I was wondering if botox or another injection can help with bruxism?

Thank you for the detailed question. Botox or other neuromodulators can be injected into the masseter muscle to help relax it and ease jaw pain caused by Temporomandibular joint dysfunction (TMJ). It can also help cause the muscle to atrophy and decreasing the squareness of a jaw line. Fillers such as hyaluronic acids can be used to refine the shape of a patient's face but does not work like Botox and cannot help relax muscles. I recommend seeing a board-certified plastic surgeon or expert injector to discuss your concerns and who can develop the right treatment plan for you. For more information please visit our webpage. 

Botox injections help calm mandibular muscles that you use to clench your jaw and grind your teeth. To treat bruxism, I inject several tiny doses of Botox into the master muscle on each side of the jaw – near the joint, in front of each ear. Results take 3 or 4 days to kick in, about 10-14 days to reach their peak, and the injections last about 3 months.

Panda, your idea is a good one. Even though a night-guard could protect your teeth from damage, the force on your jaw will prematurely damage your jaw joints (TMJs). I have found Botox to be a very good treatment for this condition. It has helped to break the grinding habit in several of my patients as well as protect their teeth and jaws joints.
The chewing muscles are located at the corners of the jaw near the ears. When these muscles enlarge (hypertrophy) it can give the face a heavy and masculine appearance. I have as many patients asking for Botox to improve their facial shape as to treat bruxism. The face ends up being more oval.