Korea masseter Botox is a course of botulinum toxin type A injections into the jaw-closing muscle that, repeated over several months, thins that muscle and softens a square lower face. One session is short: a few injection points per side after ice or numbing cream, and most people can fly home the same day. The visible change comes slowly, over weeks rather than days, and builds when a second session follows at roughly three months. For visitors who return to Busan more than once a year, the useful questions are how to space sessions, what long-term studies report, and what the jawbone does under repeated treatment.
Guide
How the jaw changes across the first year
A single treatment relaxes the masseter for a few months, then the muscle slowly regains strength. Repeating the injection before full recovery is what lets the muscle stay smaller for longer, which is why clinics in Korea usually talk about a plan rather than a one-off visit.
In a 2019 Plastic and Reconstructive Surgery study, Shome and colleagues gave 50 patients 30 units per side and found by ultrasound an average 12 percent muscle reduction at week 12. In the same study by Shome, patients given a second session reached a 26.6 percent reduction at week 24 and kept about 24 percent at four years, while a third session took the reduction to about 42 percent, largely held at four years.
That study enrolled Asian Indian patients and results vary from person to person, so the figures describe a trend, not a forecast.
Guide
Spacing visits when you travel to Busan
Because the effect builds in steps, it helps to map sessions onto trips before the first appointment. Ask the treating doctor to write down the brand, the units injected on each side and the date, so a later session, in Busan or elsewhere, can follow the same plan.
| Visit | Typical timing | Purpose | What to bring or ask |
|---|---|---|---|
| First session | Start of the plan | Assess muscle size and inject both sides | Ask for units per side and brand in writing |
| Second session | Around 12 weeks later | Inject before the muscle fully recovers | Bring the first record; mention any chewing fatigue |
| Third session | Around 24 weeks after the first | Consolidate the reduction if planned | Ask whether the dose should change |
| Maintenance | Spaced further apart | Hold the outline with fewer sessions | Review jaw comfort and facial balance |
Guide
What repeated toxin may do to the jawbone
Bone responds to muscle pull, so a weaker masseter could in theory change the bone it attaches to.
In a systematic review and meta-analysis in the Journal of Oral Rehabilitation, Moussa and colleagues found in human studies a decrease of about 6 percent in mandibular cortical thickness after injection, with no evident change in bone volume or density. Animal studies in the Moussa review showed larger bone loss, and long-term effects in people remain understudied.
For a visitor, the practical step is to mention any existing jaw joint problem, teeth grinding, dental implants or bone conditions at the consultation, and to ask whether the planned dose and frequency are the lowest that achieve the goal.
Guide
Muscle, bone or fat: who responds
Toxin only shrinks muscle. A wide lower face caused mainly by a broad jaw angle or by fat along the jawline will change little, and a doctor should say so before treating. A simple check is to clench the teeth: if a firm bulge rises at the jaw corner, muscle is a large part of the width.
Treatment is not appropriate during pregnancy or breastfeeding, with a neuromuscular disorder such as myasthenia gravis, with infection or inflamed skin over the jaw, or after a past reaction to botulinum toxin.
- Good sign: a visible bulge when clenching
- Good sign: the width feels firm rather than soft
- Poor sign: the bone angle itself flares outward
- Poor sign: width comes mostly from soft tissue or fat
Guide
Side effects that matter for the jaw
Recovery is usually short. Small bruises or tenderness at the injection points can last a few days. Some people notice tired chewing on tough food for the first weeks while the muscle weakens.
Less often, toxin spreading toward nearby smile muscles can make a smile look uneven for some weeks. In a thin face, a strongly reduced masseter can make the cheek below the cheekbone look hollow. Very frequent, high-dose sessions may raise the chance of antibodies that make the toxin work less well.
Evidence
Research behind this page
- Adverse effect of botulinum toxin‐A injections on mandibular bone: A systematic review and meta‐analysisJournal of Oral Rehabilitation · 2023 · doi:10.1111/joor.13590
A systematic review and meta-analysis of human and animal studies that found about a 6 percent decrease in mandibular cortical thickness in humans after toxin injection, with no evident change in bone volume or density.
- Efficacy of Botulinum Toxin in Treating Asian Indian Patients with Masseter Hypertrophy: A 4-Year Follow-Up StudyPlastic & Reconstructive Surgery · 2019 · doi:10.1097/prs.0000000000005944
In 50 patients given 30 units per side, two or three early sessions produced masseter reductions that were largely maintained at four-year ultrasound follow-up.
FAQ
Questions about Botox in Busan
Will my jaw return to its old width if I stop the injections?
Usually yes, gradually, because the muscle regains strength once the toxin wears off and no further sessions follow. How fast depends on how many sessions you had and on your chewing habits. Plan on occasional maintenance if you want to keep the outline.
How can I tell whether my square jaw is muscle or bone?
Clench your teeth and feel the jaw corner: a firm bulge that rises and falls suggests muscle makes up much of the width. A flared angle that stays the same when relaxed points to bone, which toxin does not change. Ask for this assessment before the first injection, since it decides whether the treatment is worth doing at all.
Does chewing gum or tough food affect the result?
Heavy chewing keeps the muscle working, so it may shorten how long the slimming lasts. Many doctors suggest softer food and less gum for the first weeks while the toxin takes effect, and steady habits afterwards. If you grind or clench at night, mention it, because that habit also loads the masseter and can influence the plan.
Can jaw toxin help with teeth grinding as well?
Some doctors use masseter toxin for clenching and grinding, but in dental practice this is off-label and should be discussed separately from cosmetic slimming. Tell the treating doctor about grinding, jaw pain or a night guard, so the dose and aims are set for your situation.
Could the injections make my cheeks look sunken?
It can happen in a thin face when the masseter is reduced a lot. The muscle supports the side of the lower face, so losing bulk there can leave a slight hollow below the cheekbone. Doctors lower this risk by adjusting the units and the injection points to your face. Ask how the plan accounts for your facial fat and age, especially before a third session.
Is it safe to treat one side more than the other?
Yes, an uneven dose is common when one masseter is visibly larger, often from chewing on one side. The doctor compares both sides by look and touch and may inject more units into the bigger muscle. Ask for the units on each side in writing so a later session can repeat or adjust the same split.