What Causes An Overbite Genetics Habits Jaw Growth?

An overbite is one of the most common dental issues, yet most people do not know exactly why it happens. The cause comes down to two main factors: genetics and habits. Your genes determine the size and shape of your jaw, while childhood habits like thumb sucking or tongue thrusting can push teeth out of alignment. In most cases, an overbite develops because the upper jaw grows larger than the lower jaw, or because the lower jaw is set further back than it should be.

What Defines an Overbite and When Is It a Problem?

An overbite is the vertical overlap between your upper front teeth and your lower front teeth. A small overlap is normal. In a healthy bite, the upper teeth overlap the lower teeth by about 2 to 3 millimeters. Anything beyond that is considered an overbite.

Many people use the word “overbite” when they actually mean “overjet.” Overjet is the horizontal distance between the upper and lower front teeth — the “buck tooth” appearance. Overbite is vertical. Both are common, but they have different causes and treatments.

Mild overbites often cause no symptoms. Moderate to severe overbites can lead to problems over time. These include excessive wear on the front teeth, gum damage, jaw pain, and difficulty chewing. Some people also develop speech issues or an appearance they feel self-conscious about.

How Genetics Shape Jaw Growth and Tooth Position

Genetics are the single biggest factor in whether you develop an overbite. Your DNA determines the size of your upper jaw, your lower jaw, and your teeth. When these parts do not match well, an overbite is the result.

The most common genetic pattern is a lower jaw that is slightly smaller than the upper jaw. This is not a defect — it is simply how some jaws grow. The upper jaw stops growing earlier in life, while the lower jaw continues growing for several more years. In some people, this timing difference creates a noticeable overbite.

Tooth size also matters. If your teeth are large relative to your jaw size, they become crowded. Crowded upper teeth can be pushed forward or angled in ways that increase the overlap. This is often a family trait. If your parents had overbites or crowded teeth, your risk is higher.

Genetics are not something you can change. But understanding that an overbite often runs in families helps explain why some children develop one despite no obvious habits.

Childhood Habits That Contribute to Overbite Development

Habits are the second major cause of overbites. These habits matter most during childhood, while the jaw is still growing and teeth are still moving.

Thumb sucking is the most well-known habit linked to overbites. When a child sucks their thumb past age 4 or 5, the pressure pushes the upper front teeth forward and the lower teeth backward. This creates both an overjet and an overbite. The longer the habit continues, the harder it is to reverse without treatment.

Prolonged pacifier use can have the same effect. The American Dental Association recommends stopping pacifier use by age 4. The earlier a child stops, the more likely their bite will correct itself naturally.

Tongue thrusting is another common habit. Normally, the tongue rests against the roof of the mouth. In some children, the tongue pushes forward against the back of the front teeth when swallowing or speaking. Over time, this constant pressure moves the teeth outward and increases the overbite.

Mouth breathing is less obvious but still significant. Breathing through the mouth instead of the nose changes the resting position of the tongue and jaw. This can narrow the upper jaw and alter how the lower jaw aligns.

These habits do not guarantee an overbite. Some children suck their thumbs for years and develop a perfect bite. But the risk is real, and early intervention reduces that risk.

Can Jaw Growth Be Guided or Corrected?

Jaw growth is most responsive to treatment during childhood and early adolescence. This is when the bones are still growing and can be guided into better positions.

Orthodontists use functional appliances to encourage the lower jaw to grow forward. These devices, such as twin blocks or Herbst appliances, are worn during the growth phase. They do not force the jaw into place — they redirect natural growth so the lower jaw catches up with the upper jaw.

For younger children with a severe overbite, early treatment can be highly effective. This is why the American Association of Orthodontists recommends that children have their first orthodontic evaluation by age 7. At this age, an orthodontist can spot jaw growth problems and habits that are likely to cause a serious overbite.

However, early treatment is not always necessary. Many children with a mild overbite simply need monitoring. Their bite may improve on its own as the permanent teeth come in and the jaw finishes growing.

Treatment Options for Overbites in Adults

Once the jaw stops growing, usually in the late teens or early twenties, an overbite cannot be corrected through natural growth. But it can still be treated.

Braces and clear aligners are the most common treatment for mild to moderate overbites. They move the teeth into a better position, reducing the vertical overlap. In some cases, elastics are used to shift the bite. This approach works well when the problem is mostly about tooth position rather than jaw size.

For severe overbites caused by a small lower jaw, orthodontics alone may not be enough. In these cases, orthognathic surgery — jaw surgery — may be recommended. The surgeon repositions the lower jaw forward to align it with the upper jaw. This is a major procedure, but it is the most reliable way to correct a skeletal overbite.

Some adults choose not to treat their overbite at all. That is a valid choice if the overbite is mild and causes no symptoms. The decision to treat should be based on function and comfort, not just appearance.

What Happens If an Overbite Is Left Untreated?

Many people live with an overbite their entire lives without serious problems. But there are real risks to leaving a significant overbite untreated.

The most common issue is tooth wear. The upper front teeth may wear down against the lower teeth over decades. This can make teeth shorter, more sensitive, and more prone to breakage.

Gum problems are another concern. The lower front teeth may bite into the roof of the mouth, causing soreness, ulcers, and gum recession. Over time, this can damage the supporting bone.

Temporomandibular joint (TMJ) problems are also linked to severe overbites. The jaw joint may be strained when the bite is misaligned. This can cause pain, clicking, or difficulty opening the mouth fully. Not everyone with an overbite develops TMJ issues, but the risk increases with severity.

There is no universal timeline for when these problems appear. Some people develop symptoms in their thirties. Others never do. Regular dental checkups are the best way to catch early signs of wear or damage.

Can You Prevent an Overbite?

You cannot prevent a genetic overbite. If your jaw is programmed to grow a certain way, no habit change will alter that.

What you can prevent is a habit-related overbite. Stopping thumb sucking and pacifier use at an appropriate age reduces the risk significantly. Addressing tongue thrusting and mouth breathing early also helps. Speech therapists and myofunctional therapists can help children retrain their tongue and breathing patterns.

For adults, prevention is not possible — the jaw has finished growing. But early detection in children is the closest thing to prevention. A child who sees an orthodontist by age 7 can often avoid a more severe overbite later.