Jaw Slimming in Korea: Which Cause Needs Which Treatment?

A wide-looking jawline usually traces to one of three causes: bulk in the masseter chewing muscle, fat and fluid swelling, or tissue that has begun to sag, and each cause points to a different treatment. Botulinum toxin for the masseter is reported to reach peak effect around three months and last roughly six to twelve months, while PDO, PCL, and PLLA thread materials break down over roughly four to eight months, one to one and a half years, and about twelve months. When sagging is the main driver, the choice starts with which tissue layer needs support, not with a device name.

Hello, I’m Dr. Kim Yeonjin, director of UH CELL Clinic’s Gangnam branch. “I want my face to look smaller, what treatment should I choose in Korea?” is one of the questions I hear most often in consultation. I don’t answer with a treatment name right away, because the same complaint can come from three different causes, and the right answer depends on which one applies to you.

Splitting the Complaint Into Three Causes

If the jaw angle feels hard and prominent when you clench your teeth, masseter muscle volume is likely contributing to jaw width. I also compare morning and evening thickness around the mid-cheek and under the chin. A face that changes noticeably within a single day points more toward fluid and swelling.

Finally, I compare the jawline lying down and sitting up. If the line looks defined lying flat but blurs again when you sit up, sagging tissue is the larger factor.

These three causes overlap more often than they appear alone. That is why I don’t describe one procedure as a complete fix. I set a sequence starting with whichever cause carries the most weight.

Masseter Botox: A Fairly Predictable Timeline

Reducing masseter muscle volume with botulinum toxin injections is one of the better-documented approaches for lower-face contouring. Kundu and colleagues, in a 2022 systematic review published in the Journal of Cosmetic Dermatology, reported that peak effect after a single injection typically appears around three months and lasts roughly six to twelve months. The same review noted that no standardized dosing guideline exists and that effective doses vary widely between studies, so exact numbers should not be treated as fixed.

Timing of onset comes from older data. Park, Ahn, and Jung, in a 2003 prospective study in Dermatologic Surgery, injected 45 patients with 25 to 30 units per side and tracked masseter thickness with ultrasound and CT. Thickness reduction continued through the third month after injection. The same study reported temporary local effects such as chewing discomfort, injection-site soreness, and speech difficulty lasting roughly one to four weeks.

Concern about chewing strength is common enough that I address it directly. A 2025 prospective clinical study published in BMC Oral Health injected 24 healthy adults with a total of 50 units across both masseters and measured lower-face volume with 3D imaging plus self-reported chewing function at four, eight, and twelve weeks. Lower-face volume decreased and satisfaction rose while self-reported chewing function held steady over that period. Twenty-four participants is a small sample, so anyone with jaw joint symptoms or heavy teeth grinding needs individual evaluation first.

The masseter route has a fairly predictable calendar. It’s easy to decide on during a short stay, but the visible change unfolds over the following two to three months after you return home.

Thread Materials: PDO, PCL, and PLLA Are Not Interchangeable

Thread lifting comes up often when sagging is the concern. All three common materials are absorbable suture-type threads, but they break down at different rates.

	PDO (polydioxanone)	PCL (polycaprolactone)	PLLA (poly-L-lactic acid)
Reported absorption time	About 4-8 months	About 1-1.5 years	About 12 months
Main action	Immediate physical lift plus collagen stimulation	Slower breakdown, longer stimulation window	Less immediate lift, more gradual collagen induction
Background	Long history as a surgical suture material	Comparatively newer to this use	Same material family as injectable collagen boosters
Evidence status	Human data exists but duration evidence is limited	Much of the comparative evidence comes from animal models	Direct human comparison data is limited

Marcelo Germani and colleagues, in a 2025 randomized comparative trial published in Aesthetic Surgery Journal Open Forum, described PDO threads hydrolyzing within four to six months while the collagen-stimulating effect can continue beyond that window. A mouse-model comparison study in the Journal of Cosmetic Dermatology reported PCL absorbing over roughly one to one and a half years, compared with about six to eight months for PDO and about twelve months for PLLA. Animal-model results and human results should not carry equal weight, so I use these figures only to explain the relative order between materials, not as a guarantee for any one patient.

The practical choice is simpler than the material names suggest. Do you need lift force right away, or is the goal to trigger a slower regenerative response in the dermis? Pronounced sagging usually calls for cogged threads with more mechanical hold, while thin, textured skin tends to benefit more from the regenerative approach. How much collagen actually forms depends on more than material choice. Thread count, insertion depth, and a person’s own regenerative capacity all play a role.

Absorption Time and Result Duration Are Not the Same Number

Patients often hear the absorption window and the result window described as if they were one figure. The evidence on this point is mixed.

Contreras and colleagues, in a 2023 case report and systematic review in the Journal of Cosmetic Dermatology, described a 52-year-old patient whose lower-face lift with PDO threads showed swelling resolve within seven days, with visible effect still present at seven months. Other findings point the other way. Aitzetmueller and colleagues, writing in Plastic and Reconstructive Surgery in 2019, measured meaningful quality variation across PDO threads sold commercially and argued that this variation needs to be taken seriously in clinical decisions. A related letter discussion in the same 2019 journal cited Bertossi’s thread-lift case series, where results declined noticeably by around six months and had largely faded by the one-year mark.

I don’t promise a duration in months during consultation because of this. What the literature does support is a direction: physical support fades as the thread absorbs, and whatever holds on beyond that comes from the tissue response the thread triggered. How much that response varies from person to person hasn’t been measured at scale yet.

When Sagging Leads, We Start With the Target Layer

Once sagging is confirmed as the main driver, our Gangnam branch starts by deciding which tissue layer needs support rather than naming a device first. Loosened deep support structures and reduced dermal elasticity call for different candidates. We match devices such as Ultherapy, Thermage, Sofwave, Onda, InMode, Volnewmer, and Potenza to target depth and heat delivery method based on the diagnosis, and we keep a treatment history so the same area isn’t treated repeatedly without reason, which also feeds into planning your next visit.

If swelling and circulation carry more of the weight in your case, I tend to focus first on recovery conditions during your stay rather than adding more procedures. Salty food, alcohol, and poor sleep are common reasons a short-stay result gets misjudged.

Sequencing a 2-7 Day Visit

For a short stay, the order you receive treatments in matters more than which treatments you choose. This is the sequence I generally recommend.

1. On arrival, keep the day to consultation and diagnosis only. Facial swelling from long-distance travel can distort an accurate skin assessment.
2. Schedule the treatments that need recovery time for the next morning, so you can track progress in person for the rest of your stay.
3. Avoid adding anything that can leave visible swelling or bruising right before you fly home.
4. Masseter botox, where change unfolds over several weeks, can go later in the schedule without a problem.

If you receive thread lifting, we advise avoiding wide mouth opening, exaggerated expressions, saunas, and steam rooms for about two weeks afterward, regardless of thread material.

Our Gangnam branch is located inside the UH FLAT SIGNATURE Gangnam building, so the distance from treatment room to guest room is short and recovery time is easy to spend indoors. Consultations and treatments take place in a private room. Guests staying at UHC group hotels can choose one complimentary option, either a 30-minute oxygen chamber session or a vitamin IV drip; using both means the IV drip is charged at 55,000 KRW. Full conditions are listed on our promotion page.

What to Confirm in Consultation

• Whether you were told which of the three causes, muscle, swelling, or sag, carries the most weight in your case
• Whether you were given a timeframe for when your chosen treatment takes effect and when it fades
• If thread lifting is being considered, whether the material, shape, thread count, and insertion sites are recorded
• Whether your treatment plan fits inside your travel window, and what needs to be checked after you return home
• Whether the interval to your next visit and what gets reassessed then are already part of the plan

Our Gangnam branch keeps Japanese, Chinese, and English interpreters on site, so you can confirm each of these points in your own language before deciding.

FAQ

Is it safe to get masseter botox the day before flying home?

The injection itself allows same-day normal activity, so placing it later in your schedule carries limited risk. You may see temporary bruising or soreness at the injection site, and the literature shows visible change typically emerging weeks after injection, so you should expect to judge the result after you’re already home.

Does repeating masseter botox keep making the jaw smaller over time?

That claim isn’t supported. Kundu and colleagues’ review noted that maintaining long-term effect may require repeat injections, while also stating that no standardized guideline or established dose exists. Whether to repeat is better decided case by case, based on how much effect remains from the previous session.

Can I get thread lifting and ultrasound or radiofrequency lifting in the same visit?

We don’t recommend concentrating both on the same area in the same window. Overlapping recovery responses make it hard to tell which treatment produced which result, and heat plus mechanical stimulation can compound. We generally separate them by target layer and space them out when both are appropriate.

My concern is a double chin rather than jaw width, where should I start?

That assessment looks at submental fat volume, the angle around the platysma muscle, and how much the jawline itself has sagged. Which one carries more weight changes the candidate list, so we palpate in person rather than deciding from photos alone.

※ Individual results and recovery timelines vary. Please consult a physician for an accurate diagnosis and treatment plan.