Jaw anti-wrinkle injections (masseter): when you'll see results, how long they last, and what if they don't work

Quick answer: jaw anti-wrinkle injections into the masseter muscle start to relax it within days, but visible slimming of the lower face builds gradually over four to eight weeks as the muscle reduces in bulk. Results vary from person to person and typically last around four months. If nothing has changed after six to eight weeks, book a review so your practitioner can reassess the cause and the dose.

"Masseter injections not working after six weeks" and "will my jaw muscle go back to normal?" are two questions we see again and again online. Often the treatment is working, just more slowly than people expect. Sometimes the cause of a wide jaw was never the muscle in the first place. And sometimes the dose wasn't right for the strength of the muscle.

This guide explains the masseter injection results timeline, how long the effect lasts, what happens when it wears off, and what to do if you're not seeing a change. If you've been treated at NassifMD, call us on 0161 877 8444 and we'll arrange a review.

Why assessment and dosing matter for the jaw

The masseter is one of the strongest muscles in the face, and it varies a lot from person to person. That's why jaw treatment should never be one-size-fits-all. At NassifMD, our medically led team tailors every treatment:

• Finding the real cause. A wide or square jaw can come from your bone structure, an enlarged masseter muscle, or both. We assess this carefully, because injections only slim the muscle part. Where bone shape is the cause, jawline contouring with dermal filler may be the better way to bring balance to the lower face.
• The right dose for your muscle. A larger or stronger masseter, often from clenching, teeth grinding or lots of gum chewing, usually needs a different amount from a smaller one. Dr Nassif's expert team uses their medical knowledge to choose the right dosage for you.
• Precise placement. Injecting into the right part of the muscle matters for a smooth, natural-looking result and a comfortable smile.
• A plan over time. Repeat treatments maintain the result and can build on it, so we look at your progress across appointments.

How long do masseter injections take to work?

There are two things happening, and they work on different timelines.

Days 3 to 10: the muscle starts to relax

Anti-wrinkle injections usually start to take effect within 3 to 10 days. For many people, this is when clenching and teeth grinding start to ease. Some notice chewing tougher foods feels more tiring for a while, which is a sign the muscle is relaxing.

Weeks 4 to 8: the jaw slims

Slimming takes much longer than relaxing. The muscle only gets smaller once it has been used less for a while, so your lower face slims progressively over four to eight weeks. This is why many people feel nothing has changed at six weeks. Comparing photos taken in the same light and angle before treatment and at eight weeks is often more telling than the mirror.

Around 4 months: the effect wears off

Results vary from person to person, and typically last around four months. Repeat treatments maintain the effect and can enhance it, as the muscle has less chance to rebuild between sessions.

What if my masseter injections aren't working?

If you've had no change at all after six to eight weeks, there's usually a reason. The most common ones are:

• It's still early. Slimming can take the full eight weeks, especially with a large muscle.
• The cause is bone, not muscle. If your jaw width comes mainly from bone structure, relaxing the muscle won't change it much.
• The dose didn't match the muscle. A very strong masseter may need a different amount, or more than one session, to see a clear change.
• Placement. Where in the muscle the injections go makes a difference.

The best next step is a review appointment with the clinic that treated you, rather than waiting and wondering. If you were treated with us, we'll look at your jaw, check how the muscle is working and talk through what to do next.

Do jaw injections help with teeth grinding and clenching?

They can. Relaxing the masseter helps stop it over-contracting, which can ease the involuntary grinding and clenching that often enlarges the muscle in the first place. Many people notice this benefit before any slimming. Your suitability is assessed at consultation.

Will my jaw muscle go back to normal?

Yes. The effect is temporary. As it wears off, the muscle gradually regains its strength, and with normal chewing and use it can rebuild its size over time. If grinding or clenching was what enlarged it, the muscle may return to its previous size, which is why many people choose regular treatments. If you're months past your last treatment and want your jaw back to how it was, time and normal use are usually all that's needed.

What to expect on the day

Treatment uses a very fine needle and most people describe a slight tingling. Small red bumps or slight bruising can appear and usually fade within a few days. Downtime is little to none, and most people carry on with their day within a couple of hours. Avoid strenuous activity, saunas and other facial treatments for 24 hours.

When to contact us

Call us on 0161 877 8444, or contact our out-of-hours concierge team using the details in your aftercare information, if you're worried about anything after treatment, including:

• Your smile looks uneven
• Bruising, swelling or tenderness that is getting worse rather than better
• No change at all after eight weeks

If you have any difficulty swallowing, speaking or breathing, or you're ever in doubt, go straight to A&E.

Frequently asked questions

How long do masseter injections take to work?

The muscle usually starts to relax within 3 to 10 days, which is when clenching and grinding often ease. Visible slimming of the jaw builds gradually over four to eight weeks.

Why haven't my jaw injections worked after 6 weeks?

Slimming can take up to eight weeks. If there's still no change, the cause may be bone structure rather than muscle, or the dose may not have matched the strength of your muscle. Book a review with the clinic that treated you.

How long do masseter injections last?

It varies from person to person, but results typically last around four months. Repeat treatments maintain the effect and can build on it over time.

Will my jaw muscle go back to normal?

Yes. The effect is temporary. As it wears off, the muscle regains its strength and can rebuild its size over time with normal use.

Do jaw injections help with teeth grinding?

They can. Relaxing the masseter helps stop it over-contracting, which can ease teeth grinding and jaw clenching. Many people notice this before the jaw starts to slim.

Is there any downtime after masseter injections?

Downtime is little to none. Small red bumps or slight bruising can happen and usually fade within a few days. Avoid strenuous activity, saunas and facial treatments for 24 hours. If you have any difficulty swallowing or breathing, or you're ever in doubt, go straight to A&E.

Worried about a weak rather than wide jaw? See our guide to weak chin and jaw treatments.

Jaw slimming and teeth grinding treatment in Manchester

At NassifMD Medical Spa in MediaCityUK, every jaw treatment starts with a consultation to find out whether muscle, bone or both are behind your jaw shape, so the plan we recommend actually suits you. Find out more about wide jaw treatment, our anti-wrinkle injections and jawline contouring, or read what dermal fillers are and how they work. When you're ready, book a consultation or call us on 0161 877 8444.