations of the above search terms yielded 70 papers. The additional search terms yielded 8, 3, 50, 55, 9, 4, 35 and 10 papers, respectively. Only 17 papers fulfilled the inclusion criteria ( Table 1 ).

Table 1
List of papers selected according to category of biomodel.
Year Author Title
Bone biomodels/biomechanical models 2005 L ohfeld et al. Biomodels of bone: a review
Computer biomodels 1995 W ittkampf & S tarmans Prevention of mandibular fractures by using constructional design principles. I. Computer simulation of human mandibular strength after segmental resections
1999 C urtis et al. Modelling of jaw biomechanics in the reconstructed mandibulectomy patient
2006 K imura et al. Adequate fixation of plates for stability during mandibular reconstruction
2006 K noll et al. Analysis of mechanical stress in reconstruction plates for bridging mandibular angle defects
2006 T ie et al. Three-dimensional finite element analysis investigating the biomechanical effects of human mandibular reconstruction with autogenous bone grafts
2008 S tavness et al. Towards predicting biomechanical consequences of jaw reconstruction
2008 S tavness et al. Tools for predicting biomechanical consequences of alterations to orofacial anatomy
2009 S chuller -G otzburg et al. 3D-FEM and histomorphology of mandibular reconstruction with the titanium functionally dynamic bridging plate
Physical biomodel 1995 W ittkampf et al. Prevention of mandibular fractures by using constructional design principles. II. A tension strength test on beagle mandibles with two different types of segmental resections
1999 Y i et al. Reconstruction plates to bridge mandibular defects: a clinical and experimental investigation in biomechanical aspects
2000 B redbenner & H aug Substitutes for human cadaveric bone in maxillofacial rigid fixation research
2000 S trackee et al. Fixation methods in mandibular reconstruction using fibula grafts: a comparative study into the relative strength of three different osteosynthesis
2004 D oty et al. Biomechanical evaluation of fixation techniques for bridging mandibular defects
2005 D e S antis et al. An experimental and theoretical composite model of the human mandible
2007 S chupp et al. Biomechanical testing of different osteosynthesis systems for segmental resection of the mandible
2008 X u et al. Review of the human masticatory system and masticatory robotics

Biomechanical models can be divided into computer based and physical biomodels ( Fig. 1 ). Computer based biomodels can be subdivided into: virtual biomodels used for visualization of biological structures, for example a three-dimensional (3D) computer image generated from computed tomographic (CT) scans ( Fig. 2 ); and computational biomodels used for performing biomechanical analysis, for example a finite element model of the mandible used for determination of stress and strain distribution ( Fig. 3 ). Physical biomodels can be categorized as: rapid prototyping model; cadaveric bone model; animal bone model; and bone substitute model; depending on the material used.

Fig. 1
Biomodels classification.

Fig. 2
Three-dimensional computed tomographic scan.

Fig. 3
A finite element model of a monkey mandible showing stress distribution.

Results

447 papers were found using the search terms ‘Biomechanics’ [Mesh] AND ‘Mandible’ [Mesh]; 333 papers with the terms ‘Models, computer’ [Mesh] OR ‘Models, computational’ [Mesh] OR ‘Computer simulation’ [Mesh] OR ‘Finite element analysis’ [Mesh] AND ‘Mandible’ [Mesh]; 1371 papers with ‘Models, Anatomic’ [Mesh] OR ‘Models, Structural’ [Mesh] OR ‘Models, Theoretical’ [Mesh] OR ‘Models, Animal’ [Mesh] AND ‘Mandible’ [Mesh]. Combinations of the above search terms yielded 70 papers. The additional search terms yielded 8, 3, 50, 55, 9, 4, 35 and 10 papers, respectively. Only 17 papers fulfilled the inclusion criteria ( Table 1 ).

Table 1
List of papers selected according to category of biomodel.
Year Author Title
Bone biomodels/biomechanical models 2005 L ohfeld et al. Biomodels of bone: a review
Computer biomodels 1995 W ittkampf & S tarmans Prevention of mandibular fractures by using constructional design principles. I. Computer simulation of human mandibular strength after segmental resections
1999 C urtis et al. Modelling of jaw biomechanics in the reconstructed mandibulectomy patient
2006 K imura et al. Adequate fixation of plates for stability during mandibular reconstruction
2006 K noll et al. Analysis of mechanical stress in reconstruction plates for bridging mandibular angle defects
2006 T ie et al. Three-dimensional finite element analysis investigating the biomechanical effects of human mandibular reconstruction with autogenous bone grafts
2008 S tavness et al. Towards predicting biomechanical consequences of jaw reconstruction
2008 S tavness et al. Tools for predicting biomechanical consequences of alterations to orofacial anatomy
2009 S chuller -G otzburg et al. 3D-FEM and histomorphology of mandibular reconstruction with the titanium functionally dynamic bridging plate
Physical biomodel 1995 W ittkampf et al. Prevention of mandibular fractures by using constructional design principles. II. A tension strength test on beagle mandibles with two different types of segmental resections
1999 Y i et al. Reconstruction plates to bridge mandibular defects: a clinical and experimental investigation in biomechanical aspects
2000 B redbenner & H aug Substitutes for human cadaveric bone in maxillofacial rigid fixation research
2000 S trackee et al. Fixation methods in mandibular reconstruction using fibula grafts: a comparative study into the relative strength of three different osteosynthesis
2004 D oty et al. Biomechanical evaluation of fixation techniques for bridging mandibular defects
2005 D e S antis et al. An experimental and theoretical composite model of the human mandible
2007 S chupp et al. Biomechanical testing of different osteosynthesis systems for segmental resection of the mandible
2008 X u et al. Review of the human masticatory system and masticatory robotics
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Feb 7, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Review of biomechanical models used in studying the biomechanics of reconstructed mandibles
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