Buck teeth is a measure of how far forward your upper front teeth are compared to your lower front teeth in the horizontal (front–back) direction. Large buck teeth are often referred to as “overjet” in common terms. Overjet is measured in millimetres, indicating the horizontal position of the upper vs. lower front teeth when the jaws are closed.
Not everyone with an overjet will actually look like they have very protruding teeth, because the appearance isn’t judged by the millimetre measurement alone—it also depends on how your lips close, the tilt of the teeth, and the jaw relationship. That’s why at the first exam, the measurements, tooth angles, and jaw position are all evaluated together, and the diagnosis is made based on these values and ratios.
How are buck teeth (overjet) measured? What is the normal range?
In a dental exam, overjet is usually measured in millimetres. In practice, the process is simple: the horizontal distance between the upper and lower front teeth is assessed. It’s normal for the upper front teeth to stick out a bit, and only beyond a certain point does the term “overjet” come into play.
So how many millimetres is “normal”? It’s more accurate to talk about a range and individual variation rather than a single “magic number”:
- It’s considered normal for the upper front teeth to be roughly 2–3 mm ahead of the lower front teeth. NHS sources consider the average overjet to be 2–4 mm. [2]
A small amount of overjet is normal. The goal isn’t always a “zero overjet”; especially in adults, if there are no complaints and jaw function is fine, small deviations can be acceptable. Not every overjet is an urgent problem.
Overjet is categorized into different risk levels (like 0–3 mm, 3–6 mm, and >6 mm). As overjet increases, the priority for orthodontic treatment goes up. An overjet of 6–9 mm falls into a “needs treatment” category, and over 9 mm is considered an even higher priority. [2]
Why do buck teeth occur: tooth-related or jaw-related?
Overjet can arise from two main scenarios, although in many patients the cause is a mix of both.
Tooth-related (Dentoalveolar) overjet
For some people, the issue is mainly about the position of the teeth: the upper front teeth might be tilted or positioned forward. In this case, the goal is to move the upper front teeth backward in a controlled way with proper planning, balancing the bite. These kinds of problems can be corrected with braces or clear aligners.
Skeletal (Jaw) overjet
In other cases, the upper front teeth themselves might not be bad on their own; the overjet just looks exaggerated because the lower jaw is positioned further back. When that happens, the treatment approach changes.
Age becomes a factor here:
- If growth is still ongoing (child/adolescent): Approaches that aim to bring the lower jaw forward (functional/orthopedic methods like the “bite corrector” approach) can be an important part of the plan. In these treatments, the decision is based on factors like the patient’s age, severity of the overjet, and functional needs.
- If growth is complete (adult): In cases of severe skeletal mismatch, orthognathic surgery can become an option. In very severe cases (e.g. over 8–10 mm), jaw surgery might be considered in addition to orthodontics.
That’s why in a thorough exam, not only the millimeter measurement but also the inclination of the front teeth, how the lips close, the jaw relationships, and the overall facial balance are all evaluated together.
Habits, tongue position, and mouth breathing
Habits like sucking on a pacifier or thumb, incorrect tongue posture or thrusting, and mouth breathing can affect how the teeth and jaws develop. [4] If a child sucks their thumb for a long time or the tongue is constantly pushing against the front teeth, the front teeth are more likely to be “pushed forward.” In addition, genetic factors and habits such as tongue thrusting, thumb-sucking, and pacifier use (especially thumb-sucking continuing after age 4) have been noted to be possibly related to overjet.
A large study using the ROMA index reported that factors like “bad habits” and “mouth breathing” were associated with increased overjet. If an active habit or functional pattern (e.g. prolonged pacifier or thumb use, tongue thrusting, mouth breathing) continues, just moving the teeth (with braces or aligners) alone may not be enough; if the habit persists, there is a risk of relapse.
Why is overjet Important? Just cosmetic or a risk issue?
When the upper front teeth are more forward and “out in front,” they are more prone to trauma in falls or impacts. That’s why overjet issues should be dealt with from a preventive standpoint, not just for cosmetics.
A prospective study of 6–13 year-olds found that among children aged 0–6, the chance of dental trauma was higher if their overjet was ≥3 mm. It was also observed that during children’s dental development, an overjet >5 mm was linked to an increased risk of trauma. [5]
Freddie Mercury is one of the most well-known public figures associated with prominent upper front teeth, often described as “buck teeth.” His smile is frequently mentioned in popular discussions about overjet, although every individual’s dental and jaw structure is unique and should always be evaluated based on their own clinical findings.
How is overjet treatment planned?
Accurate diagnosis is considered the most important step in overjet treatment, because treating overjet essentially comes down to answering three questions:
- Why did it happen? (Teeth, jaw, or both?)
- When should intervention occur? (During the growth period or in adulthood?)
- How much risk is there? (trauma, function, psychosocial impact)
Within that framework, the most common options include:
- In tooth-related overjet, braces or clear aligners can be used to reposition the upper front teeth in a controlled way. However, factors like profile aesthetics and lip support must also be considered: moving the teeth back doesn’t yield the same cosmetic result for everyone.
- In cases where the jaw relationship issue is pronounced and growth is still ongoing, functional appliances (the “bite corrector” approach) that guide the lower jaw forward can be included in the treatment plan.
- If growth is complete and the skeletal mismatch is severe, jaw surgery may be considered along with orthodontics.
- Additionally, if an underlying habit or functional issue persists during overjet treatment, even with a retainer afterward, the risk of relapse is higher. A good treatment plan addresses not just the braces/aligners but also manages the underlying cause.
When should you consider an exam for your child?
If your child still has a strong thumb- or pacifier-sucking habit after age 4–5, if the upper front teeth look clearly protruded, if they are involved in activities with frequent falls or collisions, or if their lips don’t close comfortably, it may be a good idea to have a dentist or orthodontist measure their overjet and analyse the cause.