An overbite develops when the upper front teeth overlap the lower front teeth by more than the normal 1 to 2 millimeters. The causes range from inherited jaw structure to childhood habits to changes that happen in adulthood. In a large study of children aged 10 to 12, over half had some degree of excessive overbite, with about 14% falling into the moderate or severe range. Understanding what drives an overbite helps clarify why treatment approaches vary so widely from person to person.
Skeletal vs. Dental Overbites
Not all overbites come from the same place. The distinction between a skeletal overbite and a dental overbite is one of the most important factors in determining both the cause and the treatment.
A skeletal overbite comes from the shape and position of the jawbones themselves. The most common pattern involves a lower jaw that grows in a more horizontal, forward-rotating direction than usual. This rotation shortens the lower portion of the face relative to the upper portion, which pushes the upper teeth further over the lower ones. In people with deep skeletal overbites, the back part of the jaw (the ramus) tends to be longer than average, and certain jaw angles are notably reduced. These are structural differences in bone, not just tooth position.
A dental overbite, by contrast, involves the teeth themselves being positioned incorrectly even though the jawbones may be relatively normal. The most common dental pattern is an exaggerated curve along the biting surface of the lower teeth. This curve causes the lower front teeth to sit too high while the back teeth sit too low, creating excess overlap. In roughly a third of people with deep overbites, the upper front teeth also have longer visible crowns than normal, adding to the vertical overlap.
Most people have some combination of both skeletal and dental factors. Pure cases of one or the other are less common than a mix.
Genetics and Jaw Growth
Jaw size and shape are strongly influenced by genetics, which is why overbites often run in families. If one or both of your parents had an overbite, your chances of developing one increase significantly.
The genetic component centers largely on how the lower jaw grows during childhood and adolescence. The condyle, a rounded knob of cartilage at the top of the jawbone, acts as the primary growth center for the entire lower face. Genes that regulate cartilage development and bone signaling at this site directly affect whether the jaw grows to its full potential or falls short. Research on a German population identified specific genetic variations in growth factor genes (EGF and EGFR) that were significantly more common in people whose lower jaw sat further back than normal. These genes play a role in cartilage formation at the growth centers and in overall craniofacial development. Animal studies confirm this: mice bred without functional copies of these genes developed underdeveloped lower jaws and narrow, elongated facial structures.
A recessed lower jaw, sometimes called mandibular retrognathism, is one of the most common skeletal causes of an overbite. The upper jaw may be perfectly normal in size, but because the lower jaw didn’t grow forward enough, the upper teeth end up sitting well ahead of the lower ones.
Childhood Habits That Reshape the Jaw
Prolonged thumb sucking, finger sucking, and pacifier use can physically reshape the dental arches during the years when bone is still soft and growing. These habits push the upper front teeth forward while pressing the lower front teeth backward, creating or worsening an overbite.
A study of 250 children aged 3 to 5 found that those with digit sucking habits had measurably narrower upper arches and deeper (more protruding) upper arch shapes compared to children without the habit. Thumb sucking produced more significant changes than finger sucking, particularly in the width between the canine teeth. Perhaps most importantly, some of these arch changes persisted even after the child stopped the habit, suggesting the deformation can become permanent if it continues long enough.
The critical age threshold is around three years old. The American Academy of Pediatric Dentistry recommends discontinuing pacifier use by age three, and research consistently shows that the rates of bite problems increase sharply when pacifier use extends beyond that point. The same general timeline applies to thumb and finger sucking.
Tongue Thrusting
Tongue thrust is a swallowing pattern where the tongue pushes forward against the front teeth instead of pressing up against the roof of the mouth. This matters because the forces involved, while small in any single swallow, add up over hundreds of daily swallows. Even low-level, sustained pressure is enough to move teeth over time.
The effect depends on several factors: how often the person swallows, how much force the tongue exerts, whether the lips provide enough counterforce to resist the push, and where the tongue rests between swallows. In people with tongue thrust, the muscles controlling the tongue show increased electrical activity and take longer to complete each swallow, both of which amplify the forward force on the teeth. Over months and years, this can tilt the upper incisors outward, creating a protruding overbite.
How Overbites Develop in Adults
Overbites aren’t exclusively a childhood problem. Several factors can cause or worsen an overbite in adulthood, even if your bite was previously normal.
Tooth loss is one of the most straightforward causes. When back teeth are lost and not replaced, the remaining teeth shift to fill the gaps. This disrupts the balance of forces that keep teeth in their proper positions, and the front teeth can begin to overlap more as the bite collapses vertically. The effect becomes more pronounced with each additional missing tooth.
Teeth grinding, or bruxism, wears down the biting surfaces of the back teeth over time. As those surfaces flatten, the back teeth become effectively shorter, which allows the jaw to close further than it should. The result is increased overlap of the front teeth. Chronic grinders can develop a noticeably deeper bite over years or decades, even if they started with a normal one.
The Relationship Between Overbites and Jaw Pain
A common concern is whether an overbite causes or contributes to temporomandibular joint (TMJ) problems, including jaw pain, clicking, and headaches. The relationship is more complicated than it might seem.
The idea that bite problems cause TMJ disorders dates back to the 1930s, when an ear, nose, and throat specialist proposed that changes in overbite could displace the jaw joint and trigger a cascade of symptoms. For decades, this was widely accepted. More recent research tells a different story. A 30-year prospective study of over 900 people found no clear link between overbite and an increased risk of TMJ clicking. Systematic reviews of the broader literature describe the associations between bite alignment and TMJ disorders as “sporadic, weak, and inconsistent.”
What complicates things further is that the relationship may work in reverse. TMJ disorders can themselves change how the jaw sits, gradually altering the bite. So an overbite that appears alongside jaw pain may be a consequence of the joint problem rather than its cause.
Multiple Causes Often Overlap
In practice, most overbites result from a combination of factors rather than a single cause. A child might inherit a genetic tendency toward a smaller lower jaw, develop a thumb sucking habit that pushes the upper teeth forward, and have a tongue thrust pattern that reinforces the misalignment over years. Each factor compounds the others. This is part of why overbite severity varies so much from person to person, and why treatment plans are highly individualized based on whether the root cause is skeletal, dental, or both.