Overbite vs underbite: what's the difference?

Page updated October 14, 2026. Medically reviewed by Dr. Abraham Thomas and Dr. Jennifer Loucks-Buren.

An overbite and an underbite are opposites. In an overbite, the upper front teeth overlap the lower front teeth more than they should. In an underbite, the lower front teeth sit in front of the upper ones, usually because the lower jaw extends past the upper jaw (Cleveland Clinic). Both are types of malocclusion, a "bad bite", and both are treatable at any age, though they are easiest to fix while a child is still growing.

What a normal bite looks like

In a healthy bite, the upper teeth fit slightly over the lower teeth (Healthline). Two measurements describe how the front teeth meet:

• Overbite is the vertical overlap: how far the upper front teeth come down over the lower ones. A small amount is normal and needed for the bite to work; it becomes an overbite when the overlap is more than 2 to 4 millimeters (Cleveland Clinic).
• Overjet is the horizontal gap: how far the upper front teeth sit in front of the lower ones. Most people's upper teeth sit about 2 mm in front (Cleveland Clinic).

Orthodontists also class bites by how the back molars meet. In Class I the molars meet properly, though the front teeth may still be crowded or spaced. In Class II the lower teeth or jaw sit back relative to the upper; in Class III they sit ahead (AAO).

Overbite vs underbite at a glance

Cleveland Clinic notes that Class III malocclusion, the underbite pattern, is often the most difficult type to fix (Cleveland Clinic). That's why the timing of a child's first orthodontic check matters more for an underbite.

Overbite vs deep bite

They are the same thing. The AAO defines a deep bite, or deep overbite, as upper front teeth that overlap the lower front teeth an excessive amount (AAO), and Cleveland Clinic says a vertical overbite is informally called a deep bite (Cleveland Clinic). The AAO also calls it an excessive overbite: with the back teeth closed, the upper front teeth significantly cover the lower front teeth from top to bottom (AAO).

The AAO lists what an untreated deep bite can lead to (AAO):

• Early wear of the lower front teeth, and damage to the enamel on the back of the upper front teeth
• A higher risk of decay and sensitivity
• Gum damage and recession behind the front teeth
• Sores from biting the roof of the mouth, and difficulty chewing
• Jaw discomfort and a higher risk of chipping the front teeth

Deep bites typically don't resolve on their own. Braces are the most common treatment, clear aligners are an option for some people, and surgery may be needed in severe cases, especially in adults whose jaws have stopped growing (AAO).

Overbite vs overjet (buck teeth)

Many people say "overbite" when they mean overjet. Overbite refers to vertical distance; overjet refers to horizontal distance (Cleveland Clinic). With overjet, the upper front teeth stick out forward, and Cleveland Clinic calls protrusion of 8 to 10 mm or more severe (Cleveland Clinic). You can have one without the other, or both.

Overjet doesn't resolve on its own and is corrected with orthodontics: braces, headgear, a Herbst appliance or a palate expander, with jaw surgery for severe cases. Bonding, veneers and crowns can disguise it but don't correct the underlying problem (Cleveland Clinic). Thumb or finger sucking after age 4 can contribute to it (Cleveland Clinic).

Overbite vs normal bite: how to tell

Close your back teeth together and look in a mirror at your front teeth. Cleveland Clinic says it's an overbite when your upper front teeth cover more than 30% of your lower front teeth, about 4 to 6 mm (Cleveland Clinic). If you can barely see your lower front teeth, ask about it at your next dental visit. If your lower front teeth sit in front of your upper ones, that's an underbite. If there's a gap between your front teeth when your back teeth are closed, that's an open bite.

A mirror check only tells you something looks off. Whether it's the teeth or the jaw, and how it should be treated, takes an exam with X-rays, which show the roots and jawbones (AAO). Many orthodontists offer low-cost or free first consultations (AAO).

What causes each

Overbites and underbites share similar causes (Cleveland Clinic). Many cases run in families. Childhood habits play a part too: thumb-sucking or pacifier use past age 3, tongue thrusting, nail biting and teeth grinding are linked to overbite (Cleveland Clinic), and prolonged thumb-sucking, bottle-feeding, pacifier use and tongue-thrusting to underbite (Cleveland Clinic).

Underbites are more often about the jaws themselves: a lower jaw that is larger than the upper, or an upper jaw that is underdeveloped. Less often, an injury to the face or jaw, or a tumor, is the cause (Cleveland Clinic).

Problems each can cause

A mild underbite may cause no noticeable problems and need no treatment (Cleveland Clinic). It's still worth asking about, because misaligned teeth create spots that are hard to clean (Cleveland Clinic).

How each is treated

In children, both are easier to treat because the jaws are still growing. An overbite can often be corrected with orthodontics alone: palate expanders, headgear, braces, removing baby teeth to make room, and retainers (Cleveland Clinic). An underbite is best treated between ages 7 and 10, when the bone can be modified without surgery, using palate expanders, reverse-pull headgear or a chin cap, followed by braces (Cleveland Clinic). The AAO recommends a first orthodontic check by age 7 (AAO). See palate expanders and headgear.

In adults, an overbite may be fixed with braces or clear braces, sometimes with extractions to make room, and severe cases may need jaw surgery as well (Cleveland Clinic). Underbites in adults more often need surgery, usually when less invasive options haven't worked and the underbite is severe (Cleveland Clinic). Either way, a retainer keeps the result; see types of retainers.

Cost to fix an overbite or underbite

There's no separate published price for "fixing an overbite" or "fixing an underbite"; you pay for the treatment used. Typical published prices:

For details, see cost to fix an overbite, how to fix an underbite and jaw surgery cost, or get an estimate for your state with the braces cost calculator.