The purpose of this study was to clarify the changes of the forms during firing on the dental porcelain. Specimens were two types of feldspathic porcelains and three types of aluminous porcelains. The properties investigated here were the particle distribution, the changes of the forms during firing in continuous observations (Heating Microscope), the internal structure (Microradiography), and the dimensional changes during fring on the metal die (Heating Microscope). The following conclusions were obtained;
1. The particle distribution in each porcelain was almost similar. Therefore, it seemed that the particle size distribution had almost no relation to the firing shrinkage.
2. Each grade of low bisque firing, medium bisque firing and high bisque firing was observed in all the porcelains in the changes of the forms during firing and in the internal structure.
3. In the changes of the forms during firing, the feldspathic porcelains tended to be in globular shape, while the aluminous porclains showed reduction of the size in the similar figures in the state of high bisque firing.
4. The dimensional changes in the transverse direction of the dental porcelain on the metal die were larger than those in the vertical direction. The firing shrinkage in the transverse direction on the axial wall of the die was the largest.

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As the preliminary stages for research in masticatory efficiency of denture wears, the author has made experiments to obtain on persons with natural teeth the basic informations requiring for establishment of a method to measure all inclusive masticatory ablilty in the stand point of biochemical digestive process in mastication which has never been reported enough previously.
The author paid attention to amylohydrolytic activity of salivary amylase which plays the chief part in digestive function of oral cavity. He has investigated the influences of mastication upon the digestion of Japanese rice on the basis of glucose from polished rice with a few types of preparation by mastication in human oral cavity under several conditions (differences of frequency, periods and tempo of mastication).
Glucose and maltose as glucose in the supernatant, obtained by 20 min. centrifugal separation under 6.99×10³g, from masticated rice in which the salivary amylase activity was stopped with acid, were detemined by Somogyi-Nelson method. Maltose was determined as glucose after hydrolysis by 1, 000mg/dl Maltase, 37°C, 60min., The quantity of ‘glucose+maltose’ as glucose is called in this study “total glucose”.
In this research, the term “masticatory performance” is defined to total glucose from rice after mastication and the term “high or low masticatory efficiency” is defined to the case in which masticatory performance is high or low under the same masticatory condition.
The author thinks that the effect of mastication should be determined by the difference of total glucose under the same condition between the case in which the test food is masticated and the case in which the test food in the mouth is never masticated.
To express definitely the relationship between masticatory times and periods in a test, a term “masticatory tempo” is used by the author; for example, tempo (M. M.) =60 means 60 times mastication per a minute.
“His or her own tempo” is used to mean the tempo in which he or she masticates freely without any control.
The results obtained from the author's investigations were as follows:
1. It is possible to judge the masticatory efficiency and masticatory performance by the author's biochemical method.
2. As masticatory test food, washed rice, boiled rice and boiled-dried rice are available.
3. The idea that masticatory performance is related with the increase of contact area with saliva bringing the increase the number of test food's particle is certified from the author's result that the increased masticatory frequency (times) and the increased total glucose are in direct proportion in over 50% of cases.
4. A person's own masticatory tempo against the same test food is nearly constant.
5. In the case of a person's own and adjacent tempo, the masticatory efficiency is the highest.
6. In all test food, masticatory efficiency, in slow tempo (M. M.=30) is higher than in quick tempo (M. M.=120).
7. There is seen no difference in a person's mastication during a short period (about one week), but a few difference during a long period of time (about one year); especially inFeb. and Aug., masticatory efficiency is lower and in April and June higher.
8. There is seen a few difference in masticatory efficiency in a day; especially at 11.00 O'clock, it is highest.
9. There is seen a few difference in masticatory efficiency between the right and the left masticatory side. Masticatory efficiency on a person's habitual masticatory side is higher than on his nonhabitual side.
10. There is seen no constant relationship between masticatory tempo and the volume of secreted saliva, but the types of preparation of rice influence the volume of secreted saliva; the harder the food is, the larger the salivary volume is.

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The auther measured the co-relative and individual occlusal forces of the dynamic momentary, static momentary and static occlusal forces for 50 males in the twenties with normal teeth, dentition and occlusal relationship, by the use of the occlusal force measuring apparatus with the bite element of 5.25mm thick developed by the auther.
As a result of this studies, the following conclusions were obtained.
1. In terms of the magnitude of co-relative and individual occlusal forces in dynamic momentary and static momentary occlusal forces, the teeth were in this order. They were second molars, first molars, second premolars and first molars.
However, in terms of the magnitude of static occlusal forces, the teeth were in this order. They were first molars, second molars, second premolars and first premolars. There was found a significant difference in every occlusal forces between a group of premolars and a group of molars.
2. In terms of the magnitude of three kinds of forces in the same teeth in both co-relative and individual forces, in every teeth except one tooth, the forces were in this order. They were static, static momentary and dynamic momentary occlusal forces.
In most cases dynamic momentary forces were equivalent to 35.0-45.0% of static forces and static momentary forces were equivalent to 45.0-55.0% of it.
Although there was found no significant difference in left first premolars and left second molars between co-relative dynamic momentary and static momentary forces, there was found a significant difference in every tooth between three kinds of occlusal forces in both co-relative and individual forces.
3. When the occlusal forces of the same-named teeth on left and right of the jaw were compared, there was indication that the teeth on the right had greater forces, as against the left teeth in every occlusal forces, but a significant difference was not found between the right and left teeth.
4. When the individual occlusal forces of the upper and lower same-named teeth in three kinds of occlusal forces, there was indication that the lower teeth had greater forces, as against the upper, but no significant difference was found in every tooth between the upper and lower teeth.
5. When the co-relative and individual occlusal forces were compared in each occlusal force, the both were almost the same in magnitude in dynamic momentary forces, and the individual occlusal forces were greater than the co-relative forces in every tooth in static momentary and static occlusal forces.

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Pycnodysostosis (The term pycnodysostosis was derived from the Greek pycnos=thick or dens, dys=defective, and ostosis=bone) is an interesting diseases in dentistry, because the masticatory dis turbance caused by loss of the teeth or malocclusion is often the main complaint of patients with pycnodysostosis. Many abnormalities could also be detected upon oral examination.
The symptoms presented by the patient are short stature, dysplasia of the skull, underdeveloped facial bones, flattened mandibular angle, deeply grooved palate, abnormalities of the teeth, increased roentgenographic density of alveolar bone surrounding the root apexes, prognathic jaw with open-bite, ocular proptosis, dysplasia of the terminal phalanges and increased density of bone in the entire skelton.
A special denture was constructed to fit this particular patient to restore masticatory efficiency.

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The unbalance of the reciprocal relation of the upper and lower alveolar ridges were found from the observation and measurement including its cross sections of the dental casts of the patient. It is reasonable to assume that the unbalance is caused by the underdevelopment of maxillary bone.
The length and width of the upper edentulous arch of the patient were 55-65% compared with normal. The length of the lower edentulous arch was 77.6% and the width was 88-95% compared with normal.
The interalveolar crest line angles were only 60-67.5 degrees in several regions.On the contrary, the interalveolar crest distance showed twice as large as normal distance.
The upper edentulous arch form was V shaped and the lower edentulous arch form wasoval.
The palate was deeply grooved with the upper alveolar ridge severely resorbed.

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