Those with a brachycephalic head form (a characteristic feature of Middle Europe and East Asia) have a greater tendency toward prognathism. People with a dolichocephalic head form (a characteristic feature of some white populations in northernmost and southernmost Europe, North Africa, and the Middle East) tend to have a retrognathic face. In male faces that are long and narrow, however, the more marked extent of the upper nasal prominence is such that more of the nose sometimes lies forward of the vertical line. For a female face, the vertical line generally passes through the nose at a point about halfway along its upper slope. If the chin touches this vertical line, the profile is orthognathic if it falls behind or ahead, the profile is retrognathic or prognathic. Drop a perpendicular line from this just brushing the surface of the upper lip. To identify a person’s profile type, imagine a line projecting horizontally from the orbit. In D, a prognathic profile, the chin tip lies well forward of this vertical line. The lower lip also is much less prominent. In C, a severely retrognathic face, the chin is well behind the vertical line. In B, a slightly retrognathic profile, the chin tip falls several millimeters behind this line. The cranial base angle of the brachycephalic skull tends to be more closed, and there is a greater tendency toward an orthognathic (straight-jawed) profile.įIGURE 14-3 In A, an orthognathic profile, the chin touches a vertical line along the upper lip perpendicular to the neutral orbital axis. The face appears quite flat and broad, in contrast to the more angular, narrow, deep, and topographically bold appearance of the dolichocephalic face. The eyes appear widely set and the zygomatic bones seem prominent because the nose and forehead are less prominent. The nasal bridge is lower, the nasal sides are broader, and the end of the nose often tips upward. The nose is shorter vertically as well as horizontally and tends to be more puglike. There is less protrusion by the supraorbital ridges, the glabella is less prominent, and the frontal sinus is smaller. The net capacity of the airway in both instances is thus equivalent. The nasal chambers are horizontally shorter but wider, in contrast to the narrow but more prominent nasal region characterizing the dolichocephalic head form. The round, broad facial type is characterized by a more upright and bulbous forehead, with the upper nasal part of the face less prominent than in the dolichocephalic face. These factors contribute to a downward inclination of the occlusal plane and a marked curve of occlusion.įIGURE 14-2 A, Dolichocephalic head form. The lower lip and mandible are often set in a somewhat recessive position because the long dimension of the nasal chambers leads to a downward and backward rotational placement of the lower jaw (the dolichocephalic head form also has a more open cranial base flexure, which adds to the downward mandibular rotation). The nose also is typically prominent and quite long, and its point has a tendency to tip downward. Because the face is relatively narrow, the eyes appear close set, and the nose is correspondingly thin. There is a tendency toward an aquiline or Roman nose because the more prominent upper part of the nasal region induces a bending or curving of the nasal profile. The glabella and supraorbital rims are prominent, and the nasal bridge is high. A larger frontal sinus than is characteristic of the broad facial type because of the greater separation of inner and outer bony tables of the forehead, whereas the inner table remains fixed to the dura of the frontal lobe of the cerebrum. The forehead slopes because the forward growth of the upper part of the face carries the outer table of the frontal bone with it. The narrow facial type tends to have a convex profile with a prognathic maxilla and a retrognathic mandible. These are the long and narrow (leptoprosopic) facial type, and the round and broad (euryprosopic) facial type.Īlthough many intermediate types of head forms and facial patterns exist in any general population, these two skull configurations ( Figure 14-2) tend to be associated with characteristic facial features. Each type gives rise to corresponding general facial types. There are two general head types the dolichocephalic head is relatively narrow and long, and the brachycephalic head wider and rounder.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |