Could bruxism cause daytime sleepiness?

If it disturbs sleep: If the night-time grinding bruxism, disturbs you from having a normal series of sleep cycles that usually last about 90 minutes each, then you may have daytime sleepiness. You should see a dentist who treats bruxism & if you do not have improvement, get a sleep study to check for sleep apnea or other sleep disturbances that they can measure.

Bruxism: Maybe. Bruxism is usually due to high stress levels. If you're stressed you might not be getting the proper rest that you need. There also might be other issues that are more underlying such as sleep apnea. I would recommend a consultation with both a dentist and a physician to discuss your options.