Masseter muscle hypertrophy is enlargement of the masseter muscle, and can contribute to a harsh, square look at the angle of the jaw. The masseter muscle is one of the muscles activated during chewing. It’s located at the “angle of the mandible”, or “angle of the jaw”. Botox can be used to relax this muscle, and to soften the look of the lower face. It is recommended to start with 50 units of botox (25 units on each side). When Botox is used to relax the facial muscles that cause fine line, the maximum effect is seen in 7-10 days. When Botox is used to reduce masseter muscle hypertrophy, the maximum effect is not seen for 3 months. Results can last up to 9 months.