It is of great interest to investigate how malocclusion affects oral hygiene, caries, periodontal diseases and so forth. Young adults 19 to 28 years of age, students in a dental school, a school for dental hygienists, a school for dental technicians and so on, were selected as subjects. Conditions of malocclusion were observed by means of OFI (Occlusion Feature Index), Malalignment Index, LI to 1-6 angle, LI to 1-7 angle, and an orthodontic judgement. Conditions of oral hygiene were observed by means of DI (Debris Index), CI (Calculus Index), and OHI (Oral Hygiene Index), conditions of caries by means of DMFT-I (DMFT Index), and DMFS-I (DMFS Index) and conditions of periodontal diseases by means of PMA-I (PMA Index) and PI (Periodontal Index). Stature, body, weight and girth of the chest were of help in the to observation of physical conditions. Mean values and standard variations in all subjects, and separate values for males and females were obtained. In addition, a significant diffrence between males and females was sought by an analysis of variance, and correlations between the various items were reviewed in detail, and relations, between orthodontic judgements by the author and OFI were also examined. In conclusion, significant differences for each item in males and females, and correlations between the various items were shown.

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Though Takeuchi and his group have clarified epidemiological phenomena of caries attack in parmanent teeth, no study of this sort has been done in deciduous teeth. Therefore, this study was made to obtain basic epidemiological patterns of caries attack in the deciduous teeth for each type of tooth when the annual sugar consumption per head (represented as p) was constant.
For this purpose, the central part of Kameoka City near Kyoto (Fig, 1), was chosen as the place of investigation. The standard of living in this place was about the average of Japan (Table 1) and the flouride content in the drinking water was insignificant in relation to caries attack (Table 6) . Considering all of the infants aged 0, 1 and 2 years in 1965 in this area as population, a semi-annual oral examination for longitudinal study was carried out in the same individuals for 3.5 years (Table 2) . During this period (p) was 19-22 kg. Examination was performed by a dentist (the author) with an explorer and a dental mirror, considering as carious the pits and fissures that were clearly sticky or worse and the surfaces that were rough or had worse changes.
Only the teeth observed from their post-eruptive tooth age 0 were calculated at every half-year, putting the teeth of the same denomination of both sexes and left and right sides together, and separating those of different types, using a tooth or a surface as the unit of caries attack (Table 3) . Three kinds of indexes were calculated by the following method
Caries incidence rate during post-eruptive tooth age x (Mx) = Number of teeth newly attacked by caries during post-eruptive tooth age (x-0.5 yr. ) to x-yr. / Number of sound teeth at the post-eruptive tooth age (x-0.5 yr. ) ×100 The number of teeth newly attacked by caries during the post-eruptive tooth age x (per six monthes) per initial 1, 000 teeth (Cx) was calculated with Mx as follows: Tooth age Number of sound teeth (Sx) Cx 0 S₀ = 1, 000 S₀×1O M₀=C₀ 0.5 (S₀-C₀) = S_0.5 S_0.5×1O M_0.5 = C_0.51.0 (S_0.5-C_0.5) = S_1.0 S_1.0×1O M_1.0=C_1.0The cumulative number of carious teeth up to the post-eruptive tooth age x-year (per six monthes) per initial 1, 000 teeth (ΣCx) is the accumulation of Cx. The same methods were used in the calculations of the tooth surface. Furthemore, the e^-kx line was drawn by the method shown in Fig. 2, and from the polygonal lines of Cx and ΣCx, their trend lines were plotted.
The three indexes of caries (Mx, Cx and ΣCx) were shown in Table 4. In graphs the polygonal lines of Mx are shown in Figs. 3 and 4. The polygonal line of Cx is shown in Fig. 5 and the polygonal line of Cx in Figs. 7 and 8. The trend lines of Cx and ΣCx, and the e^-kx line are as shown in Fig. 9. The angle between the e^-kx line and the 1-line and the post-eruptive tooth age at which Cx trend line reached its summit are shown in Table 9.
It was conceivable that Fig. 9 shows a typical pattern of caries attack on the deciduous teeth in Japanese infants when (p) is around 20 kg. It was noticed that the Cx trend line of this figure coincides with integrals of exponential probability and that the e^-kx line is a straight line. From these facts it was deduced that at least in the case of deciduous teeth and when (p) is constant, caries occurs as a phenomenon in which the resistance of the tooth makes the normal distribution as a process in the first stage, then as the second stage, an initial carious change appears in accordance with the chance of caries which is constant (Fig. 10).
Patterns of proximal surface caries were also discussed (Figs. 6, 11, 12).

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Scientific studies on the dentist's clinical posture and positions are almost nonexistant except for those by H. Fukumoto and O. Yamamoto. Therefore, the determination of the posture and positions of the dentist and his patients, and the layout of the dental equipment in the dental operation room has been merely based on the dentist's personal experience, not on scientific reasons.
Many dentists have been complaining about fatigue and physical pain. The author examined the dentist's operational posture and positions by E. M. G. in this study. According to the reports by H. Fukumoto and O. Yamamoto, the optimum is to keep the patien's mouth at the level of the dentist's nipples from the viewpoint of the dentist's fatigue and his operational efficiency.
In the present study, the author observed muscular movements of the dentist in different conditions-standing and sitting; keeping the patient's mouth in the area between 15 cm higher and 15 cm lower than the level of the optimum.
The findings through the examination of thirty-two (32) muscles are as follows :
1) Seven (7) muscles of the dentist showed active movements when he engaged in his clinical work standing and four (4) muscles, sitting.
2) When the patient's mouth was kept at the level of the dentist's nipples, the number of muscles showing active movements was less than when the patient's mouth was at different levels.
3) This study also revealed which muscles on the right arm and hand of the dentist more often showed active movements when he engaged in cavity preparation, scaling with a hand sealer, removal of slftened dentine with an excavator, and extraction with extracting forceps, and the characteristics of each muscle on various occasions.

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I. On the operation room pollution by bacteria
1) The number of bacterial colonies which was counted by Koch's method was between 14.0 to 38.3.
2) The number of air bacteria in the operation room largely depended upon whether or not there were any ventilation facilities. More air bacteria were counted when visitors were allowed to enter the room with their shoes.
3) The number of air bacteria counted increased with the lapse of time. The number at the end of the office hours was 2.4 to 2.8 times the number at the opening of the office.
4) The number of bacterial colonies on the bracket table at the closing time of the office was 299.0 which was 7.8 to 9.0 times the number at the time just before opening the office.
II. On the contamination on the dentist's person through his clinical work
1) After wearing the dentist's uniform for one day, 434 colonies were counted at eight (8) fixed spots on the uniform, and the number increased to 26 times, after wearing the same uniform for three (3) days.
2) On the first, second and third fingers of the dentist's right hand, 160 to 192 colonies were counted at the end of his office hours, in spite of the fact that he washed his hands in an antiseptic solution after each patient.
III. On the operation room pollution caused by the air turbine engine
1) The operation room was notably polluted by bacteria when the air turbine engine was used. The area 20 cm to 40 cm from the cutting point was the most polluted. This means- that the dentist and his assistant are working in the most polluted area.
2) Since air turbine gripe was exceedingly contaminated, the dentist's fingers were constantly cotaminated through clenching the gripe as well as using a towel and brush.
IV. Some measures to counter the pollution by scattering backeria
1) If the dental vacuum apparatus is properly installed when air turbine engine is used, the expected pollution at distances of 20 cm to 40 cm from the cutting point effectively decreases.
2) If the bracket table and the engine gripe are sterilized by antiseptic solution at each time, the expected contamination can be fairly reduced. 1 % Osvan was most effective.
3) If the softened dentine is removed as much as possible by the sterilized excavator before using air turbine engine, the expected contamination can be redued.
4) It is effective to carry on thorough gargle before cutting by air turbine engine. 3 % Laboris was more effective.
5) It is possible to reduce the air pollution in the operation room through the use of the ventilation facilities.

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applied cyanoacrylate-polymethyl methacrylate sealant to the pits and fissures of 1703 occlusal surfaces of 990 school children of 6 schools and the same numbers of opposite surfaces were left untouched as. a control. The different criteria regarding the caries and the sealing procedure among the various collaborators were well coordinated before the trial. Cyanoacrylate monomer and polymethyl methacrylate containing a suitable amount of calcium hydroxide were mixed on an acetate sheet and then the mixture was applied to an occlusal surface preconditioned by approximately 40% phosphoric acid. The caries reduction figure was obtained in comparison with different incidences of cavities produced on both the test and control teeth. The reductions in the caries incidence, 60.7 % after 6 months and 38.3 % after one yeaf produced statistically significant differences. Retention figures of the sealants were 76.7% after 6 months and 52.6% after 12 months respectively.

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