About 5 years ago I began getting botox in my jaw (masseter) muscle to help with tmj. It really works to ease that pain and I would recommend it for anyone who has tmj. Also, it does shrink the muscle and makes my face look thinner.
My doctor does this all time, and I've never had any problems with my injections. In fact, now I get them in my temple too to help with headaches - and this works great as well.