Original article
Clenching occurring during the day is influenced by psychological factors

https://doi.org/10.1016/j.jpor.2010.11.003Get rights and content

Abstract

Purpose

We investigated the relationship between clenching occurring during the day under natural conditions and psychological attributes.

Method

Subjects were 37 dentistry students and staff (14 women, 23 men; mean age 27.4 ± 4.7 years). A portable EMG recording device was used to record muscle activity in the temporal muscles for a continuous 5-h period under subjects’ natural conditions, including having lunch. Clenching was identified by electromyography, and subjects were categorized into clenching and non-clenching groups. Psychological testing was performed during the same period using the Modified Taylor Manifest Anxiety Scale (MAS), the Self-rating Depression Scale (SDS), and the Cornell Medical Index (CMI), and the psychological attributes of clenching and non-clenching groups were compared.

Results

Of the 37 subjects, 23 were assigned to the clenching group and 14 to the non-clenching group. Thirteen of the 23 subjects of the clenching group and none of the 14 subjects of the non-clenching group were determined to have psychological problems according to the MAS, with a significant difference observed between the clenching and non-clenching groups in terms of anxious tendency (p < 0.001; Fisher's exact test). Total muscle activity in the clenching group, excluding eating and talking, was 3.5 times greater compared with the non-clenching group, and a significant difference between the groups was observed (p < 0.05; Mann–Whitney U-test).

Conclusions

Daytime clenching was shown to be associated with anxious tendency. Total muscle activity in the clenching group was 3.5 times greater compared with the non-clenching group.

Introduction

Bruxism refers to grinding and clenching of the teeth and psychological factors are believed to contribute to its development. As bruxism can be a major risk factor for problems such as dental attrition, temporomandibular disorder (TMD), periodontal disease, tooth fracture, and breakage of prosthetic devices, its causes require elucidation. A range of studies of nocturnal bruxism have been reported [1], [2], [3], [4], [5]. With respect to daytime clenching, however, although some people are aware of their own bruxism, in other cases it is suspected from oral findings [6]. Although there have been some laboratory studies of daytime clenching using electromyography (EMG) for objective evaluation, it is difficult to define in daily life because natural conditions are affected by psychological factors.

In the present study, we investigated the relationship between clenching occurring during the day and psychological characteristics. To evaluate these parameters we used temporal muscle EMG measurements on the habitual chewing side in daily living, obtained using a portable EMG recording device, and three different psychological tests.

Section snippets

Subjects

Subjects were 37 students and staff (14 women, 23 men; mean age 27.4 ± 4.7 years) at Iwate Medical University School of Dentistry. Eligibility criteria were (1) not having a denture fitted and (2) individual normal occlusion. Exclusion criteria were (1) orofacial pain; (2) current treatment for acute symptoms of TMD; (3) current orthodontic treatment (including the retention period); (4) severe periodontitis; and (5) unstable occlusion. Informed written consent was obtained from each subject

Results

  • 1.

    Of the 37 subjects, 23 (6 women, 17 men) were assigned to the clenching group and 14 (8 women, 6 men) to the non-clenching group based on the EMG measurement results (Fig. 4).

  • 2.

    Thirteen (3 women, 10 men) of the 23 subjects of the clenching group and none of the 14 subjects of the non-clenching group were determined to have psychological problems according to the MAS, with a significant difference observed between the clenching and non-clenching groups in terms of anxious tendency (p < 0.001;

Discussion

In this study, significantly more subjects in the clenching group than the non-clenching group were determined to have psychological problems according to the MAS, indicating an association between daytime clenching and severe anxious tendency. In addition, although the differences were not significant, the fact that some subjects who had psychological problems according to the MAS also had problems according to the SDS and CMI indicates that the involvement of psychological factors may be

Conclusions

From EMG recordings of temporal muscle activity under natural conditions and psychological test results, (1) daytime clenching occurring under natural conditions was shown to be associated with severe anxious tendency; and (2) total muscle activity in the clenching group, excluding during eating and talking, was 3.5 times greater compared with the non-clenching group.

Acknowledgments

The authors wish to thank Professor Kanji Ishibashi, Division of Fixed Prosthodontics, School of Dentistry, Iwate Medical University, for his helpful advice. This research was supported in part by a Grant-in-Aid for Scientific Research (No. 21791914) from the Japan Society for the Promotion of Science.

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