An overjet is a horizontal gap between the upper and lower front teeth, where the top teeth protrude forward beyond the bottom teeth. Some degree of overjet is normal, but when the gap becomes excessive, it’s commonly known as “buck teeth.” The distinction matters because overjet is often confused with an overbite, which is a different type of misalignment entirely.
Overjet vs. Overbite
The easiest way to understand overjet is to compare it to the more familiar term “overbite.” Both involve the upper teeth extending past the lower teeth, but in different directions. An overjet is horizontal: your upper front teeth angle outward and sit in front of your lower teeth, creating a visible gap when you look at someone’s profile. An overbite is vertical: the upper teeth overlap the lower teeth from top to bottom, covering too much of them when you bite down.
Almost everyone has a small overjet and a small overbite simultaneously. These only become a problem when they’re excessive. Think of it this way: overjet is how far forward your top teeth stick out, while overbite is how far down they cover the bottom ones.
What Causes It
Overjet develops from a mix of genetics, jaw growth patterns, and childhood habits. The skeletal structure of your face plays a major role. If your upper jaw grows further forward than your lower jaw, or if your lower jaw is smaller or set further back than typical, your upper teeth will naturally sit ahead of the lower ones. Most Class II bite problems (where the upper jaw is positioned ahead of the lower jaw) have a strong genetic component.
Childhood habits can make things worse. Prolonged thumb sucking, pacifier use past age 3 or 4, and tongue thrusting (where the tongue pushes against the front teeth during swallowing) all put outward pressure on the upper teeth over time. These forces can tilt the teeth forward even when the underlying jaw relationship is normal.
Certain genetic conditions are also associated with overjet. Marfan syndrome, a connective tissue disorder, frequently produces a recessed lower jaw, a narrow palate, and increased overjet. Roughly 70% of patients with Marfan syndrome are referred for orthodontic treatment because of crowding and a large overjet. But for most people, overjet is simply a product of how their jaws grew relative to each other, shaped by both inherited traits and environmental influences during childhood.
Why It Matters for Your Health
An excessive overjet isn’t just cosmetic. The most well-documented risk is dental trauma. When upper front teeth stick out significantly, they’re far more exposed to injury during falls, sports, or everyday accidents. A systematic review and meta-analysis found that children under 6 with an overjet of 3 mm or more had more than three times the odds of experiencing a traumatic dental injury. In older children with mixed or permanent teeth, an overjet greater than 5 mm roughly doubled the risk.
Speech can also be affected. Research published in The Angle Orthodontist found a strong association between increased overjet and difficulty producing several sounds, including “f,” “ch,” “p,” “b,” “t,” and “d.” These sounds require precise coordination between the lips, tongue, and teeth, and when the front teeth don’t align properly, that coordination breaks down. Children with significant overjet may also struggle with lip seal, which affects how air flows during speech.
Chewing efficiency drops too. When your front teeth don’t meet properly, biting into food becomes awkward, and the jaw muscles have to compensate. Studies have found that people with Class II bite problems (the category overjet falls into) show altered activity in the muscles responsible for chewing, which can contribute to jaw pain and fatigue over time.
How It’s Treated
Treatment depends on whether the overjet comes from the teeth, the jaws, or both, and on how severe the protrusion is.
For mild to moderate cases, braces or clear aligners can gradually move the upper teeth back and the lower teeth forward to close the gap. Rubber bands (elastics) stretched between upper and lower brackets are a common tool for guiding the jaw relationship into better alignment during treatment.
When the lower jaw itself is positioned too far back, orthodontists may use a functional appliance to encourage it forward. The Herbst appliance is one of the most widely used. It’s a fixed metal device that connects the upper and lower jaws and holds the lower jaw in a more forward position. Over months of wear, the steady pressure gradually shifts the jaw relationship. These appliances work best in growing children and teens whose bones are still developing.
Severe cases, particularly in adults whose jaw growth is complete, may require surgery. A survey of orthodontists found that a positive overjet greater than 8 mm was generally considered beyond what braces alone could fix. At that point, orthognathic (jaw) surgery to reposition the upper jaw, lower jaw, or both becomes the more predictable option. Surgery is typically combined with braces before and after the procedure to fine-tune the tooth alignment.
The Value of Early Treatment
The American Association of Orthodontists recommends that children have their first orthodontic evaluation by age 7. At that age, enough permanent teeth have come in for an orthodontist to spot developing problems like excessive overjet, even if full treatment won’t start for several years.
Early intervention, sometimes called interceptive orthodontics, won’t necessarily fix a bite problem completely, but it can make a meaningful difference. Reducing a child’s overjet early on lowers their risk of traumatic injury to those exposed front teeth, which is especially valuable during the active, accident-prone years of childhood. It can also improve a child’s quality of life and self-confidence during a socially sensitive period.
There’s a practical benefit as well. By reducing the severity of a bite problem during an early phase of treatment, the second phase (typically full braces in the teen years) tends to be simpler and shorter. In some cases, early correction can shift a child’s condition from one that insurance considers medically necessary to one classified as elective, which changes the treatment timeline and options available.