What Is an Underbite?
An underbite is a dental condition where the lower front teeth sit in front of the upper front teeth when the mouth is closed. In a normal bite, the upper teeth overlap the lower teeth slightly. When this relationship is reversed, it is called an underbite, or in clinical terms, a Class III malocclusion.
Underbites can be dental, skeletal, or a combination of both. A dental underbite means the teeth are tilted in the wrong direction, but the jaws themselves are properly sized. A skeletal underbite means the lower jaw is too large, the upper jaw is too small, or both. Understanding which type you have is critical because it determines whether braces alone can fix the problem or whether jaw surgery is also needed.
What Causes an Underbite?
- Genetics: Underbites run in families. If a parent or grandparent had a prominent lower jaw, their children are more likely to develop one.
- Jaw growth patterns: The upper and lower jaws grow at different rates. If the lower jaw grows faster or longer than the upper jaw during childhood and adolescence, an underbite develops.
- Childhood habits: Prolonged thumb-sucking, pacifier use, or tongue-thrusting can influence tooth position and jaw development.
- Missing upper teeth: When upper teeth are missing or small, the lower teeth may shift forward into the gap.
How Braces Correct an Underbite
Braces correct underbites by applying controlled pressure to move teeth into their proper positions. The specific mechanics depend on whether the underbite is dental (tooth-related) or skeletal (jaw-related) and the patient's age.
Class III Elastics (Rubber Bands)
The most common tool for correcting an underbite with braces is Class III elastics. These are small rubber bands that hook from the lower front teeth to the upper back teeth. The tension pulls the upper teeth forward and the lower teeth backward, gradually shifting the bite into alignment.
Patients need to wear elastics consistently, typically 20 to 22 hours per day, for them to work effectively. Removing them only for eating and brushing is standard. Inconsistent elastic wear is one of the most common reasons underbite treatment takes longer than planned.
Reverse-Pull Headgear (Facemask)
For children whose upper jaw is underdeveloped, a reverse-pull headgear (also called a facemask) can encourage the upper jaw to grow forward. This device attaches to the upper teeth or a palatal expander and hooks to a frame that rests on the forehead and chin. The forward pull stimulates bone growth in the upper jaw.
Reverse-pull headgear is most effective in children ages 7 to 10, while the sutures in the upper jaw are still open and responsive to growth modification. It is typically worn 12 to 14 hours per day, usually during evening and nighttime hours. Once the jaw position improves, braces refine the tooth alignment.
Palatal Expander
A palatal expander widens the upper jaw by applying gentle pressure to the palatal suture (the growth plate in the roof of the mouth). Expanding the upper jaw creates more space for the upper teeth and allows the upper jaw to move forward more effectively, especially when used in combination with reverse-pull headgear.
Expanders are cemented to the upper molars and activated daily by the patient or parent using a small key. The expansion phase typically takes 2 to 4 weeks, followed by several months of wearing the expander passively while the new bone solidifies.
Lower Tooth Extraction
In some cases, removing one or two lower premolars creates the space needed to retract the lower front teeth and correct the underbite. This approach is used when the lower arch is crowded and the teeth are contributing to the underbite. After extraction, braces close the gaps by pulling the lower front teeth backward.
When Braces Alone Work vs. When Surgery Is Needed
One of the most important questions for underbite patients is whether braces can fix the problem on their own or whether jaw surgery (orthognathic surgery) is also necessary.
Braces Alone May Be Sufficient When
- The underbite is mild to moderate (the lower teeth are 1-3mm ahead of the upper teeth)
- The underbite is primarily dental rather than skeletal (the jaw sizes are normal, but the teeth are positioned incorrectly)
- The patient is a child or teenager with remaining jaw growth, allowing growth modification with elastics, headgear, or expanders
- The facial profile is acceptable to the patient even without jaw repositioning
Surgery Is Typically Needed When
- The underbite is severe (more than 5-6mm of lower jaw protrusion)
- The underbite is skeletal, caused by a significant size discrepancy between the upper and lower jaws
- The patient is an adult whose jaw growth is complete, making growth modification no longer possible
- There are functional problems like difficulty chewing, speech issues, or jaw pain that braces alone cannot resolve
- The facial profile is significantly affected and the patient wants correction beyond what tooth movement can achieve
How Long Does Underbite Correction Take?
The timeline for correcting an underbite with braces depends on the severity of the case and the treatment approach used.
Children (Phase 1 Treatment)
Early intervention with a palatal expander and reverse-pull headgear typically lasts 9 to 18 months. After this phase, the child may take a break from active treatment while permanent teeth continue to erupt. A second phase of braces (Phase 2) is often needed in the early teen years, lasting an additional 12 to 24 months. The total active treatment time across both phases is typically 2 to 3 years, spread over several years of growth.
Teenagers
Teenagers with mild to moderate underbites typically wear braces for 18 to 30 months. If elastics are the primary corrective tool, compliance with wearing them consistently is the biggest factor in staying on schedule. Cases that require tooth extraction and space closure may take closer to 24 to 30 months.
Adults
Adult underbite treatment with braces alone (for mild dental underbites) typically takes 18 to 36 months. Adults who need surgery can expect 12 to 18 months of pre-surgical braces, the surgery itself, and 6 to 12 months of post-surgical braces, for a total treatment time of approximately 2 to 3 years.
Why Age Matters for Underbite Treatment
The American Association of Orthodontists recommends that children have their first orthodontic evaluation by age 7. For underbites specifically, early evaluation is particularly important because the window for growth modification is limited.
Between ages 7 and 10, the sutures in the upper jaw are still open and responsive to force. This is the ideal time for interventions like reverse-pull headgear and palatal expansion that guide jaw growth. Once these sutures begin to fuse in the early teen years, these appliances become less effective.
By adulthood, the jaws have finished growing and the bones are fully mineralized. Growth modification is no longer possible. Adult underbite treatment is limited to moving teeth within the existing bone (with braces or Invisalign) or surgically repositioning the jaws. This is why orthodontists often recommend early intervention for underbites, even before all permanent teeth have erupted.
Cost of Braces for Underbite Correction
Underbite correction with braces typically costs $3,500 to $8,000, with the wide range reflecting differences in case complexity, treatment duration, and geographic location. Cases requiring only braces and elastics fall at the lower end. Cases requiring palatal expanders, headgear, or extractions fall in the mid-range. Cases requiring surgery in addition to braces are the most expensive.
If orthognathic surgery is needed, the surgical fee is separate and typically ranges from $20,000 to $40,000. Medical insurance (not dental insurance) often covers a portion of jaw surgery when it is deemed medically necessary for functional reasons. Dental insurance may cover a portion of the orthodontic braces, usually up to a lifetime orthodontic benefit of $1,000 to $2,500.
Most orthodontic practices offer monthly payment plans that spread the cost over the treatment period. HSA and FSA accounts can also be used to pay for orthodontic treatment with pre-tax dollars. Costs vary by location and provider.
What Happens at an Orthodontist Evaluation
An orthodontist evaluates an underbite using a combination of clinical examination, X-rays, and photographs. A lateral cephalometric X-ray shows the relationship between the upper and lower jaws and helps determine whether the underbite is dental, skeletal, or both.
Based on this evaluation, the orthodontist will explain whether braces alone can correct your underbite or whether additional appliances or surgery are needed. They will outline the expected treatment timeline, describe the appliances involved, and provide a cost estimate. Many orthodontists offer free or low-cost initial consultations.
If surgery may be needed, the orthodontist will typically refer you to an oral surgeon for a joint evaluation. The orthodontist and surgeon collaborate on the treatment plan to ensure the best outcome. Learn more about orthodontic specialization on our [orthodontics specialty page](/specialties/orthodontics).
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