No effect of conscious clenching on simple arithmetic task in healthy participants

This study aimed to investigate whether clenching aids performance in a task requiring mental concentration in healthy participants. Twenty healthy participants (an average of 26.8±2.0 years, nine females and 11 males) were recruited from our department. Participants performed four sets of hundred-square calculations as a mental arithmetic task. Among these sets, the third and the fourth sets were randomly divided into two conditions: one condition where participants made an effort to not allow their teeth to touch (‘no tooth-contact’ condition), and another where they made a conscious effort to rhythmically clench their teeth (‘clenching’ condition) during the task. Surface EMG was recorded from the left masseter muscle. Arithmetic performance was compared between the tooth-contact and clenching conditions using paired t-tests. In addition, we computed Pearson product–moment coefficients of the correlations between the difference in EMG activity and arithmetic performance in the two conditions. No significant change in arithmetic score was found between the no tooth-contact (68.8±12.2) and clenching conditions (66.5±12.7; P=0.27). No significant correlation was found between the difference in EMG activity and changes in arithmetic performance (r=0.32, P=0.17). In healthy participants, conscious clenching was not associated with any benefit in arithmetic performance. Although our study was limited by only measuring the short-term effects of clenching on a simple arithmetic task, the results indicate that it may not be harmful for clinicians to encourage their patients to refrain from clenching their teeth.