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Mouth Breathing in Children: Effects on Teeth, Jaws and the Bite
Mouth breathing is when a child breathes mainly through the mouth instead of the nose, often because the nose or airway is blocked. Over time it may affect how the jaws grow and how the teeth meet. At Yonsei Baro near Isu Station, Dr. Sally Chaekyung Lee checks the bite and suggests an ENT evaluation when needed.
Mouth breathing at a glance
| Question | In brief |
|---|---|
| What it is | Habitual breathing through the mouth, awake or asleep, instead of through the nose |
| Common causes | Enlarged adenoids or tonsils, allergies or a frequently blocked nose, a deviated septum; sometimes a habit that continues after the cause is treated |
| Usually noticed | Preschool and school age: lips apart at rest, snoring, a dry mouth, or a tired child in the morning |
| How it’s assessed | Lip and tongue posture, bite and jaw-width check, X-rays or 3D CT (a CT can show the airway and jaw shape), growth analysis; ENT referral for the nose and throat |
| Treatment options | ENT assessment and treatment of the airway; upper-jaw expansion; habit or functional appliances; lip and tongue exercises; later braces or aligners |
| Typical approach: children | Treat the airway cause first; then correct narrow jaws or bite problems while the child is growing |
| Typical approach: adults | Orthodontic treatment of the bite; an ENT or sleep specialist for breathing and sleep concerns |
Why does mouth breathing matter for teeth and jaws?
When a child breathes through the mouth, the lips stay apart and the tongue tends to rest low in the mouth instead of against the roof. The tongue normally helps shape the upper jaw, so long-term mouth breathing has been associated with:
- A narrow upper jaw and crossbite
- Crowding of the teeth
- An open bite or a long, vertical facial pattern
- Dry mouth, which can increase the risk of gum inflammation and decay
Researchers still debate how much mouth breathing causes these changes and how much they simply occur together. Most orthodontists agree, though, that it is worth identifying and addressing during growth.
Signs your child may be a mouth breather
- Lips apart when relaxed, watching TV or concentrating
- Snoring, noisy breathing or restless sleep
- Waking with a dry mouth, or drooling on the pillow
- Frequent blocked nose, allergies or repeated colds
- Daytime tiredness or difficulty concentrating
If your child snores most nights, pauses in breathing during sleep, or gasps, see a doctor promptly. These can be signs of sleep-disordered breathing, which is a medical question for a paediatrician or an ENT specialist.
Does my child need to see an ENT doctor?
Often, yes. An orthodontist can recognise the signs of mouth breathing and its effects on the bite, but diagnosing and treating the cause belongs to an ENT (ear, nose and throat) doctor. Enlarged adenoids and tonsils, allergies and nasal blockage are common causes in children. If Dr. Lee suspects an airway problem, she will suggest an ENT evaluation, and can provide a letter describing her findings to take along.
How is mouth breathing treated orthodontically?
Once the airway has been checked, Dr. Lee may recommend:
- Upper-jaw expansion when the upper jaw is narrow, which is easier while a child is still growing
- Habit or functional appliances to encourage nose breathing, lip seal and a higher tongue position
- Simple exercises for the lips and tongue to support new habits
- Braces or aligners later to align teeth once growth-related problems are addressed
Orthodontic appliances do not treat a blocked nose or enlarged tonsils, and they are not a treatment for sleep apnoea in children. They work alongside medical care, not instead of it. See also early orthodontic treatment .
How Dr. Lee assesses a mouth-breathing child
Dr. Lee looks at lip posture, tongue position, swallowing and the width of the upper jaw. A RAY Quantum 5D CT scan shows jaw shape and can give a view of the airway, though it does not replace an ENT examination. Growth analysis helps time expansion. As a mother herself, she explains each step to parents and children in plain English.
Mouth breathing FAQs
Can mouth breathing change the shape of my child’s face?
Long-term mouth breathing in growing children has been associated with a narrower upper jaw and a longer, more vertical face, although researchers still debate how strong the effect is. Because growth is involved, it is worth identifying the cause early. An orthodontic check and, if needed, an ENT evaluation can guide what to do.
Will removing adenoids or tonsils fix my child’s bite?
Not by itself. Treating an airway blockage can help a child breathe through the nose, and some studies suggest jaw growth may become more favourable afterwards. Existing problems such as a narrow upper jaw, crossbite or crowding usually still need orthodontic treatment. The decision about surgery belongs to the ENT doctor.
Is mouth taping at night safe for children?
Taping a child’s mouth at night is not generally recommended. If a child cannot breathe comfortably through the nose, taping can be unsafe, and it does not treat the underlying cause. A child who mouth-breathes during sleep should be assessed by a doctor first.
Can a palate expander help my child breathe better?
Expanding a narrow upper jaw widens the floor of the nose, and some children breathe more easily afterwards. The effect varies, and expansion is primarily an orthodontic treatment for a narrow jaw or crossbite, not a breathing treatment. Dr. Lee recommends it only when the bite needs it.
At what age should a mouth-breathing child be checked by an orthodontist?
An orthodontic check by about age 7 is a good general guide, but if your child mouth-breathes, snores or has a visibly narrow jaw or crossbite, an earlier visit is reasonable. Signs of a sleep breathing problem should be raised with a paediatrician or ENT doctor without waiting.
Medically reviewed by Dr. Sally Chaekyung Lee, DDS, PhD
Board-certified orthodontist (Korea Ministry of Health and Welfare) · Adjunct Professor of Orthodontics, Yonsei University · Last updated October 2026
This page is general information, not a diagnosis. Treatment results and duration vary from person to person. Orthodontic treatment can cause temporary discomfort and, in some cases, root shortening, gum recession or tooth decay if oral hygiene is poor; teeth can relapse if retainers are not worn as instructed.
Worried about your child’s breathing and bite?
Book an orthodontic check. Dr. Lee will look at the jaws and bite, explain in English what she sees, and suggest an ENT evaluation if needed. Isu Station Exit 2 · Open until 9 PM Mon & Thu · Saturdays 9 AM–2 PM.