Overjet is the horizontal distance between your upper and lower front teeth. In a normal bite, the upper front teeth sit roughly 2 millimeters ahead of the lower ones. When that gap exceeds 2 millimeters, it’s considered an excessive overjet, sometimes casually called “buck teeth.” The larger the gap, the more likely it is to cause functional problems or increase injury risk.
How Overjet Differs From Overbite
People often use “overjet” and “overbite” interchangeably, but they describe two different measurements. Overjet is horizontal: how far forward the upper teeth stick out past the lower teeth. Overbite is vertical: how much the upper teeth overlap downward over the lower teeth when you bite together. You can have one without the other, or both at the same time.
A simple way to picture it: if you close your teeth together and look in a mirror, overjet is the forward gap you’d see from the side, while overbite is how much your top teeth cover the bottom ones from the front. Both are normal in small amounts. Problems start when either measurement gets too large.
What Causes Excessive Overjet
Genetics is the most common factor. If a parent or sibling has a pronounced overjet, you’re more likely to develop one too. This can show up as teeth that angle outward or as a mismatch in jaw size, where the upper jaw grows further forward than the lower jaw.
Childhood habits play a significant role as well:
- Thumb or finger sucking is natural in young children, but continuing past age 4 puts steady forward pressure on the upper front teeth and can push them out of alignment.
- Prolonged pacifier use creates the same type of pressure and carries a similar risk after age 4.
- Tongue thrusting happens when the tongue pushes against the back of the upper front teeth during swallowing. Babies do this normally, but when the habit persists into later childhood or adulthood, it can gradually shift the teeth forward.
In some cases, the issue isn’t the teeth at all. A skeletal discrepancy, where the upper and lower jaws are different sizes or positioned unevenly, can produce a large overjet even if the teeth themselves are straight within each arch.
Why a Large Overjet Matters
A mild overjet of 2 to 3 millimeters is considered normal and rarely causes issues. Once the gap grows beyond that, several problems become more likely.
The most well-documented risk is dental trauma. Upper front teeth that protrude are exposed and less protected by the lips, making them vulnerable during falls, sports, or any impact to the face. A systematic review found that children with an overjet larger than 3 millimeters are roughly twice as likely to suffer a traumatic dental injury compared to children with a smaller overjet. At 6 millimeters or more, the risk jumps considerably: a prospective study published in Progress in Orthodontics found that children in this range were about 3.4 times more likely to experience trauma to their front teeth.
Beyond injury risk, a significant overjet can make it harder to bite into food effectively, since the upper and lower teeth don’t meet the way they should. Speech can also be affected, particularly sounds that require the tongue and teeth to work together, like “s,” “z,” and “th.” And for many people, the cosmetic appearance of protruding teeth is a source of self-consciousness that motivates them to seek treatment.
How Overjet Is Measured
Your dentist or orthodontist measures overjet with a small ruler or probe while your back teeth are closed together. They measure the horizontal distance from the outer edge of the most prominent upper front tooth to the front surface of the corresponding lower tooth. The result is recorded in millimeters. Anything at or near 2 millimeters is considered ideal. Measurements of 3 to 5 millimeters are mildly to moderately increased, and anything above 6 millimeters is typically classified as severe.
Treatment Options
Treatment depends on whether the overjet comes from the teeth, the jaw, or both, and on how severe the measurement is.
Braces and Clear Aligners
For mild to moderate overjet caused mainly by tooth position, traditional braces or clear aligners can gradually pull the upper teeth back into alignment. This is the most common approach in both children and adults. In some cases, one or two premolars (the teeth between the canines and molars) are removed to create space for the front teeth to move backward. Treatment timelines vary, but most people wear braces or aligners for one to three years depending on the severity.
Growth Modification in Children
When the overjet has a skeletal component, meaning the jaws themselves are mismatched, orthodontists can take advantage of a child’s ongoing growth. Functional appliances worn during the pre-teen years can encourage the lower jaw to grow forward or restrain upper jaw growth, reducing the overjet before the bones fully mature. This window closes once growth is complete, usually by the mid to late teens.
Jaw Surgery for Severe Cases
In adults with a significant skeletal discrepancy, braces alone may not be enough. Severe cases, particularly those with overjet measurements in the range of 10 to 12 millimeters or more, often require orthognathic surgery. This involves repositioning the upper jaw, the lower jaw, or both to correct the underlying bone structure. Braces are typically worn before and after surgery to fine-tune the tooth alignment. Recovery from jaw surgery generally takes several weeks before returning to normal activities, with full bone healing over a few months.
Preventing Overjet in Children
You can’t change genetics, but you can reduce the environmental factors that contribute to overjet. Encouraging your child to stop thumb sucking and pacifier use by age 4 is the single most effective preventive step. If you notice your child pushing their tongue hard against their front teeth when swallowing, mention it to your dentist. Tongue-thrusting habits can sometimes be corrected with simple exercises or a referral to a specialist called a myofunctional therapist. Early orthodontic evaluations, typically recommended around age 7, can catch developing overjet before it becomes severe enough to require extensive treatment later.