Square Jaw

A square jawline most commonly results from masseteric hypertrophy, an enlargement of the masseter, the primary chewing muscle sitting at the angle of the jaw. Like any muscle, it responds to overuse by getting bigger. Chronic teeth grinding (bruxism), constant clenching, heavy chewing gum habits, and unconsciously tensing the jaw through stress all drive masseter hypertrophy over time, thickening the lower face. Because the cause is muscular rather than skeletal, it is highly treatable without surgery.

Bone also contributes for some people. A naturally wider mandible creates a square shape regardless of muscle size. In practice, most people presenting with a square jaw show a combination of both factors, and treatment planning accounts for each one separately. On palpation, a hypertrophic masseter balls up visibly when you clench. That simple test usually tells us which component is leading.

Presentation differs by sex. In women, a square jaw is almost always muscle-driven and often accompanied by jaw tension, morning soreness, or a diagnosed teeth grinding habit. In men, bony width is more common as a naturally masculine feature. We do not alter it unless someone specifically wants a softer jawline or feels their facial structure is too strong. One anatomical note: a heavy lower face isn’t always the chewing muscle. Enlarged salivary glands and submental fat can mimic the look, so Dr. Borakowski rules those out before recommending any jaw-slimming treatment.