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Many people with a square jaw caused by well-developed masseter muscles get botulinum toxin injections to improve their facial contour. But why does a small muscle bulge pop out after the injection? Do the chewing muscles compensate? This article explains what muscle compensation is, the causes and effects of masseter hypertrophy, and what to watch for after face-slimming botulinum toxin to extend the slim-face results.
Causes of Masseter Hypertrophy
Chewing takes four muscles: the masseter, temporalis, medial pterygoid, and lateral pterygoid. All four connect to the mandible and work together to bite and chew. The masseter is the main muscle responsible for chewing, contributing over 70% of the force. “Chewing muscle hypertrophy,” as it is commonly called, refers to “masseter hypertrophy,” and common causes include:
1. Teeth grinding
People who have teeth grinding or snoring at night, or who habitually clench their teeth, breathe through their mouth, or zone out with their mouth open, keep the jaw constantly open or closed. The masseter's function is to keep the jaw stable, and frequent contraction makes the masseter larger.
2. Eating habits
People who have a habit of chewing betel nut or gum for long periods, or who like to eat harder, chewier foods, use their muscles forcefully and often. The facial muscles can become more and more developed and firm, causing masseter hypertrophy.
3. Family heredity
Most masseter hypertrophy is due to inherited factors from birth, and clinical studies have also confirmed familial masseter hypertrophy.
Effects of Masseter Hypertrophy
1. Difficulty biting
Bad habits over a long time cause the muscle to be overused, leading to muscle fiber proliferation and scar formation, which causes masseter hypertrophy. This extra tissue may interfere with normal contact between the teeth and may prevent the mouth from closing fully or cause discomfort when eating.
2. Jaw joint pain
Constant contraction of the masseter causes pain, which is usually located in front of the ear or at the angle of the jaw, and sometimes connects to the head or neck. The pain may be intermittent or constant, and in severe cases even affects daily activities.
3. Square jaw / uneven face size
Masseter hypertrophy makes a large chunk of facial muscle bulge outward, and the most visible effect is a square jaw. In addition, people with a more developed masseter on one side also get uneven face size and facial asymmetry, which affects overall looks.
How Aesthetic Botulinum Toxin Slims the Face
If masseter hypertrophy gives you a square jaw you are bothered by, it is usually improved with aesthetic botulinum toxin:
- How to self-test whether your masseter is thick?
Clench your upper and lower teeth hard, and at the back of the cheek near the ear you can feel a hard bulge. That is the masseter. The larger and harder the bulge, the thicker the masseter, and the more units of botulinum toxin are usually needed.
- How does botulinum toxin slim the face?
Botulinum toxin is a natural protein extracted and purified from Clostridium botulinum with advanced technology. It inhibits acetylcholine, which nerve endings release to make muscles contract and to stimulate gland secretion. Based on different antigenicity, it is divided into seven serotypes, A to G, and among them type A botulinum toxin has the strongest potency and the longest duration. Botulinum toxin is injected into the masseters on both sides, and by inhibiting muscle contraction it shrinks the face and improves a square jaw, sculpting the contour.
Common botulinum toxin brands for face slimming: Botox, Neuronox
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What Is Masseter Compensation?
- Understanding compensation
“Compensation” is a protective mechanism in the body. It means that when some muscles in the body cannot work normally, other muscles temporarily step in to help complete the movement.
- Compensatory reaction after masseter botulinum toxin
After botulinum toxin is injected into the masseter, this muscle cannot contract normally for about 1-2 months and is in a weakened state. At this time, the temporalis, medial pterygoid, and lateral pterygoid muscles compensate, which may cause a small compensatory muscle bulge on the face. Physicians therefore advise not eating overly hard foods during this period, to extend the slim-face effect.
Aftercare for Face-Slimming Botulinum Toxin
1. Within 4 hours after injection, do not lie flat, do not massage the injection area, do not lie down to sleep, and keep your neck upright as much as possible
2. For one week, do not take baths, use saunas or steam rooms, or get facials or facial massages
3. Occasional bruising or swelling at the injection site can be relieved with an ice pack and will gradually recover after about 2-3 days.
4. After a masseter injection, you can chew gum for 5 minutes right away to help the botulinum toxin spread more evenly. For the next 3 weeks, do not bite hard foods or foods that require long, repeated chewing (such as gum, tapioca pearls, and betel nut), to avoid forming compensatory muscle
5. Wait 3 months between injections in the same area
Botulinum toxin works by paralyzing the muscle. Not only must the physician's technique be on point to ensure results, but patients must also care for themselves properly after the injection. When treating a square jaw, you should avoid chewing overly hard foods and other behaviors that work against the treatment, so the results last longer and the muscle is not trained into becoming increasingly stubborn, which would be an unwelcome aftereffect.
This article is for general information only. Results vary from person to person; please consult a doctor in person before deciding on any treatment.
