Overbite and underbite: what they are and how they are corrected

Upper teeth that stick out, lower teeth that close in front of the upper ones, front teeth that do not meet at all: these are all problems with how the teeth bite together. This guide explains, in simple words, what "overbite", "underbite" and the other terms mean, where these problems come from, at what age to have them checked and what can be corrected in a growing child or in an adult. It is here to inform you; it does not replace an examination.

What is a normal bite?

When you close your mouth with your back teeth together, the upper front teeth normally sit slightly in front of the lower front teeth and partly cover them, by a few millimetres. The upper back teeth sit slightly outside the lower back teeth, all the way round. When this relationship is off, dentists speak of a malocclusion (a bad bite).

Bite problems are very common. A review of 77 studies in children and teenagers found malocclusion in 56% of them worldwide, with large differences between regions (81% in the African studies, 72% in the European ones); the figures vary a lot from one study to another (Lombardo et al., 2020, PubMed). Many of them are mild.

Overjet, overbite, underbite: the words explained

In everyday English, "overbite" is often used for upper teeth that stick out. Dentists use two separate words: overjet (how far the upper teeth are in front, measured forwards) and overbite (how much they cover the lower teeth, measured up and down).

How to tell if you have an overbite or an underbite

Close your back teeth together and look in a mirror:

• if your upper front teeth are well in front of the lower ones, you may have an increased overjet;
• if you cannot see your lower front teeth at all, you may have a deep bite;
• if there is a gap between the upper and lower front teeth, you may have an open bite;
• if your lower front teeth are in front, you have a reverse bite (underbite) on those teeth;
• if your chin shifts to one side when you close, there may be a crossbite at the back.

This is only a first look: only an examination confirms it.

Why does a bite go wrong? Bones, habits and teeth

There are three main causes, often combined:

1. The jaws (skeleton): one jaw is larger, smaller, more forward or more backward than the other. This often runs in families, especially for an underbite, and is the hardest part to correct.
2. Habits: sucking a thumb, finger or dummy for a long time, breathing through the mouth, or resting the tongue between the teeth. A meta-analysis of 33 studies found that sucking habits that last longer, or happen every day, are linked to a higher risk of open bite in children (Gao et al., 2025, PubMed).
3. The teeth themselves: teeth that are tipped, crowded, missing, or that came in in the wrong place, and baby teeth lost too early.

At what age should a bite be checked?

In a child, a first check-up around age 7 is useful, when the first adult front teeth and molars are in. It helps to spot a narrow upper jaw, a forward lower jaw, very prominent front teeth or a harmful habit early. Often the answer is simply to monitor and see the child again later.

In a teenager or an adult, there is no age limit for a check-up: what changes is what can be corrected (see below).

What can be corrected in a growing child?

While the child is growing, some appliances can guide the growth of the jaws. But early treatment is not always better: it depends on the problem.

• Upper teeth that stick out: a Cochrane review (27 trials, 1,251 children) found that early treatment, between about 7 and 11 years old, did not give a better final result than a single treatment in adolescence. Its one clear benefit was fewer injuries to the front teeth: 19% of children treated early had a new injury, compared with 30% in the group treated later (Batista et al., 2018, PubMed).
• Underbite: in another Cochrane review (29 trials, 1,169 children aged 5 to 13), appliances such as the facemask improved the bite and the relationship between the jaws just after treatment (moderate-certainty evidence). In the only long-term study, the benefit had shrunk after 3 years and was no longer clear after 6, although treated children were judged less likely to need jaw surgery later (low-certainty evidence) (Owens et al., 2024, PubMed).
• Crossbite at the back: in children aged 7 to 11, widening the upper jaw with an appliance corrects the crossbite far more often than simply watching it (Ugolini et al., 2021, PubMed). See the guide on palatal expansion.
• Open bite caused by a habit: stopping the habit comes first; the bite sometimes improves on its own.
• Deep bite: a review of six studies found that results tended to be more stable when the deep bite was treated at the end of the mixed-teeth stage or in early adolescence than very early (El Guennouni et al., 2024, PubMed).

What can be corrected in an adult?

Once growth is over, appliances can no longer change the jaws, but they can still move the teeth: this is often enough when the problem is mild or mainly dental.

• Fixed braces move teeth at any age, as long as the gums are healthy (see the guides on braces and gum disease).
• Clear aligners suit mild to moderate cases. For bite problems in adults, a review of 18 studies (low-certainty evidence) suggests they may correct a mild to moderate open bite, but that their effect on a deep bite is still limited (Ben Mohimd et al., 2026, PubMed). See the guide on clear aligners.
• Jaw surgery (orthognathic surgery): when the problem comes mainly from the jaws, for example a large underbite, moving the teeth alone can hide part of the problem but not correct it. Treatment then combines braces and an operation on the jaws, carried out by a specialist orthodontist and a maxillofacial surgeon.

Dr Ghenia is a general dentist and does not present himself as an orthodontist. When a case needs a specialist, for example a large jaw discrepancy or a plan combined with jaw surgery, the assessment is also used to refer you to a specialist orthodontist or a maxillofacial surgeon, with your X-rays and a summary of the case (see orthodontics in Rabat).

What happens if you do nothing?

A mild bite problem often causes no trouble and does not need treatment. A more marked one can, depending on the case:

• expose prominent upper front teeth to injury in a fall or a blow;
• make the lower front teeth bite into the gum behind the upper teeth, in a deep bite;
• cause uneven wear of the teeth, or a jaw that shifts to one side on closing, with a crossbite;
• make biting, cleaning or some sounds harder, or bother you because of how your smile looks.

What cannot be promised

• No treatment can guarantee a result: it depends on growth, on the cause, and on wearing the appliances and the retainer as advised.
• Teeth tend to move back after treatment: a retainer is needed to keep the result.
• Jaw pain: a recent review concludes that well-conducted orthodontic treatment neither causes nor cures problems of the jaw joint (Almuzian and Ouazzani, 2026, PubMed).
• Veneers, exercises or devices bought online do not correct a jaw problem. Veneers change the shape of the front of the teeth, not the bite (see veneers); and on tongue exercises, see the guide on mewing.
• Before-and-after photos show other people's cases and say nothing about your result: this page shows none.

When should you see a dentist quickly?

• After a blow to the face, if your bite suddenly feels different, if a tooth is loose or broken, or if you cannot close your mouth properly: see a dentist or go to the emergency department straight away; a knocked-out adult tooth is an emergency.
• If your jaw locks, open or closed.
• If your bite changes gradually as an adult, or your face becomes asymmetrical.
• If you have swelling of the face, fever, or difficulty swallowing or breathing: go to the emergency department straight away.

Booking an appointment

Consultations take place in Rabat, Monday to Friday from 9 am to 6 pm and on Saturday from 9 am to 2 pm; the address is given when you book. The easiest way is to send a WhatsApp message stating the patient's age and the reason (for example "bite check for my 8-year-old"). See the appointment section. The cost of any treatment depends on the type of appliance, its duration and how complex the case is; it is explained after the assessment, before any decision.

Frequently asked questions

What is an overbite?

Strictly speaking, the overbite is how much the upper front teeth cover the lower ones; a small overbite is normal, and when it is large it is called a deep bite; in everyday language, "overbite" is also used for upper teeth that stick out, which dentists call an increased overjet.

What is the difference between an overbite and a normal bite?

In a normal bite, the upper front teeth sit slightly in front of the lower ones and cover them by a few millimetres; in an overbite in the everyday sense, the upper teeth are much further forward, or cover the lower teeth much more.

How do you fix an overbite?

It depends on the cause and the age: in a growing child, appliances can guide jaw growth; in a teenager or an adult, braces or sometimes clear aligners move the teeth; when the jaws themselves are the problem in an adult, surgery combined with braces may be discussed with a specialist.

How do you fix an underbite in an adult?

If the underbite comes from the teeth or is mild, braces can sometimes correct it; if it comes from the jaws, moving the teeth is not enough, and treatment combines braces and jaw surgery, planned with a specialist orthodontist and a maxillofacial surgeon.

Can veneers fix an overbite?

No: veneers change the shape and colour of the front of the teeth, but they do not move the teeth or the jaws, so they do not correct the bite; the bite is always assessed before any veneer.

Is an underbite genetic?

It often runs in families, especially when it comes from the size or position of the jaws; but some underbites come mainly from the teeth or from a narrow upper jaw, which is why an examination is needed to find the cause.

Why is there no before-and-after photo on this page?

Because every bite is different and a photo of another person's result says nothing about yours; the options, their limits and the expected duration are explained to you after your own examination.