An overjet is the horizontal gap between your upper and lower front teeth. When you bite down normally, your upper teeth sit slightly ahead of your lower teeth. That forward distance, measured in millimeters, is your overjet. A small amount is normal, but when your upper teeth protrude more than about 2 millimeters past your lower front teeth, it’s considered excessive and is often called “buck teeth.”
How Overjet Is Measured
Overjet is measured with your teeth together in your normal bite. A dentist or orthodontist places a small ruler against the front surface of your lower front teeth and measures the horizontal distance to the edge of your upper front teeth, keeping the ruler parallel to your biting surface. Most people have some degree of overjet, and a measurement between 1 and 2 millimeters is considered ideal. Once the gap exceeds about 2 millimeters, it falls into the range that orthodontists typically flag for evaluation.
Severity is generally grouped by how far the upper teeth protrude. Mild cases fall in the 3 to 5 millimeter range, moderate cases between 5 and 9 millimeters, and anything at or above 10 millimeters is considered severe. That 10-millimeter threshold is significant because it’s the point where orthodontic treatment alone starts to become less predictable, and jaw surgery enters the conversation.
Overjet vs. Overbite
These two terms get mixed up constantly, but they describe different things. Overjet is a horizontal measurement: how far forward your upper teeth stick out past your lower teeth. Overbite is a vertical measurement: how much your upper teeth overlap downward over your lower teeth when you bite together. Think of overjet as the gap you’d see looking at someone’s profile, while overbite is the overlap you’d notice looking at their smile head-on.
A deep overbite means your upper teeth cover too much of your lower teeth vertically. An excessive overjet means your upper teeth jut out too far in front of your lower teeth horizontally. You can have one without the other, or both at the same time.
What Causes Excessive Overjet
The most common cause is simply the way your jaws grew. If your upper jaw developed further forward than your lower jaw, or your lower jaw is set further back than average, the result is a mismatch that pushes the upper teeth ahead of the lower ones. This skeletal pattern is largely genetic, which is why overjet often runs in families.
Childhood habits play a role too. Prolonged thumb sucking, pacifier use past age 3 or 4, and tongue thrusting (a habit where the tongue pushes against the front teeth during swallowing) can gradually push the upper teeth forward or prevent the lower teeth from developing into their proper position. These habits matter most during the years when the jaw bones are still growing and malleable.
In some cases, the jaw bones are fine but the teeth themselves are angled incorrectly. Upper front teeth that tilt outward or lower front teeth that tilt inward can create the appearance and measurement of an overjet even when the underlying bone structure is normal. This distinction matters because tooth-only problems are generally easier to fix than skeletal ones.
Why It Matters Beyond Appearance
An excessive overjet isn’t just a cosmetic concern. Upper front teeth that protrude significantly are more vulnerable to injury. Falls, sports impacts, and even everyday bumps are more likely to chip or fracture teeth that stick out past the protective cushion of the lips. Studies on dental trauma in children consistently show a strong link between increased overjet and front tooth injuries.
Functional problems are common too. A large gap between the upper and lower front teeth can make it difficult to bite into food cleanly. Speech can be affected, particularly sounds that require the upper and lower teeth to work together, like “s,” “f,” and “th.” Some people with significant overjet also have trouble keeping their lips comfortably closed at rest, which can lead to dry mouth and increased risk of gum problems on the front teeth.
Treatment Options
How an overjet gets corrected depends on whether the problem is in the teeth, the jaw bones, or both.
For mild to moderate cases where the issue is primarily tooth position, braces are the standard approach. Traditional metal braces or clear aligners can gradually pull the upper teeth back and, in some cases, bring the lower teeth forward. Elastics (small rubber bands hooked between the upper and lower braces) are a common part of this process, creating the force needed to shift the bite relationship. Treatment with braces typically takes 18 to 30 months for overjet correction, depending on severity.
In children and adolescents whose jaws are still growing, functional appliances can help guide jaw development. These devices encourage the lower jaw to grow forward or restrain the upper jaw from growing too far ahead. Timing matters here: this type of treatment works best during growth spurts, typically between ages 8 and 14.
For adults with severe skeletal overjet, especially measurements at or above 10 millimeters, orthodontics alone may not be enough. When the underlying problem is a significant mismatch in jaw size or position, orthognathic (jaw) surgery combined with braces is often the most effective route. Research on treatment outcomes shows that orthodontic-only approaches become less reliable when skeletal discrepancies are large, with cases involving overjet of 10 millimeters or more being particularly prone to incomplete correction without surgery.
Clear Aligners for Overjet
Clear aligners can handle mild overjet effectively, and newer aligner systems have expanded what’s treatable without traditional braces. However, moderate to severe overjet often requires the kind of precise tooth movement and bite correction that braces with elastics deliver more reliably. If you’re considering aligners, the key question is whether your overjet comes from tooth angulation (more treatable with aligners) or skeletal jaw position (less so).
What to Expect During Correction
Overjet correction is one of the more noticeable orthodontic changes you can experience. Because the upper front teeth are moving backward (or the lower teeth forward), you’ll see your profile change gradually over the course of treatment. Many people notice their lips sit differently as the teeth shift.
Retention after treatment is critical. Once braces come off or aligner therapy ends, retainers keep the teeth in their new position. Overjet cases are particularly prone to relapse, meaning the teeth tend to drift back toward their original position if retainers aren’t worn consistently. Most orthodontists recommend a permanent bonded retainer behind the front teeth, a removable retainer worn at night, or both.