Faculty-supervised measurements of the face and of mandibular movements on young adults

Abstract

Purpose: The purpose of this study was to determine the average facial proportions and mandibular movement capacity of 316 first-year dental students who carefully recorded them on each other.

Materials and methods: This early exacting clinical experience was closely supervised by the authors in Columbus, Ohio during 1969-70. Five vertical and six horizontal distances were measured on each subject's face. An ala-tragus line and an occlusal line were drawn on the left side of the face to determine if these two lines were parallel. Measurements of mandibular movements involved maximum normal and hinge opening at the incisors and maximum amounts of right, left lateral and protrusive excursions of the mandible.

Results: The ala width and distance between the tips of upper right and left canine cusps averaged (35.2 mm and 34.8 mm) but with very large individual variations. The distance between ala to occlusal plane lines was 29.9 mm at the tragus and 31.3 mm near the ala. The angle between orbitale and ala-tragus averaged 13.6 degrees.

Conclusion: The upper lip length was the most variable and the distance between the pupils was the most stable of the eleven facial measurements. The ala-tragus line and the occlusal plane lines were for all practical purposes parallel. Maximum jaw opening averaged 51.2 mm which was 3.0 times larger than maximal hinge opening of 17.2 mm. The maximum right plus left side jaw excursions (9.2 and 9.4 mm) totaled 18.6 mm, 2.3 times more than the 8.0 mm mean maximum forward protrusion.

Keywords: Ala-tragus line; Anthropometry; Maximum and normal mandibular openings and excursions; Measurements of the face; Occlusal plane.

Fig. 1

Landmarks on the face: Trichion (tr) is the point on the hairline in the midline of the forehead, gnathion (gn) is the lowest median landmark on the lower border of the mandible, endocanthion (en) is the point at the inner commissure of the eye fissure, exocanthion (ex) is the outer or lateral eye commisure, (sto) is the imaginary midline point, and cheilion (ch) is the most lateral point on each side of the gently closed lips. Tragions (t) is the notch on the upper margin of the tragus, zygions (zy) is the most lateral point of each zygomatic arch, pupil (p) is the center point of the pupil with the head relaxed and the eyes looking straight forward.

Fig. 2

Depicts the four lines drawn on the side of the faces of 316 dental students in order to measure angles (A, B, and C) below the exocanthion to tragus line with a protractor.

Fig. 3

Two lines were drawn on the left side of each subject's face: one was continuous with and parallel to the tongue depressor which extended about 25 mm in front of the lips while the subject closed firmly on it. The second line was an ala to tragus line. The distance between these two lines was measured in three places: near the ala, at the midpoint, and near the tragus.

Fig. 4

The maximum opening (MO), and hinge opening (HO), was measured between the edges of the upper and lower central incisors using a millimeter ruler with the jaw open. The vertical incisal overlap of the incisors (from dental casts) was added to each mouth measurement in order to include the entire opening distance.

Fig. 5

Measuring the maximum protrusive (MP), maximum left (ML), and maximum right (MR), lateral excursions of the mandible. The distance measured in the mouth between the facial surfaces of the opposing teeth was added to the horizontal overlap of these teeth which had previously been measured on casts in order to include the total amount of jaw excursion in each direction.