Congenital Anomalies of Oral Cavity
Median craniofacial malformations include a spectrum of diseases, ranging from agenesis or hypoplasia or insufficient tissue to hyperplasia and excessive tissue, including median anomalies with clefting and normal tissue volume. Median craniofacial dysplasia refers to normal tissue volume clefting, which results from an incomplete fusion of facial structures during embryogenesis or gestation. Cleft lip and/or palate are the second most common birth anomalies, with a cumulative incidence of 1 per 700 live births varying by race and gender. Although cleft lip and/or palate may occur as part of a congenital syndrome, most often they occur in isolation. Genetics, dietary deficiencies, alcoholism, illicit drugs, medications, maternal infections, and environmental conditions are risk factors in the pathogenesis of these anomalies.
In 1976, Tessier presented a descriptive classification of clefting syndromes, ranging from 0 in the midline of the lower face to 14 in the upper facial midline and proceeding in a counterclockwise direction.
A true median cleft is an isolated cleft of the lip with or without insufficient or excessive tissue. In this type of anomaly the cleft passes between the central incisors. The cleft may continue posteriorly to involve the hard or soft palate. The cleft lip, cheiloschisis, originates most often at the junction of the maxilla and median nasal process; unilateral or bilateral, ranging from a notching of the lip margin to a complete cleft extending into the nasal fossa. When confined to the lip, it remains a prealveolar cleft, but it may also involve the alveolar ridge and palate (classified as “alveolar” and “postalveo- lar cleft”). The nose is deviated, with a distinct flattening of the alae of the affected side, and the margin lies at a lower level than the unaffected side. The columella is tilted. If not directly involved in the defect, the alveolar bone may be deformed in its midportion, owing to the deflection of the nasal septum. A flattening of both alae without other deviation or asymmetry is seen in bilateral clefts.
A cleft of the palate (palatoschisis or uranoschisis) may extend from the uvula forward and may involve part or all of the soft and hard palates (respectively, incomplete or complete). It is frequently associated with a cleft of the alveolar process (gnathoschisis), which, if complete, separates the premaxilla and the maxilla on one side, with the nasal septum attached to the palatal process of the opposite side. A bilateral alveolar cleft isolates the premaxilla, which is pulled upward and forward and continues as a median cleft of the palate. The nasal septum is free in the midline. The alveolar cleft either usurps the position of the lateral incisor or separates this tooth from the central incisor or cuspid. The dental arch tends to be fairly normal when the alveolar ridge is intact, but extensive clefts show irregular occlusion, with missing, rotated, and misplaced teeth. The alveolar and postalveolar defect interferes with sucking, resulting in aerophagia and nasal regurgitation. Eustachian tube infections, otitis media, labyrinthitis, or hearing impairment are serious consequences that can result from concurrent embryogenesis of the ear canal, complicated by feeding abnormalities. Undernourishment may account for chronic infections and failure to thrive. Failure of palatopharyngeal fusion allows air to escape through the nasal cavity, resulting in speech delays requiring surgical repair. The time of surgical intervention, around the second year, is considerably later than for cleft lip, which occurs much earlier, at 4 to 6 weeks of age.
Ankyloglossia, another congenital abnormality, rarely results from abnormal fusion of the tongue and floor of the mouth but more often as an excessive lingual frenulum attachment. The tongue arches in the midportion rather than protruding beyond the teeth. The degree to which reduced mobility associated with this abnormality results in pain, eating abnormalities, and speech and psychosocial development remains subjective and difficult to characterize. Torus palatinus (and, similarly, torus mandibularis) is excessive dense bone growth, or exostosis with little or no spongiosa, in an elliptical or nodular shape in the midline of the palate, which is likely a result of both genetic and environmental factors. Development begins in adolescence but may go unnoticed until it interferes with the construction of a denture. Micrognathia is a common congenial anomaly of the facial structures resulting in a hypoplastic mandible. Although this is most often associated with a congenital syndrome, it can occur in isolation. It is typically associated with dental abnormalities, specifically poor teeth alignment.