Effect of jaw functional status on neck muscle endurance

Effect of static and dynamic jaw positions on postural stability among people with blindness

BACKGROUND

In comparison with the people with normal sight, the mean center of gravity (COG) velocity is significantly higher among blind people. A strong relationship has been shown between jaw and neck sensorimotor and postural control. The purpose of this study was to determine the effect of different static and dynamic jaw positions on postural stability among subjects with blindness.

METHODS

Postural stability was measured as COG velocity in 39 blind subjects under the following five conditions: resting jaw (natural jaw position with no instructions, control), open jaw (teeth of both jaws slightly apart), clenched jaw (teeth tightly closed across each other), chewing (a standard bolus of gum at the natural palace), and tongue position (positioned behind the upper incisors) while standing on firm and foam surfaces.

RESULTS

The mean COG velocity while standing on the firm surface during resting, open jaw position, clenched jaw position, chewing, and tongue positions were 0.54, 0.50, 0.44, 0.59, and 0.46 deg/s, respectively. The mean COG velocity while standing on the foam surface during resting, open jaw position, clenched jaw position, chewing, and tongue positions were 1.42, 1.23, 1.10, 1.14, and 1.06 deg/s, respectively. Compared to the firm surface, the COG velocity was significantly higher on the foam surface in all five conditions (p < .001). In the comparison between the conditions, there were no significant differences in either the firm or foam surface in all five conditions (p > .05).

CONCLUSION

People with blindness behave in the same way as sighted subjects on firm and foam surfaces. However, changes in static and dynamic jaw positions do not affect postural stability among them.

Can jaw position affect the fine motor activity of the hand during writing?

BACKGROUND

Jaw and neck systems have been shown to be functionally related and changes in either system can modulate gross motor functions, such as posture control. It remains to be seen if any change in jaw position can affect fine motor skills. The objective of this study was to determine the effect of resting, open and clenched jaw positions on various handwriting parameters while standing on firm and unstable surfaces.

METHODS

Handwriting samples were collected from 36 healthy male participants (age, 15-35 years) using a digitizer tablet (WACOM Intuos 4) with noninking pen in the resting, open and clenched jaw positions while standing on firm and unstable surfaces. The measured handwriting parameters included duration, vertical size, horizontal size, absolute size, average absolute velocity, and absolute jerk. Recordings and analyses were performed using NeuroScript MovAlyzeR software.

RESULTS

All handwriting parameters varied among the resting, open, and clenched jaw positions on both the firm and unstable surfaces. However, based on statistical analyses, there were no significant differences in the handwriting parameters among three jaw positions on both surfaces (p > .05).

CONCLUSION

This study revealed that all handwriting parameters varied among the resting, open, and clenched jaw positions on both the firm and unstable surfaces, showing that change in the jaw motor system may potentially affect the fine motor skills. However, on statistical analysis, there was no significant effect of 3 studied jaw positions on fine motor skills as seen on gross motor skills among healthy individuals.

Effects of denture wearing on coordinated features of jaw and neck muscle activities during chewing in partially edentulous elderly patients

PURPOSE

This study was performed to examine how denture wearing improves jaw and neck muscle coordination during chewing in partially edentulous elderly patients.

METHODS

Sixteen patients classified as Eichner's index B2 or B3 and 16 young dentate subjects were enrolled. Jaw and neck muscle activities during chewing were recorded using electromyography with and without denture wearing, then analyzed using intermuscular Electromyography (EMG)-EMG transfer and EMG-EMG coherence function analyses to clarify quantitative, temporal, and functional coordination of jaw and neck muscle activities while chewing. Occlusal force and masticatory scores were also determined.

RESULTS

Denture wearing increased the power values for jaw closing muscle activities, and improved occlusal area and force, and masticatory score. Gain values for jaw closing and opening muscle activities were decreased in those wearing dentures compared to those not wearing dentures. Denture wearing resulted in equivalent gain values for jaw closing and opening muscle activities as compared to the young subjects. Coherence values for chewing and non-chewing side neck muscle activities were increased as compared to not denture wearing.

CONCLUSIONS

The suitability of denture wearing can be evaluated from the viewpoint of gain as a quantitative parameter showing coordination between jaw closing and opening muscle activities. Such evaluation can be performed from the viewpoint of coherence as a parameter of functional coordination between jaw and neck muscle activities during chewing in partially edentulous elderly patients. The gain parameter in regard to jaw muscle activities may be compensated to a state equivalent to that seen in young subjects by wearing an appropriate denture.

Influence of different jaw positions on dynamic balance using Y-balance test

BACKGROUND

Jaw sensory-motor system has been shown to affect static balance of the body. It would be interesting to know whether it can influence dynamic balance as well. The objective of this study is to examine the influence of different jaw positions on dynamic balance using the Y-balance test.

METHODS

Eighty healthy male participants aged 20-35 years were invited to participate in this study. Dynamic balance was measured by the Y-balance test in three directions (anterior, posteromedial, and posterolateral) for each leg separately in three jaw positions: resting jaw (control), open-jaw, and clenched jaw.

RESULTS

There were no significant differences in reach distances between the different jaw positions except in the posterolateral direction. In comparison with resting jaw position, reach distance was significantly higher in open-jaw position for the right leg and in clenched and open-jaw positions for the left leg in the posterolateral direction.

CONCLUSIONS

Although various studies have shown direct or indirect influence of jaw sensory-motor system on static postural control, results of this study point to limited relation with dynamic postural control among healthy subjects. However, it supports the potential of the jaw sensory-motor system to affect motor control during functional tasks in patients with postural instability or similar disorders.