Masseter Botox: Jaw Slimming, Teeth Grinding, Units and Cost

Masseter Botox is one of the few injectable treatments that can change the shape of your face rather than just smooth a line. By relaxing the large chewing muscle at the back of your jaw, it can soften a square jaw into a slimmer, more tapered lower face. It can also ease the ache that comes from clenching and grinding your teeth. It is also a treatment where the details matter: how many units, where they go, how long you wait for the result, and whether the shape of your jaw comes from muscle or bone. This guide covers all of it, with our own prices, so you know what to expect before you book.

What the masseter muscle does

The masseter is the thick muscle that runs from your cheekbone down to the angle of your jaw. Put your fingers just in front of your earlobes and bite down: the muscle that bulges under your fingers is the masseter. It is one of the strongest muscles in the body for its size, and it does most of the work when you chew. Like any muscle, it grows when it works hard. People who clench during the day, grind their teeth at night or chew gum a lot often develop a larger masseter, which makes the lower face look wider and more square. Genetics play a part too. Botox (onabotulinumtoxinA) blocks the nerve signal that tells the muscle to contract. The muscle can still move enough for normal eating and speaking, but it works less hard. Over the following weeks, a muscle that is used less becomes smaller, and that is what slims the jaw.

Two reasons people get masseter Botox

Many people come in for one reason and notice the other. Someone who books for a slimmer jaw often finds their morning jaw ache has gone, and someone who books for clenching often likes the softer jawline.

Who it suits, and who it does not

Masseter Botox works on muscle, so the most important question is whether muscle is what makes your jaw look wide. A quick check: clench your teeth with your fingers on the angle of your jaw. If you feel a firm bulge that pushes outward, there is muscle to work with. If your jaw looks wide but the area feels flat when you clench, the width probably comes from bone, and Botox will change very little.

• A square jaw that bulges when you clenchA good candidate. This is where masseter Botox works best.
• You clench or grind, with jaw ache or headaches at the templesOften helpful. Your dentist should still check your teeth and joint.
• Your jaw width comes from boneBotox cannot change bone. Jawline filler can improve definition instead.
• Loose skin or early jowls along the jawSlimming the muscle can make sagging look worse. Skin tightening such as Sofwave or Morpheus8 may suit you better.
• Fullness under the chinThat is fat, not muscle. Kybella or CoolSculpting treat it.
• Pregnant or breastfeedingWait until afterwards. Botox has not been studied enough in pregnancy.

When you will see results

Masseter Botox is a slow treatment, and knowing the timeline saves a lot of worry. The muscle relaxes within days, but it takes weeks for it to shrink. In an ultrasound study that measured the masseter over six months, the muscle was at its thinnest at about 11 weeks after treatment, roughly a quarter thinner than before, and then slowly recovered without fully returning to its original size by the end of the study. For most people the result lasts around 4 to 6 months, which is longer than Botox in the forehead or around the eyes. Because a muscle that has been relaxed for a while does not bounce back straight away, many people find that after two or three treatments they can wait longer between appointments. If you have an event in mind, such as a wedding, plan masseter Botox about three months ahead so the slimming is at its best on the day.

How many units, and what it costs

Because the masseter is a large, strong muscle, it needs more units than lines on the face. Most people need 30 to 50 units of Botox across both sides of the jaw, split between several injection points in the lower part of each muscle. A larger muscle, a strong clencher or a man’s jaw often needs the higher end of that range.

Typical totals for both sides at Glow Theory. Botox is $14 per unit and Dysport is $4.65 per unit. Your exact units and price are confirmed at your visit, before we begin.

Dysport works just as well in the masseter. It needs roughly three times as many units, so the total comes out about the same; our Dysport vs Botox guide explains the difference. Our Glow Getter VIP membership lowers the per-unit price of both, which adds up for a treatment you repeat two or three times a year.

Is masseter Botox covered by insurance?

Usually not. Jaw slimming is cosmetic, so insurance does not cover it. For clenching and TMJ pain, Botox is used “off-label”: the FDA has not approved it for TMJ disorders or teeth grinding, and most insurance plans will not pay for off-label use. Some people have had partial cover after a specialist’s referral, so if your jaw pain is severe it is worth asking your insurer, but plan for it to be a self-pay treatment.

Masseter Botox for TMJ, clenching and grinding

When the masseter is overworked, it can ache, feel tight in the morning, cause headaches around the temples and wear down your teeth. Relaxing it often eases that tension. Research supports this, but with some honesty needed: a 2022 review of the evidence found good support for using Botox to reduce an enlarged masseter, but mixed results for jaw pain from muscle problems, and very little evidence for problems inside the jaw joint itself. In practice, that means:

• It can help muscle pain and tension. Many people with daytime clenching or a tired, aching jaw feel the difference within a couple of weeks.
• It does not cure grinding. Botox makes each bite less forceful, but the habit is still there. Keep wearing your night guard.
• It is not a fix for the joint. Clicking, locking or pain inside the joint needs a dentist or a TMJ specialist to look at the cause.

What before and after usually looks like

Masseter Botox before and after photos can look dramatic online, often because of lighting, angles or filters. A realistic result is a softer angle at the back of the jaw and a lower face that narrows toward the chin, so the face looks more oval or heart-shaped from the front. It does not change your bone, your chin or your cheekbones, and friends usually say you look “rested” or “slimmer” rather than different. The biggest change is seen in people with a clearly enlarged muscle. If your masseter is only slightly prominent, the change will be subtle. You can see real results from our patients in our before and after gallery.

Side effects and risks

Masseter Botox is a common, well-studied treatment, and most people have nothing more than mild tenderness. These are the side effects worth knowing about:

• Tenderness, small bumps or a bruise at the injection points, usually gone within a day or two.
• Chewing fatigue. Steak, crusty bread or gum can feel like hard work for the first few weeks. It improves as you adjust.
• An uneven smile. If product reaches the small muscles that pull the corners of your mouth, your smile can look uneven for a few weeks. Careful placement in the lower, back part of the muscle makes this rare.
• Paradoxical bulging. A small bulge can appear when you clench if part of the muscle was not relaxed. A few extra units at your follow-up usually fixes it.
• Hollowing or sagging. In people with thin or loose skin, a smaller muscle can leave the cheek looking hollow or make jowls more visible. This is why we assess your skin before treating.

As with any Botox treatment, call us straight away or seek urgent care if you have trouble swallowing, speaking or breathing after treatment. This is very rare, especially at cosmetic doses.

How we do masseter Botox at Glow Theory

We start by watching your jaw at rest and while you clench, feeling the size and edges of each muscle, and checking whether one side is larger than the other. We also look at your skin along the jaw, because that decides how much slimming will flatter you. We then tell you how many units you need on each side and what it will cost before we begin. The injections themselves take a few minutes and most people describe them as a firm pinch. You can go straight back to work, but avoid massaging the jaw, facials and hard workouts for the rest of the day; our Botox aftercare guide covers the details. We see you again at two weeks to check that both sides are even and add a few units if needed. If you would like to know whether masseter Botox will slim your jaw or ease your clenching, book a consultation at our South Carlsbad studio on El Camino Real, or read more about Botox at Glow Theory.