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.
