Does bruxism cause gingivitis?

Gingivitis is mainly caused from poor oral hygiene. If you already have gum disease than bruxism will exacerbate this problem, if you don't have gum disease, than you are at risk of developing it from bruxism. See your dentist for a mouth guard if you are a bruxer.

No. Gingivitis caused by bacteria. In other words, your Oral Hygiene program is failing. As gum disease is progressive, failure to treat is risky. You need to see a General Dentist, or preferably a gum specialist, a Periodontist, for removal of all of the gunk that you have been neglectfully avoiding. The professional that you see can then reteach you how to effectively care for your oral health.