The Purpose of this Two-Dimensional Photoelastic studies are based on getting the solution for dynamical answers in planning of pin-restration. The most important factors in pin-restration are length, size, numbers, and location of pins. These factors are Discussed in this investigations. Under the influence of pin length and size for stress concentrations were reported in part I. Under the influence of a space between two pins for stress concentrations were reported in part II. In part III, I studied and discussed about the infiuence of pin location for stress concentration in specimen. As the results of these efforts, the following conclusionand clinical application are obtained.
1) When appling the compress force on pin axis, the resistance of specimen for load was decreased and the compress stress was increased in pin apex area. These findings were caused by the pin closer to outer surface, the thickness of specimen became thinner from outer surface to the pin. The stress concentrations under pin apex region were varnished toward the outer surface. Futther more, the stress fringes were increased in the region of pin apex conected to outer surface. These findings of increased stress in thinn specimen area were indicated that the fracture in this region. From all of these findings and the results in part I, I could summarize that increased of the force applied on a pin axis, the pin should be placed in tooth least same distance of pin diameterinside from the outer surface.
2) When appling the perpendicular bending force on pin axis from outer surfacce of specimen, the resistance of specimen for load was decreaied, and the moment of force and spling back action of pin were increased. These findings were caused by the pin closer to outer surface, the thickness of specimen became thinner from outer surface to the pin. The changing of stress concentrations in specimen was found that the compress stress was increased on the top side pin, and was decreased under side of pin neck. Tensile stress in outer surface of specimen and stress fringes which collected from outer surface of specimen to the top side of pin apex were found. These findings of increased stress in thinn specimen area were indicated that the fracture in this region. From all these findings and the results in part I, I could summarized that in case of the force applied to a. pin perpendiculary from outer surface to the pin, the pin should be placed in tooth least twice more of pin diameter inside from the outer surface.
3) When appling the perpendicular bending force on pin axis to outer surgace, the resistance of specimen for load was decreased, and the moment of force was increased, also thinn outer surface area getting the bending force directry from pin. These findings were caused by the pin closer to outer surface, the thickness of specimen became thinner from side of pin to outer surface. The compress stress under side of pin neck, top side of apex, and under side of apex were decreased. Tensile stress under side of apex and compress stress in outer surface of specimen were extremely increased within this region. From all of these findings and the results of part I, I could summarized that in case of the force applied to a pin perpendiculary to outer surface of specimen, the pin should be placed in tooth least four times of pin diameter inside from the outer surface.
4) More greater stress concentration was found in case of appling the bending force to outer surface of specimen than the same force was applied from outer direction.
5) From all of these findings, the followin conclusion are obtained.
Planning of the pin-restration should be discussed about the direction of applied force and the amount of the force, all of these be based upon the sever condition.
In the small pin-restration, the location of pin should be inside from outer surface as same distance as the diameter of pin.

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The mandibular position can be interpreted the meaning of occlusal and condylar position. Furthermore, it is the subject to must be made clear as occlusion is studied in the same way of the mandibular movement.
Two experiments were conducted in the two groups, 8 men aged from 19 to 24 (adolescence group) and 6 men aged from 48 to 65 (advanced age group). First, occlusal positions and position of the condyle in swallowing position and capsular position as mandibular retruded position were registered by means of pantograph, and these positions were calculated three-dimentionally. Second, swallowing position and capsular position of the condyle, and lateral position of the condyle were surveyed by radiograph. Then the distance from above measured various occlusal positions and centric occlusion, and the distance from above measured various positions of the condyle and the con. dyle position in centric occlusion were calculated.
The following conclusions were obtained:
1. Swallowing occlusal position and capsular occlusal position were both located more rear-inferior to centric occlusion in advanced age group than in adolescence group. And capsular occlus al position was located rear-inferior to swallowing one in both groups.
2. Swallowing position, capsular position and terminal hinge position of the condyle were all located more rear-inferior to stable condylar position in advanced age group than in adolescence group. Swallowing position of the condyle was located far distant in all, and capsular position, terminal hinge position were followed.
3. The amount of rear-inferior-outward mov ement of left and right lateral occlusal positions from centric occlusion was greater in advanced age group than in adolesceece.
4. In both adolescence and advanced age, lateral position of the condyle on the left and right, was moved in working side rear-sup rioroutwards of and in balancing side pro-inferiorinwards of stable condylar position. The amount of the movement was greater in adolescence than in advanced age.
5. Aboved mentioned findings were proved to be correct by means of radiographic survey, too.

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Researching for the mastication, the digestion in mouth, that is physical and chemical, comes into a question. The masticating movement is to be regarded as the former. By way of its stueies, the determination of masticatory area, the distributive observation of crushed foods, the measurement of masticating forces, the electromyographic investigation of masticatory muscle, the electric analysis in jaw movement and radiographic method have been carried out.
The personally developed apparatuses for measurement of biting and masticating forces using the semi-conductor are put in the upper first molars on complete dentures wearers (10 males) from 50 to 60 in age. The biting forces, the masticating forces and the forces in swallowing period are recorded at the same time as the electrimyography of masseter and temporalis of left and right.
As the result of these efforts, the following conclusions are obtained.
1. The biting forces in upper first molars are 14.7-15.1 kg in the intercuspal position, 13.6-14.1kg in the working side of lateral position, 7.7-8.2kg in ballancing side and 5.1-5.5kg in the protrusive occlusion.
2. When the muscle activity is observed at each jaw position, the masseters and temporalis in the intercuspal position, the masseter of the working side in lateral occlusion and the masseter in the protrusive occlusion are marked active. Furthe-rmore, the muscle activities begin than the biting forces.
3. The masticating forces in upper first molar are 9.2-12.9kg by peanut, 7.3-12.2kg by ham and 9.5-12.5kg by pickled radish. The masticating forces in first period are differed from other periods, then the scond, third and fourth period are larger values. Regarding the duralation of masticating forces, the first period is largest value (0.33-0.39 sec) and the fourth period is smallest value (0.27-0.29 sec). As for the term, the fifth period is largest (0.73-0.76 sec). As regards the forces of the upper first molars in swallowing period of all foods, each period is smallest (6.4-7.2 kg).
4. When the electromyography in masticatory movement of peanut, ham and pickled radish are observed by means of the masticatory rhythm, the following finding are obtained.
As for the duration, the first period in all foods is largest (0.35-0.41 sec) and the fifth period is smallest (0.28-0.31 sec). Among foods, the peanut is largest. In order next comes ham and pickled radish. Regarding the interval, the fifth period is largest (0.41-0.47 sec) and the second period is smallest (0.29-0.34 sec). Among foods the ham is largest, then the peanut and pickled radish is smallest. As for the term, the first and fifth period are largest (0.68-0.77 sec) and the second, third and fourth period are smaller (0.58-0.70 sec) in all foods. Among foods the ham is largest, furthermore, in order next comes the peanut and pickled radish. As regards the ratio of the term to the duration, the first period is largest (0.51-0.55) and the fifth period is smallest (0.30-0.43) in all foods. Among foods the peanut is largest, in order next comes ham and pickled radish. The pattern in the swallowing period is largest, then it is differed from the masticatory rhythm in the duration, interval and term.
5. The masticatory rhythm of masticating for ces and electromyography and the pattern of the swallowing period are almost alike in all periods of peanut, ham and pickled radish. The muscle activitis begin and finish earlier than the masticating forces in all periods. It is tendency that the masseters begin and finish earlier than the temporalis.

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