Hi, Hypertrophic and big masseter muscles can make the jaw wider and appear as what is known as "square jaw" which contributes to more of a masculine look. With Botox injection, we can cause shrinkage of this muscle and make the jawline oblique (V-shape) which is more of feminine look. This procedure is called jaw slimming by Botox and the result typically lasts for 8 to 10 months. If done carefully by an experienced physician, there won't be any interference with normal chewing, eating or smiling. Depending on the strength and size of the muscle, I usually inject between 20 to 35 units of Botox in each side. By the way, like every other muscles in our body, continuous usage and "exercise" makes the masseter muscle bulkier and more noticeable. Chewing gum is a common "exercise" for masseter muscle that can lead to a square jaw, and hence I always advise my patients who prefer a more feminine jawline to avoid chewing gums. I hope it helps and good luck!
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