Clenching occurring during the day is influenced by psychological factors

Abstract

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