Why does one side of my jaw bulge more when I clench?

The muscle along each side of your jaw becomes easier to see when you clench. One side may naturally look more noticeable, or that muscle may be larger because of how you chew, clench or grind. However, not every jaw bulge comes from the muscle itself. A dentist can examine the area and help find the cause. 

What you will learn in this article: 

• The masseter is the strong chewing muscle that stands out when you clench. 

• Chewing or clenching more on one side may make that muscle look larger over time. 

• Dentists compare both sides at rest and during a clench to find the source of the difference. 

• A new, growing, painful or firm bulge should be checked because it may not be simple muscle growth. 

If you've noticed one side of your jaw looks bigger or feels tighter when you clench, schedule an appointment with an Aspen Dental provider. Your care team can check your bite and jaw muscles and help you understand what's causing the change. 

What is the masseter muscle? 

The masseter is one of the main muscles used for chewing. It runs from your cheekbone to the outer part of your lower jaw. You can feel it tighten by placing your fingers near the back of your cheek and gently clenching. 

You have one masseter on each side of your face. They may not look perfectly even, especially when you bite down. 

Why does one side look bigger when you clench? 

Several things can make one masseter look more noticeable. A case report in Case Reports in Dentistry notes that one-sided chewing or clenching, grinding, bite problems and temporomandibular disorders have all been reported in people with masseter enlargement.¹ 

Why do some people favor one side when they chew? 

You may favor one side because of habit, a missing tooth, tooth pain or another chewing problem. Using one side more may make that masseter work harder and become more noticeable. 

When the muscle itself is enlarged on only one side, the condition is called unilateral masseter hypertrophy. A dental provider needs to confirm that the bulge is coming from the muscle before making that diagnosis. 

Can clenching or grinding cause an uneven jaw muscle? 

Clenching and grinding activate your masseter muscles. If the habit is stronger on one side, that muscle may stand out more. This can happen while you are awake or asleep. 

However, an uneven bulge does not prove that you grind your teeth. A dental provider can look for other signs, such as tight jaw muscles or worn teeth. 

Can a jaw joint problem cause muscle asymmetry? 

The National Institute of Dental and Craniofacial Research explains that temporomandibular disorders can involve the jaw joints or the muscles used for chewing. Symptoms may include jaw pain, stiffness, locking, painful clicking or a change in how your teeth fit together.² 

These symptoms may make one side feel tighter or work differently, but a bulge alone does not prove that you have a joint disorder. Tell your dental provider if you also notice jaw clicking or locking or if your jaw feels stuck. 

How can a dental provider check for jaw muscle asymmetry? 

A dental provider will compare both sides of your face while your jaw is relaxed and while you clench. They may gently feel each masseter as it tightens. This makes it easier to compare the size and firmness of the two muscles.¹ 

Your dental provider may also ask which side you chew on and whether you have pain, grinding, clicking or trouble opening your mouth. If the cause is not clear, an X-ray or referral to a specialist may be needed. 

Is jaw muscle asymmetry something to worry about? 

A small, stable difference between the two sides does not always mean something is wrong. Still, appearance alone cannot confirm that the masseter is causing the bulge. Have the area checked if the change is new or still visible when your jaw is relaxed. 

Treatment depends on what the exam finds. For confirmed masseter enlargement, botulinum toxin injections may temporarily reduce the muscle’s size. Their effect may wear off after about six months. Surgery can remove part of the muscle and, in some cases, reshape part of the jawbone.¹ These procedures have risks and are not right for everyone, so the cause should be confirmed before treatment is considered. 

What should you do if you notice jaw asymmetry? 

Start by noticing whether the difference appears only when you clench or remains visible when your jaw is relaxed. Also watch for pain, tightness, clicking, limited movement or a change in how your teeth meet. 

A dental provider can examine your muscles, joints, teeth and bite together. Depending on the cause, the next step may be monitoring the area, addressing a chewing or clenching habit or seeing a specialist. 

Noticing a difference between the two sides of your jaw can be unsettling, but you don't have to guess what's causing it. Contact your local dental provider to have your jaw muscles and bite checked, and get a clear plan for what to do next. 

Why does one side of my jaw bulge more when I clench? FAQs 

Still have questions about jaw muscle asymmetry? These answers cover a few common concerns. 

Can stress cause one side of my jaw to look bigger? 

Some people clench more when they feel stressed. If you tend to clench more strongly on one side, that muscle may feel tighter or look more defined. Stress alone cannot confirm why your jaw looks uneven, so mention the change to your dentist. 

Does jaw muscle asymmetry go away on its own? 

It depends on the cause. Temporary tightness may improve when clenching decreases. If one muscle has grown larger, the difference may remain. A dental provider can check the area and track whether it changes over time. 

Can a mouthguard fix an uneven jaw muscle? 

A night guard fits over your teeth and may help with a clenching habit, but it is not guaranteed to make the two sides of your jaw look even. Evidence that these appliances improve the pain from temporomandibular disorders (TMD) is limited.² If a guard causes pain, stop using it and contact your dentist. 

Can jaw muscle asymmetry affect my bite or chewing? 

Not always. However, tell your dental provider if your teeth begin meeting differently or chewing feels uneven. A muscle or jaw joint problem may be involved, but the difference in appearance does not prove what caused the change. 

Sources 

¹ National Institutes of Health, PubMed Central, Case Reports in Dentistry: "Management of Unilateral Masseter Hypertrophy and Hypertrophic Scar—A Case Report." https://pmc.ncbi.nlm.nih.gov/articles/PMC3400329/ 

² National Institute of Dental and Craniofacial Research: "TMD (Temporomandibular Disorders)." https://www.nidcr.nih.gov/health-info/tmd