<prompt> In which phase of sleep, does the bruxism occur?NREM 2NREM 3REM sleepNREM 4  <response>: Bruxism occurs in both stage I and stage II. But more common in stage II.Note: OSA is not associated with a reduction in total sleep time, but individuals with OSA experience a much greater time in stage 1 NREM sleep from an average of 10 of total sleep to 3050 and a marked reduction in slow-wave sleep stages 3 and 4 NREM sleep. The pathophysiology of OSA includes both a reduction in neuromuscular tone at the onset of sleep and a change in the central respiratory drive.Reference: Ganongs Review of Medical Physiology T W E N T Y - F I F T H E D I T I O N page no 276 