Brushing one's own teeth is very important for oral hygiene in mentally retarded, autistic, hyperkinetic, or otherwise handicapped. The purpose of this study was to evaluate the effect of a training system for personal tooth-brushing in mentally retarded children with abnormal behavior. We devised a training system containing a brushing program to which the operant conditioning theory was applied, and trained 7 mentally retarded subjects ranging from 4 years 3 months to 8 years 9 months old.
The following results were obtained.
(1) By training, 3 subjects learned to brush their own teeth.
(2) All subjects impruved in the degree of personal tooth-brushing.
(3) Before training the oral hygiene index of 7 subjects averaged 4.1and after training 1.4.
(4) Concerning the caries activity test, before training 6 subjects were _??_, and after training 1 was _??_, 4 were +, and lwas-.
We think this training system, which put stress on the mother as trainer and on training at home, may be an effective method for mentally retarded children to learn to brush their own teeth.

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Gingival color gives important information for the diagnosis of periodontal disease. However, it is not easy to use gingival color as objective data because color is dependent many factors.
We propose a Color Discrimination Index (CDI) based on three-band photometry with colorfilm, the index is independently determined from many factors such as the light conditions to avoid the difficulties reported previous paper.
In this study, the CDI was used to measure the gingival color of fourty one people with healthy teeth. The CDI of five portions of the inter dental papilla and six portions of the marginal gingiva to 3_??_3 of the upper part in each subject was measured.
The xy chromaticity coordinates of those parts were also measured and compared with the CDI.
The xy chromaticity coordinates on the color film were affected by the cosine law and other illuminant conditions since an oral eye camera was used to take pictures. On the other hand, the CDI is not influenced by those factors as shown in previous experiments. It became evident that the CDI is far better than the traditional xy chromaticity coordinates measuring gingival color.

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Representative strains of Streptococcus mutans serotypes a through g, which have been maintained in our laboratory, were reexamined for cariogenic virulence in golden hamsters reared on a high sucrose diet for 42 days. Six of the 20 strains tested became easily established on molars and produced significant levels of plaque and caries in all trials. Another 8 strains also produced caries significantly but occasionally and at lower levels than the above strains. They became established and persisted on teeth at a relatively later stage and in relatively smaller numbers. The remaining 6 strains induced no caries in any trials. No consistent difference was found among the 3 groups in the growth rate, acid production, and sucrose-dependent adherence to wire. Dissociation of one or more of the traits thought to be involved in cariogenicity of S. mutans from the virulence of serotype e and g strains has been discussed.

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The purpose of this paper is to estimate the number of actually available dentists at the present time and to analyze the effect of currently increasing the number of dental colleges (including dental schools of universities) which are expected to supply more than enough dentists to our society in the future.
The basic data on the number of registered dentists were obtained from “The Research for Physicians, Surgeons, Dentists and Pharmacists” published by the Ministry of Health and Welfare in 1954.
The period being analyzed was divided into three stages.
The first was 1955 to 1980, the second from 1981 to 1986, and the third from 1987 to 2015.
1. The number of dentists actually at work in 1979 was estimated to be 55, 338, whic differed from the number of dentists (50, 821) registered in 1979 by 4, 517, Approximately 8.2% of the dentists who were at work in 1979 were not registered.
2. In 1980, the unmber of dentists is estimated to have been 57, 624 (49 dentists per 100, 000 population).
3. During the 1990's when population growth rate will be stable, the number of dentists will be 138, 417 (99.8 dentists per 100, 000 population).
4. When the availability of dentists is compared to the U.S.A. and European countries, the number of dentists per 100, 000 population was equal to that of the U.S.A. and West Germany in 1980, and will equal that of Norway in 2005, Denmark in 2010, and Sweden in 2015.

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The teeth, the temporomandibular joint and the neuromuscular system are the trinity of the stomatognathic function. The purpose of this study was to observe the relation between the stomatognathic system and dental caries.
66 randomly selected 6-year-old school children, 31 males and 35 females, and 111 students and oral hygienists, 49 males and 62 females ranging in age from 18-20 years were surveyed. The biting force was measured on the bilateral 1st molars with the biting force measuring apparatus MPM-2401 (NIHON KOHDEN).
In the biting force, the 20-year-old group showed a higher level than the 6-year-old group (p<0.01). In the 20-year-old group, males showed a higher level than females (p<0.01). The average number of DMFTs and the DMFT rate showed a significant difference between the two groups (p<0.01). In the relation between the number of DMFTs and the biting force, each group showed a negative correlation, especially the 6-year-old females (left side: p<0.05) and the 20-year-old males (right side: p<0.05, left side: p<0.01). In the relation between the DMFT rate and the biting force, each group showed a negative correlation, especially the 6-year-old males (right side: p<0.05), the 6-year-old females (left side: p<0.05), and the 20-year-old males (left side: p<0.01).
These results show that caries prevalence brings about a decline in the biting force.

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In previous paper, a trial study on the gloss meter (VM 2D) was reported.
The system has been developed further in order to obtain optimum results for the measurement of tooth gloss and for brushing teeth with dentifrice abrasives. Signal-to-Noise (S/N) ratios were calculated to obtain the optimum conditions, and the results demonstrated that the following conditions were most favorable:
1) The angle between incidence and reflection was 60°.
2) The mean of two maximum values from the gloss and reflex values, which were taken from the picture drawn by the X-Y recorder, was the most precise.
3) The most suitable number of brushing strokes was 600, and the most suitable brushing load was 800 grams.
In addition, morphological observation of enamel surface demonstrated that the enamel surface was abraded by the dentifrice abrasive M₁, but gloss value was high.
On the other hand, the abrasive M₂ showed opposite results, with low abrasion but low gloss value.
The abrasive M₃ was significantly superor in making a glooy enamel surface.

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CF#1 strain mice were used to investigate the influence of fluoride intake on fluorine concentrations in bones of adults and their pups in three generations.
Eight experimental groups were fed a low fluoride diet (F=0.55ppm) and given drinking water containing 0, 0.25, 0.5, 1, 2, 10, and 20ppm fluorine as sodium fluoride for the duration of their lives. A control group was given an ordinary breeding diet (F=33ppm) and tap water (F=0.1ppm). Mice in all groups received the diet and drinking water ad libitum during the experiment.
Samples for determination of the fluorine concentration were a femur from each adult mouse and the 4 limbs of pups. The samples were separated from the body, soft tissues were removed from the bone surfaces, and the bones were dried at room temperature. Fluoride in the bone was separated by diffusion with hexamethyldisiloxane, and was measured with a fluoride sensitive electrode.
In the experimental groups, the bone fluorine concentrations of adult mice rose linearly with statistical significance, in proportion to the increase of fluoride in the drinking water. In the case of newborn pups, bone fluorine concentrations showed no appreciable increase in the 0-2 ppm groups, but increased proportionally to maternal fluorine contents in the 5-20 ppm groups. In the adults, the bone fluorine concentration in the 20 ppm group was approximately 113 times higher than in the 0 ppm group, but in the newborn pups, it was only approximately 6times higher.
Futher comparing the bone fluorine concentrations of adults and newborn pups, the level of pups was 138% that of adults in the 0ppm group, 37.9% in the 0.25ppm group, 14.4% in the 1ppm group, and only 7.7% in the 20ppm group. In consequence the pups' level was significantly higher than the adults' in only the 0ppm group, and the adults' level was higher than the pups' in all the other groups, indicating that the difference between adults and pups increased with increasing fluoride intake.
From these results, it is assumed that the amount of fluoride passed to fetuses through the placenta is maintained constant in the case of low fluoride intake by the mother, and the amount increases with higher fluoride intake when the fluoride intake is higher than a certain level.
The change in bone fluorine concentration after birth shows a peculiar pattern with aging. Namely, it decreased during the period of lactation, showing the lowest value just before weaning, and increased with age after weaning. These results suggest that the fluoride intake from breast milk in lactation, when pups grow vigorously, is less for bone neogenesis than the fluoride supplied in the womb or from feed.
The fluoride intake in the control group was equivalent to the intake in the 20ppm experimental group, the bone fluorine oncentration of adult mice in the control group showed a level between that of the 5 ppm and that of the 20ppm experimetal group, and the concentration of pups in the control group was a little higher than that in the 10ppm experimental group.

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