People often notice that their smile looks lopsided in photos even though their teeth are straight. In most cases nothing is wrong with the teeth at all. The face may be a little uneven from side to side, the centre line between the front teeth may not sit on the centre of the face, or the biting plane may tilt. These are three separate findings, and a plan aimed at the wrong one can change very little.
First, rule out a new change
Everything below is about asymmetry that has been part of your face for as long as you can remember. A change that appears over hours, days or weeks is different. New drooping on one side of the face, numbness, weakness, trouble closing one eye or slurred speech need medical care straight away. Sudden facial drooping or weakness can be a sign of stroke, so call 000. Other causes, such as Bell's palsy, also need a doctor's assessment. If you are unsure how urgent it is, treat it as urgent. This is not a cosmetic question.
No face is perfectly symmetrical
Small differences between the left and right sides are normal. A Finnish study that followed 70 children from birth with 3D facial photographs (Launonen and colleagues, European Journal of Orthodontics, 2023) found asymmetry could be measured from early childhood, and that on average the face became more symmetrical between 12 months and six years. Sleeping position and flattening of the back of the head in infancy were among the possible contributing factors.
How common noticeable asymmetry is depends on who is being examined and how. In a review of 1,460 patients assessed at the University of North Carolina dentofacial clinic (Severt and Proffit, 1997), 34% had clinically apparent facial asymmetry. When it was present, the chin was involved in 74% of cases and the biting plane was tilted in 41%. That was a group of people already seeking help for jaw and bite problems, so the figure is higher than you would find in the general community, and studies using X-rays or 3D scans pick up smaller differences that no one would see in a mirror.
Three findings that look alike
This page focuses on the face. The centre line of the teeth has its own article on why a smile looks off centre. The table sets out how the main findings differ.
| Finding | What you notice | Usual causes |
|---|---|---|
| Facial asymmetry | One side of the face, often the chin, sits differently from the other | Normal growth variation; less often a jaw joint growth problem or a muscle cause |
| Dental midline shift | The gap between the two upper front teeth is not under the centre of the face | Tooth size differences, crowding, early tooth loss, drifting teeth |
| Tilted (canted) biting plane | The teeth show more on one side when you smile | Uneven vertical jaw growth or long-standing tooth positions |
| Jaw sliding to one side on closing | The face looks even at rest but uneven when the teeth are together | A bite problem such as a crossbite that guides the jaw sideways |
These can occur together. A chin that sits to one side often comes with a tilted biting plane, for example, but they are still diagnosed one at a time.
A perfectly centred midline is less common than people think
A classic study of natural teeth (Miller and colleagues, Journal of Prosthetic Dentistry, 1979) found the upper midline sat in the exact middle of the mouth in about 70% of people, and the upper and lower midlines failed to line up with each other in almost three quarters. Many attractive smiles would not pass a ruler test.
The more useful question is how the teeth relate to the face. Centring the upper teeth on the lower teeth is not the same as centring them on the face, and on a face that leans slightly one way, a midline measured only between teeth can end up looking more off than before. This is why smile planning starts from facial reference points such as the eyes, nose and the groove of the upper lip.
When the biting plane is tilted
If the biting surfaces slope up on one side, the smile looks crooked even when every tooth is straight and the midline is spot on. A simple check is to bite on a flat instrument and photograph the face from the front. If the instrument tilts compared with the line of the eyes, the plane is canted.
Mild tilts can sometimes be disguised with orthodontics or careful restorative work. Larger tilts that come from the jaw bones themselves may need jaw surgery planned by a specialist team. Lumi Dental does not provide jaw surgery and refers those cases.
Why a face develops this way
Ordinary growth differences
Most long-standing asymmetry simply reflects the two halves of the face growing slightly differently. It does not need treatment unless it bothers you.
A bite that pushes the jaw sideways
When back teeth meet unevenly, often in a crossbite, the lower jaw can slide to one side to find a comfortable bite. The jaw may be symmetrical, yet the face looks uneven whenever the teeth are together. A dentist checks for this by comparing the jaw at rest with the jaw fully closed. It is worth finding, especially in children, because correcting the bite can remove the shift.
Muscle and nerve causes
Lasting weakness after Bell's palsy or another nerve or muscle condition can leave one side of the face moving and resting differently. Here the asymmetry lies in the soft tissues and their movement, which limits what dental work can change.
One-sided chewing
Some people chew mostly on one side for years, often because a tooth on the other side is sore or missing. Its effect on facial shape is thought to be modest, and the better question is why that side is being avoided.
Overgrowth of a jaw joint
Condylar hyperplasia is a condition in which the rounded top of the lower jaw on one side, where it meets the skull near the ear, keeps growing more than the other. The chin gradually shifts, the bite changes and the jaw joint may become uncomfortable. Because it can continue to progress, any asymmetry that is changing in an adult deserves a proper assessment, which may include 3D imaging and referral.
How we work out which one you have
An assessment looks at the face at rest and smiling, from the front and the side, then compares the jaw at rest with the jaw closed, checks the midline against facial landmarks and checks whether the biting plane is level. Clinical photographs help make small differences visible, and a 3D X-ray may be used if a bone difference is suspected. Our articles on digital smile design and why one tooth looks longer than the others explain related parts of this process.
Treatment then follows the finding. A midline difference that most people would not notice may need nothing. A sideways jaw slide may be dealt with by correcting the bite. Tooth position can be changed with orthodontics, which Lumi provides with fixed braces and clear aligners; our article on how crooked teeth are straightened covers the options. Bonding or veneers can soften how an asymmetry reads without changing the bone underneath, and a trial smile or mock-up lets you see a proposed change before committing to it. Marked skeletal differences are referred for specialist assessment. What should be avoided is a plan that assumes straighter teeth will fix an uneven face.
What patients ask about a lopsided smile
Is it normal for my face to be uneven?
Yes. Some asymmetry is normal, and in young children it tends to become less marked as they grow. A difference that has always been there and is not changing is usually just part of how your face formed.
Can braces fix facial asymmetry?
Braces and aligners change the position of the teeth. They can correct a midline shift, remove a jaw slide caused by the bite and disguise a mild tilt, but they do not reshape the jaw bones. Severe skeletal asymmetry needs specialist surgical care.
When should facial asymmetry worry me?
When it is new or getting worse, or comes with numbness, weakness, drooping, eye or speech changes. See a doctor promptly, and call 000 for sudden symptoms.
Talking it through
If your smile looks uneven in photos and you are not sure whether the cause is your teeth, your midline or your face, Lumi Dental in Melrose Park offers a free cosmetic consultation, starting with working out which finding is present. Other offers are on our current offers page, and you will usually receive a written treatment plan before any treatment is agreed. If your asymmetry is new or changing, please see a doctor first.
This article is general information only and is not personal dental or medical advice. Facial proportions, bite and jaw growth vary from person to person, and treatment suitability and outcomes vary. Please speak with a dentist, orthodontist or doctor about your own circumstances before making a decision.
