[Doctor's Column] If You Are Worried About Sagging After Square Jaw Botox: Why You Must Examine Both the Masseter Muscle and Skin Condition Together

"I heard that getting square jaw Botox causes the face to sag later on. Is that okay?"

I often hear these kinds of concerns while counseling.
There are many stories on the internet about facial sagging after square jaw Botox. Conversely, there are also people who say they experienced no problems at all.

There is not just one reason why the results are different. Masseter muscle volume reduction and existing skin and soft tissue condition due to Botox It can have an impact together. Sagging is one of the side effects that must be explained during the consultation.

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Q1. What is the principle behind square jaw Botox?

Square jaw Botox is a procedure that reduces muscle contraction by injecting Botox into the masseter muscles on both sides of the jaw.

If the masseter muscle contracts strongly and repeatedly, the muscle becomes hypertrophied, and the area under the jaw appears wider.
When Botox temporarily inhibits nerve transmission in the muscles, the masseter muscle gradually atrophies, reducing lower facial volume.

In a retrospective 3D study examining 43 patients with masseter muscle hypertrophy, changes in lower facial width and soft tissue in the jawline area were reported before and after the procedure [2]. However, these results cannot predict the timing or extent of individual changes.

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Q2. But why do some people experience sagging?

After the masseter muscle volume decreases, the contours of the skin and soft tissues change, which may cause the jawline to appear blurred or sagging.

Changes may vary depending on existing elasticity, skin thickness, facial volume, and the degree of sagging. Having good elasticity does not mean there will be no side effects, nor does being older necessarily mean sagging will occur.

Image: Produced by Maypure Doctor Column

In comprehensive reviews, sagging of the cheeks and jawline is also treated as a reported side effect [1]. Since subjects and evaluation methods vary by study, a single incidence rate is not applied to all patients.

3D analysis studies have also confirmed that the clarity of the mandibular margin (jawline) may change after masseter muscle Botox.

The items to be checked together during the consultation are as follows.

1) In cases where existing skin elasticity has decreased (age, UV damage, etc.)
2) Cases where the skin is thin and soft tissue is scarce
3) Cases where volume loss is already in progress in addition to the masseter muscle

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Q3. What do you check before getting square jaw Botox?

We evaluate not only the size of the masseter muscle but also the condition of the skin and soft tissues, as well as the history of previous procedures.

At our Yeonsinnae branch, we perform square jaw Botox treatments. The decision regarding the procedure, dosage, and injection intervals is made after examining the individual's structure and condition. We do not claim that a specific dosage or splitting the injections will necessarily prevent sagging.

For example, if you are concerned about sunken cheeks or a sagging jawline, please let us know during the consultation what other changes you are worried about besides simply reducing the width of your jaw.

If you have separate concerns about elasticity
At our Yeonsinnae branch, we select CoolSonic, Density, InMode FX, etc., after verifying the purpose and application area of ​​each device. It is not an essential combined procedure to prevent sagging from square jaw Botox.

When you have concerns about skin texture and dryness together
You can consult separately regarding the suitability of skin texture improvement procedures such as Livishine and Livicol. It is not assumed that skin boosters enhance skin adaptation or prevent sagging after Botox.

When planning to use energy equipment and heat-sensitive injectables together, we proceed with the energy equipment first, in accordance with the policy of our Yeonsinnae branch.

※ Bruising, swelling, temporary weakening of chewing ability, asymmetry when smiling, sunken cheeks, or sagging jawline may occur after square jaw Botox. Please inform the medical staff if you experience any discomfort or unexpected changes after the procedure. Suitability and effectiveness vary from person to person.

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Q4. If I have a square jaw, do I absolutely have to get Botox?

In addition to the masseter muscle and bone structure, various factors such as fat and skin condition can contribute to the appearance of a wide jaw. Specifically, we will examine masseter muscle hypertrophy and the shape of the mandibular angle.

1) Masseter hypertrophy - Cases where the muscle is large, making the area appear wide
2) Development of the mandibular angle (bone) - Cases where the bone itself is wide

Since Botox acts on muscles, it is effective when masseter muscle hypertrophy is the primary cause.
If the bone is wide, it is difficult to achieve the expected changes with Botox alone.

If you have a habit of clenching or grinding your teeth, the masseter muscle is prone to hypertrophy, so correcting this habit along with the procedure is helpful.

During the consultation, it is important to determine whether to proceed with the procedure after checking both the size of the masseter muscle and the bone structure.

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Skin concerns vary from person to person. After a consultation, we will guide you to the most suitable treatment based on your records.

Maypure Clinic Yeonsinnae Branch
3rd Floor, Metro Tower, Directly Connected to Yeonsinnae Station (856 Tongil-ro, Eunpyeong-gu, Seoul)
02-389-9980

Chief Director Sim Dong-gyu of Maypure Clinic Yeonsinnae Branch
Graduated from Korea University
Graduated from Korea University School of Medicine

※ This post is intended to provide general information about the procedure, and the effects and recovery period may vary depending on individual skin conditions.
※ Please be sure to consult thoroughly with medical staff before the procedure. Swelling, bruising, and redness may temporarily occur after the procedure.

References
1. Ferrillo M et al. The Role of Botulinum Toxin for Masseter Muscle Hypertrophy: A Comprehensive Review. Toxins (Basel). 2025;17(2):91. PMID: 39998108
2. 3D Assessment of Mandibular Margin Morphological Change after BTX-A Injection for Masseter Hypertrophy: A Retrospective Study. Aesthetic Plast Surg. 2025;49(9):2328-2337. PMID: 39627334

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