An underbite, or mandibular prognathism, is a Class III malocclusion characterized by abnormal protrusion of the lower teeth, or of the lower jaw and teeth. It is the exact opposite of overbites, which we discussed in this past article.
Underbites are far less common than overbites, but can be more extreme and may require more invasive treatment if not corrected early.
What causes an underbite?
Underbites are most often the result of a malformation of the lower jaw, which causes it to be drastically larger than its upper counterpart. Like most malocclusions, underbites can be hereditary.
The argument for heredity is strengthened by underbites appearing more frequently in certain cultures. The prominence of underbites among the Asian population may be what has led to the high number of Asian double jaw surgeries in recent years. You can read more about the phenomenon in this NY Daily News article.
Underbites can also be influenced by environmental factors such as mouth breathing, tongue thrusting and poor chewing habits.
Mouth breathing and tongue thrusting may cause the tongue to press on the lower front teeth and jaw in some cases. This consistent pressure can encourage lower jaw growth, as well as influence lower front teeth to jut forward. Prolonged nasal congestion also encourages mouth breathing, and discrepancies between the upper and lower jaws and teeth.
Complications Involving Underbites
Complications involving underbites include:
- Facial asymmetry– You can get a good idea of the asymmetry an underbite sufferer sees when they look in the mirror by pushing your lower jaw forward until your bottom teeth protrude farther than your upper teeth. While this distinct asymmetry might look cute on bulldogs, it is a major source of insecurity for underbite sufferers.
- TMJ disorders – An underbite places increased pressure on the jaw joints, which can lead to temporomandibular joint dysfunction. TMJ disorders are characterized by pain associated with the joints and chewing muscles.
- Speech impediments- Some underbite sufferers have difficulty with pronunciation of certain words and sounds.
- Enamel wear- Enamel can become worn where teeth overlap improperly.
- Receding gums- Extreme underbites can cause the upper front teeth to rest on the gum line along the inside of the lower front teeth. This constant pressure causes the gums to recede, and once they are gone, they are gone.
- Teeth grinding
Correcting a malocclusion can help prevent these problems and may even change your child’s facial structure for the better. Current TMJ disorder sufferers may also find relief in underbite treatment.
Early Diagnosis of Underbite is Key
Early diagnosis of your child’s malocclusion increases the treatment success rate and may eliminate the need for invasive surgery.
Optimal treatment for an underbite is determined by a number of factors related to the severity of the case and the age of the patient. Braces can be used to treat cases involving misaligned teeth alone, but craniofacial appliances or surgery are required to treat problems that stem from skeletal discrepancies.
Craniofacial appliances can prevent the need for invasive surgery, but are most effective when used to treat children who are still growing. This is why early diagnosis is key to successful treatment. The American Association of Orthodontists suggests parents have their children seen by an orthodontist by age 7, or at the first sign of a problem. This gives us the greatest number of options to use when treating your child’s malocclusion.
Appliances Used to Treat Underbites in Children
Maxillary expander – This is the first line of corrective appliance used in cases where the lower jaw is outgrowing the upper jaw. An expander is fitted in the roof of the mouth and is gradually adjusted each day with the turn of a key. Once the appropriate width is achieved, the appliance is no longer adjusted, but left in place for at least three months to stabilize the palate.
Reverse-pull headgear- This appliance is used to encourage upper jaw growth by coercing it forward. The appliance consists of two pads – one that rests on the forehead, and one that rests on the chin – connected by a vertical frame. This type of headgear is also referred to as a facemask because of its unique appearance.
Elastic bands attach the vertical frame to either braces or molar bands worn on the upper molars to exert the pulling force that encourages the upper jaw to catch up with the lower jaw. Reverse-pull headgear is typically worn at night, but can also be worn after school, depending on the severity of the case.
Chin cap – A chin cap wraps around the chin and over the top of the head to suppress lower jaw growth. Chin caps can be used in addition to the above appliances to treat severe cases.
Orthodontic treatment (braces)- Braces are prescribed to treat underbites involving only misaligned teeth, but may still be a part of treating skeletal crossbites. Even with early intervention and successful treatment using craniofacial appliances, your child’s teeth may still require refinements that can only be achieved with comprehensive orthodontic treatment.
Oral surgery – Seeking orthodontic treatment for your child at an early age is the best way to avoid the need for oral surgery, but may not rule it out. If your child must be referred to an oral surgeon, it is because the complexity of the case has ruled out all other options.
Adult Underbite Treatment
Skeletal underbites are increasingly more difficult to treat in adults than children, due to the ineffectiveness of certain craniofacial appliances on their fused jaws and palate. But that doesn’t mean surgery is the only option.
Braces can provide improvement of malocclusion related purely to misalignments of the teeth. Most adults are happy to learn we offer several types of invisible adult braces at Orthodontics Only.
Whether you or your child has crooked teeth or a misaligned bite, it should be evaluated to determine if early interceptive treatment will help avoid future complications. Call today for an initial consultation.