A mesiodens is a type of extra tooth, known scientifically as a supernumerary tooth, that develops in the midline of the upper jaw between the two central incisors. This dental anomaly is relatively common, affecting approximately 0.15% to 1.9% of the general population. While mesiodens can occur in both primary (baby) and permanent dentition, they are seen more frequently in permanent teeth. Early identification and management are recommended to prevent potential complications to the developing bite and surrounding teeth.
What Exactly is a Mesiodens?
A mesiodens is defined by its characteristic location in the premaxilla, the area of the upper jaw containing the front teeth. It can occur as a single tooth or in multiples, a condition sometimes referred to as mesiodentes. Only about 25% of these extra teeth fully erupt into the mouth; the majority remain impacted within the jawbone.
The physical appearance of a mesiodens can vary, but three main types are commonly described. The conical form is the most frequent, appearing small and peg-shaped. The tuberculate type is barrel-shaped with more than one cusp, while the supplemental type closely resembles a normal tooth in size and shape. The extra tooth may be positioned vertically, inverted, or horizontally within the bone, which influences the risk of complications for adjacent teeth.
What Complications Can Mesiodens Cause?
The presence of a mesiodens can interfere with the normal development and alignment of other teeth. One frequent complication is the delayed or blocked eruption of the permanent central incisors, occurring in up to 52% of cases. The extra tooth physically obstructs the path of the developing permanent tooth, sometimes leading to its complete failure to erupt.
The mesiodens can also cause the displacement or rotation of adjacent teeth, resulting in malocclusion, or a misaligned bite. This displacement affects 28% to 63% of cases. The physical presence of the extra tooth can also create or widen a gap, known as a diastema, between the two front teeth.
Severe Complications
Less common but more severe problems include the formation of a dentigerous cyst around the crown of the impacted tooth (4% to 9% of cases). Mesiodens can also cause root resorption, where the structure of the neighboring permanent tooth root is dissolved or damaged. In rare instances, an abnormally positioned mesiodens may erupt ectopically into the nasal cavity.
How Are Mesiodens Treated and Managed?
The standard management for a mesiodens is extraction, though the timing of this procedure is carefully considered. Early diagnosis, often using imaging like panoramic or periapical X-rays, is important for planning the intervention. For unerupted mesiodens, the goal of extraction is to promote the spontaneous eruption and alignment of the permanent incisors.
The recommended time for removal is often in the early mixed dentition stage, usually around five to seven years of age, before the permanent incisors have fully developed their roots. Removing the mesiodens during this period allows natural eruptive forces to guide the permanent teeth into correct positions, potentially reducing the need for extensive future orthodontic treatment. Delaying the procedure increases the chance that the permanent tooth will not erupt spontaneously or will emerge misaligned.
The extraction procedure varies depending on whether the mesiodens is erupted or impacted. If impacted, a surgical approach is required, involving an incision to access the tooth within the bone. Following removal, monitoring is necessary to ensure the permanent incisor begins to erupt. If it fails to appear within six months to three years, further treatment like surgical exposure and orthodontic guidance may be needed. In rare cases where the mesiodens is asymptomatic, not interfering with other teeth, and the risk of surgical damage is high, observation may be recommended instead of immediate removal.
Understanding the Causes of Mesiodens
The exact biological cause of mesiodens is not fully understood, but current theories suggest a multifactorial origin. The most widely accepted explanation is the hyperactivity theory of the dental lamina. This theory proposes that excessive, localized growth of the dental lamina—the tissue band responsible for forming tooth buds—leads to the development of an extra tooth germ.
Another hypothesis, known as the dichotomy theory, suggests that a normal tooth bud splits into two parts, resulting in a normal tooth and a smaller supernumerary tooth. Genetic factors also play a role, as mesiodens often appear to run in families. The condition can be associated with certain genetic syndromes, such as Cleidocranial Dysplasia and Gardner’s syndrome, though most cases occur without an underlying systemic condition.