Biomechanical, Developmental, and Genetic Determinants for Rate of Orthodontic Tooth Movement in Humans: Dr. Iwasaki and her collaborators have found that teeth translate (both crown and root move in the same direction by the same amount) up to 21-times faster in some people compared to others for equivalent mechanical conditions (same applied stress). Consequently, they are working to identify and quantify the factors important to the speed of human tooth movement. To date their studies have demonstrated that magnitude of applied stress, stage of development, ratio of 2 inflammatory mediators - interleukin-1β and interleukin-1 receptor antagonist (IL-1β/IL-1RA) - in gingival crevicular fluid, and specific IL-1 gene cluster polymorphisms are important determinants for the speed of tooth movement. This research should lead to more predictable orthodontic treatment planning and may shed light on other aspects of individual-specific bone physiology.
Behavior, Biomechanics and Gene Polymorphisms in Temporomandibular Disorders: Dr. Iwasaki and her collaborators are investigating jaw behavior and mechanics plus genetic susceptibilities for inflammation and pain in people with and without temporomandibular disorders (TMDs). Environmental sampling methods and ambulatory electromyography of the masticatory muscles are being employed to capture jaw behaviors, while jaw mechanics are being studied via validated numerical models of the human jaw system. Women and men are also being compared to uncover some of the reasons why 2 – 3 times more women than men are afflicted with TMDs.
Pathomechanics of Degenerative Joint Disease (Osteoarthritis) of the TMJ: Dynamic stereometry and validated numerical models of the human jaw system are being used to characterize the 3-dimensional contact mechanics of the TMJ in living humans. Specifically, Dr. Iwasaki and her colleagues are applying these approaches to determine the amount and location of work done and energy densities applied to joint tissues during normal tasks and compare these in healthy and diseased joints. This information will be useful to identify susceptible people whose disease could be prevented, diagnose problematic structural relationships that could be corrected by treatment, and provide needed guidelines for the engineering of replacement tissues for damaged TMJs.
Biophysical Properties of the TMJ Disk: Mechanical failure of the TMJ disc may be an important predisposing factor leading to the relatively early degenerative changes seen commonly in the TMJ. Hence, Dr. Iwasaki and her collaborators are studying tractional forces as potential sources of mechanical fatigue leading to degenerative joint disease (DJD). Tractional forces are the result of frictional and plowing forces produced by the deformation of the cartilage matrix as a stress-field translates over the surface of the disk. Laboratory studies to measure these forces under different static and dynamic loading conditions are helping to characterize the poroviscoelastic properties of the TMJ disk. This information will improve the understanding of the role of the disk in health and disease.
Analyses of Friction in Orthodontic Appliances: Dr. Iwasaki and her collaborators have been investigating the variation in clinical ligation forces, the apparent coefficient of static friction associated with sliding an orthodontic bracket along an arch-wire in vivo, and the effect of vibration - from functions like chewing - on this friction. Improved knowledge in this area should lead to improved orthodontic treatment efficiency.