Could muscles in jaw/lower face overreact/compensate after a large dose of Botox in the forehead.

Botox relaxation of forehead muscles should not affect how your lower face functions or feels. If the provider injects the very outer of the forehead where the temple actually is located, there is a small component of a chewing muscle that inserts there. I can not imagine first of all, that they would inject your temple for a cosmetic benefit with Botox except for the outer eyebrow lifting or crows feet and those are not the actual temple. Secondly, even if the upper temporalis muscle was affected, the majority of the muscle's function resides in the lower cheek and that wouldn't be affected.  See your provider for an evaluation and if needed see a dentist or other specialist who deals with TMJ (temporomandibular joint syndrome) for a work up. Best wishes.

Thanks so much for this question. Other muscles do not overcompensate for forehead Botox. Perhaps, you’re grinding your teeth at night. Talk to your injector. 

Thanks for your question. The forehead muscles are part of the muscles of facial expression. They have a specific nerve inervation that is unique in that they are both voluntary and involutary. That is why you can't stop laguhing or smiling even if you want to. The jaw muscels are not like this. They are used for chewing and are inervated by a completely seperate nerve. Both muscles can be treated with Botox or Dysport but I dont think treating the forehead could cause the lower jaw to enlarge. I suppose you never know but I can't see the relationship. Hopefully the problem will resolve on it's own. Give it some time.