Underbites are strongly influenced by genetics, especially when the cause is a structural mismatch between the upper and lower jaw. Most orthodontic problems are inherited, and skeletal underbites in particular tend to run in families. That said, not every underbite traces back to your parents. Some develop from childhood habits or dental issues, and the severity of a genetic underbite can be shaped by environmental factors along the way.
The Genetic Link Behind Underbites
An underbite, clinically called a Class III malocclusion, occurs when your lower front teeth extend beyond your upper front teeth. The skeletal version, where the lower jaw itself is physically larger or more forward than the upper jaw, has the strongest genetic component. Genome-wide studies have identified susceptibility regions on multiple chromosomes, including 1p36, 6q25, and 19p13.2, all linked to mandibular prognathism (an oversized or forward-positioned lower jaw).
Research in a Hispanic population found that Class III malocclusion, particularly cases driven by an underdeveloped upper jaw, follows an autosomal dominant inheritance pattern. In simple terms, that means a single copy of the relevant gene variant from one parent can be enough to produce the trait. If one of your parents has a noticeable underbite, there’s a meaningful chance you could develop one too.
Studies in Han Chinese families have narrowed down additional candidate genes on chromosome 14 that play a role in jaw growth. These genes are involved in signaling pathways that regulate how bone and cartilage develop during fetal and childhood growth. The genetics are complex, though. Multiple genes contribute, and different combinations appear to matter in different ethnic populations. This is not a single-gene trait like eye color.
How Common Underbites Are Across Populations
Globally, about 6% of people have a Class III malocclusion, making it the least common type of bite misalignment. But prevalence varies significantly by ethnicity. In East Asian populations, the rate averages around 9.6% in permanent teeth and climbs to nearly 11% in children with a mix of baby and adult teeth. In Caucasian populations, the average is closer to 5.9%, and in African populations it drops to about 3.8%.
These differences across ethnic groups are themselves evidence of a genetic basis. If underbites were purely caused by habits or environment, you wouldn’t expect to see such consistent variation between populations living in very different conditions around the world.
Non-Genetic Causes of Underbites
Not all underbites are inherited. A dental underbite, where the jaw bones are properly sized but the teeth themselves are misaligned, can develop from environmental factors during childhood. Early loss of baby teeth due to cavities can cause permanent teeth to erupt into the wrong positions before the dental arch has fully developed. Poor oral hygiene, nutritional deficiencies, and habits like chronic tongue thrusting can also contribute.
The distinction matters because a dental underbite is generally easier to correct than a skeletal one. If your jaw bones are the right size and in the right position, the fix involves moving teeth. If the bones themselves are mismatched, treatment becomes more involved.
Skeletal vs. Dental Underbites
A skeletal underbite means your lower jaw is overdeveloped, your upper jaw is underdeveloped, or both. This is the type most likely to be genetic. You can sometimes spot it by looking at the face in profile: the chin projects forward noticeably, and the middle of the face may appear flat or recessed.
A dental underbite, by contrast, involves teeth that have shifted or erupted into a crossbite position even though the underlying bone structure is relatively normal. The profile may look balanced, but the teeth don’t meet correctly. Many underbites fall somewhere between these two extremes, with both a mild skeletal component and some dental compensation happening on top of it.
When Underbites Become Apparent
The American Association of Orthodontists recommends that children have their first orthodontic evaluation by age 7. At that age, the mix of baby and permanent teeth makes it possible to spot developing problems early, including underbites with a genetic origin. Early detection doesn’t always mean early treatment, but it gives orthodontists the ability to monitor jaw growth and intervene at the right time if needed.
Jaw growth is not finished in childhood. The lower jaw continues growing well into the late teens and even early twenties, particularly in males. Research tracking Danish males found measurable mandibular growth between ages 16 and 17, with growth not fully stopping until around age 21 or 22. Significant growth periods occur between ages 14 and 20. This means a mild underbite in a 12-year-old can worsen considerably during puberty, and a child who appears to have a normal bite can develop a noticeable underbite as a teenager. For girls, jaw growth typically finishes somewhat earlier, but late growth spurts can still shift the bite.
How Genetic Underbites Are Treated
Treatment depends on the severity and whether the underbite is primarily skeletal or dental. Mild to moderate cases, especially dental underbites, can often be managed with braces or clear aligners that reposition the teeth to compensate for the bite discrepancy. This approach, sometimes called orthodontic camouflage, works well when the jaw size difference is small enough that moving teeth alone can create a functional bite.
For more severe skeletal underbites, jaw surgery (orthognathic surgery) may be the better option. The decision involves several factors: how much the bite discrepancy exceeds what braces alone can fix, whether camouflage treatment would actually worsen facial appearance by masking the underlying skeletal problem, and how important facial profile improvement is to the patient. In some cases, surgery combined with orthodontics can achieve results faster than braces alone, sometimes avoiding the need for tooth extractions entirely.
In children, early intervention with expanders or growth-modifying appliances can sometimes redirect jaw development before the bones finish growing. This is one reason early evaluation matters. Once jaw growth is complete, typically by the late teens for females and early twenties for males, the only way to change the bone structure is surgery.
Can You Predict Whether Your Child Will Have One?
If both parents have underbites, the likelihood their child will develop one is high. If one parent has one, the risk is still elevated, particularly given the autosomal dominant inheritance pattern observed in some populations. But genetics are not destiny for every case. A child might inherit a mild tendency toward a larger lower jaw that never becomes a clinical problem, or environmental factors during development might tip a borderline case in either direction.
There is no genetic test currently used in clinical practice to predict underbites. The practical approach is monitoring. If you or your partner have an underbite, having your child evaluated by an orthodontist by age 7 gives you the earliest possible window to identify the trait and plan accordingly.