Segmental odontomaxillary dysplasia

Segmental odontomaxillary dysplasia is a painless, unilateral enlargement of the upper jaw. The cause is unknown, and the disease affects the jaws, teeth, and adjacent soft tissue. The premolars may be congenitally missing, and the primary teeth (baby teeth) may be smaller than usual.

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Segmental odontomaxillary dysplasia (SOD) is a rare disorder characterized by unilateral enlargement of the right or left maxillary alveolar bone and gingiva in the region from the back of the canines to the maxillary tuberosity. In the enlarged region, dental abnormalities such as missing teeth, abnormal spacing and delayed eruption occur. The term segmental odontomaxillary dysplasia was introduced by Danforth et al. in 1990. Up to 2005, 32 cases of SOD had been described. SOD is often diagnosed in childhood both in males and females. The main clinical features include: 1) an alveolar process characterized by unilateral enlargement of the maxillary alveolar bone and gingiva. Buccal as well as palatal enlargement of the alveolar bone is observed, although it is more pronounced on the buccal side. 2) Dentition is marked by abnormal spacing between erupted primary molars and adjacent teeth. The first permanent molars are often distally displaced. A depression in the palate can appear in the molar region. The canines erupt normally. Malformations of the primary molars, absence of one or both premolars and delayed eruption of adjacent teeth are regular findings. 3) On radiograph, the bone appears dense and sclerotic. Decreased size of the maxillary sinus in the affected side is observed. 4) Histological findings reveal immature bone with irregular trabecular and basophilic cemental lines resulting from alternating bone resorption and bone formation. Sparse narrow spaces with only a few fat cells are observed. The gingiva shows slight fibrosis without pathological changes. Primary teeth are characterized by enlargement of pulps and an irregular pulp/dentin interface. Tubular defects in the coronal dentine are present. A deficient osteoblast layer and widespread external resorption is also observed. The etiology of SOD remains unknown. There is however a vascular theory for the origin of regional odontodysplasia. The condition does not appear to be inherited. SOD is apparently a non progressive developmental disorder. Differential diagnosis includes hemimaxillofacial dysplasia (HMD), regional odontodysplasia, fibrous dysplasia, focal cemento-osseous dysplasia, and hemifacial hyperplasia. In HMD, ipsilateral facial hypertrichosis is present in addition to the SOD symptoms. Some authors consider SOD and HMD to be different manifestations of the same syndrome. Regional odontodysplasia is characterized by delayed eruption or failure of eruption of discoloured and atypically shaped teeth. It is similar to SOD, but the incisors and canines of the permanent dentition are commonly involved and agenesis of premolars is not a typical feature. In regional odontodysplasia the radiographic appearance is described as teeth showing poorly demarcated enamel and dentition with a blotchy appearance. The pulp chambers are large and the roots short with open apices. Both primary and permanent teeth are said to be affected in this condition. Fibrous dysplasia also causes enlargement of bone tissue, but in this case affected bone growth is out of proportion with that of unaffected bones, and tooth malformations and missing premolars are not characteristics of the disease. Focal cemento-osseous dysplasia occurs in adults. Gingival enlargements and absence of teeth does not occur. Hemifacial hyperplasia results in unilateral facial enlargement and precocious eruption and enlarged teeth in the affected region. Absence of premolars has not been reported. Treatment of SOD should include long-term follow-up as it is important for guidance in the management of this disorder. Due to the possibility of a vascular origin for regional odontodysplasia, all patients with this syndrome must be carefully examined in the face and neck region for vascular malformations of any type, bearing in mind that vascular skin lesions (birthmarks) may fade during childhood. Implants have been successful in one reported case. *Author: Prof. I. Kjaer (May 2006)*.

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