The author undertook the statistical investigation on the laboratory findings of tubercle bacilli from the patients' sputa in a general hospital having about eighty beds exclusive for tuberculosis patients in the suburbs of Tokyo. The period of this investigation was five years starting from August 1954 until July 1959, and the results obtained were the following.
For the smear examination, both modified Ziehl-Gabbet's staining method and the fluoro-microscopic method were employed. For the cultivation, preoperated by 8% NaOH, KH₂PO₄ Ogawa's media were introduced in this investigation.
The effect of airation by the rubber stopper with the small air passage and the ratio of contamination by the micro-organisms were also studied.
Generally speaking, the results of culture method were superior to that of smear method for the detection in the monthly clinico-bacteriological examination through the full periods with few exceptions.
The relation between the Gaffky's scale and the results of cultivation was found as follows.
The Gaffky's scale and the duration until the growth of bacillus was visible, related reversely, and the Gaff ky's scale and the number of colonies related directly. Those close numerical relations approved intensive correlation between smear method and culture method. Some new findings on the specimen of Gaffky's scale “O”was shown here.
The colony type of tubercle bacilli was substantially “Rough-type”, however the author identified 3 forms, and they were changeable within them even in the strain derived from the same sputum.

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In 1949, 376 boys and girls in a certain primary school in Tokyo, who were aged 7 to 10 who were dispersed on account of the present World War II, and those non-dispersed in 1944 to 1946, the dispersions of which are further classified according to the districts such as cities, towns and farming fishing villages and their ages; and the caries of deciduous teeth (surface caries, deep-seated caries, root stump caries) and def in 1949 and the condition of 1950 and the increase and decrease during the year in these boys and girls was observed, which resulted as follows: -
1. Those dispersed compared to non-dispersed are generally under aged 9 in 1949, especially aged 7 in 1949 and 1950 show a high degree contraction in both deciduous caries and def, but aged 10 show a low degree one in both 1949 and 1950.
2. Those who were dispersed to farming and fishing villages, compared to those dispersed to cities and towns were generally under aged 9 in 1949, especially aged 7 show a low degree contraction in both deciduous caries and def, but show a high degree one in both 1949 and 1950.
3. At the period of dispersion we can guess that the boys and girls dispersed in cities and towns, farming and fishing villages were in the circumstances of being easily attacked by deciduous caries than those in Tokyo, and between farming, fishing villages, and cities, towns, this suffering tendency was remarkable in the former than in the latter from a standpoint of dispersion districts.

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Operative treatment, paticularly an amalgam restoration as the early treatment of dental caries should be still one of our most reliable and effective methods of controlling dental caries.
However, the dental electric motor units as we have generally used are apt to prolong the operation because of its law efficiency and give discomfort both to patients and operators such as pain, heat generation or vibration.
Thease undesirable factors make it difficult to protect collectively a large group of children from any of the dental abnormalities.
The air dental Unit (abridged ATE here after for clearness) has been largely improved to exclude such undesirable properties described, and to testify its efficiency some experimental comparisons with the older dental electric unit (abridged DE here after for clearness) has been made.
The results obtained are as follows.
1) Forty-seven qupils (male 26, female 21) aged 12 to 13 of a certin Yokohama middle school are selected in this study.
The two caries molars, which initiated in the pits. or grooves, one is right and the other is left on the mandibular, are selected with each pupil.
The questionnaire was asked by the operator immediately after finishing the restoration. According to thier answers, when ATE was use, 100 percent felt no discomfort, 17 percent had slight pain, 100 percent felt no temperature rise and only 6.4 percent complained of vibration, while 30 percent felt discomfort, 40 percent had pain 70 percent felt temperature rise and 70 percent complained of vibration when DE was used.
Those who complained of pain during the operation were examined by Recording Psychogalvanometer.
The hight of the drawing curve of ATE was half as high as that of DE.
2) The average time required for cavity preparation when carbide burs were used, was 33.5 seconds with ATE and 102.2 second with DE, therefore ATE was not only three times as effective as DE as cutting instrument, but also ATE can afford much more complete cavity preparation than DE.
3) The following minor test was also conducted.
Extracted natural teeth were cut for a certain fixed time in order to compare the effectiveness of using ATE and DE which was shown as the weight reduces of the teeth cut off and the depth of the cavities. From the test it was proved that ATE was three or four times more effective than DE. Including the time factor, ATE was ten or twelve times more effective than DE.
4) When the enamel portion of extracted natural teeth were cut off with diamond point for 40 minutes without resting, one operator using ATE and another using DE, and the weight reduces of the teeth were determined, it was shown that ATE was seven or nine times more effective in cutting capacity than DE. Adding to this test, the comparative fatigue of the fingers was measured befor and after the test by the Smedley's dynamometer.
The results show that any change was not found with ATE between start and end, while the reduction of 4.5-9.0 was found with DE.
5) Although the noise produced when using ATE and DE was 100-103 phone at its maximum with ATE and 75-80 phone with DE, no distinguishabl differences were observed during the cutting operation.
Thease tests proved that the Air dent unit could afford a great contribution to the preventive dentistry because of its highest efficiency.

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