Underbite Explained: Causes, Risks and Treatment Options

06 / 08 / 2026

Underbite Explained: Causes, Risks and Treatment Options

If your lower teeth sit in front of your upper teeth when you close your mouth, you have an underbite. It is one of the less common bite problems we see and also one of the most treatable.

This guide covers what an underbite is, why it develops, the problems it causes if left alone, and how it is corrected. It was written by the specialist orthodontic team at Bright Orthodontics, who treat bite problems like this every day across five practices in Liverpool, Warrington, Ormskirk, Skelmersdale and Widnes.

An underbite rarely corrects itself, and it does not respond to jaw exercises or the techniques circulating online. The reassuring part is that a proper assessment tells you exactly where you stand, usually in one appointment.

What Is an Underbite?

An underbite occurs when the lower jaw and lower teeth sit further forward than the upper ones. Clinically it is a Class III malocclusion, and you may also hear it called a reverse bite or a reverse overjet.

In a healthy bite the upper front teeth rest slightly in front of the lower ones. With an underbite that is reversed, and severity varies:

• Mild. The front teeth meet edge to edge, or one or two lower teeth sit ahead of the uppers.
• Moderate. The lower front teeth clearly overlap the uppers and the bite feels wrong when chewing.
• Severe. The whole lower arch sits in front of the upper arch and the chin looks prominent in profile.

What matters most is whether the problem is dental or skeletal. A dental underbite means the jaws are in proportion but the teeth are tipped wrongly. A skeletal underbite means the jaw bones themselves are mismatched. That difference decides which treatments will realistically work.

Underbite vs Overbite: What Is the Difference?

They are opposites. An overbite describes upper front teeth sitting too far over the lower ones, either vertically as a deep bite or horizontally as an increased overjet. An underbite is the reverse. Both are malocclusions, but they are corrected quite differently.

What Causes an Underbite?

Inherited Jaw Shape

Genetics is by far the most common cause. Jaw size, jaw position and tooth size are strongly inherited, so underbites often run in families. If a parent or grandparent has a prominent lower jaw, there is a reasonable chance a child will too.

Childhood Habits and Airway Problems

Habits that place sustained pressure on developing jaws can contribute, particularly past about age four. Prolonged thumb sucking, extended dummy use and tongue thrusting all count. Chronic mouth breathing, often from enlarged tonsils or nasal congestion, can also affect upper jaw development.

These habits rarely create a severe underbite alone. More often they make an existing genetic tendency more pronounced.

Missing Teeth, Injury and Medical Conditions

Missing or unusually small upper teeth can let the lower arch sit forward. A jaw fracture healing in the wrong position can shift the bite permanently. Cleft lip and palate commonly affects upper jaw growth and is associated with Class III bites.

The Health Risks of an Untreated Underbite

An underbite is not purely cosmetic. When the bite does not meet properly, the effects build up gradually over years.

• Chewing difficulty. Front teeth that cannot meet make biting into food hard, so the back teeth carry more load than they were built for.
• Uneven tooth wear. Misdirected forces wear enamel in patches, leading to sensitivity, chipping and restorative work later.
• Jaw joint strain. Some patients develop clicking, tenderness, muscle fatigue or headaches linked to the temporomandibular joints.
• Speech difficulties. Tongue and lip position depend on tooth position, so a pronounced underbite can make some sounds harder to form.
• Decay and gum disease. Crowded or overlapped teeth are harder to clean, raising the risk of both.
• Breathing and sleep. Where jaw position narrows the airway, an underbite can contribute to snoring and disturbed sleep.
• Confidence. Many adult patients tell us their profile has bothered them for years. That is a legitimate reason to seek treatment.

Not every underbite needs correcting. A very mild one causing no functional problems can reasonably be monitored instead. What matters is having it properly assessed rather than guessing.

How an Underbite Is Diagnosed

Diagnosis needs more than a look in the mouth, because the purpose is to separate a dental problem from a skeletal one.

At a free consultation we would normally take clinical photographs, a digital scan and X-rays. A lateral cephalogram, which is a side-profile X-ray, lets us measure the relationship between the jaws directly rather than estimating by eye.

For patients under 18 we also assess against the Index of Orthodontic Treatment Need, the system used to determine NHS eligibility. A reverse overjet, where the lower teeth sit more than 3.5mm in front of the uppers alongside functional difficulty, falls into the highest category of clinical need. Our patient journey explains each stage.

Underbite Treatment Options

Early Treatment for Children

Childhood is the one window in which jaw growth can be influenced rather than worked around. Orthodontists recommend a first assessment by about age seven, once enough adult teeth have come through to show how the bite is developing. The British Orthodontic Society publishes guidance for patients.

For a growing child, options include a rapid maxillary expander to widen a narrow upper jaw, a protraction facemask to encourage the upper jaw forward, and functional appliances that hold the jaws in a better position while growth continues. Started at the right age, this can reduce severity considerably and sometimes remove the need for surgery.

Braces for Teenagers and Adults

Once growth is complete, treatment focuses on the teeth. Fixed metal braces remain the most precise option for correcting bite problems, and they are what NHS treatment uses. Where appearance matters, ceramic braces work identically using tooth-coloured brackets that are far less noticeable.

For mild and moderate cases, braces with elastics, and occasionally removing one or two teeth, can produce an excellent outcome without surgery. Orthodontists call this camouflage treatment: the jaw relationship stays as it is, but the teeth are repositioned so the bite works properly.

Clear Aligners for Milder Cases

Removable aligners can treat some mild underbites, particularly where the issue is tooth position rather than jaw position. We offer Invisalign and Angel Aligners, both using clear, removable trays. They are not right for every Class III case, and any provider promising otherwise before seeing your X-rays should be treated with caution.

Jaw Surgery for Severe Skeletal Cases

When an underbite comes from a genuine mismatch in jaw size, orthodontics alone cannot correct it in an adult. These cases are managed jointly by an orthodontist and a maxillofacial surgeon: braces to align the teeth, orthognathic surgery to reposition one or both jaws, then a further spell in braces. For severe cases it is the only route to a stable result.

Retainers and Holding Your Result

Whichever route you take, teeth drift back unless held. Retainers are not optional. We provide them at the end of every course of treatment and expect nightly wear long term.

Can You Fix an Underbite Naturally?

No, and this deserves stating plainly because so much misleading content exists online. Tongue posture exercises and jaw stretching cannot reposition adult jaw bones or move teeth through bone in any controlled way. The British Orthodontic Society has urged patients to be sceptical of any claim that a treatment will significantly alter jaw position or facial structure.

In children, jaw growth can be guided, but only with properly fitted appliances under specialist supervision. In adults the honest options are orthodontics, surgery, or accepting the bite as it is. Waiting allows enamel wear and joint symptoms to accumulate.

NHS and Private Underbite Treatment

Around a third of children need some form of orthodontic treatment according to the NHS, and a significant underbite is among the clearest examples of clinical need. NHS orthodontic treatment is free for eligible under 18s who score highly enough on the Index of Orthodontic Treatment Need, though waiting lists are long.

Adults are only rarely eligible, usually where jaw surgery forms part of the plan. For everyone else, private treatment is the practical route, and it costs less than most people assume. Our treatment costs and monthly payment options set out current figures, with braces from £52 per month. You can also browse before and after results.

When to See a Specialist Orthodontist

Book an assessment for a child by around age seven if you notice their lower teeth sitting forward, or sooner if you are worried. For adults there is no upper age limit. We regularly treat patients in their thirties, forties and well beyond.

Frequently Asked Questions

Can Braces Fix an Underbite?

In many cases, yes. Braces correct dental underbites and mild to moderate skeletal ones through camouflage treatment. Severe skeletal cases usually need braces combined with jaw surgery.

Is an Underbite Genetic?

Usually. Inherited jaw proportions are the most common cause, which is why Class III bites often appear across generations of one family.

At What Age Should an Underbite Be Treated?

It can be assessed at any age, but the ideal window for influencing jaw growth is roughly seven to ten years old. Treatment after that is still very effective, it simply works differently.

How Long Does Underbite Treatment Take?

Most orthodontic cases run 18 months to two and a half years. Early treatment in children may take under a year. Cases involving jaw surgery typically span two to three years.

Does Underbite Treatment Hurt?

Expect tenderness for a few days after braces are fitted and after adjustments, rather like bruised teeth. It settles quickly, and ordinary painkillers manage it well.

Can Invisalign Treat an Underbite?

Sometimes. Invisalign can handle mild underbites caused by tooth position. Moderate and severe skeletal cases generally need fixed braces, surgery, or both.

Will My Underbite Get Worse If I Do Nothing?

It will not usually improve. In growing children a Class III tendency often becomes more pronounced as the lower jaw develops. In adults the bite tends to stay stable, but enamel wear and joint strain can build up.

Book a Free Underbite Assessment

If you or your child has an underbite, the most useful next step is finding out precisely what type it is. Our specialist orthodontists offer a free, no-obligation consultation at all five practices. You will leave knowing the cause, the options, the timescale and the cost.

Book your free consultation online or call your nearest Bright Orthodontics practice in Liverpool, Warrington, Ormskirk, Skelmersdale or Widnes to arrange a time that suits you.