As regards the dynamic studies on dowel crowns, the solid photoelastic specimens of seven root surfaces consisted of plane, plane and slope, two planes type, these three types with pin-hole and plane type with shoulder, are made by the epoxy resin (type B) and hardner #901 as the injection method. Threedimentional photoelastic studies are carried out what dynamic effect the differences of root surfaces and the setting up indirect retainer have on the abutment tooth.
The following conclusion are obtained on various types of dowel crown from points of dynamic view.
1. Judging dynamic points of view, the root surface of two plane type is best out of various types in these studies.
2. Pin-hole and shoulder of every types as indirect retainer, are dynaminically useful because the stress distribution and concentration are decentralized and decreased by them.
3. The plane and slope type with indirect retainer is best from dynamic point of view.
4. The most clinical and rational root surface of dowel crown is the two plane type; furthermore, it with pin-hole located at palatal side of root surface is most logical. The plane and slope type with shoulder is good.

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In order to clarify the stimulating characteristics and their effects of a Myo-monitor and to investigate the mandibular position, 10 normal and 5 edentulous subjects without stomatognathic symptoms were studied. After examination of the direct output pulse and percutaneouspulse, the Myomonitor was used according to the instruction manual. The evoked EMG was recorded from anterior portion of the temporal, the masseter, anterior venter of the digastric, the orbicularis oris and the buccinator muscles. Mandibular movement was recorded with a pin-pointed miniature lamp luminograph in three dimensions.
The results obtained were as follows:
1. The Myo-monitor employed was a kind of constant voltage device and the stimulation was made with a common cathode stimulation method.
2. The duration of the stimulating pulse was about 1 msec which generating every 1.5 second. In the dial 2 and 4 of the overclosure scale, 4 and 8 pulses of about 1 msec duration were delivered at 10 msec intervals in groups with the same intensity and frequency of the singlepulse.
3. The stimulating intensity of the percutaneous pulse on the subject was gradually increased from 1 to 10 in amplitude scale.
4. Following the investigation of evoked EMG, it was clarified that the Myo-monitor pulse stimulates the nerve trunks of the Vth and VII th cranial nerves at the superior mandibular notch percutaneously and it appeared to have afferent and efferent effects.
5. The maxillomandibular relationship during the Myo-monitor stimulation (myocentric) in normal subjects coincided with centric occlusion (habitual occlusion) in 7 out of 10subjects and three showed a slightly posterior position (0.2-0.4mm) from centric occlusion, but anterior from centric relation (retruded position or terminal hinge position). In edentulous subjects without upper denture, the vertical movement distance of the mandible was gradually increased following increased stimulating intensity showing individual maximum values between 4.6mm and 7.2mm.
6. The mandibular position during the pause of stimuli, both in normal and edentulous subjects, was constantly stable in a range of clinical rest position.

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