The association between sleep bruxism and awake bruxism: Polysomnographic and electromyographic recordings in women with and without myofascial pain

Abstract

Background: Sleep bruxism (SB) and awake bruxism (AB) are masticatory muscle activities that are rarely assessed in the same individuals and are thought to be associated with different behaviours. Objectives: To investigate whether individuals engaging in SB also engage in AB, that occurs during rest and during stress-related activity, and to investigate whether SB and AB are associated with different characteristics. Methods: Females with myofascial pain (N = 122) and non-myofascial pain controls (N = 46) were evaluated for SB events and for AB events at rest and AB during stress-related activity, using electromyographic (EMG) recordings and a standardised scoring of bruxism events. The joint distributions between SB and AB events and EMG activity were evaluated, and the characteristic qualities of SB and AB were assessed. Results: Neither SB event rates nor the EMG activity associated with those events was associated with AB events rates or EMG activity, either at rest or during stress-related activity. On the contrary, event rates and EMG activity when awake and at rest were positively associated with events and activity during stress-related activity. SB was characterised mainly by grinding, while AB was characterised mainly by clenching. Conclusion: Sleep bruxism and awake bruxism do not tend to occur in the same individuals.