Elsevier

Gait & Posture

Volume 31, Issue 1, January 2010, Pages 122-125
Gait & Posture

Influence of voluntary teeth clenching on the stabilization of postural stance disturbed by electrical stimulation of unilateral lower limb

https://doi.org/10.1016/j.gaitpost.2009.09.010Get rights and content

Abstract

Studies on the relationship between dental occlusion and body balance have suggested that occlusion status contributes to the maintenance of postural balance. However, little has been reported about the effects of voluntary teeth clenching on the stabilization of postural stance in novel environments. In the present study we investigated whether teeth clenching influenced adaptation to the perturbation introduced by electrical stimulation of a unilateral lower limb. Subjects (12 adults) stood on a force plate, from which motion data were obtained in the horizontal plane with and without voluntary teeth clenching and were instructed to maintain the position throughout the experiment. We evoked a novel environment by supramaximal percutaneous electrical stimulation of the common peroneal nerve. Electromyograms (EMG) were recorded from the masseter and the peroneus longus (PL) muscles with bipolar surface cup electrodes. When the disturbed postural stance was generated by electrical stimulation, the maximum reaction force in the anterior–posterior (A/P) direction with teeth clenching (CL) was significantly smaller than that without voluntary teeth clenching (control; CO) (p < 0.05) and the peak time of the ground reaction force/body mass (GRF/BM) in the A/P direction occurred earlier in the CL condition than CO (p < 0.05). There were no significant differences in the peak-to-peak amplitude of GRF/BM and the peak time of GRF/BM, in the M/L direction under both CL and CO conditions.

Thus, the present study showed that voluntary teeth clenching contributed to stabilization of the postural stance perturbed transiently by electrical stimulation. We concluded that voluntary teeth clenching plays an important role in rapid postural adaptation to the anterior–posterior perturbation in the upright position.

Introduction

In recent years, an increasing number of analyses have been made of the possible correlation of teeth clenching with the efficiency of motor performance as well as muscle strength of the extremities [1], [2], [3], [4]. Previous studies in our laboratory investigated the relationship between teeth clenching and isometric muscle strength of the upper and lower extremities in healthy volunteer subjects, and revealed a possible correlation between the magnitude of muscle strength required and the force of teeth clenching [1], [3]. Moreover, Sumita et al. studied the relationship between voluntary teeth clenching and the isokinetic strength of lower extremities in healthy volunteer subjects, and demonstrated that teeth clenching had the effect of increasing isokinetic muscle strength at lower angular velocities [2].

On the other hand, studies on the relationship between dental occlusion and body balance have suggested that occlusion status contributes to the maintenance of postural balance. As an example, it has been reported that altering dental occlusion by wearing an occlusal splint could make certain subjects modify their postural attitude through the use of Fukuda-Unterberger experimental stepping test to check the postural attitude [5]. Additionally, Hosoda et al. demonstrated that occlusion could bring about the maintenance of postural balance when unexpected swaying occurred in the standing position by use of EquiTest (MPS-3100, NeroCom, OR, USA) dynamic posturographic model [6]. To date, however, little has been reported about the effects of voluntary teeth clenching on the stabilization of postural stance in perturbation, which was introduced by electrical stimulation of a unilateral lower limb. In the present study, we elucidated whether teeth clenching influenced adaptation to the novel environment.

Section snippets

Subjects

Experiments were performed on 12 young adults (10 males and two females: aged 28.50 ± 4.64 years; height 170.88 ± 8.39 cm; body mass 64.16 ± 12.92 kg mean ± SD). All subjects had stable intercuspal position without malocclusion, toothache, pain of orofacial muscles, temporomandibular joint problems or a previous history of injury in the lower extremities. The study was approved by the Ethical Committee for Human Research, Faculty of Dentistry, Tokyo Medical and Dental University and the subjects gave

Results

Fig. 3 illustrates an example of the time course of GRF/BM after electrical stimulation of the right lower limb obtained from a subject. Every component wave comprising the GRF/BM in the A/P direction decreased in amplitude during CL compared to CO.

Table 1 shows the values of the peak-to-peak amplitude and the peak time of GRF/BM, in the A/P and M/L directions, respectively. The peak-to-peak amplitude of GRF/BM in the A/P direction under conditions of CL was significantly smaller than that of

Discussion

The present study demonstrated that when a disturbed postural stance was generated by electrical stimulation of a unilateral lower limb: (1) the peak-to-peak amplitude of GRF/BM in the A/P direction with CL was significantly smaller than that with CO, (2) the peak time of GRF/BM in the A/P direction occurred earlier in CL than in CO, and (3) the integrals of the GRF/BM under conditions of CL tended to be smaller than those of CO in the A/P direction.

Numerous analyses of the possible correlation

Conflict of interest

No authors have any conflict of interest that may have biased this work.

References (14)

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