Mastication and Swallowing

Mastication includes the preparation and positioning of food in the mouth, crushing and grinding of the bolus, and various other intra-oral events leading to the definitive swallowing sequence. The lips, cheeks, tongue, jaw, teeth, palate, pharynx and larynx all participate in a highly-coordinated manner, and the respective muscles are arranged in a complex spatial framework linking the mandible to the hyo-laryngeal suspensory apparatus. Not surprisingly, the system is highly susceptible to changes in its structural components, and to defective neural function. Masticatory dysfunction can occur after radical jaw resection and reconstruction, or with intra-articular anomalies; and difficulties in both mastication and swallowing can take place after stroke.

System Models

The musculoskeletal biomechanics of mastication and swallowing are hard to study in humans. Many structures are inaccessible, and the methods used to record movements, forces and muscle responses are often invasive. A limited number of parameters can be recorded simultaneously, and the small samples usually studied encourage investigators to link structure and function by association, and/or by retrospective analysis. For these reasons, modelling is being used with increasing frequency to understand cause and effect. Factors encouraging this trend include modern biomedical imaging, and current software which permits, for example, the finite-element analysis of tissue stress, strain and deformation, and the prediction of rigid-body motion.

Simulation of mastication and swallowing is a major undertaking because these acts are so complex. Assembling the anatomical components needed to simulate the jaw, tongue, and oropharynx can be difficult; the many tissues involved require definition of their physical properties, and muscles have to be controlled in a coordinated way. Nevertheless, modelling an integrated system is an attractive goal because mastication and swallowing (and for that matter, speech and other upper airway functions) all share a common substrate.

Projects

Our overall aim is to study the musculoskeletal biomechanics of mastication and swallowing in health and disease. To date, we have successfully used rigid-body dynamics and the Artisynth platform to simulate the resting jaw, maximum jaw gape, and a swallow-like laryngeal elevation. Recently, we modified this model to generate a realistic chewing cycle. The current model includes plausible jaw and hyoid movements, and we plan to integrate this with functioning models of the tongue and pharynx. Successful simulation of normal mastication and swallowing will permit study of the disorders affecting these acts.

We are also currently investigating some of the finer details of the masseter muscle during mastication using state-of-the-art finite element modelling. The masseter has a complex multipennate structure that enhances its ability to generate strong isometric forces. Inside the muscle are internal tendon sheets that transmit those forces to the attached bones. There is a strong interplay between the pennated fibres and the tendons that allow us to chew with such strong forces. By creating a highly detailed finite element model that includes both the complex muscle architecture and the internal tendon sheets, we are able to study the complex interactions.

Other current projects underway include tissue-segmentation from cone-beam CT and MR images, digitizing dental casts, developing and registering mesh-models of the jaw and related structures, controlling muscle activation for our forward- and inverse-dynamic models, and colliding complex components like the teeth.

Personnel

Key personnel in the project are Sidney Fels (Electrical and Computer Engineering, UBC), Ian Stavness (Computer Science, University of Saskatchewan), Antonio Sanchez (Electrical and Computer Engineering, UBC), John Lloyd (Computer Science, UBC), and Alan Hannam (Oral Health Sciences, UBC). Key collaborators include Arthur Miller and Don Curtis at the University of California in San Francisco (segmental mandibular defects and dysphagia), Christie Ludlow at the National Institutes of Health (laryngeal modelling and dysphagia), Jeffrey Palmer at Johns Hopkins (submandibular biomechanics in chewing and swallowing), and Mark Nicosia at Widener University (food bolus). Members of the OPAL team collaborate on other aspects of the project.

Relevant Publications

Alan Hannam, Ian Stavness, John E. Lloyd and Sidney S. Fels (2008) A Dynamic Model of Jaw and Hyoid Biomechanics during Chewing.. . (BibTeX)

Sidney S. Fels, John E. Lloyd, Ian Stavness, Florian Vogt, Alan Hannam and Eric Vatikiotis-Bateson (2007) ArtiSynth: A 3D biomechanical simulation toolkit for modeling anatomical structures.. . (URL) (BibTeX)

Ian Stavness, Alan G. Hannam, John E. Lloyd and Sidney Fels (2006) An Integrated, Dynamic Jaw and Laryngeal Model Constructed From CT Data.. . (URL) (BibTeX)

Chewing Videos

Larynx Videos

Links

• ArtiSynth Demo Page for Jaw / Laryngeal Model