K. Kubota, one of the authors, has applied the following two methods of silver-impregnation : One is the Seto's method, introduced by Dr. Seto, Professor of Anatomy at the Tohoku University and the other is the Suzuki's method, modified by Dr. Suzuki, Professor of Anatomy at the Osaka City University. Based on these methods, the authors have accomplished their modification of staining peripheral nerves for frozen sections, which seems to be much easier for beginners than any other methods.
Staining Procedures.
1. Fixation of material :
Freshly isolated materials are fixed in 10% formol-alcohol for 10 days, then kept in 10-20 % formalin for a month. Hard tissues of teeth should be broken before fixation in order to fix the dental pulp.
2. Decalcification of hard tissues :
After washing in running water, the formalin-fixed materials are immersed in the decalcifying solution of Morse (prepared by mixing equal amount of 20% solution of sodium citrate and 50% solution of formic acid) for a few days, changing the solution every day, until the specimens become rubber soft.
3. Again immerse in 10-20% formalin.
4. Cut frozen sections at 20-40 microns and keep in 10% formalin.
5. Pretreatment for staining :
a. Immerse in neutral formalin for 7-14 days.
b. After washing in distilled water, immerse in the mixture of 10 cc. of formic acid and 90 cc. of neutral formalin for about 4 days.
c. After washing in distilled water, immerse overnight in the solution made up by mixing equal amount of absolute alcohol, neutral formalin and saturated solution of acid arsenous.
d. After washing in distilled water, immerse in the mixture made up by mixing equal amount of 5% sodii bicarbonate solution, 15 % solution of hexaminum and neutral f ormal in for about 30 minutes.
6. Wash thoroughly in distilled water.
7. Immerse in 20% solution of silver nitrate for one -2 days at roomtemperature or for about 60 minutes at 37°C.
8. Wash rapidly in 10 % f ormalin, then wash quickly in distilled water two or three times.
9. After sucking up the water from the specimens with blotting paper, immerse in an ammoniacal silver solution (made up by adding 30% cold ammonia water drop by drop in 20 % solution of silver nitrate until dark brown precipitate completely dissolves) for about 10 minutes. Much better result was obtained by warming the solution slightly, for example, by immersing the container in a water bath.
10. Deoxidization of silver :
a. Wash briefly in 10% cold solution of potassium sodium tartrate.
b. Immerse in 10% warmed (30°C.-45°C.) solution of potassium sodium tartratea until the sections change to light yellow-brown color.
11. Wash in distilled water.
12. Toning :
Immerse in very dilute solution (0.1-0.05 %) of gold trichloride for more than 3 hours.
13. Wash in distilled water.
14. Immerse in 10% solution of sodium hypo-sulfite (made up by dissolving 10 grams of ammoniumrhodanid in 100 cc. of 10% solution of sodium hypo-sulfite) until the sections change to beautiful violet-red color.
15. Wash in distilled water and dehydrate.
16. Clear in a carbol-xylol and mount with canada balsam.

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Satisfactory application of the electromyographic method as a research tool has not been made as yet in the field of dentistry. Very few reports, therefore, are available for understanding the functions of orofacial muscles from this point of view.
The aim of this report is to describe the findings on the functions of masticatory muscles which were obtained through studying their myograms and, if necessary, the mandibular movements as well as the bite pressure recorded simultaneously.
The results and conclusoins are summarized as follows:
1) The discharge of the neuromuscular units composing the group of masticatory muscles was of a pattern similar to those of the limb muscles. In some units, the magnitude of spike discharge was measured a few milivolts. The spike duration was 2-5 milisec., a little shorter than that in the limb muscles and there were found some units with their discharge frequencies of more than 70 C.P.S.. From these results it is possible to consider that the innervation ratio for the masticatory muscles is smaller than that for the limb muscles.
2) In the rest position of the mandible, when the Frankfort plane of the subject was kept to be in paralell with the horizontal, no discharge was recorded from all the masticatory muscles under examination.
3) Determination was made of the rest position of the mandible through studying the myograms of the masseter, the temporal and the digastric muscles. The rest position thus obtained was 2.6 mm as to the masseter and the temporal, and 6.1 mm to the digastric muscle, having the clearance of 3.5 mm as their mean value. From this finding, it is probable that the rest position of the mandible can directly be determined by way of electromyography.
4) The followings are the findings on functions of muscles as to the mandibular movements which were obtained from their myograms in the movements in six directions (i.e., upward, downward; forward, backward; leftward, rightward) where the rest position was taken as starting position for the movements.
a) The elevation of the mandible is accomplished by the contraction of the masseter, the temporal and the internal as well as external pterygoid muscles of both sides.
b) The digastric muscles of both sides take parts in the forward and backward movements. The masseter and the internal pterygoid muscles participate in the forward movement, while the temporal and the external pterygoid in the backward.
c) To the lateral muandibular movement toward one side contribute the masseter and the internal pterygoid muscles of the same side but also the temporal and external pterygoid muscles of the other side and further the digastric muscles of both sides. Further investigation by way of electromyography is necessary to make more clearer the functions of the internal and the external pterygoid muscles as to the mandiblular movements.
5) The followings are the informations obtained from simultaneous recording of the mandibular movements with reference to the discharge of the muscles involved.
a) In biting, the superficial and the deep head of the masseter muscles function together, but in the case of the mouth closing the superficial alone.
b) The anterior, the middle and the posterior belly of the temporal muscle function together in biting, but in closing the mouth there functions the middle belly in chief.
c) The digastric and the sternohyoid muscles take part in the mouth opening. But the discharge in the sternohyoid muscles was not observed before the opening advanced to a great extent, so that the suprahyoid muscles seem to participate in the action of the mouth opening, partly aided by the infrahyoid muscles.
d) At the maximal opening of the mouth the masseter and the temporal muscles showed discharges which are considered to be elicited by their proprioceptive reflex. And this phenomenon is likely to indicate that there exist some muscle spindles in the masticatory muscles.

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This is a study on iontophoresis by Dentatron which gave special current combined with high frequency and direct current.
The author treated 14 cases of the infected root canals in situ and 12 extracted teeth planted on Agar-Agar model with Dentatron, and compared with our iontophoresis used non-polarisable electrode and direct current about the effectiveness on the root treatment.
Then the author obtained the following results.
1) The transport of the medicament [Ag (NH₃) ₂OH] into the wall of root canal with Dentatron iontophoresis was inferior to our routine method on model experiments.
2) In the most of cases it needed 1-2 times of the treatment to get the sterility of the root canals, for there were 8 cases cured by a single treatment, 3 cases by twice, and the others were abondoned because of its severe irritation on the periodontal membrane.
3) On the contrary to W. Mach's report the intensity of the current which could applied without pain was small relatively, for there were counted about 2-3 mA equal to our method nearly.
4) The total amount of current necessary to secure the negative culture was 20-60 mA'.

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