The shape of the lower face has a significant influence on overall facial harmony. A wide, squared lower face – often the result of enlarged masseter muscles – can affect how balanced and proportionate the face appears, and it is a concern that both men and women bring to us at Harley Street Clinic Surrey.
Equally, jaw clenching, teeth grinding (bruxism), and the headaches and jaw pain that accompany them are functional problems that affect a significant number of people and for which botulinum toxin offers a remarkably effective solution.
Masseter botulinum toxin – commonly referred to as jaw slimming injections or masseter Botox – is one of our most popular non-surgical treatments.
This comprehensive guide explains the anatomy involved, how the treatment works, what results you can expect, and how to know whether it is right for you.
Understanding the Masseter Muscle
The masseter is one of the primary muscles of mastication – the group of muscles responsible for chewing. It originates on the zygomatic arch (cheekbone) and inserts into the ramus and angle of the mandible (the lower jawbone).
It is one of the strongest muscles in the body relative to its size, capable of exerting enormous force during chewing.
In most people, the masseter is proportionate to the rest of the face. In others – particularly those who habitually clench or grind their teeth, or who have a genetic predisposition to masseter hypertrophy – the muscle becomes significantly enlarged through overuse.
Visually, this creates a wide, angular, squared appearance to the lower face that many patients feel is at odds with the rest of their facial features.
What Is Masseter Botulinum Toxin Treatment?
Masseter botulinum toxin treatment involves the precise injection of botulinum toxin A directly into the body of the masseter muscle on both sides of the face.
The toxin temporarily blocks the nerve signals that cause the muscle to contract with full force – reducing its functional activity. Over a period of six to eight weeks following treatment, the muscle undergoes a gradual reduction in size (atrophy) due to reduced use.
The result is a visibly slimmer, more tapered, and more refined lower face and jawline. To learn more about how we perform this treatment, visit our dedicated jawline slimming masseter treatment page.
The treatment does not affect the patient’s ability to chew – the masseter is one of several muscles involved in mastication, and reducing its bulk and strength does not impair normal eating. Patients consistently report that chewing feels perfectly normal after treatment.
The Cosmetic Benefits: Jawline Slimming
For patients whose primary concern is aesthetic – the appearance of a wide or overly angular lower face – masseter botulinum toxin delivers a meaningful and visible change to facial shape. As the muscle gradually reduces in volume over the six to eight weeks following treatment, the lower face becomes narrower and more tapered, creating a more oval or heart-shaped facial profile.
The effect is particularly striking in patients who have significant masseter hypertrophy.
Before and after photographs at the three-month mark – when results are at their peak – consistently demonstrate a compelling change in the width and shape of the lower face.
The slimming effect is subtle enough to look entirely natural while being sufficiently significant to be clearly visible.
Who benefits most from jaw slimming with masseter botulinum toxin?
- Patients with a noticeably wide or squared lower face caused by enlarged masseter muscles
- Those who feel their facial shape lacks harmony between the upper and lower face
- Patients who want to create a more typically oval or heart-shaped facial profile
- Those interested in achieving a similar result to buccal fat removal through a non-surgical, reversible approach
The Functional Benefits: Bruxism and TMJ Treatment
Beyond its cosmetic application, masseter botulinum toxin is one of the most effective treatments available for bruxism – the habitual clenching and grinding of the teeth, which frequently occurs during sleep.
Bruxism causes significant wear to tooth enamel, can lead to cracked or fractured teeth, and produces chronic jaw pain, facial tension, earache, and headaches that significantly affect quality of life.
By reducing the force with which the masseter contracts, botulinum toxin dramatically reduces the intensity of nocturnal clenching and grinding.
Most patients report a significant reduction in jaw pain, morning headaches, and facial tension within two to four weeks of treatment.
Dentists frequently notice a slowing or cessation of tooth wear in patients receiving regular masseter botulinum toxin treatment, making it a clinically valuable intervention beyond its cosmetic benefits.
Patients with bruxism and TMJ pain who benefit from this treatment include:
- Those who wake regularly with jaw pain, facial soreness, or headaches
- Patients whose partners have noted teeth grinding during sleep
- Those with diagnosed temporomandibular joint (TMJ) dysfunction
- Patients whose dentist has noted significant tooth wear consistent with bruxism
- Those who have found night guards helpful but want a more comfortable long-term solution
What Does the Treatment Involve?
Masseter botulinum toxin treatment at Harley Street Clinic Surrey is a straightforward, in-clinic procedure that takes approximately twenty to thirty minutes from consultation to completion.
Following a brief facial assessment to confirm the size and position of the masseter muscles – we ask patients to bite down firmly so we can palpate the muscle accurately – the injection sites are identified and cleaned.
A series of small injections are administered into each masseter using an ultra-fine needle. Most patients describe the sensation as a mild, brief sting with each injection; the procedure is very well tolerated without anaesthetic.
There is no downtime following treatment. Patients typically return to their normal day immediately.
We advise avoiding vigorous massage of the injection area and strenuous jaw exercise such as chewing very hard foods for the first twenty-four hours.
Results: Timeline and Longevity
The onset of muscle relaxation from masseter botulinum toxin is gradual – unlike anti-wrinkle treatment where results are visible within a week, the slimming effect from masseter treatment develops progressively over six to eight weeks as the muscle atrophies. Peak results are typically seen at around ten to twelve weeks post-treatment.
Masseter botulinum toxin results last significantly longer than most other cosmetic botulinum toxin applications – typically six to nine months, and in some patients up to a year.
This extended longevity reflects the size and strength of the masseter muscle and the higher dose required to achieve a meaningful effect. With repeated treatments, many patients find that the results last progressively longer as the muscle adapts to being less active over time.
Combining Masseter Treatment with Other Jawline Treatments
At Harley Street Clinic Surrey, masseter botulinum toxin is frequently combined with jawline filler to create a comprehensive lower face rejuvenation.
While masseter treatment reduces the width and bulk of the lower face, jawline filler defines and sharpens the mandibular border – creating a crisp, well-defined jaw profile.
The combination of these two complementary treatments produces a result that significantly enhances lower face structure and definition non-surgically.
For a complete non-surgical facial refresh, many of our patients combine masseter treatment with a Botox brow lift to balance the upper and lower face in a single visit.
Book a jaw slimming consultation: 01737 930400
