Why Is One Side of My Jaw More Defined?

An uneven jawline can be bothersome, mostly because facial symmetry can play a huge factor in attractiveness.

One side of people’s jaws is usually more defined because of facial asymmetry. Chewing more on one side is frequently a culprit. Other factors like teeth alignment, large jaw muscles, congenital disabilities, etc., can make one side of your jaw look significantly more defined than the other side.

Why Is One Side of My Jaw More Defined?


Facial symmetry is a universally attractive trait (Little et al., 2011). However, no one has a perfectly symmetrical face. While some people will have better symmetry than others, everyone has at least some degree of asymmetry. It is normal for one side of your face to be bigger than the other, particularly your jaw.

However, most uneven jawlines are hard to notice unless you focus right on them.

Teeth Alignment and Malocclusions

Teeth misalignment and malocclusions can make you have an uneven jawline. If you have this, your jaw cannot rest properly, which causes one side to look more defined. 

For instance, a crossbite can be the cause of an uneven jawline. A crossbite means that your upper teeth are inside the bottom teeth. It can occur in one or both jaw sides. Most people can wear braces and bite appliances to correct their alignment. 

For info on how malocclusions affect facial aesthetics, check out this Looks Theory episode:

Birth Defects

Some people are born with conditions that make their jawline visibly uneven. For instance, some people naturally have a crooked jaw or a “faulty jaw.” Faulty jaw refers to the malposition of the jaws.

Masseter Muscles

Your masseter muscles are your primary chewing muscles. They are at the sides of your jaw, right behind your cheeks. 

Masseter Hypertrophy

Chewing Using One Side of Your Mouth

As stated earlier, you primarily use your masseter muscles to chew your food. Like any other muscle, these muscles will grow larger the more you use them. It can also be why one side of your jaw is more defined. For instance, your jaw’s left side can be much larger and sharper if you favor chewing on the left side of your jaw. However, trying to chew your food on the opposite side may not work for you either. You may end up overdoing it on the other side, and you will still wind up with an asymmetrical jaw.

Over time, chewing more on one side than the other doesn’t just hypertrophy your masseter muscles but also changes the shape of your jaw, especially if you’re still growing.


TMJ is a disorder that affects the chewing muscles and joints that connect the lower jaw to the skull. TMJ can cause facial asymmetry in two ways. The first is that TMJ can make one side of your jaw higher than the other. This often happens because of grinding or chewing episodes that wear down teeth on one side of the mouth, leading to a lopsided jaw.

The second is because of the jaw muscles. As stated earlier, overusing your masseter muscles can make them grow. TMJ can make the jaw muscles on one side of your face harder than the other, causing one side to be bigger and muscular. 

Most people who have an uneven jawline because of their jaw muscles can try Botox. Botox can help relieve jaw tension and TMJ symptoms. 

Additionally, Botox can relax the masseter muscles to create a smaller, more even jawline. A surgeon can strategically inject Botox into your masseter muscles so one side of your jaw will match the other.

Of course, it will depend on your case. For instance, some people need full mouth reconstruction because conditions like TMJ damaged their teeth. 

It’s best to avoid triggering TMJ in the first place with mewing and proper oral posture. See our article on the subject.

Environmental Factors

Certain environmental factors like smoking, certain sleeping positions, etc., can cause facial asymmetry. For instance, continually sleeping on one side of your body and face can eventually lead to asymmetry.

sean o'pry jawline
A crisp jawline

A study using identical twin participants showed how environmental factors cause facial asymmetry (Liu et al., 2014). Each subject completed questionnaires regarding their personal and medical history. 

They also took digital photographs of each participant from different angles. They used Adobe Photoshop to measure eight facial features from the photos. The researchers used the facial features to analyze them against the survey responses between the twins.

The results showed that environmental factors affect symmetry. For instance, twins who slept in a specific sleeping position had greater mouth and nose bridge asymmetry. 

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