Is there a first night effect on sleep bruxism? A sleep laboratory study.

A retrospective polysomnographic (PSG) analysis was performed of data from a sample of SB patients (12 females, 4 males; age range: 17-39 years) recorded in a sleep laboratory over 2 consecutive nights. Sleep parameters and jaw muscle activity variables (i.e., rhythmic masticatory muscle activity [RMMA]) for SB were quantifi ed and compared between the 2 nights. Subjects were classifi ed into groups according to severity of RMMA frequency, such as low frequency (2-4 episodes/h and/or < 25 bursts/h) and moderate-high frequency (≥ 4 episodes/h and ≥ 25 bursts/h).