Functional adaptability of temporomandibular joint mechanoreceptors after an increase in the occlusal vertical dimension in rats.
OBJECTIVE
To investigate the effects of an experimentally-induced increase in the occlusal vertical dimension (iOVD) on the functional characteristics of temporomandibular joint (TMJ) mechanoreceptors in rats.


METHODS
Sixty 13-week-old male albino Wistar rats were divided into control and iOVD groups (30 animals each). The vertical dimension between the maxillary and mandibular molars in the iOVD group was increased by 2.0 mm with a build-up of resin on the maxillary molars. Single-unit activities of TMJ mechanoreceptors were evoked by passive jaw movement. Recording was performed from the gasserian ganglion 1 day and 1, 3, 5, 7, and 9 weeks after the establishment of iOVD.


RESULTS
Compared with the control group, the firing threshold was significantly lower at 1, 3, and 5 weeks after iOVD in the iOVD group. There were no significant differences in the firing threshold at 1 day, or 7 or 9 weeks. The maximum instantaneous firing frequency was significantly higher at 1, 3, and 5 weeks after iOVD in the iOVD group, but there were no significant differences at 1 day, or 7 or 9 weeks. There were no significant differences in the average firing frequency during the experimental period.


CONCLUSIONS
The present study findings suggest that TMJ mechanoreceptors in adult rats may ultimately adapt to iOVD.
Department of Orofacial Development and Function, Orthodontic Science, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo, Japan.
Satomi
S
Naito
Takayoshi
T
Ishida
Satoshi
S
Kokai
Koichi
K
Fujita
Mai
M
Shibata
Tadachika
T
Yabushita
Takashi
T
Ono
D000200:Action Potentials / Q000502:physiology; D000222:Adaptation, Physiological; D000818:Animals; D003769:Dental Occlusion, Traumatic / Q000503:physiopathology*; D004558:Electric Stimulation; D008297:Male; D008465:Mechanoreceptors / Q000502:physiology*; D009431:Neural Conduction / Q000502:physiology; D009473:Neuronal Plasticity; D051381:Rats; D017208:Rats, Wistar; D013704:Temporomandibular Joint / Q000294:innervation*; D012668:Trigeminal Ganglion / Q000502:physiology; D014716:Vertical Dimension
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