Masseter muscle reduction. Is there a more permanent solution than Botox?

The appearance of a square jaw could be due to masseter hypertrophy, prominent jaw bone, or both. Repeated Botox injection into the masseter muscle is a non-permanent but safe means of inducing masseter atrophy for a more oval face. Surgical reduction of the jaw has been described but only a small number of surgeons perform them. I do not perform jaw reduction, otherwise known as reduction gonioplasty, in my practice.  This form of surgery generally involves shaving or burring down the angle of the jaw with or without partial resection of the masseter muscle. Reduction gonioplasty  has the added benefit inducing masseter atrophy through the disruption of the muscle’s attachments.  This type of surgery is not without its complications, however. Potential risks of the surgery, particularly with overly aggressive or improperly performed masseter resection, can include bleeding, injury to parotid gland (a salivary gland behind the masseter), injury to the facial nerve and chin and lower lip numbness. Therefore, it is important to find a facial plastic surgeon experienced in facial re-contouring who has written extensively on the subject matter for an in-person examination and consultation to determine your treatment options.

Hi coco1227,
What you are doing is exactly right at this point - Botox is safer and is fast becoming the standard for treating masseter hypertrophy. Masseter muscle surgery is prone to complications and is potentially disfiguring. 
You'll be pleased to know that there have been documented reports on maintaining size reduction after regular Botox injections. This shrinkage is impressive over time.
Discuss your options with your doctor who can assess whether your issue is a thickened masseter muscle or a large mandibular angle. With the latter, surgery is not as simple as resecting the muscle but operating on the bone as well. 
Hope this helps, 
Justin Harper, M.D.