Overbite, underbite, crossbite: what's the difference?

An overbite, an underbite, and a crossbite are all bite problems, and the difference comes down to which teeth sit where when your mouth closes. In an overbite, the upper front teeth cover too much of the lower ones. In an underbite, the lower front teeth sit in front of the upper ones. In a crossbite, some upper teeth close inside the lower teeth instead of outside them.

Orthodontists call any of these a malocclusion, which simply means the teeth and jaws do not meet the way they are meant to. Below is what each one looks like, what tends to cause it, and what treatment usually involves, so you know what to ask at a consultation.

What is a "bite," and what counts as a normal one?

Your bite is the way your upper and lower teeth fit together. In a well-aligned bite, the upper teeth sit slightly in front of and over the lower teeth, and the back teeth meet in a stable, interlocking way. The American Dental Association's MouthHealthy site describes the goal of orthodontics as a healthy bite in which teeth meet the opposing teeth properly.

Two terms come up often in an orthodontic exam:

• Overjet is the horizontal distance between the upper and lower front teeth.
• Overbite (in the strict clinical sense) is how far the upper front teeth overlap the lower ones vertically.

Some overlap is normal. A bite problem is a pattern that is outside the usual range or that affects how the teeth and jaws work. Whether it needs treatment is a decision for an exam and X-rays, not a mirror.

What is an overbite?

An overbite means the upper front teeth overlap the lower front teeth more than expected. People also use the word to describe upper teeth that stick out far forward, which an orthodontist would call increased overjet. The two often travel together.

Common contributors include:

• Jaw size or position. The lower jaw may be set back relative to the upper jaw.
• Genetics. Bite patterns often run in families.
• Habits. Long-term thumb, finger, or pacifier sucking can push the upper front teeth forward.
• Tooth position. The upper front teeth may simply have tipped forward.

A deep overbite can cause the lower teeth to press into the gums behind the upper teeth or wear against them. A prominent overjet also leaves the front teeth more exposed to injury, which matters for kids who play sports. Our post on braces and school sports in Bakersfield covers mouthguards in more detail.

What is an underbite?

An underbite is the reverse arrangement: the lower front teeth sit ahead of the upper front teeth when the mouth is closed. It can come from a lower jaw that is larger or further forward than the upper jaw, an upper jaw that is smaller, or a combination.

Underbites are worth checking early. The American Association of Orthodontists lists underbite among the problems that an orthodontist can often spot by age 7, and early evaluation gives the orthodontist more options while a child is still growing. It does not mean treatment starts at 7. It means someone qualified is watching.

What is a crossbite?

A crossbite happens when one or more upper teeth close inside the lower teeth rather than outside them. It can involve the front teeth (an anterior crossbite) or the back teeth (a posterior crossbite), on one side or both.

Two points are worth knowing:

• A narrow upper jaw is a common cause of a posterior crossbite. The upper arch is too narrow to fit around the lower arch.
• Some crossbites come with a jaw shift. The AAO notes that a jaw that shifts to one side as the teeth come together is one of the signs worth an evaluation. The child may slide the lower jaw sideways to find a comfortable closing position, which can go unnoticed at home.

Because a crossbite can affect how the jaw grows and how the teeth wear, it is usually better evaluated sooner than later.

What is an open bite?

An open bite is the one people forget about. The upper and lower teeth do not touch in some area when the mouth closes. In an anterior open bite, the back teeth meet but the front teeth stay apart. In a posterior open bite, it is the other way around.

Thumb-sucking and similar habits are well-known contributors, as is the way the tongue rests or pushes. Jaw growth patterns and genetics play a part too. An open bite can make biting into certain foods awkward and, in some people, can be linked to how they swallow or speak. An orthodontist can tell you whether that applies to you.

Can a bite problem fix itself?

Generally, no. Children's jaws and teeth do change as they grow, and some mild patterns improve with time, which is exactly why monitoring is useful. But established overbites, underbites, and crossbites do not usually correct on their own once the permanent teeth are in. If one looks like it is getting better or worse, that is a reason to have it watched, not a reason to wait and see indefinitely.

How are bite problems treated?

The right plan depends on the cause: teeth, jaws, or both. An orthodontist builds it from a clinical exam, X-rays, and records.

• Braces. Traditional braces, including aesthetic options such as clear or gold braces, move teeth into better positions and can correct many overbites, underbites, and crossbites. Adjustments to the bite happen gradually; our post on how braces move teeth explains the biology behind it.
• Clear aligners. For suitable cases, Invisalign and Invisalign Teen can address bite problems. Which cases suit aligners is a matter for an exam. See our comparison of Invisalign vs. braces.
• Growth-guiding appliances. In a growing child, an orthodontist may use an appliance to widen a narrow upper jaw or influence how the jaws develop. These are used selectively, and timing depends on the child.
• Jaw surgery. When the problem lies mainly in the size or position of the jaws and a patient has finished growing, orthodontic treatment may be combined with surgery by an oral surgeon. The practice also handles complex cases that call for coordinated care.

Treatment length varies with the problem. For a general idea, read how long braces take.

Do bite problems cause jaw pain or TMJ issues?

Not necessarily, and the relationship is not simple. Many people have an imperfect bite and no jaw trouble at all. Still, jaw clicking, soreness when chewing, or morning headaches alongside a noticeable bite problem are worth mentioning to an orthodontist. Dr. Mendivil treats roughly 40 TMJ cases a year, and our guide to TMJ symptoms lists the signs worth knowing. The practice's TMJ treatment page has more on how that care works.

When should you see an orthodontist about your bite?

Book an evaluation if you notice any of the following in yourself or your child:

• Upper front teeth that stick out noticeably, or lower teeth that sit in front of the upper ones
• A jaw that shifts to one side when closing
• Front teeth that do not touch when the back teeth are together
• Upper teeth that close inside the lower teeth
• Difficulty biting or chewing, or frequent cheek biting
• Jaw pain, clicking, or headaches with a visible bite concern
• A child who is approaching age 7 and has not had an orthodontic screening

Adults are not left out. Bite problems can be corrected well after the teen years; see our guide to adult braces in Bakersfield.

Dr. Mendivil has treated patients in Bakersfield since 1989, and the practice offers a free consultation where you can have your bite looked at and your questions answered. You can schedule a consultation online or call 661-323-5910. Treatment questions are also covered in our FAQ.