Overbite and underbite explained

Reviewed by Dr. Samar Fadavi, DDS

Short answer: An overbite is when the upper front teeth overlap the lower ones too much, and an underbite is when the lower teeth sit in front of the upper teeth. Both can come from jaw growth, family traits or childhood habits. Mild cases may need nothing; others are treated with braces, aligners, growth appliances or, for severe adult jaw differences, surgery.

What are an overbite and an underbite, and how are they treated?

Dentists use the word “bite” to describe how your upper and lower teeth meet when you close. In a typical bite, the upper front teeth sit slightly in front of the lower front teeth and cover them by a few millimetres. The back teeth fit together like gears. When the teeth or jaws meet in a different way, it is called a malocclusion. Overbites and underbites are two of the most common types.

• Deep bite (overbite). The upper front teeth cover too much of the lower front teeth from top to bottom. In a severe deep bite, the lower teeth can touch or bite into the gum behind the upper teeth.
• Overjet. The upper front teeth stick forward, well ahead of the lower teeth. People often call this an overbite too, though dentists measure it separately.
• Underbite. The lower front teeth sit in front of the upper front teeth when you close. This often happens because the lower jaw has grown more than the upper jaw, or the upper jaw is small.
• Related bite problems. A crossbite is when some upper teeth sit inside the lower teeth. An open bite is when the front teeth do not meet at all.

A bite problem can be dental, meaning the teeth are tipped or positioned unusually, or skeletal, meaning the jaws themselves are different sizes or positions. Many people have a mix of both. That difference shapes which treatments will work.

Why bite problems matter

Plenty of people have a small overbite and never need treatment. A bite becomes worth treating when it affects health, comfort or function. Common effects include:

• Worn or chipped teeth. When teeth meet at awkward angles, some take more force than they should. Edges chip and enamel wears faster.
• Injury risk. Upper front teeth that stick out are more likely to break in a fall, a sports collision or a playground accident.
• Gum damage. In a deep bite, lower teeth can press into the gum behind the upper teeth, causing soreness and recession over time.
• Jaw strain. An uneven bite can add to muscle tension and jaw joint discomfort, especially in people who clench or grind.
• Chewing and speech. Biting through food with the front teeth can be hard, and some sounds may be affected.
• Cleaning. Teeth that overlap or crowd are harder to brush and floss, which raises the risk of decay and gum disease.
• Confidence. Some people simply feel self-conscious about how their teeth look when they smile or speak.

What causes them? Jaw size and shape often run in families. Habits also play a part: thumb or finger sucking and long-term pacifier use after the adult front teeth begin to arrive can push teeth forward. Tongue thrusting, breathing mainly through the mouth, losing baby teeth early, missing adult teeth and jaw injuries can all change how the bite develops.

Bite problems at different ages

Toddlers and preschool children. Baby teeth give early clues. A dentist looks at whether the front teeth meet, whether the jaw shifts when closing, and whether a thumb, finger or pacifier habit is pushing teeth forward. Most habits stop on their own before adult teeth arrive, and treatment at this age is rare.

Ages six to nine. Adult front teeth and first molars come in while many baby teeth remain. This is when crossbites, narrow upper jaws and some underbites are often easiest to address, because the bones are still growing quickly. Short, targeted treatment at this stage can make later treatment simpler, or sometimes unnecessary.

Preteens and teens. The growth spurt around puberty is a useful time to correct overjet and many overbites, since jaw growth can be guided while braces or aligners move the teeth. Most comprehensive orthodontic treatment happens at this age.

Adults. Jaw growth has finished, so treatment focuses on moving teeth into a healthy, comfortable position. Adults often seek treatment because of worn teeth, crowding that makes cleaning difficult, gum problems, or a wish to improve their smile. Healthy gums and bone matter more than age.

How a bite is checked at a regular visit

At check-ups, the dentist watches how the teeth meet, looks for wear and chipping, checks the jaw joints for clicking or tenderness and asks about headaches, grinding or chewing problems. For children, the dentist tracks which teeth are coming in and whether there is enough room for them.

What happens if you or your child has a bite problem, step by step

1. An early check. Bite problems are easiest to guide while a child is still growing. Around age seven, when the first adult molars and front teeth are in, is a good time for a dentist to look at how the jaws are developing. Many children need nothing at that age, but some benefit from early help.
2. A full assessment. The dentist looks at how the teeth meet, how the jaw moves and whether teeth are crowded or spaced. Photos, x-rays and a scan or model of the teeth help plan treatment.
3. Working out the cause. The key question is whether the problem is mostly in the teeth or in the jaws, and how much growth is left. This guides every decision that follows.
4. Treatment for growing children. Options may include an appliance to help stop a thumb habit, an expander to widen a narrow upper jaw, a removable or fixed appliance that encourages the lower jaw forward in some overjet cases, or, for some underbites in young children, an appliance that supports the upper jaw’s growth.
5. Treatment for teens and adults. Braces or clear aligners move teeth into a better position. Small elastic bands that hook between the upper and lower teeth help correct how the jaws meet. When jaw growth has finished, the aim is often to bring the teeth into a healthy, comfortable bite even if the jaw sizes stay different.
6. Surgery for severe skeletal cases. When an adult’s jaws are very different in size, the most complete correction may combine orthodontic treatment with jaw surgery performed by an oral and maxillofacial surgeon. This is usually considered only after growth has finished.
7. Keeping the result. Teeth tend to drift back. Retainers, worn as directed, hold the new position. Some people wear them at night for many years.

Our page on Invisalign and braces explains the treatment choices we offer, including orthodontic appliances for children.

What to avoid

• Waiting for a child to “grow out of” an underbite without a check. Underbites rarely correct on their own, and some are easier to manage early.
• Letting a thumb or pacifier habit carry on once adult front teeth start coming in. Gentle encouragement, reminders and, if needed, a habit appliance can help.
• Ordering mail-in aligners without an exam. Moving teeth without checking gums, roots and jaw position can cause problems that are hard to undo.
• Skipping your retainer after braces or aligners. Relapse is the most common reason adults need treatment again.
• Ignoring jaw pain, clicking or locking. These can have several causes and are worth assessing.

Habits that can shape the bite in children

Jaws and teeth develop over many years, and some everyday habits influence how they grow. Thumb-sucking or soother use that continues past about age four can push the upper front teeth forward and create an open bite or overjet. Mouth breathing, often linked to allergies or enlarged tonsils and adenoids, can affect the shape of the palate. Tongue thrusting, where the tongue presses forward against the teeth when swallowing, can hold front teeth apart. Early loss of baby teeth from decay can let neighbouring teeth drift and crowd the space adult teeth need.

The good news is that many of these can be spotted early at regular check-ups. Gentle habit-breaking strategies, treatment of the underlying breathing issue with your doctor, and space maintainers after early tooth loss can all reduce how much correction is needed later.

Living with a bite problem as an adult

Many adults have a mild overbite or underbite and no symptoms at all. Others notice uneven wear, chipped front teeth, jaw soreness, trouble biting into foods, or gum recession on certain teeth. If you have symptoms, it is worth an assessment. Options for adults range from monitoring and a night guard to orthodontic treatment with braces or clear aligners, and in more severe skeletal cases, a combination of orthodontics and jaw surgery planned with an oral surgeon. Your dentist can explain which group you fall into and what each path involves before you decide.

When to see a dentist

Book a visit if you notice any of the following in yourself or your child:

• Upper front teeth that stick out a lot, or lower teeth that sit in front of the upper teeth.
• A jaw that shifts to one side when closing, or a chin that looks off centre.
• Front teeth that do not meet, or difficulty biting through food.
• Worn, chipped or sore teeth, or gums hurting behind the upper front teeth.
• Crowded or overlapping adult teeth.
• Jaw aches, especially in the morning. Our night guards and TMJ page explains how clenching and grinding are managed.

For children, our children’s dentistry page covers growth checks at each age.

Questions about overbites and underbites

Is a small overbite normal?

Yes. A slight overlap of the upper front teeth over the lower front teeth is part of a typical bite. Treatment is considered when the overlap is large or causes problems.

Can an underbite fix itself?

Rarely. Because underbites often involve jaw growth, an early check helps decide whether to watch or treat.

Can an adult correct an overbite without surgery?

Often, yes, when the problem is mainly in the position of the teeth. Braces or aligners, sometimes with elastics, can bring the bite into a healthier position. Large skeletal differences may need surgery for full correction.

Do clear aligners work for bite problems?

Aligners can treat many overbites and some underbites, often with elastics or small tooth-coloured attachments. Some cases move more predictably with braces. Your dentist explains which suits your bite.

How long does treatment take?

It varies a great deal. Minor corrections can take months, while full treatment commonly takes one to two years or more, followed by retainers.

Does insurance cover bite treatment?

Coverage for orthodontic treatment varies widely between plans. We bill insurers directly and can send a request to your plan before treatment starts so you know where you stand.

Can a bite problem cause jaw pain?

It can add to it. Jaw pain usually has several causes, including clenching, grinding, stress and joint changes. A bite assessment is one part of finding out what is going on.

Can an overbite come back after treatment?

Teeth can drift over time, especially if retainers are not worn. Following the retainer instructions is the most reliable way to hold the result.

At what age should my child have a bite check?

The dentist looks at the bite at every children’s check-up. Around age seven is a good point for a closer look, because enough adult teeth are in to show how the bite and jaws are developing. Come sooner if you notice the lower teeth in front of the upper teeth or the jaw shifting to one side.

Can a crossbite affect how the jaw grows?

Some crossbites make the lower jaw slide to one side to close. Over time this can encourage uneven growth. These are often easier to correct while a child is young, sometimes with a simple expander.

Will teeth need to be removed for braces?

Not usually. Expanding the arch, reshaping or gently moving teeth often creates the room needed. In some cases with severe crowding or protrusion, removing a few teeth gives a better balance; the dentist explains why before anything is decided.

Related guides

• Invisalign or braces for adults?
• Braces, aligners and other options
• TMJ jaw pain: causes and relief