A malocclusion is a misalignment of the teeth and jaw. In a Class 3 malocclusion, commonly known as an underbite, the lower jaw and teeth are positioned forward of the upper jaw and teeth. This condition can range from a minor misalignment of the teeth to a significant skeletal discrepancy involving the jawbones. The severity of the underbite influences both its visual characteristics and the approach to treatment.
Characteristics and Identification
A Class 3 malocclusion presents with a distinct facial profile, often characterized by a prominent chin and a concave or “dished-in” appearance. When a person with this condition bites down, their lower front teeth will sit in front of their upper front teeth. The severity of the underbite influences its visual characteristics and can vary significantly from one individual to another.
Contributing Factors and Causes
The development of a Class 3 malocclusion is strongly influenced by genetic and hereditary factors. This type of bite often runs in families and can be associated with certain ethnic backgrounds, with a higher prevalence observed in some Asian populations. A distinction is often made between a skeletal Class 3 malocclusion and a dental Class 3 malocclusion.
In a skeletal case, the jawbones themselves are mismatched in size or position. For instance, the lower jaw may be genetically programmed to grow more than the upper jaw. In a dental Class 3, the jaw relationship is relatively normal, but the teeth are tilted in such a way that the lower teeth are in front of the upper teeth. While genetics are a primary driver, other factors such as trauma, certain genetic syndromes, or habits like tongue thrusting can also contribute to the development of this condition.
Associated Health and Functional Issues
Beyond the cosmetic appearance, a Class 3 malocclusion can lead to a number of functional problems. The misalignment of the jaws and teeth can make it difficult to bite and chew food properly, which can in turn affect digestion. This improper bite can also lead to accelerated and uneven wear of the teeth, as they do not meet in the way they are designed to.
The position of the jaw in a Class 3 malocclusion can also impact speech, sometimes causing a lisp or other difficulties with pronunciation. The strain placed on the jaw from the misalignment can lead to discomfort, headaches, and in some cases, contribute to the development of temporomandibular joint (TMJ) disorder.
Corrective Treatment Options
The approach to correcting a Class 3 malocclusion is highly dependent on the patient’s age and the severity of the condition. For growing children, early or “interceptive” treatment is often recommended to guide the growth of the jaws into a more favorable relationship. This can involve the use of orthodontic appliances such as a palatal expander, which widens the upper jaw, or a reverse-pull headgear (facemask) that helps to pull the upper jaw forward. These early interventions can sometimes reduce the need for more invasive procedures later in life.
For adults whose jaws have finished growing, treatment for a skeletal Class 3 malocclusion typically involves a combination of orthodontics and surgery. Braces are used to align the teeth within each jaw, and then orthognathic surgery is performed to reposition the jaws themselves. During this surgery, an oral and maxillofacial surgeon will make cuts in the jawbones to move them into the correct alignment, which is then secured with small plates and screws. In milder cases, or where the malocclusion is primarily dental, orthodontics alone, sometimes involving the extraction of teeth to create space, may be sufficient to correct the bite.