An underbite, also known as a Class III malocclusion, is when the lower teeth overlap the upper—giving a bulldog-like appearance in severe cases. Individuals with underbite often struggle to eat and speak. It can even cause mouth and face pain due to misalignment of the jaw.
Fortunately, you don’t have to settle for surgery. Let’s take a closer look at the causes and what treatment options are available.
An underbite is where the lower jaw is positioned further forward than the upper jaw.
The effects of this malocclusion range from chronic pain to low self-esteem.
Oral health problems such as injury and long-term habits can affect a person’s jaw development and the position of their front teeth.
Treatment options range from clear aligners to jaw surgery in cases of a severe underbite.
It is best to correct an underbite as early as possible in children to prevent severe cases from developing.
Underbite is known as a Class III malocclusion. Here, the lower jaw is pushed forward, and the lower teeth overlap the upper teeth. Severe cases can involve a gap between the lips, as the lower lip is also pushed forward [1].
An underbite is more than just a cosmetic issue. For example, a case study of a child described difficulty swallowing and speaking, alongside poor muscle tone in the tongue [2]. You may also have chronic jaw pain and temporomandibular joint disorder from long-term functional impairment.
The protruding jaw seen in underbites makes many people dissatisfied with their appearance, causing untreated adults to seek out intervention.
Underbite is a rarer form of malocclusion among people of European, Caucasian, and African descent. A study on Brazilian teenagers found that only 4% had this dental condition, while 21% had abnormal spacing, 13% had overcrowding and 9% had an overbite [3].
Only 4% of the Brazilian teenagers presented with an underbite
On the other hand, East Asian populations, including people of Japanese, Taiwanese and Korean descent, have much higher rates of underbite—with rates of up to 15-23% being recorded [4].
Underbite is a category of malocclusion where the lower teeth and jaw are positioned forward, causing difficulty eating and speaking. It is most common in East Asia.
Causes of an underbite include:
An underbite can cause, and be worsened by, childhood habits such as tongue thrusting. Poor muscle development may promote the habit of pushing the tongue forward when speaking and swallowing, which further worsens muscle tone. It may also add on other orthodontic issues such as anterior open bite [2].
Additionally, some children may have the habit of pushing their lower jaw forward, eventually training it to stay in the underbite position [4].
Severe facial injuries can cause permanent damage to the jaws. Broken jawbones can be fixed, however, the jaws don’t always align the same way as they previously did, which could cause an underbite.
Furthermore, injuries sustained in early childhood can affect the upper and lower jaws’ development and position, too.
While not technically an injury, cleft lip or cleft palate may affect jaw growth by causing the upper jaw to remain underdeveloped. The multiple surgeries required to repair a cleft palate often further impair upper jaw growth, making the lower jaw appear more prominent [4].
Most cases of underbite are genetic, and the majority of studies on genes linked to malocclusion involve this category. A number of genes involved in bone development, such as COL2A1, IGF1, and DUSP6, contribute to underbite [1].
However, when comparing the rates of underbite in people with and without a family history, there seems to be no real difference. This means that a combination of genetic and environmental factors is most likely the cause [4].
Some endocrine conditions can be contributing factors to the appearance of this misalignment. Acromegaly, gigantism, and adenomas of the pituitary gland lead to excessive growth hormone production, which affects bone development.
Additionally, enlarged tonsils can contribute to a child’s underbite by obstructing the nasal airways, contributing to poor oral habits that shift the lower jaw forward [4].
A combination of genetic and environmental factors, including excess growth hormone production, facial injuries, and tongue thrusting, can contribute to an underbite.
There are several ways to fix an underbite for adult patients, depending on its severity:
At-home aligners may be an effective braces alternative for teenagers with mild cases and a relatively normal jaw position. Aligners can give a shorter overall treatment time compared to metal braces, but they are less effective for more severe misalignments [5].
Aligners can be removed before brushing your teeth, reducing the risk of bacterial infections, tooth decay, and gum disease. Lack of adhesives means they won’t damage the tooth enamel either, making aligners the better choice for healthy teeth [6].
The different types of braces can apply more force to the teeth, through metal bands fastened around the brackets and regular tightening. An upper jaw expander can be added to help correct an underbite caused by the underdevelopment of the bone.
Braces may be effective for moderate levels of severity, but there is a higher risk of tooth decay and gum disease as you cannot remove them to brush your teeth. They can also only disguise a misaligned jaw, not fix it.
You may be able to achieve near-perfectly aligned teeth if the upper front teeth are shifted to flare out more while the lower teeth are shifted to protrude less [7].
Ceramic and clear braces are also excellent options so you can enjoy the barely-there look even if your underbite is too severe for aligners.
In cases of more severe underbite among older patients, surgery may be required to set the jaw in its correct position. Surgical correction methods may involve bringing the upper jaw forward, lower jaw back, or combining the two procedures. In either case, jaw surgery involves making an incision in the bone so its position can be shifted.
Orthodontic treatment is often used alongside surgery to achieve the best jaw position possible. Some people need to have one or more teeth removed, too [4].
Many cases of underbite are fixed without surgery, especially in recently diagnosed children. Unfortunately, after the permanent teeth have finished developing and the bones have stopped growing, orthognathic jaw surgery may be necessary.
Whether you are able to correct underbite without jaw surgery depends on the angles between your bones and teeth, which will be measured by your orthodontist or other specialists [7].
It is possible to correct an underbite naturally—if you define it as avoiding surgery. With functional treatment, including habit correction, and orthodontic treatment with necessary add-ons such as an upper jaw expander, you can avoid the need for jaw surgery [4].
It is best to correct underbite as early as possible, preferably while the adult teeth are just beginning to emerge. Devices such as a reverse-pull face mask or chin cup, strapped around the child’s head, are commonly used to correct a bad bite before the bones mature [4].
However, the genetic basis of underbite means that thorough monitoring is necessary until adulthood to prevent surgery [2].
Treatments range from clear aligners in mild cases, to orthognathic surgery in severe underbites. Children have a wider range of treatment options when it comes to avoiding surgery.
Both underbite and overbite are types of malocclusion, as the teeth do not completely meet each other. In cases of underbite, the bottom teeth overlap the top teeth, whereas an overbite is when the top teeth overlap the bottom.
When comparing overbite vs underbite, the major difference is that the lower jawbone is smaller or protracted. However, both have a combination of genetic and environmental causes, including oral habits, both can cause difficulty speaking or eating, and are treated with aligners, braces, or surgery depending on the severity.
The main difference between overbite and underbite is that the front teeth are positioned forward in cases of overbite. Both conditions have similar causes, symptoms, and treatments.
Still have unanswered questions? Let’s answer some common questions concerning underbite.
Although similar to other malocclusions in terms of its causes and symptoms, the positioning of the lower teeth in front of the upper teeth makes underbite a particularly unpleasant and less common issue.
If your child is currently struggling with this type of misalignment, early treatment is essential. The increasing severity with age and a greater number of treatment options in childhood means that starting as soon as possible can help them achieve the best results and avoid the need for surgery.
