Dental Anomalies Health Article

Definition

Dental anomalies are craniofacial abnormalities of form, function, or position of the teeth, bones, and tissues of the jaw and mouth.

Description

Dental anomalies can range from missing or stained teeth to cleft palates. Many are expressions of other, more complex disorders. The National Institute of Dental and Craniofacial Research (NIDCR) estimates that in the United States a baby is born every hour with a craniofacial defect.

Causes and symptoms

Many dental anomalies are caused by inherited genetic defects or result from spontaneous genetic mutations. The Center for Biotechnology Information recognizes 1,250 gene loci for craniofacial diseases and disorders. Dental deformities may also have environmental, traumatic, or nutritional causes; these may develop or become clinically apparent at any time during an individual's life.

Genetic defects

The most common genetic craniofacial deformity is clefting of the lip and/or palate, a defect estimated by the NIDCR to occur once in every 500 births. A family history of clefting increases the chances of inheriting the disorder. Seen more often in boys than in girls, cleft lip is usually unilateral, appearing three times more frequently on the left side than on the right. Less common is a bilateral cleft, a condition formerly known as "harelip." An incomplete cleft stops short of the nostril; a complete cleft extends into the nostril. Both types frequently involve the palate as well. The typical patient with cleft palate and cleft ridge exhibits large defects in the roof of the palate with a direct opening into the nasal cavity.

Dentinogenesis imperfecta type II (DGI-II), another genetic defect, causes severely discolored teeth that break easily. Amelogenesis imperfecta produces only a soft, thin layer of tooth enamel. This lets the dentin show through, making teeth look yellow, and leaves them weak, easily damaged, and susceptible to decay.

Other genetic anomalies are less debilitating. Malocclusion, meaning bad or misaligned bite, is caused by crowding teeth, extra teeth, missing teeth, or jaws that are out of alignment. Most malocclusions are inherited genetically, although some can be caused by accidents, early or late loss of baby teeth, or prolonged thumb sucking. Orthodontia usually corrects this problem.

Relative microdontia is an inherited condition that produces smaller-than-normal teeth, usually in the upper jaw. To correct this condition crowns or veneers are applied to make the teeth the same size as the others. Microdontia is neither painful nor harmful; treatment is intended to improve the patient's bite and appearance.

Partial anodontia, or congenitally missing teeth, is a condition in which one or more permanent teeth fail to appear, although primary (baby) teeth usually erupt. Third molars are absent in as many as 35 percent of all subjects examined. Maxillary lateral incisors and maxillary and mandibular second premolars (bicuspids) also frequently fail to appear. When this happens, many dentists choose to leave the primary tooth in place to prevent the malocclusion that might otherwise occur. If this is not feasible, a dentist may extract the tooth and close the space with braces or cover it with a bridge.

Idiopathic anomalies

Stafne's bone cavity, also called static bone cyst or lingual mandibular bone concavity, is an anomaly of unknown etiology. A painless condition, it is an indentation of the jawbone that may contain muscle or salivary tissue. The skin covering this area is soft to the touch and feels concave. No treatment is required, although biopsies are often performed to rule out the presence of a malignant tumor.

Condylar hyperplasia, another idiopathic anomaly, affects the temporomandibular joint and surrounding tissues. The condition is characterized by unrestrained growth of the condyle, which deforms the face, jaw, and bite. Surgery is usually required to restore order, although once growth has stopped orthodontics are often helpful. Condylar hypoplasia occurs when one condyle is markedly shorter than the other, a condition that also causes facial and dental deformities. Surgery can restore balance, and orthodontics are indicated as well.