Masseter Muscle reduction with botox

Over the years, botulinum toxin (Botox) injections have been successfully used in reducing the bulky appearance of the masseter muscle and contouring the mandible area. Masseter muscle reduction with Botox was first introduced in 1994. However, it has not gained enough attention due to the rarity of the condition among Caucasians, who already have long, narrow faces.

The growing demand for the procedure was driven by Asian countries, such as South Korea. Asians tend to have shorter and wider faces. Asian women dislike a square jaw because it accentuates a wider face, which they deem unfeminine. In some patients, large masseter mass is secondary to hypertrophy. Although it can be a normal anatomic variant, it can also be the result of bruxism and long-term dental problems.

The off-label use of botulinum toxin for posterior mandible contouring is fairly new in the United States. The contour of the mandible plays a big role in the overall beauty and youthfulness of the face. East Asians’ preference for the V-shaped or heart-shaped face is rising in popularity. It would be useful for a practitioner to gain knowledge and deep understanding of how to effectively perform the procedure with natural outcome and low risk of asymmetry and other complications.

Who would be interested in this procedure?


The procedure benefits most healthy adult patients with masseter hypertrophy or square jaw, but it is enormously popular among female patients of Asian descent. Non-invasive cosmetic enhancements have taken over the Asian communities. In fact, South Korea is dubbed as the plastic-surgery capital of the world. The Economist reported that the country has had the most cosmetic procedures per capita since 2009.3 Before Botox, angular bone reduction surgery was the only option available for patients who want a more oval and tapered facial contour.

With botulinum toxin, it is easier to get rid of the masculine-looking jawline with a quick, simple, and less risky procedure. In Australia and the United States, the average cost of Botox per unit ranges from $9 to $20. Since large doses are needed to treat the masseter area, the base price can go as high as $350.


Botox does not only result in the slimming of the jawline but can also help alleviate chronic teeth grinding and temporomandibular joint disorder (TMJ). The physician must inform the patient that botulinum toxin may have little effect on a square face that is due to bone structure.

When injected into the masseter, Botox inhibits the movement of the muscle, causing it to atrophy and shrink over time. Hallowing of the cheeks may occur, making the cheekbones appear lifted, and the face more contoured. The result will only become visible after a few weeks once the muscle has decreased in size.

Techniques for professionals

For masseter muscle reduction, deep injections are recommended, rather than superficial or medium depth injection. Shallow injections can weaken the rizorius muscle attached to the masseter and cause changes of facial expressions (e.g., asymmetric smile).

  • Mark the injection site by asking the patient to clench their teeth and outline the anterior and posterior borders of the masseter.
  • Estimate the location of the parotid duct by connecting an imaginary line from the tragus to the middle part of the upper lip. The parotid is along the middle third of this line. Make 5–6 injection points below this line.
  • The recommended dose is 30–40 units per side depending on the size of the masseter. Administer at least 5 units for each injection point.

Adverse events can be reduced by using proper injection techniques and carefully assessing the patient’s condition. Avoid treating patients with prominent cheeks, as atrophic masseter may accentuate this area. Care should also be taken not to inject too medially as it can cause truncation of the lateral extent of smile, leading to a more rounded cheeks and chipmunk-like face.

  • Decrease in biting force: this will improve within 3 weeks through compensation of other masticating muscles.
  • Speech disturbance: this is only temporary and may last up to 4 weeks at most.
  • Asymmetric smile: this can be minimized by injecting deep and intramuscular at least 1cm inside the anterior margin of the masseter.
  • Pain and swelling: the application of an ice pack within 24-48 hours can be helpful.

How long will the results last?

The atrophic effects of the neurotoxin start within 10–14 days, but maximum results become noticeable after a few months. The atrophied muscle will recover within 4 to 6 months. Repeat injections are recommended every 6 months to stop the muscle from growing back to its original size.

Treatment: before and after

Botox can reduce the masseter muscle volume for up to 30%. Significant reduction is seen around 3 months after injection. Improvement in the facial contour has been reported between 3 to 6 months. The patient’s face will appear slimmer when the jaw muscles have shrunk. Jaw reduction, when performed properly, should not hinder a patient from smiling or eating.