Underbite

An underbite is a bite relationship in which one or more lower front teeth sit in front of the upper front teeth when the mouth is closed. Some people first notice it because their lower teeth are visible in front of the upper teeth when biting, while others become aware of difficulty biting into food, uneven tooth contact, tooth wear, or a change in the appearance of their smile or facial profile.

Underbite is a useful patient term, but it does not describe one single orthodontic diagnosis. The same visible front-tooth relationship can result from the position of individual teeth, a forward functional movement of the lower jaw during closure, the underlying relationship between the upper and lower jaws, or a combination of these factors. For this reason, an underbite should not automatically be considered a skeletal Class III malocclusion.

How an underbite can affect everyday function

The most recognizable sign is that the lower incisors close in front of the upper incisors. The change may involve only one or two teeth or a larger part of the front bite.

Depending on its extent and cause, an underbite may be associated with:

• difficulty biting through foods with the front teeth
• an unusual chewing pattern or uneven tooth contact
• increased wear or chipping of particular front teeth
• gum irritation or recession around teeth that receive abnormal contact
• jaw muscle or jaw joint discomfort in some patients
• concern about the appearance of the smile or facial profile

Changes in facial profile are not a medical problem by themselves, and facial appearance varies naturally between people. However, if the relationship between the jaws is pronounced, some patients may notice greater prominence of the lower jaw or a flatter appearance of the middle part of the face and may wish to discuss this as part of their orthodontic assessment.

Common causes of an underbite

Position of individual teeth

Sometimes the jaw relationship is generally balanced, but one or more upper incisors erupt or tilt behind the lower incisors. This is primarily a dental problem. The treatment possibilities can be quite different from those used when the underlying jaw relationship is responsible.

Functional forward shift of the lower jaw

In some patients, the first tooth contact during closing prevents the jaws from meeting comfortably. The lower jaw then moves slightly forward to reach a position where more teeth can come together. This can create an anterior reverse bite that resembles a skeletal Class III pattern even though the underlying jaw relationship may be different. Orthodontists sometimes describe this as a functional or pseudo-Class III pattern.

Skeletal relationship between the jaws

An underbite can also be associated with the way the upper and lower jaws have developed. The upper jaw may be relatively less prominent, the lower jaw may be relatively more prominent, or both factors may contribute. Genetic influences can be important, which is why family history is often discussed during an orthodontic assessment.

Growth and development also matter. A bite pattern seen in a growing child cannot always be interpreted in exactly the same way as the same appearance in an adult whose facial growth is complete.

When an underbite should be assessed

A longstanding underbite is usually not an emergency, but an orthodontic assessment is useful when the front teeth consistently close in reverse, when the bite interferes with chewing, when tooth wear is developing, or when the patient is concerned about jaw growth or facial balance.

Assessment is particularly important during childhood because the orthodontist can determine whether the problem is mainly dental, functional, or related to developing jaw growth. Early assessment does not mean that every child needs immediate treatment. It allows the orthodontist to decide whether monitoring is appropriate or whether intervention during growth could be useful.

Adults can also be assessed after growth has finished. At that stage, treatment planning focuses on the existing position of the teeth, the established jaw relationship, oral health, function, and the patient's priorities.

A sudden change in the bite after facial trauma, an inability to open or close the jaw normally, severe new pain, marked swelling, or signs of dental infection should be assessed promptly rather than treated as a routine orthodontic concern.

How an underbite is usually diagnosed

Orthodontic and functional assessment

A detailed orthodontic examination usually includes assessment of the teeth, bite, facial proportions, jaw movement and the way the teeth first contact as the mouth closes. This functional part of the examination is particularly useful when the orthodontist needs to distinguish a true skeletal discrepancy from a forward functional shift of the lower jaw.

The orthodontist may also ask when the bite difference was first noticed, whether similar jaw relationships occur in the family, whether chewing is affected, and whether previous orthodontic treatment has been performed.

Digital records and imaging

Digital intraoral scanning can create an accurate three-dimensional record of the teeth and bite. Clinical photographs can document tooth position and facial proportions. Radiographic imaging may be recommended when it is needed to assess tooth development, bone structures, jaw relationships or growth. Depending on the case, this can include panoramic or cephalometric imaging. Not every patient requires every type of image.

The aim of these records is not simply to confirm that the lower teeth are in front. They help establish why the reverse bite is present, because that distinction determines which treatment options are realistic.

What the next step may involve

Treatment depends on age, growth, severity and whether the main cause is dental, functional or skeletal. The visible appearance of an underbite alone is not enough to choose an appliance.

For a localized dental reverse bite, orthodontic tooth movement may sometimes be sufficient. Fixed braces, removable appliances or clear aligners may be considered in selected cases depending on tooth position and the overall bite.

In growing children, treatment may sometimes include appliances intended to correct functional interference or influence developing jaw relationships. The timing of treatment is individualized because growth pattern, dental development and the specific cause of the underbite all matter.

In adolescents and adults, orthodontic treatment may move the teeth and improve the bite when the discrepancy can be managed within the limits of tooth movement. Braces and aligners cannot, however, correct every significant skeletal jaw discrepancy.

For pronounced skeletal differences, an interdisciplinary assessment may be appropriate after growth is complete. This can involve orthodontic evaluation together with a maxillofacial surgical opinion to determine whether orthodontics alone or a combined approach is more appropriate. This is a general treatment pathway and should not be interpreted as confirmation that jaw surgery is provided by a particular ZagrebMed orthodontic practice.

ZagrebMed already includes a dedicated correction of reverse bite service as part of its broader bite correction pathway. The appropriate option should be selected only after the cause and extent of the underbite have been assessed.

Retention and follow-up after treatment

Correcting the active bite relationship is not always the final step. Teeth can move after orthodontic treatment, and growth-related changes may continue in younger patients. Retainers and follow-up appointments are therefore commonly used to help maintain the corrected tooth positions and monitor stability.

The type of retainer, how long it should be worn, and how often follow-up is needed depend on the treatment performed and the patient's individual risk of relapse. Growing patients may also require longer-term observation of jaw development.

What to prepare before a medical appointment

Before an orthodontic assessment or ZagrebMed inquiry, it is helpful to provide:

• the age of the patient and whether growth is still ongoing
• how long the reverse bite has been noticeable
• whether only one tooth or several lower front teeth bite in front
• any difficulty with biting, chewing, tooth wear or jaw discomfort
• previous orthodontic treatment or dental trauma
• relevant dental X-rays, scans or orthodontic records if already available
• family history of a similar jaw or bite pattern
• what you would most like the orthodontist to clarify, such as function, treatment options or facial balance

If an underbite is persistent, developing during growth, or affecting function, you can send ZagrebMed a short description of the bite and any existing dental records. ZagrebMed can help direct the inquiry toward an appropriate orthodontic assessment and explain which next step in Zagreb may be relevant.