Overbite vs Underbite: What’s the Difference and How to Fix Them?

Bite problems are one of the most common reasons people seek orthodontic treatment but the terminology can be confusing. Overbite, overjet, underbite, crossbite, open bite – what does it all actually mean, and does it really matter if your bite isn’t perfect?

The short answer is yes, it can matter quite a lot. Here’s a clear explanation of the difference between overbites and underbites, why they are worth treating, and what orthodontic options are available to fix them.

What Is an Overbite?

An overbite, sometimes called a deep bite, refers to the amount the upper front teeth overlap the lower front teeth vertically when you bite together. A small overbite is completely normal and helps protect the teeth during chewing.

A problem develops when the overlap becomes excessive. In moderate to severe cases, the upper teeth can cover most or all of the lower front teeth. Sometimes the lower teeth even bite into the roof of the mouth, causing discomfort and damage to the soft tissues.

What Causes an Overbite?

A deep overbite may result from:

• Genetics and inherited jaw shape
• Over-eruption of the front teeth
• Jaw growth differences
• Tooth wear or missing back teeth in some adults
• Certain childhood habits that affect jaw development

Problems Associated With an Overbite

A significant overbite may contribute to:

• Excessive wear of the front teeth
• Gum recession behind the upper front teeth
• Jaw discomfort or TMJ symptoms
• Difficulty biting into food
• Increased risk of damage to the lower front teeth
• A smile that appears “closed” because the lower teeth are hidden

What Is an Overjet?

An overjet describes how far the upper front teeth project forward horizontally compared with the lower front teeth.  Many people mistakenly call this an overbite, but it’s actually a different type of bite problem.

A slight overjet is normal. However, when the upper teeth protrude too far forward, they become more vulnerable to injury and can affect both function and appearance.

What Causes an Overjet?

An increased overjet may be caused by:

• Genetics
• A lower jaw that develops further back than the upper jaw
• Prolonged thumb sucking or dummy use
• Tongue thrusting habits
• Tooth crowding or spacing

Problems Associated With an Overjet

An untreated overjet can lead to:

• Greater risk of chipping or breaking the front teeth
• Difficulty achieving proper lip closure
• Speech difficulties in some patients
• Increased tooth wear
• Cosmetic concerns about protruding teeth

 

What Is an Underbite?

An underbite occurs when the lower front teeth sit in front of the upper front teeth when biting together. Unlike an overbite or overjet, where the upper teeth sit ahead of the lower teeth, an underbite reverses this relationship and is often caused by differences in jaw growth. 

While underbites are less common than overbites,  they tend to be more noticeable and often have a more significant functional impact.

What Causes an Underbite?

Underbites are often hereditary. They can result from:

• Lower jaw overgrowth or upper jaw undergrowth
• Genetics – underbites often run in families
• Certain childhood habits that affect jaw development

Problems Associated With an Underbite

An untreated underbite can cause:

• Difficulty biting and chewing food effectively
• Accelerated wear on the front teeth
• Jaw pain and joint stress (TMJ issues)
• Speech problems, including difficulties with certain sounds
• Self-consciousness about facial profile and smile appearance

 

Overbite vs Overjet vs Underbite: What’s the Difference?

Although these bite problems all affect the way the upper and lower teeth meet, they describe different types of alignment.

• Overbite – too much vertical overlap of the upper front teeth over the lower teeth.
• Overjet – too much horizontal distance between the upper and lower front teeth, causing the upper teeth to stick out.
• Underbite – the lower front teeth sit in front of the upper front teeth.

It’s possible to have more than one of these conditions at the same time. For example, many patients have both a deep overbite and an increased overjet. Your orthodontist will assess your bite carefully to determine exactly what’s contributing to the problem and recommend the most appropriate treatment.

 

Can Overbites and Underbites Be Fixed?

Overbites, overjets and underbites can all be treated successfully with orthodontics. Treatment depends on whether the problem is caused mainly by tooth position, jaw growth, or a combination of both. Braces, clear aligners, elastics and, in some cases, growth-modifying appliances or jaw surgery may all play a role in correcting the bite. 

Treatment During Childhood and Adolescence

When bite issues are identified early – ideally during the jaw growth years – there are more options available and treatment is often more straightforward. For children and teens, treatment may include:

• Braces – fixed braces remain one of the most effective tools for correcting bite issues, often used with elastics to help shift jaw position.
• Functional appliances – removable or fixed appliances that help guide jaw development in younger patients whose jaws are still growing.
• Invisalign Teen – clear aligners can be used to address some bite issues in teenagers, sometimes in combination with other techniques.

Treatment in Adults

Adults can absolutely be treated for these bite issues, though the options depend on the severity.  For mild to moderate cases:

• Braces – highly effective for repositioning teeth and improving bite alignment in adult patients.
• Invisalign – can address many bite issues in adults, sometimes with the addition of elastics or other attachments.

For more severe cases where skeletal jaw discrepancy is significant – particularly pronounced underbites – a combination of orthodontic treatment and orthognathic (jaw) surgery may be recommended. This is relatively uncommon but produces excellent outcomes when indicated.

Your orthodontist will assess your bite thoroughly and recommend the most appropriate treatment pathway for your individual situation.

Compare braces and Invisalign for bite correction: ethosorthodontics.com.au/blog/braces-vs-invisalign-which-is-best/

See patient results: ethosorthodontics.com.au/your-ethos-experience/before-and-afters/

How Long Does Bite Correction Take?

Treatment time varies significantly depending on the type and severity of the bite issue, the treatment used, and the age of the patient. As a general guide:

• Mild bite issues in children may resolve within 12 to 18 months
• Moderate cases in teens typically take 18 to 24 months
• More complex adult cases may take 24 months or longer

Your orthodontist will give you a personalised estimate at your initial consultation, based on what they find during your assessment.

Get Your Bite Assessed at Ethos Orthodontics

If you’re concerned about your bite, whether it’s an overbite, underbite, or something else. The best next step is a proper orthodontic assessment. Bite issues don’t fix themselves, and in many cases they become more complex (and more costly to treat) over time.

At ethos Orthodontics, our specialist orthodontists assess bite issues every day across our 13 Queensland clinics. Your first consultation takes around an hour, and gives you a clear picture of what’s happening and what your options are.

👉 Book your consultation at ethosorthodontics.com.au/contact-us/

 

Frequently Asked Questions

What is the difference between an overbite, overjet and underbite?

An overbite is an excessive vertical overlap of the upper front teeth over the lower teeth. An overjet is when the upper front teeth protrude too far forward. An underbite occurs when the lower teeth sit in front of the upper teeth. Although they’re often confused, they’re different bite problems and require different orthodontic assessments and treatment approaches.

Can an overbite, overjet or underbite fix itself?

No. Bite issues don’t self-correct and typically become more complex to treat over time if left untreated. Early assessment and treatment – particularly while the jaw is still growing – generally produces the best results.

Is it painful to correct an overbite, overjet or underbite?

Orthodontic treatment for bite correction is not painful in the way many people expect. Some mild soreness when braces or appliances are first fitted or adjusted is normal, but this settles quickly and is manageable with over-the-counter pain relief.

Can Invisalign fix an overbite, overjet or underbite?

Invisalign can treat many bite problems, particularly mild to moderate cases. For more significant bite discrepancies, braces or a combination approach may be more appropriate. Your orthodontist will advise based on your individual assessment.

At what age should bite problems be treated?

Early assessment around age 8 to 10 is recommended. Treatment timing depends on the type and severity of the issue – some bite problems are best addressed during jaw growth, while others can wait until more permanent teeth have come through.

Will I need jaw surgery for these bite problems?

Most bites can be corrected with orthodontic treatment alone. Surgery is typically only considered for very severe skeletal discrepancies that cannot be fully addressed with braces or aligners. Your orthodontist will discuss all options clearly at your consultation.