Until the present, artificial teeth that varied form, size and shade are used, and studied in large numbers. But it did'nt at the same time biting forces, masticating forces and the electoromyography of differences from occlusal form of artificial teeth of complete dentures. By way of finding out how the occlusal form of artificial teeth has a influences upon the masticatory functions of complete dentures, the author uses the semi-conductor apparatus developed by Moriya and Fukamizu. The biting forces, masticating forces and forces in the swallowing period of the upper first molars on the complete denture wears (6 males) from 50 to 60 in age at differences from occlusal form of artificial teeth are recorded at the same time as the electoromyography of masseters and temporalis of left and right side.
As the result of these efforts, the following conclusions are obtained.
1. The biting forces in upper first molars of the 30 degree cusp teeth are larger than 0 degree cusp teeth. Especially the biting forces of the 0 degree cusp teeth are'nt found at eccentric occlusion.
2. The masticating forces in all foods of the 30 degree cusp teeth are smaller than 0 degree cusp teeth, but forces in the swallowing period are larger.
3. As for amount of electoric discharge activity of the masseter and temporalis during masticating each foods, 30 degree cusp teeth have a tendency to be small quantity to 0 degree cusp teeth.
4. Interval of electoric discharge activity of masseter and temporalis are'nt found difference between each teeth, but as for the duration, term and proportion of duration to term, 30 degree cusp teeth have a tendency of to be small to 0 degree cusp teeth.

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The purpose of this investigation is to determine what are the diatoric forms of the posterior porcelain tooth possessing both sufficient toughness for impact and retentiveness to denture materials.
In this article, an experiment with 10 types 27 sets of home-made artificial porcelain teeth (molars and premolars) consists of
(1) the observation of the ratio of the diatoric form's area (SII) to the ridge lap surfaces of teeth (S_I), the ratio S_II/S_I.
(2) In the retention hole on the cross-sectional area of the porcelain tooth, the measurements of the height, the width, the undercut wells of them and the angle of intersection between the axis of crown and that of the retention hole.
(3) tensile test.
(4) repetitive impact test in distilled water at 37±1°C.
The specimens for the both test were made by planting a porcelain tooth in a resin-block along the axis of crown and then were immersed in distilled water at 18°±2°C.
Through these experiments, the following results were obtained.
The ratio S_II/S_I was not constant in all types and molds. Preferably there was a tendency that the larger the crowns became, the smaller ratio S_II/S_I became. The height, the width and the undercut wells had similarly no relation. But the angle of inclination was closely resemble every molars and premolars regardless of upper or low teeth, and the premolars were higher than the molars.
Conserning with the tensile strength, each porcelain tooth was as follow: 5, 8.5±2.1kg; 5, 8.6±2.5kg; 6, 11.4±2.7kg ;6, 11.6±2.8kg; on each mean, which indicated that the molars were always higher than the premolars although there was no constant relation with every mold. The tensile strength was affected by the diatoric designs, upon which not only the depth of the undercut wells but the height, the width, and the angle of inclination had seemingly great influence.
After the test, fractures of the porcelain were left on the resin-blocks in the case of the specimens with high strength.
As to the impact test, about the half of specimens were satisfactory. The rest of them were broken preceding 4000 strokes. Among them, the relation could be found in the molars that the number of the upper teeth broken was more than the low, but in the premolars could not.
An important characteristics of this test was the effect of the air vent holes in mesio and distal surface of the porcelain teeth.
The porcelain teeth with them generally had lower impact strength, and their crack (by the impact) always went through the air vent holes, which had frequently been seen in a clinic.
Therefore the question was raised whether they were necessary.

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The diatoric designs of posterior porcelain teeth without airvent holes were decided on the basis of the results of part 1. They were composed of three sizes of diameter, height, angle of inclination of the axis of crown and two sizes of the depth undercut wells.
The molars amounted to 43 sets, the premolars 45 sets. Specimens were made in a similar manner of a previous paper. This experiments consisted of
(1) tensile test, Experiment (I)
(2) repetitive impact test and measurement of mobility of teeth planting in resin-blocks, Experiment (II)
(3) after mechanical and thermal stimuli were applied to the specimens selected from the experiment (I) and the experiment (II), tensile test, Experiment (III)
(4) The two foregoing tests of porcelain teeth with the airvent holes, Experiment (IV)
The results of this study were as follow;
Experiment (I): Molar-Among 43 sets, there were 12 sets whose values of the strength was higher than that of control, 0.55±1.54kg. A maximal strength was obtained with No.24, 19.51±2.31kg, a minimum was No.2, 6.75±1.74kg. Premolar-the values of 20 sets out of 45 sets were higher than the control, 8.38±1.17kg. The maximum was No.43 of 6.48±1.81kg, and the minimum No.8, 3.55±1.09kg.
Experiment (II): In the impacti strength, the values of the molars were higher than the premolars, but in the mobility the elative composition was entirely reversed. The specimens of the higher impact strength was not necessarily those of the low obility. Though the specimens with the porcelain having the small diameters surely took high values of the strength, for em to have the appropriate height or angle, their strength was also high.
In the molars there were 17 sets that were superior to their control, 123.93×10².
In the premolars 20 sets were higher than their control, 74.09×10²
Experiment (III): The specimens which took the higher values than the controls of both the impact and the tensile strength as No.17, 22, 24, and 28 of the molars, similarly of the premolars were No.14, 20, 21, 30 and 32. It could not be found that eir strength became low even after providing the mechanical and thermal stimuli, which suggested that the change of the etention of teeth had little to do with time.
Experiment (IV): In tensile test, their values were not change as usual, but in the repetitive impact test they became low. onsequently setting the air-vent holes in the porcelain teeth only brought about the fragibility of them.
Judging from these results, the diatoric form in the posterior porcelain teeth with the sufficient retention and toughness was, the molar their diameter, 3.0mm; their height, 2.3mm; their angle of inclination, 20°and their depth of the undercut wells 4mm.
In the premolar, their diameter, 3.2mm or 2.3mm; their height, 1.8mm their angle, 20°or 40°; and their undercut wells 0.4mm, oreover these teeth should have no air-vent holes.

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