Mesiodens

Mesiodens is a supernumerary tooth in the midline of the maxilla, between or behind the central incisors. It is the commonest supernumerary tooth, accounting for about 80 to 90% of cases, with a prevalence of 0.15 to 1.9% in the permanent dentition.

It is found about twice as often in males. About one in four are erupted and the rest remain unerupted. Forms are conical (the commonest), tuberculate and supplemental, and orientation may be normal, inverted or transverse.

Pathophysiology. Hyperactivity of the dental lamina in the premaxilla produces an extra tooth germ. The tooth often sits palatal to the incisor roots and can block, delay or deflect the central incisors.

Conical teeth tend to be inverted in about a third of cases and may erupt into the nasal cavity. Some cases are associated with cleidocranial dysplasia and Gardner syndrome.

A missing or delayed central incisor beyond 8 to 9 years of age or a significant difference in eruption timing between the central incisors, a midline diastema, rotated or displaced incisors, an erupted conical peg between the incisors, and sometimes a nasal complaint such as discharge or an obstruction when the tooth is in the nose.

Often no symptoms and found on routine radiographs. Cyst formation can cause a swelling.

Rapid swelling, infection or a cyst need prompt assessment, and multiple supernumerary teeth need review for a syndrome.

• Clinical examination of the incisors, eruption timing and palpation of the palatal and labial sulcus.
• Periapical and occlusal radiographs, with a second view at a different angle (parallax) to find the labiopalatal position, and a panoramic view.
• Cone beam CT for the exact position, orientation, relation to the incisor roots and nasal floor, and for surgical planning.
• Screening for syndromes when teeth are multiple.
• Histology of the extracted tooth and any cyst lining.

Differential diagnosis.

• Compound odontoma
• Other supernumerary teeth (paramolar, supplemental incisor)
• Retained primary incisor
• Impacted or delayed central incisor from trauma or dilaceration
• Dentigerous cyst or nasopalatine duct cyst
• Fused or geminated incisor
• Cleidocranial dysplasia with multiple teeth

• Remove a mesiodens that blocks or delays the eruption of the central incisors, causes a diastema or displacement, forms a cyst, or interferes with orthodontic treatment. The usual timing is at 6 to 8 years of age, when the roots of the central incisors are half to two thirds formed, because earlier surgery risks damaging the developing tooth germs.
• Removal at 4 to 5 years of age is considered when the mesiodens is causing displacement or likely to prevent eruption and conditions allow.
• Asymptomatic, inverted conical mesiodens with no effect on the incisors may be observed with regular radiographs, because some erupt or remain stable.
• Surgery under local anaesthesia or general anaesthesia (in young children), through a palatal flap or a labial approach, with care of the incisor tooth germs and nasopalatine bundle. Any associated cyst is enucleated.
• If the central incisor does not erupt within 6 to 12 months after removal, expose it and use orthodontic traction.
• Antibiotics are not required for routine removal. A single dose of amoxicillin 500 mg to 1 g orally or cefazolin 2 g intravenously may be used for selected patients, with children dosed by weight.
• Analgesia: paracetamol 15 mg/kg every 4 to 6 hours (maximum 75 mg/kg daily) with ibuprofen 5 to 10 mg/kg every 6 to 8 hours in children, or paracetamol 1 g every 6 hours (maximum 4 g daily) with ibuprofen 400 mg every 8 hours with food in adults.

Monitoring. Review at 1 week for the wound, then every 3 to 6 months for 12 to 24 months for the eruption of the central incisors, with radiographs at 6 and 12 months. Check the vitality of the incisors.

Referral and escalation. Refer to paediatric dentistry, orthodontics or oral and maxillofacial surgery. Refer to genetics when supernumerary teeth are multiple, and urgently for infection or a cyst.