Can Someone Intentionally Chew Gum To Increase The Size, Girth, and Squareness Of Their Jaw Angle?

I'm not sure why someone would want to excessively "chew" to increase the size of the masseter muscle as it would be exceedingly taxing on the joints. The masseters aren't the only muscles involved in chewing - the temporalis is also included.

The masseter muscle can respond like any other muscle.  With exercise and exertion, the muscle can grow.  So chewing gum should contribute to growing the muscle.    If, however, you are trying to expand the jawline for aesthetic concerns (e.g. you are worried that you face is too thin), then I would consider treatments like Sculptra to enhance the jawline.  I would seek a consultation with someone who is an expert at non-surgical shaping of the jawline with the use of Botox/Dysport to narrow the jawline or Sculptra (or other fillers) to redefine the jawline.

That would make sense, as you can build up the muscle in a similar way as any other muscle in your body. However, it would be difficult to predict by how much you could build up the muscle and if it would achieve a symmetric result.

Just like any muscle in your body, with repetitive and continuous use it will increase in strength and bulk.  

Thank you for your question juttingjute. I understand your concern. Botox is a purified protein used to address wrinkles associated with facial expression. When injected into the skin Botox will relax the muscles and smoothen out the overlying wrinkles. The most common areas of treatment are in the upper face. These include the horizontal lines seen on the upper forehead when one raises the brows, the vertical lines seen between the brows when one frowns (frown lines), and the crow's feet seen around the eyes when one smiles.It is difficult to make an assessment without a formal exam in the office where I can view the skin in multiple angles and observe wrinkles formed with facial expression. However, I hope the information provided here is useful.Botox can be placed in the masseter muscle in the lower face to contour the lower face and address pain associated with TMJ. In this area 20-40 units of Botox are used per side. Depending on the reason for the enlargement of the muscle, permanent results may be achieved. For example, some people have a habit of grinding, clenching, or biting their teeth subconsciously. Often times this happens in their sleep when they are not aware of it. Botox placed in this muscle will relax the muscle and the grinding, clenching, and/or biting will decrease. This will reduce the size of the muscle. If the brain gets accustomed to this and the person stops grinding, clenching, or biting, then the muscle will not become enlarged or as enlarged again. However, if the habit starts again, the muscle will likely get larger.Some people desire the opposite effect; that is enhancement of the jaw area and lower face. Just like muscles on the body, when muscles on the face such as the masseter are used more they will get larger. However, the temporalis muscle in the upper face is also used when biting so this muscle may get enlarged as well. Also, the chewing must be performed equally on both sides to prevent asymmetry. Further, this may lead to problems with TMJ pain.With any injection, there are risks such as pain, bleeding, bruising, redness, swelling, tenderness, and infection. We take special precautions to minimize these risks such as using a painless technique. We also treat bruises with a laser as early as the next day. Bruises usually resolve within two weeks if untreated. After a laser treatment bruises usually resolve in 1-3 days, but may still take two weeks for full resolution. In addition to these risks, with Botox there is also a risk that the product spreads or diffuses to nearby structures. Spread to nearby muscles can lead to side effects such as the temporary appearance of droopy eyelids or a temporary asymmetric smile.After a Botox treatment, I recommend that my patients avoid heat exposure, alcohol consumption, and strenuous exercise for 24 hours and not lie down flat for four hours. This is because all of these activities may possibly lead to the movement of the product and consequent side effects such as droopy eyelids as described above. Although there have been no definitive studies shown that these actually occur and some physicians do not provide such aftercare instructions, in the absence of data I err on the side of caution and recommend that my patients avoid such activities.Please consult with a doctor for specific recommendations. Good luck!