A longitudinal study of soft tissue facial structures and their profile characteristics, defined in relation to underlying skeletal structures

Abstract

The primary objective of this study was to define the soft tissue profile on a longitudinal basis. An attempt was made to determine whether the soft tissue profile was closely related to the underlying skeletal profile. For the purposes of this study serial cephalometric radiographs obtained on thirty subjects from 3 months to 18 years of age were traced and studied. Changes incident to growth were evaluated by acceptable methods of superimposition and measurement. With growth, both the skeletal and integumental chins assumed a more forward relationship to the cranium. The integumental chin tended to be closely related to the degree of prognathism of the underlying skeletal framework. The bony facial profile tended to become less convex with age. Rather than the decrease in facial convexity which was characteristic of the skeletal profile, the total soft tissue profile (including the external nose) was found to increase in convexity with progression in growth. The soft tissue profile, excluding the nose from profile analysis, showed a tendency to remain relatively stable in its degree of convexity. In this regard, the soft tissue changes were not analogous to those manifested by the skeletal profile. It was pointed out that, with growth, changes take place in the dimension of the soft tissue covering the bony profile. These changes can have some effect on the configuration of the facial profile. It also was demonstrated that the soft tissue nose continues to grow in a downward and forward direction from 1 to 18 years of age. The disproportionate rate of growth of the nose explains the finding that the total soft tissue profile increases in convexity with increment in age. The upper and lower lips were found to increase in length as a function of growth. After the full eruption of the maxillary central incisors, the upper lip was found to maintain a fairly constant vertical relationship to prosthion and the incisal edge of the central incisors. Similarly, the lower lip showed the same relative stability in its vertical relationship to infradentale and the incisal edge of the mandibular central incisors. It can be generalized that both lips showed a fairly constant vertical relationship to their underlying alveolar processes and anterior teeth. The anteroposterior posture of the lips also was found to be closely related to the teeth and alveolar processes. In general, it was observed that the labial alveolar plates and central incisor teeth tended to recede and upright relative to the facial plane with increment in age. The vermilion aspect of the lips, especially of the lower lip, was concomitantly observed to become more retruded in relation to the facial profile. Thus, it may be generalized that lip posture is closely related to underlying structures, the teeth and alveolar processes. The composite results of this study indicate that all parts of the soft tissue profile do not directly follow the underlying skeletal profile. Some areas were found to diverge in soft tissue contour from underlying skeletal structures, while other areas showed a strong tendency to follow skeletal changes directly.