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In this study, we examined brain activity using functional magnetic resonance imaging (fMRI) during clenching with or without a bite plate increasing occlusal vertical dimension to mandibular rest position, and identified the effect on brain activity of clenching with a bite plate. Subjects comprised five healthy men aged 20 to 40 years with normal occlusion and no artifacts on preliminary imaging. fMRI time-series were acquired with and without the plate inserted. During each series, the subjects alternately performed persistent teeth clenching (occlusal force at 25%-35% of maximum voluntary clenching) for 22 sec and non-clenching for 22 sec for a total of 458 sec. The results were as follows. 1) During clenching in the intercuspal position, brain activity was shown in the bilateral primary somatosensory area. 2) When the bite plate was inserted to change the occlusal vertical dimension to the mandibular rest position, brain activity was shown in the bilateral primary motor area during clenching (compared with non-clenching). These findings suggest that clenching with a plate increasing vertical dimension to mandibular rest position activates the primary motor area. [ABSTRACT FROM AUTHOR]

Abstract: Introduction: Our recent report of ocular tremor in Parkinson's disease (PD) has raised considerable controversy as to the origin of the tremor. Using an infrared based eye tracker and a magnetic head tracker, we reported that ocular tremor was recordable in PD subjects with no apparent head tremor. However, other investigators suggest that the ocular tremor may represent either transmitted appendicular tremor or subclinical head tremor inducing the vestibulo-ocular reflex (VOR). The present study aimed to further investigate the origin of ocular tremor in PD. Methods: Eye movements were recorded in 8 PD subjects both head free, and with full head restraint by means of a head holding device and a dental impression bite plate. Head movements were recorded independently using both a high sensitivity tri-axial accelerometer and a magnetic tracking system, each synchronized to the eye tracker. Results: Ocular tremor was observed in all 8 PD subjects and was not influenced by head free and head fixed conditions. Both magnetic tracking and accelerometer recordings supported that the ocular tremor was fully independent of head position. Conclusion: The present study findings support our initial findings that ocular tremor is a fundamental feature of PD unrelated to head movements. Although the utility of ocular tremor for diagnostic purposes requires validation, current findings in large cohorts of PD subjects suggest its potential as a reliable clinical biomarker. [Copyright &y& Elsevier]

Objective: To evaluate the intra-arch displacements of the molars and the change in molar relationship following the use of a maxillary lip bumper combined with a bite plate. Materials and Methods: The material comprised study casts taken before and after the treatment of 40 consecutive patients with mixed dentition. The sagittal and transversal displacements were evaluated by a three-dimensional digitizer using the palatal rugae as an indirect fixed reference. The displacements were expressed as translation mesiodistally and buccolingually and rotation around the long axis and tipping mesiodistally. The change in molar relationship was measured to the nearest millimeter at the level of the occlusal plane. Results: The tooth movements were predominantly of distal rotation (mean, 9.7°; range, 6.5° to 26°) and distal tipping (mean, 5°; range, 5.8° to 18°). The distal displacement was a modest mean (mean, 0.3 mm; SD, 1.6 mm) and more pronounced to the buccal (mean 1.6 mm; SD, 1.5 mm). The molar relationship improved in all but four sites, and a full Class I was obtained in 65 of 80 sites. Conclusions: The early treatment with the lip bumper and bite plate can be recommended from a cost-benefit point of view. [ABSTRACT FROM AUTHOR]

Postural support alters anticipatory postural adjustments (APAs). Efficient adaptation to changes in postural support in reactive and centrally initiated postural synergies is impaired in Parkinson's disease (PD). This study examined whether APAs are affected differently by familiar and novel supports in people with PD, ON and OFF levodopa. The effect of PD and levodopa on the ability to immediately adapt APAs to changes in support and refine with practice was also investigated. Fourteen people with PD and 14 healthy control participants performed 20 single rapid leg lift tasks in four support conditions: unsupported, bilateral handgrip (familiar), bite plate (novel) and a combined handgrip+bite plate condition. APAs, identified from force plate data, were characterized by an increase in the vertical ground reaction force under the lifted leg as a result of a shift of weight toward the stance limb. Results showed the ability to incorporate familiar and novel external supports into the postural strategy was preserved in PD. Controls and PD patients in the OFF state further refined the postural strategy with practice as evidenced by changes in amplitude of vertical ground reaction forces and forces applied to support apparatus within conditions between the initial and final trials. In the ON state, people with PD failed to refine the use of postural supports in any condition. The results suggest that immediate postural adaptation is intact in people with PD and unaffected by levodopa administration but the ability to refine postural adaptations with task experience is compromised by dopamine therapy., (Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.)