Malocclusion: Symptoms, Causes and Treatment

Malocclusion is a bite that does not fit together well. This guide explains the types, the causes, the symptoms and the treatments.

Key points

• Malocclusion means teeth or jaws that do not fit together well, and many people with it have no symptoms.
• The main kinds are crowding, spacing, protruding teeth, overbite, underbite, crossbite and open bite.¹
• Causes include genetics, early loss of baby teeth, childhood habits, jaw growth differences and missing, extra or impacted teeth.
• Treatment is advised when the problem makes cleaning, chewing or speech difficult or affects your confidence.
• Options include fixed braces, clear aligners, extractions, other appliances and, for some jaw problems, surgery with braces.

"Occlusion" means how your upper and lower teeth meet. Malocclusion is the term for teeth or jaws that do not line up, and it is very common. Some people have a mild form that causes no problems. Others have a bite that affects chewing, speech, cleaning or appearance. Understanding what it is helps you decide whether to treat it.

Types of malocclusion

The NHS lists several reasons people have braces, which also describe the main kinds of bite problem.¹

• Crowding. Teeth that are growing too close together, overlap or twist.
• Spacing. Large gaps between teeth.
• Protruding teeth. Teeth that stick out.
• Overbite. The upper front teeth overlap the lower ones too much.
• Underbite. The lower teeth sit in front of the upper ones.
• Crossbite. Some upper teeth sit inside the lower teeth when you bite.
• Open bite. The front teeth do not meet when the back teeth do.

You can read about some of these on our pages for crooked teeth and gaps between teeth.

Causes

Malocclusion usually has more than one cause.

• Genetics. The size of your jaws and teeth is inherited, so a small jaw and large teeth can lead to crowding.
• Early loss of baby teeth, which lets neighbouring teeth drift.
• Habits in childhood, such as prolonged thumb sucking or dummy use.
• Jaw growth, if the upper and lower jaws grow at different rates.
• Injury or disease, which can alter jaw growth or tooth position.
• Missing, extra or impacted teeth.
• Mouth breathing and tongue position, in some people.

Symptoms and effects

Many people with malocclusion have no symptoms at all. When symptoms occur, they can include:

• teeth that are hard to clean because of where they sit;¹
• difficulty biting or chewing;¹
• speech problems with certain sounds;
• wear on certain teeth;
• jaw discomfort in some people;
• concern about appearance.

Does malocclusion cause disease?

The link with disease is weaker than many people think. A review of four cross-sectional studies found an association between malocclusion and dental caries in adolescents,² and a review of 19 studies found that crowding and lack of spacing may be associated with higher odds of gingivitis in people under 18, but with very low-certainty evidence, and cause cannot be inferred.³ So do not expect straightening alone to prevent disease, although teeth that are easier to clean are easier to keep healthy.

Assessment

An orthodontic assessment looks at your teeth, gums and bite, and usually includes X-rays, photographs or scans to plan the treatment.¹ The orthodontist tells you what type of malocclusion you have, how it is likely to behave and what the options are, including no treatment.

Treatments

Fixed braces. Brackets bonded to the teeth and joined by a wire. They are the most common type of appliance and can move teeth very precisely, for most types of malocclusion.⁵ They usually stay on for 18 to 24 months.⁵

Clear aligners. Removable trays, worn full-time, most often used where the teeth can be lined up without taking any out, for example in mild to moderate irregularity.⁴ A review found Invisalign viable for mild to moderate problems in non-growing patients that need no extractions.⁶

Extractions. In some cases, teeth are removed to make space, as part of a braces plan.

Other appliances. Elastics, expanders or functional appliances can guide jaw growth in children or move teeth in particular ways.

Jaw surgery combined with braces. For problems that come from the size or position of the jaws, which braces alone cannot fix.

Read our guides to what kind of braces are right for me and our page on braces treatment.

When to treat

Treatment is advised when the problem causes difficulty with cleaning, chewing or speech, or when it affects your confidence. Braces are often recommended for children and teenagers after all the adult teeth have come through, but adults can have them too.¹ A mild malocclusion that does not bother you may not need treatment.

Risks of treatment

Braces make decay and gum problems more likely if the teeth are not kept clean,¹ and teeth tend to move back without a retainer. Our article on whether braces can damage your teeth describes the risks and how to reduce them.

After treatment

All fixed brace treatment is followed by a retainer, because teeth tend to move back without one.⁵ See our guide to why wear retainers after orthodontic treatment.

Questions to ask

1. What type of bite problem do I have?
2. What happens if I do not treat it?
3. What are my options?
4. How long will each take?
5. What are the risks?

Terms you may hear at an assessment

Your orthodontist may use words that sound technical. A few of them mean:

• Overjet: how far the upper front teeth stick out in front of the lower ones.
• Overbite: how much the upper front teeth cover the lower ones when you bite.
• Crossbite: an upper tooth or teeth that bite inside the lower ones.
• Midline: the line between the two upper front teeth, which may not match the line of the lower teeth.
• Class I, II and III: shorthand for how the upper and lower jaws sit relative to each other.
• Crowding and spacing: too little or too much space for the teeth.

Ask your orthodontist to point to these on your own teeth in a mirror or on the photographs. Seeing each term makes the plan easier to follow.

Children: why an early check helps

Children's teeth and jaws are growing, so a bite problem can sometimes be guided as the child grows. The NHS notes that braces are often recommended once all the adult teeth have come through, but a check earlier can tell you whether anything needs watching and when treatment would start.¹ A dentist can refer a child to an orthodontist if there is a concern, such as teeth that do not meet, a jaw that seems to sit forward or back, or early loss of baby teeth.

Early checks do not always lead to early treatment. Sometimes the answer is simply to wait and review. That is a useful answer in itself.

Adults thinking about treatment for the first time

Many adults live with a bite problem for years before asking about it. Teeth can move at any age, and adult treatment is common.¹ Adults often come because teeth have shifted, because they want a more discreet appliance or because a restorative plan, such as a crown or implant, would be easier with straighter teeth. The assessment is the same: a look at the teeth, gums and bite, X-rays, photographs or scans, and a plan. The gums must be healthy first, and some adults need other dental work before braces begin.

Myths and facts about crooked teeth and bites

Myth: only children can have their bite corrected. Braces are often recommended for children and teenagers after all the adult teeth have come through, but adults can have them too.¹

Myth: a bite problem always needs treatment. Many mild problems cause no trouble. The decision depends on cleaning, chewing, speech and how you feel.

Myth: treatment is only about looks. Looks matter, but treatment can also make teeth easier to clean and more comfortable to use.¹

Fact: how teeth meet can be assessed by anyone trained to look. Your dentist can say whether to see an orthodontist.

Living with a bite problem if you choose not to treat it

If you decide not to have treatment, you can still look after your teeth well. Clean carefully around crowded or overlapping teeth with interdental brushes, keep regular check-ups, and tell your dentist if you notice new wear, loose teeth or jaw discomfort. A bite that is stable and causes no trouble is a legitimate choice.

Frequently asked questions

Is malocclusion serious?

Often not. It is very common and ranges from mild to complex. Your orthodontist can tell you where yours sits.

Can malocclusion be corrected in adults?

Yes, in most cases. Adults can have braces too.¹

Will braces fix an underbite?

Some are treated with braces, and some, particularly those caused by jaw size, need other approaches. An assessment decides.

Does malocclusion run in families?

Jaw and tooth size are inherited, so bite problems often run in families.

Can a child's bite problem be treated early?

Sometimes. Timing depends on the problem and on growth, and an assessment decides.

Does tooth size matter?

Yes. Jaw size and tooth size together decide whether there is room for all the teeth.

Can a bite problem cause jaw pain?

In some people, yes, though the link is weaker than many assume. If you have jaw pain, clicking or difficulty opening, ask your dentist to examine the jaw as well as the teeth.

Does malocclusion get worse with age?

Teeth can drift over time, particularly without retainers after treatment or after teeth are lost, so some bite problems change. A dentist can tell you whether yours is likely to.

About the author

Sources

1. NHS website. Braces and orthodontics (patient information). Page review date 29 June 2026. https://www.nhs.uk/conditions/orthodontics/
2. Sa-Pinto AC, Rego TM, Marques LS, Martins CC, Ramos-Jorge ML, Ramos-Jorge J. Association between malocclusion and dental caries in adolescents: a systematic review and meta-analysis. European Archives of Paediatric Dentistry, 2018;19(2):73-82. https://pubmed.ncbi.nlm.nih.gov/29594971/
3. Szyszka-Sommerfeld L, Machoy-Rakoczy M, Belova A, Lipski M, Schuster L. The relationship between malocclusion and periodontal health in children and adolescents: a systematic review and meta-analysis. Journal of Clinical Medicine, 2026;15(3):1155. https://pubmed.ncbi.nlm.nih.gov/41682835/
4. British Orthodontic Society. Clear aligners (patient information leaflet). https://www.bos.org.uk/Public-Patients/Patient-Information-Leaflets/Clear-Aligners
5. British Orthodontic Society. Conventional fixed braces (patient information). https://bos.org.uk/conventional/
6. Papadimitriou A, Mousoulea S, Gkantidis N, Kloukos D. Clinical effectiveness of Invisalign orthodontic treatment: a systematic review. Progress in Orthodontics, 2018;19(1):37. https://pubmed.ncbi.nlm.nih.gov/30264270/

Medically reviewed by Dr Anupam Sinha, BDS, MDS – Orthodontics, on 23 October 2026. General information for patients from Orion Dental Clinic, last updated 23 October 2026. It is not advice for one person, so ask a dentist what suits you. To report an error, contact us.