Normal Postural Changes of the Soft Tissue Facial Profile During Function

Abstract

A sample of 32 adolescents with acceptable facial proportions was procured. Using the Bolton method, cephalometric records were taken on each patient. Radiographic and developing techniques were used which gave the maximum definition to hard and soft tissues. Four basic positions were recorded. Two variations of lip posture, relaxed and light closure, were taken at two mandibular positions, rest and centric. Two exposures of each position were taken so that mean values could be used and aid in the accuracy of the study. Integumental landmarks were established relative to hard tissue structures. A horizontal plane was constructed by using hard tissue areas sella and nasion, SN-6. A perpendicular to this plane was constructed through sella. Linear measurements in a horizontal and vertical direction to the SN-6 ° located the landmarks in space. These planes also served as guide lines to superpose various positions so movements of soft tissue points could be observed. Mandibular rest position with the lips relaxed was used as the basic position for superposing. Variation in soft tissue points were related to this position designating movements in a plus or minus direction. Means of the differences were determined to evaluate the special movement of the integumental landmarks. The following conclusions have been established by this study: In normals soft tissue movement when significant are low in value. To effect lip closure from a relaxed position integumental landmarks moved minimally. In general vertical movements are greater than horizontal movements. Greatest activity of soft tissue landmarks occurs when the lips are closed from mandibular rest position. In most cases the lips when relaxed do not touch. This is true in both rest and centric position of the mandible. Only four cases of the 32 touched in centric position, and none touched in rest position. The average distance of inter-labial gap in rest position was 3.7 mm. The average distance of inter-labial gap in centric position was 1.9 mm. The upper lip plays a minor role relative to the lower effect lip closure. Subnasale and superior labial sulcus moved only in a vertical direction during closure. Labrale superior moved posteriorly and inferiorly during closure. In the lower lip, labrale superior moves only in a superior direction during lip closure. Inferior labial sulcus moves both anteriorly and superiorly. Menton moves superiorly with no significant horizontal deviations when considering only lip closure. Its horizontal deviation is only present when the mandible moves from rest to centric position. The integumental landmarks of the profile show a great deal of independence from mandibular positioning. The vertical positioning of the mandible from rest to centric position does not move soft tissue points equally or proportionately. Only one integumental landmark, menton, moves anteriorly during mandibular closure from rest position. A standard for normals has been developed and a graphic picture, a grid, of normal lip behaviour has been presented. The grid was developed to better understand the information gathered in this study. It is hoped that it will prove a valuable tool to evaluate soft tissue variations in a sample of malocclusions.