title: XROMM analysis of tooth occlusion and temporomandibular joint kinematics during feeding in juvenile miniature pigs.
abstract: Like humans, domestic pigs are omnivorous and thus are a common model for human masticatory function. Prior attempts to characterize food-tooth interactions and jaw movements associated with mastication have been limited to aspects of the oral apparatus that are visible externally (with videography) and/or to 2D movements of oral structures (with monoplanar videofluoroscopy). We used XROMM, a 3D technique that combines CT-based morphology with biplanar videofluoroscopy, to quantify mandibular kinematics, tooth occlusion and mandibular condylar displacements within the temporomandibular joint (TMJ) during feeding. We observed that the pig TMJ moved detectably in only three of six possible degrees of freedom during mastication: two rotations, pitch and yaw; and one translation, protraction-retraction. Asymmetrical yaw around a dorsoventral axis produced the observed alternating left-right chewing cycles responsible for food reduction. Furthermore, the relative motions of the upper and lower premolars contained a substantial mesiodistal component in addition to the buccolingual component, resulting in an oblique (rather than a strictly transverse) power stroke. This research demonstrates the capacity of XROMM to explore the kinematic underpinnings of key masticatory movements, such as the occlusal power stroke, by integrating tooth, joint and rigid body jaw movements. XROMM also allowed us to test kinematic hypotheses based on skeletal anatomy with actual kinematics observed during naturalistic feeding behaviors. We observed that the soft tissue structures of the TMJ appear to play a significant role in limiting the range of motion of a joint, and thus analyses based solely on osseous morphology may over-estimate joint mobility.
authors.affiliation: Department of Biomedical and Applied Sciences, Indiana University School of Dentistry, Indianapolis, IN 46202, USA rmenegaz@iu.edu.
authors.forename: Rachel A
authors.initials: RA
authors.lastname: Menegaz
authors.affiliation: Department of Biology, Providence College, Providence, RI 02918, USA.
authors.forename: David B
authors.initials: DB
authors.lastname: Baier
authors.affiliation: Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Yeshiva University, Bronx, NY 10461.
authors.forename: Keith A
authors.initials: KA
authors.lastname: Metzger
authors.affiliation: Department of Orthodontics, University of Washington, Seattle, WA 98195, USA.
authors.forename: Susan W
authors.initials: SW
authors.lastname: Herring
authors.affiliation: Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02912, USA.
authors.forename: Elizabeth L
authors.initials: EL
authors.lastname: Brainerd
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D003766:Dental Occlusion; D005471:Fluoroscopy; D021621:Imaging, Three-Dimensional; D008335:Mandibular Condyle / Q000502:physiology; D008409:Mastication; D009068:Movement; D016059:Range of Motion, Articular; D013552:Swine; D013556:Swine, Miniature; D013704:Temporomandibular Joint / Q000502:physiology*; D014741:Video Recording
keywords: Jaw kinematics; Mastication; Power stroke; TMJ; Tooth cusp