My research goal is to improve our understanding of how biomechanical structure limits function and adaptation of human jaws and teeth. Use of orthodontics and orthognathic surgery to modify the position and morphology of teeth or to realign elements of the facial skeleton theoretically alters mechanical loads on the jawbone, jaw joints, and teeth. Fractures of the mandibular condyle and congenital defects in jaw development, such as hemifacial microsomia, eliminate structures used to support the jaw during biting. Severe neuromuscular disease such as Spinal Muscular Atrophy, weaken the jaw muscles and limit its victims? ability to chew a normal diet. Little is known about how the neuromuscular system responds to such changes or how the altered loads affect growth and maintenance of mandibular tissues. Without such understanding evaluation of effective treatments is difficult if not impossible.
Current work on functional outcomes involves measurements of jaw movement, jaw muscle activity levels, jaw muscle volumes, and bite force generation in human subjects. These studies utilize the techniques of quantitative electromyography, spectral analysis of EMG, ultrasound imaging, magnetic and optical jaw tracking, and piezoelectric and strain gage transducers. Functional patterns are compared among groups of dentofacial deformity patients and within patient groups before and after treatment, supplying objective outcome measures on the effectiveness of treatment. Similar studies have been carried out in patients after fractures of their condylar process, patients with spinal muscular atrophy, and patients with a variety of malocclusions. Most recently, I have begun studies of how supporting dentures with osteointegrated implants alters jaw muscles strength. Because traditional dentures are unstable, patients are limited in how much force their jaw muscles can generate during biting and chewing. I am first testing to determine if these patients have weaker than normal jaw muscles and whether stabilizing the denture allows them to strengthen their jaw muscles. The conditions of these patients are used as ?natural experiments? to test basic hypotheses of jaw function.
In addition to the functional testing, I have carried out studies of the distribution of stresses in the human mandible, using strain gages both in vitro on human cadaver mandibles and in vivo in animals. Using an in vitro technique that I designed, my colleagues and I have looked at how the use of bone plates to immobilize mandibular fractures alters the mandible?s strain patterns, how biting at different tooth positions alters strain at the condylar process, and we have measured the strain patterns produced by some orthodontic appliances.
Understanding a system as complex as the human masticatory apparatus requires a combination of experimental information and theoretical calculations. My research interests currently center on the collection of functional and biomechanical data about the jaws in order to better understand what factors control the kinematic pathways of the human mandible during mastication. Collaborative studies with colleagues in the United States and in Japan will look at how morphological variables and different physical properties of foods affect normal chewing patterns. Collaboration with colleagues at Baylor College of Dentistry will lead to better quantitative models of jaw muscle function that can be used to assess patients functional deficits and evaluate treatment outcomes. These studies will continue to improve our understanding of patients? response to disease and treatment of their jaws.
RESEARCH INTERESTS
Human anatomy, especially head and neck anatomy
Biomechanics of the jaw
Kinesiology of mastication
Electromyography of jaw muscles
Ultrasound Imaging of Soft Tissues of Face
RECENT PUBLICATIONS
Anderson, K., Throckmorton, G.S., Buschang, P.H., Hayasaki, H., "The effects of bolus hardness on masticatory kinematics." Oral Rehabilitation, 29/7:689-696, 2002
Throckmorton, G.S., Ellis, E., III, Hayasaki, H., "Masticatory motion after surgical and non-surgical treatment for unilateral fractures of the mandibular condylar process." J. Oral Maxillofac. Surg, 62: 127:127-138, 2003
Wintergerst, A.M., Buschang, P.H., Throckmorton, G.S, "Reducing within-subject variation in chewing cycle kinematics: A statistical approach." Archs. Oral Biol, 49:991-1000, December 2004
Ellis, E., III and Throckmorton, G.S., "Treatment of mandibular condylar process fractures: Biological considerations" J. Oral Maxillofacial Surgery, 53:115-134, 2005
Toro, A., Buschang, P.H., Throckmorton, G., Roldan, S., "Masticatory efficiency in children and adolescents with Class I and Class II malocclusions." Europ. J. Orthodont, 28:112-199, 2006
SIGNIFICANT PUBLICATIONS
Throckmorton, G.S., Talwar, R.M., and Ellis, E., III, "Changes in masticatory patterns after bilateral fractures of the mandibular condyles." J. Oral Maxillofac. Surg., 57:500-508, 1999
Ellis, E., III and Throckmorton, G.S., "Facial symmetry after closed and open treatment of fractures of the madibular condylar process." J. Oral Maxillofac. Surg., 58:719-728, 2000
Throckmorton, G.S. and Ellis, E., III, "The relationship between surgical changes in dentofacial morphology and changes in maximum bite force." J. Oral Maxillofac. Surg., 59:620-627, 2001
Throckmorton, G.S., Buschang, P.H., Hayasaki, H., Santos Pinto, A., "Changes in the masticatory cycle following treatment of unilateral posterior crossbite in children." American Journal Orthod. Dentofac. Orthoped., 120:521-529, 2001
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