Masseter Botox: jaw slimming, teeth grinding, and what to expect

Masseter Botox is one of the fastest-growing injectable treatments. It serves two distinct patient groups: people who grind or clench their teeth (bruxism/TMJ) and people who want a slimmer, more tapered lower face. Often the same patient has both concerns. Here's everything you need to know.

The masseter muscle: what it is and why it matters aesthetically

The masseter is a powerful, thick muscle located at the angle of the jaw. It's the primary chewing muscle — the same muscle you feel flex when you clench your teeth. When you inject botulinum toxin into the masseter, you weaken it. The muscle becomes less active and, over 4–8 weeks, gradually atrophies (shrinks in size).

This creates two outcomes:
Functional: Reduced clenching force → less jaw pain, fewer headaches, reduced tooth wear
Aesthetic: Smaller masseter → narrower lower face, more tapered/oval face shape, reduced jowl heaviness

Both effects from the same injection.

Who benefits from masseter Botox

Bruxism and TMJ patients:
Nocturnal teeth grinding (bruxism) — often unconscious and diagnosed by a dentist finding tooth wear
Daytime clenching (common in high-stress periods)
TMJ pain (temporomandibular joint pain) — masseter hyperactivity is a major contributor
Morning headaches and jaw tightness

Aesthetic patients:
Patients who find their face "too square" or "too wide" at the jawline
Patients with asymmetric masseters (common — often from unilateral chewing habits)
Patients with a hypertrophied masseter from previous heavy clenching
East Asian patients seeking face-slimming effect (this is one of the most common uses in Korean aesthetic medicine)

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Dosing

Masseter Botox requires significantly more product than forehead or crow's feet treatment — the masseter is one of the strongest muscles in the body.

Typical dosing per side:
Mild reduction / functional only: 20–30 units
Moderate aesthetic slimming: 30–40 units
Significant hypertrophy / marked slimming goal: 40–50+ units

Total treatment: 50–100+ units (both sides combined). This is why masseter Botox costs more than forehead treatment.

Botox vs. Dysport: Either product works. If your provider uses Dysport, the unit count will be higher (Dysport units ≠ Botox units; ~2.5–3 Dysport units = 1 Botox unit).

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What to expect: timeline

Days 1–5: No visible change. The neurotoxin takes time to work.

Weeks 1–2: Clenching force and jaw pain begin reducing. Patients with bruxism often notice this benefit first — the aesthetic slimming comes later.

Weeks 4–8: The masseter begins to visibly shrink. The jaw contour narrows. This is the timeline patients need to understand before booking — the aesthetic result is not immediate.

Months 3–4: Full aesthetic effect visible. Muscle has atrophied to its treated size.

Months 4–6: Muscle begins to regain activity; slimming effect gradually reverses as the toxin wears off. With repeated treatment, the atrophy can become more persistent and patients often need less product over time.

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How long does masseter Botox last?

For jaw pain (functional): 3–4 months before the treatment needs repeating.

For aesthetic slimming: The slimming effect lasts 4–6 months, sometimes longer. Unlike forehead wrinkles, which return fairly predictably, masseter atrophy can be more durable — some patients who treat consistently for 2 years find their results lasting 8–12 months between sessions.

Key point: Repeated treatment over 1–2 years produces progressively longer-lasting results as the muscle atrophies more significantly.

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Cost

| Dosing | Typical cost |
|---|---|
| Light (40–60 units total) | $500–$900 |
| Standard (60–80 units total) | $700–$1,200 |
| Heavy hypertrophy (80–100+ units) | $900–$1,600 |

Masseter Botox costs more than forehead Botox because of the volume of product required, not because the injection is more technically complex. Providers who charge standard per-unit pricing will quote based on units used.

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What the injection feels like

The masseter injection is typically more uncomfortable than forehead or glabellar Botox because the muscle is denser and the needle needs to penetrate more deeply to reach the muscle belly. Most providers:
Use a slightly longer needle (30–32 gauge, 13 mm vs the 30 mm needles used for superficial face work)
Inject 3–5 points per side in a grid pattern across the masseter
Apply topical numbing cream beforehand (optional but common)

Total treatment time: 10–15 minutes.

After treatment: Mild soreness when chewing for 1–3 days (similar to a sore muscle after exercise). Avoid vigorous chewing (gum, hard foods) for 24 hours.

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Potential complications

Masseter Botox is generally very safe when performed correctly. Risks:

Smile asymmetry: If the toxin spreads to the nearby risorius or zygomaticus muscles, it can cause a temporary asymmetric smile. This resolves as the toxin wears off (4–6 weeks). Injection technique that avoids the anterior masseter border reduces this risk.

Difficulty chewing: Over-injection can weaken chewing function. This is why conservative dosing and bilateral symmetry are important — the masseter is a functional muscle.

Hollow cheeks: As the masseter shrinks, patients with already thin faces may experience a slightly hollow or gaunt appearance. Providers should assess pre-existing fat and volume before recommending masseter Botox in thin-faced patients.

Asymmetry: Existing masseter asymmetry (common — most people have a larger masseter on their dominant chewing side) should be assessed before treatment and differential dosing used if significant.

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Masseter Botox vs. surgical jaw reduction

Surgical jaw reduction (mandible reduction) physically removes bone from the jaw angle — a permanent, dramatic reduction. Masseter Botox reduces the muscle, not the bone.

If a patient's wide lower face is primarily from the bone (the jaw angle itself projects wide), Botox will produce minimal effect. If it's primarily from muscle bulk, Botox produces significant improvement.

Providers can usually distinguish between bony and muscular jaw width on examination — ask your provider to assess which is contributing.

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Questions to ask before booking

Based on my jaw anatomy, is my width primarily from muscle or bone?
What dosing do you recommend for my masseter size and my goals (functional vs. aesthetic)?
How many masseter patients do you treat, and do you have before-and-afters specific to this treatment?
How do you assess for existing asymmetry, and will you use differential dosing?
If I'm concerned about aesthetic slimming but I also grind my teeth — which goal should we prioritize in dosing?

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