Mesiodens are considered supernumerary teeth and they typically develop in the midline between the maxillary incisors of the maxillary arch (Figures 4 and 5). The second most common region of the oral cavity is the third molar region where the supernumerary tooth is known as a fourth molar (paramolar). In fact, mesiodens of the permanent dentition are the most common cause of maxillary incisors failing to erupt. Although mesiodens can occur with primary dentition, it is rare. Mesiodens can develop laterally or bilaterally, single or multiple (mesiodentes), erupted or impacted, upright or inverted, typically present in the maxilla and in rare cases in the mandible. Eighty-two percent of mesiodens occur in the maxilla and are positioned palatal to the central incisors. There are three types: conical or peg-shaped, tuberculate, and supplemental. The most common type is conical. Unerupted mesiodens can cause complications such as malocclusion, root resorption, and in some cases cystic lesion formation. The mesiodens development begins before birth in approximately 50% of the cases but develops later than the primary central incisor dentition. The amount of prenatal enamel found in the extracted mesiodens, postulates the development of mesiodens with a third tooth germ during the last trimester of pregnancy. Compared to primary and permanent central incisor development, mesiodens display a defective morpho-differentiation and lack of mineralization or an incomplete mineralization. When extracted mesiodens are examined, their mineralization is impaired, with a chemical composition showing higher amounts of organic ions and less inorganic ions.1-6
Demographics: In the general population, the reported prevalence of mesiodens ranges from .15-3.8% and is more common in males than females with a 2:1 predilection. Mesiodens can be more commonly seen in individuals with physiological conditions including cleidocranial dysotosis, Down syndrome, Gardner syndrome, Nance-Horan syndrome, Ehlers-Danlos syndrome, and trichorhinophalangeal syndrome.5
Clinical Notes: The etiology is unclear. A genetic predisposition toward hyperdontia, such as X-linked inheritance has been documented, as well as the dichotomy theory with developing tooth buds and the hyperactivity theory of the restricted increase in the activity of the dental lamina.7-8
Treatment: It is difficult to determine when to extract a mesiodens due to its close proximity to developing roots of adjacent permanent teeth. Another factor is the age and cooperation of the child patient.7-8 CBCT is the preferred imaging technique when diagnosing and treating anomalies.