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Abstract
Using functional magnetic resonance imaging (fMRI) in eight healthy human subjects, the present study measured blood oxygenation level-dependent (BOLD) signals during clenching in a malocclusion model, using a custom-made splint that forced the mandible to a retrusive position and a splint of no modification for control, and compared the results to the BOLD signals during the corresponding resting conditions. An individual visual analog scale (VAS) score was also examined during clenching to evaluate the interactions between fMRI data and psychiatric changes. During both clenchings, activations in four brain regions (premotor cortex, prefrontal cortex, sensorimotor cortex, and insula) were seen. However, clenching in the malocclusion model, with psychological discomfort, increased additionally BOLD signals in the anterior cingulate cortex and the amygdala. Furthermore, there was a parallel relationship between BOLD signal intensities and VAS scores in these two regions. The findings may suggest the involvement of clenching with malocclusal conditions in the emotion and/or pain-related neural processing in the brain.
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Notes on contributors
Takero Otsuka
Dr. Takero Otsuka is a special post doctoral researcher in the Department of Craniofacial Growth and Development Dentistry, Kanagawa Dental College. He received his D.D.S. from Nihon University in 2003 and a Ph.D. in 2008 from Kanagawa Dental College. Dr. Otsuka’s primary research interest is correlation between dysfunction of the masticatory organ and brain function.
Kazuko Watanabe
Dr. Kazuko Watanabe is a professor in the Department of Physiology, the Faculty of Care and Rehabilitation, Seijoh University. She received a Ph.D. in 1985 from the Gifu University School of Medicine and currently investigates the relationship between aging and cognition in the area of neuroscience. Dr. Watanabe is especially interested in the relationship between dysfunctional mastication and cognition in the elderly.
Yoshiyuki Hirano
Dr. Yoshiyuki Hirano is a postdoctoral visiting fellow at the National Institutes of Health. He received his D.V.M. degree from Gifu University in 2000 and a Ph.D. in 2003 from the same university. His primary research interest is neurovascular coupling in nonhuman primates.
Kinya Kubo
Dr. Kinya Kubo is an assistant professor in the Department of Oral Anatomy, Division of Oral Structure, Function and Development, Asahi University School of Dentistry. He received his D.D.S. degree from Asahi University in 1986 and a Ph.D. from Gifu University in 1991. His primary research interest is the effects of masticatory function on the central nervous system.
Shinjiro Miyake
Dr. Shinjiro Miyake is an assistant professor in the Department of Craniofacial Growth and Development Dentistry, Kanagawa Dental College. He received his D.D.S. degree in 2002 from Kanagawa Dental College and a Ph.D. in 2007 from the same school. His primary area of research interest includes function and dysfunction of the craniomandibular system and behavior under stress.
Sadao Sato
Dr. Sadao Sato is a professor and head of the Department of Craniofacial Growth and Development Dentistry, Kanagawa Dental College. He received his D.D.S. degree in 1978 from Kanagawa Dental College and a Ph.D. in 1978 from the same school. Since 1992, he has been a member of the EH Angle Society of Orthodontists. Dr. Sato’s primary research interests are function and dysfunction of the masticatory organ, emotional role of bruxism activity, and craniofacial growth and malocclusion.
Kenichi Sasaguri
Dr. Kenichi Sasaguri is an assistant professor at the Department of Craniofacial Growth and Development Dentistry, Kanagawa Dental College. He received his D.D.S. degree in 1985 from Kanagawa Dental College and a Ph.D. in 1989 from the same school. His primary research interests include function and dysfunction of the craniomandibular system and molecular mechanisms in stress and masticatory organ function.