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3. MEASUREMENT OF LIP MOVEMENTS 
3.1 Material and Method 
Lip movements of dentulous subjects with normal occlusion 
were measured during mastications using this system. 
Subjects were 13 men and 5 women with a mean age of 25 
years ( range 19 to 27). The tracking point of lip movements 
was a small ball covered with the reflecting tape at the right 
corner of the subject's mouse. This point was tracked by two 
video trackers and three dimensional movements were 
measured. For measurement of the mandibular movements, 
one tracking point was placed on the subjects chin, and 
tracked by one video tracker. Mandibular movements were 
measured in two dimensional coordinates for the reference of 
jaw opening and closing. 
Subject's head was fixed in the grand control points using ear 
rods and head rest. 6 control points on cubical shape (Fig.8) 
were used for calibrations of two trackers. The other control 
points were used for stereophotogrammetry of two 35mm SLD 
cameras to establish the standard axis on the subject's head. 
The coordinates of lip movements were transferred to this 
standard axis. 
8 types of test-foods (chewing gum, caramel, gumi-jelly, 
peanuts, cookies, carrot [1X 1 X lcm], boiled fish paste[1 X 1 
X lcm, 2X2 X 2em]. At first the subjects were instructed to 
put the food on their tongue and relax their facial muscles and 
  
Fig.8 Subject’s head was fixed in the grand control points 
using ear rods and head rest. 6 control points on cubical 
shape. 
  
then chew on their right molars. 
3.2 Results 
Dividing one cycle of mastication into 20 periods, mean positions of mouth corner on each period were showed in Fig.9. On the 
frontal plane, the movement of the mouth corner had the figure that is similar to the mandibular movement. On the horizontal and 
sagittal plane, it traced out a tear-drop shape, whose top means anterior, and bottom means posterior. In details each subject had 
his or her own shape of movement, but in a general view their movements were oval or tear-drop shape. 
The distance from the start point of each chewing cycle to the most distal point was evaluated as the index of lip movement. The 
mean distances of all strokes of each test food were showed in Fig10. 
One sequence of a test food mastication was divided into three (first, middle and last) stages. Time depending changes of the 
mean distance on each stage were evaluated in all test foods(Fig.11) With the progress of mastication, the mean distance in all test 
foods except for carrot and chewing gum. 
4. CONCLUSION 
The resolution of this system(3-D Auto Tracking System) was 0.10 X 0.10 X 0.10 mm, when the measurement was carried out in 
the area of 24.0(X)X20.0(Y)X20.0(Z)mm with the working distance of 500 mm and with the frequency of 120 Hz. The 
measurement accuracy of this system meets the requirements for analysis of lip movements. 
The lip movements during mastication depended on the physical property ( cohesiveness ) of food and the analysis of lip 
movements was useful method to evaluate the masticatory function of making bolus. 
IAPRS, Vol. 30, Part 5W1, ISPRS Intercommission Workshop "From Pixels to Sequences", Zurich, March 22-24 1995 
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