Why Is My Lower Lip Curling Inward? Causes, Warning Signs, and Fixes

By Dr. Boris Zusin · Published October 10, 2026

If your lower lip looks like it's rolling or folding inward, whether you've noticed it in the mirror or someone else pointed it out, the explanation is most often a dental one: the lip has lost some of the support that used to sit behind it. That's good news, because it's usually fixable. But there are a few less common causes worth ruling out, and a handful of signs that mean you should be seen promptly. Here's how we think it through.

The Most Common Causes (Dental and Functional)

1. Not enough support behind the lip

Your lips rest on your teeth and, if you wear one, the flange of a denture. When teeth are missing, worn, or tipped back, or when a denture or partial is too thin or sits too far back, the lip loses its scaffold and the red part of the lip rolls inward. Studies of complete-denture wearers show that reducing lip support flattens the lip profile and changes the angle under the nose, and that the lower-lip profile is shaped largely by the position of the artificial teeth and the denture flange. In people with their natural teeth, how the upper and lower teeth relate to each other has a bigger effect on lower lip shape than the skeleton does.

2. A bite that has closed down

Severe tooth wear, missing back teeth, or years in a worn-out denture can reduce the vertical height of your bite (the occlusal vertical dimension, or OVD). The lower third of the face then collapses, the chin comes forward and up, and the lips fold in. It's the classic “aged” look of long-term tooth loss, and it's reversed by rebuilding the bite height and lip support with the right prosthesis.

3. A deep overbite

When the upper front teeth overlap the lower ones too much, the lower lip gets pulled up and tucked behind the upper teeth. Research on lip position shows the lower lip tends to follow the position of the lower front teeth.

4. A recessed lower jaw

If the lower jaw and lower teeth sit back relative to the upper jaw (a Class II pattern), there's less to hold the lower lip out. See our overview of bite types and malocclusion.

5. A tight, overactive chin muscle

The mentalis is the muscle of the chin. If it's overactive, the chin bunches up and the lower lip is pushed up and in whenever you try to close your lips, especially if your lips don't naturally meet at rest.

6. Habits and a poorly set-up prosthesis

Habitually biting or sucking the lower lip can tuck it inward, and so can front teeth that are positioned incorrectly in a denture or restoration. Both are assessed by watching you and examining the prosthesis.

If You Have Your Own Teeth: What Usually Causes It

When someone still has their natural teeth, the problem is usually the bite itself rather than denture support. The most likely explanations, roughly in order, are:

• Deep overbite with the lip tucked behind the upper teeth. This is the classic cause. When the upper front teeth overlap the lowers by a large amount (more than about 5 mm is considered severe) and lean backward, the lower lip gets drawn up and in behind them, sometimes irritating the gum or the lip itself. In one analysis of deep-bite patients, the most common underlying features were an exaggerated curve of Spee (the curve of the lower biting surfaces, in about 78%) and a reduced jaw angle (about 37%). Our bite types guide shows what a deep bite looks like.
• Lower front teeth that lean backward or sit back. The lower lip follows the position of the lower incisors, so teeth that are tilted or tucked in take support away from the lip and let it roll inward. The upper front teeth have an influence too, particularly when there's a large overjet.
• A bite that has worn down. Heavy tooth wear from grinding or acid erosion shortens the teeth and lowers the height of the bite, so the lower face collapses slightly and the lips fold in. Tooth wear is now common in every adult age group. Before any change to bite height, we check the space between your teeth at rest, how much front tooth shows, how you speak, and how your face looks. See Restoring Your Bite After Severe Tooth Wear.
• A recessed lower jaw. A small or set-back lower jaw gives the lip less to rest on.
• An overactive chin muscle, which commonly goes along with a deep bite and lips that don't close easily.
• Lip biting or sucking, which can both result from and perpetuate the bite relationship.

Less Common Causes We Check For

• Oromandibular dystonia. This is a neurological movement disorder in which the muscles around the mouth contract involuntarily. Clues include movements that are triggered by a particular task (like speaking or eating), relief from a “sensory trick” such as touching the lip or chin, neck involvement, or a medication that can cause it (certain antipsychotic and anti-nausea drugs). Diagnosis is made by a neurologist.
• Muscle diseases affecting the face. Conditions such as facioscapulohumeral and myotonic muscular dystrophy weaken the muscle that rings the lips. Typical signs are difficulty puckering or whistling, a flat or “transverse” smile, and drooping of the lip. Measured lip strength is much lower than in someone with a purely dental cause.
• Nerve or stroke-related weakness. Weakness of the facial nerve branch that moves the lower lip can make one side of the lip look different. A sudden change on one side of the face is an emergency (see below), and a weakness that develops gradually and doesn't recover needs further investigation rather than watchful waiting.
• A functional movement disorder. This can pull one side of the lower lip downward (a “smirk”) along with the neck muscle, without the speech involvement or sensory trick typical of dystonia. A neurologist can tell the two apart.

Signs That Need Prompt Attention

Call us, your doctor, or emergency services right away if you notice:

• Sudden facial drooping or weakness on one side, especially with trouble speaking or weakness elsewhere. Treat this as a possible stroke and call 911.
• A sore, crusted, thickened, or non-healing area on the lower lip. The lower lip is a common site for lip cancer, and a persistent lesion needs a biopsy rather than being put down to the way the lip sits. Our oral cancer screening includes the lips.
• A swelling that pulses, which is occasionally caused by an enlarged artery just under the lip surface and should be evaluated before anyone takes a biopsy.
• Involuntary spasms or movements around the mouth, particularly with a new medication. Your doctor or a neurologist should evaluate these.

How We Evaluate It

We start with a few questions: whether the change came on suddenly or gradually, how old your denture is and whether anything has recently been adjusted, whether you bite your lip or grind your teeth, which medications you take, and whether you have trouble whistling, eating, or speaking. Then we look at your face at rest and in motion: lip support and the height of your bite, the position of your teeth and dentures, how your upper and lower teeth overlap, chin muscle activity, and whether your lips close comfortably and evenly. We also feel the lip for anything firm or unusual.

When the bite is the likely culprit, we may also take impressions or scans of your teeth and a side-view X-ray of the head. These show whether a deep bite is mainly in the teeth or in the jaw, and how much the curve of your bite contributes.

If the cause is dental, we don't have to guess at the fix. Before any permanent step, we can try the new lip support and tooth position in wax or a temporary mock-up so you can see the result and so we can confirm that the lip looks natural and speech feels comfortable. Depending on what we find, treatment might be a new or relined denture, rebuilding worn teeth as part of a smile makeover, or orthodontic correction, which can include clear aligners for suitable deep bites. Any increase in bite height is tested with a reversible trial phase first, before anything permanent is made.

If your lower lip has been folding inward and you're not sure why, book an exam. It tells us whether this is a lip-support problem we can fix or something that needs a specialist's input.

This article is for general education and isn't a diagnosis. Sudden facial weakness or a non-healing lip lesion should be evaluated promptly.