While a strong, square jawline can be an attractive facial feature for men, for women a softer and more triangular shape is often more desirable. Masseter hypertrophy is a clinical phenomenon characterized by a soft swelling near the angle of the mandible that changes the feminine features of the lower face.
Bone structure varies in ethnicities; the lower third of Asian faces is typically wider than that of Caucasians and is determined by the size and width of the mandibular bone and the thickness of muscles and subcutaneous fat surrounding it. However, masseter hypertrophy can appear in other ethnicities as personal habits can be directly responsible for the enlargement of the masseter: excessive gum chewing, chewing hard items or stress and joint misalignment can lead to bruxism (grinding the teeth at night). The swelling may be associated with facial pain and can be prominent enough to be considered aesthetically unattractive.
Changing the shape of the lower face from square to a more triangular one has become an increasingly popular procedure, particularly for Asian females, and Botulinum toxin type A (BTTA) has significantly advanced our ability to create an aesthetically slim, smooth and more feminine jaw contour line without surgical intervention. Reducing the thickness of the masseter also contributes to the projection of the cheekbone, which further enhances the ‘heart shaped’ face.
BTTA is a powerful neurotoxin produced by the anaerobic organism Clostridium botulinum. When injected into a muscle it causes interference with the neurotransmitter mechanism by producing selective weakening and subsequent atrophy of the muscle. The toxin selectively remodels the masseter over time, leading to an overall reduction in size and projection of the jaw. Careful analysis of the facial contours and anatomy of the facial muscles, in addition to skilful and precise placement of the neurotoxin are critical in achieving aesthetically pleasing results. Patients typically notice softening of the masseter muscle at two weeks and reshaping of the jawline at six weeks. With two injections spaced three months apart it is reasonable for patients to expect long-term benefits however it will not yield permanent changes.