Overbite vs. Underbite: How the Two Bite Problems Differ

An overbite and an underbite describe different relationships between the upper and lower front teeth:

• Overbite: The upper front teeth overlap the lower front teeth vertically. Some overlap is normal; an excessive overbite is also called a deep bite.
• Underbite: The lower front teeth sit ahead of the upper front teeth when the mouth closes.

The important treatment question is not simply which label applies. An orthodontist must determine whether the relationship comes mainly from tooth positions, jaw growth or both.

Overbite vs. underbite at a glance

The American Association of Orthodontists (AAO) describes a deep bite as excessive vertical coverage of the lower front teeth by the upper front teeth. It describes an underbite by the lower front teeth sitting in front of the upper front teeth (AAO).

An overbite is not the same as overjet

These terms are often mixed up:

• Overbite is the vertical overlap of the front teeth.
• Overjet is the horizontal distance between the upper and lower front teeth.

A person may have excessive overbite, excessive overjet or both. Upper teeth that appear to “stick out” may indicate overjet rather than a deep overbite. The distinction matters because each relationship can require different tooth movements.

An underbite is also a front-to-back relationship: the lower front teeth close ahead of the upper front teeth. It is therefore not simply the opposite of a deep overbite, which is measured vertically.

Dental versus skeletal causes

Either problem can be predominantly dental or skeletal.

A dental problem comes mainly from how the teeth are angled, positioned or erupted. A skeletal problem comes mainly from the size or position of the upper and lower jaws. Many cases include both components.

For example, an underbite may involve lower front teeth tipped forward, upper front teeth tipped backward, differences in upper- or lower-jaw growth, or some combination. Cleveland Clinic notes that underbites can reflect jaw anatomy or tooth position and may run in families (Cleveland Clinic).

A mirror or selfie cannot reveal the complete cause. An orthodontic assessment may include an examination and records such as photographs, scans or X-rays (NHS).

When might either bite need treatment?

A mild variation does not automatically require correction. The reasons to discuss treatment become stronger when there is tissue injury, tooth wear or difficulty with normal function.

With a deep overbite, the lower teeth may contact the tissue behind the upper teeth, or the upper teeth may traumatize tissue around the lower teeth. Significant cases can also be associated with wear or discomfort; the AAO lists tooth damage, sensitivity, gum problems and jaw pain among possible consequences (AAO).

A pronounced underbite can make biting or chewing difficult and may be associated with speech problems, tooth wear or jaw discomfort (AAO). Arrange a dental or orthodontic assessment if teeth are injuring the gums or palate, chewing is difficult, wear is visible, or a child’s lower front teeth consistently close ahead of the upper teeth.

How treatment can differ

When tooth position is the main problem

Braces can move teeth and change how the upper and lower arches meet. Clear aligners may also be suitable for some deep bites and underbites. The choice depends on the movements required, the supporting teeth and gums, the need for added components such as elastics, and whether aligners would be worn as prescribed.

The appliance name alone does not show whether the underlying jaw relationship can be corrected. Compare braces and aligners by the proposed tooth movements and monitoring plan, not visibility alone. Our braces and aligners comparison explains the daily-life differences.

When jaw growth contributes in a child

Growth status matters when jaw development contributes to the bite. Selected children may be offered interceptive treatment at a particular stage of development; others may be monitored until treatment would be more useful.

The AAO recommends an orthodontic check by age seven while emphasizing that an early visit does not necessarily lead to immediate treatment (AAO). Age seven is a screening point, not a braces deadline. See our guide to early treatment versus monitoring.

When there is a severe jaw mismatch

Orthodontic appliances move teeth; they do not eliminate every mismatch in jaw size or position. Nottingham University Hospitals says jaw surgery may be offered when there is a large size mismatch or asymmetry and braces alone cannot provide a good bite (Nottingham University Hospitals NHS Trust). Treatment in such cases generally combines orthodontics with orthognathic, or jaw, surgery.

Surgery is not the default for every adult overbite or underbite. The decision depends on the size and nature of the discrepancy, symptoms, treatment goals, general and oral health, and whether moving the teeth without changing the jaws could produce an acceptable result.

Questions to ask at a consultation

Ask the orthodontist to show you:

1. Whether the problem is excessive vertical overbite, horizontal overjet, an underbite or a combination.
2. How much comes from tooth position and how much from jaw position.
3. What treatment can realistically change at the current age and growth stage.
4. Whether the plan corrects the jaw relationship or moves the teeth to compensate for it.
5. Why braces, aligners, growth-related treatment or surgery is being considered.
6. What is likely to happen if the bite is monitored rather than treated now.
7. How long active treatment and retention are expected to last.

The label identifies the direction of the bite problem. The balance between tooth position and jaw structure determines the meaningful treatment options, so individual assessment is more useful than comparison with photos online.