Aside from malformation of the upper jaw, cleft palate, there are arrest of development in one or both sides of either jaw and a failure of union in the two halves of the lower jaw. Anomalies about the temporomaxillary joint interfere with its function and may prevent separation of the jaws.
Malformation and misplacement of the teeth are extremely common. Thus a tooth may develop in an abnormal position by displacement of its body, or it may project in an abnormal direction; while teeth may be lacking in number or in eruption, so that a given tooth, usually a molar, completely fails to appear. Absence of a number of teeth is more rarely noted. Numerous cases are on record where a third set of teeth has succeeded the second instead of the latter remaining permanent. Abnormalities of tooth formation extending to the dignity of tumors of the dental tissues have been referred to in the chapter on Tumors, under the head of Odontomas. Cysts of congenital origin not infrequently develop around unerupted or misplaced teeth, and constitute tumors which at birth are scarcely noted and which may not develop until later in life.
Persistent remains of the thyroglossal or thyrolingual ducts may be seen early in childhood, or not until late in life. Their consequence is occasionally noted in the existence of fistulas, but more often of cysts or dermoid tumors, which, though having their origin in the middle line, may become displaced to one side, and when seen by the surgeon have a lateral position.
CLEFT PALATE.
Cleft palate is a congenital defect due to failure of coalescence between the nasal and maxillary processes, which, proceeding from either side, should meet and unite in the middle line. The defect may be so slight as to produce only a small notch in the alveolar border, or a small opening in the roof of the mouth, or it may be so complete as to constitute a separation with the formation of but a small part of the roof of the mouth, leaving but little tissue serviceable for any possible operation. The relation between the products of lateral growth and the downward projection and formation of the intermaxillary bone by the midfrontal and nasofrontal processes is too complex to be described here ([Fig. 465]). In some instances there is but little evidence of the formation of such a bone, while at other times it has not only bone formation but is relatively overdeveloped, in such a way as to make the lower anterior angle of the septum and its own part of the alveolar process project far beyond the level of the surrounding tissues, thus producing a snout-like appearance, which not only makes the case more disfiguring, but seriously complicates operative procedure. Usually the lower border of the nasal septum will be found attached to one side of the cleft ([Fig. 466]). The soft palate presents the same fissure, and the uvula is often neatly separated into halves.
Fig. 465
Double cleft palate.
Fig. 466
