Lactulose is adisaccharide which fructose bounds to galactose by β-1, 4 linkage, and has a sweetness of about 60 percent that of confectionary sugar. Lactulose is also known as a growth factor for Bifidobacterium. The effect of lactulose on cariogenic factors of Streptococcus mutanswas studied using the methods previously described (Infect. Immun., 19, 444, 1978; Int. Dent. J., 32, 33, 1982). Lactulose was not utilized for the growth and lactic acid production of serotype a-g strains of S. mutans. It did not serve as a substrate for plaque formation and cellular aggregation of S. mutans (a-g), and insoluble glucan synthesis by glucosyltransferase from strains used. In the cellular adherence experiment using lactulose, heat killed cells of S. mutans (c, g) labelled with ³H and GTase, the amount of cells that adhered to the smooth surface was almost O. Further, lactulose inhibited sucrose-dependent insoluble glucan synthesis and cellular adherence. Antibiotic-suppressed SD rats infected with S. mutansstrain 6715 were fed a diet containing 26% lactulose or 26% sucrose for 68 days. A significantly (p≤0.01) lower caries score (mean±SE, 33.6±2.1) was observed in the rats fed a diet containing lactulose than in the controls (71.1±3.6). These results indicate that lactulose, in addition to being a sweetening agent and a growth factor for Bifidobacterium, may be of value in controlling human dental caries. Lactulose is freely used in food and drink in Japan, without legal regulation requiringthat it be indicated on the label.

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Since the percent of plaque removal is in proportion to the product of the brushing force and the number of strokes, a conscious increase of one or both of these factors increases the plaque removal effect. But the larger the number of brushing strokes per twenty seconds becomes, the smaller the brushing force becomes; and the number of brushing strokes has a tendency to decrease when the brushing force becomes stronger than 400g or 600g.
In this study, the brushing force was specified during observation of each brushing force wave with a cathode-ray tube oscillograph, and the number of brushing strokes was specified by synchronization with the sounds of a metronome.
It was concluded that a larger percentage of plaque removal was obtained by brushing with a force of 800g and 30 strokes per twenty seconds than by brushing with a force of 600g and 40 strokes, or with 1, 000g and 24 strokes per twenty seconds, even though the product of the brushing force and number of strokes is the same (24, 000). Also six days of instruction in tooth brushing resulted in a greater degree of plaque removal than lesser amounts of instruction time (Tables 1-4 and Figs 5-8).

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The preventive effect of mutanase (from Pseudomonas sp.) and dextranase (from Corynebacteriumpseudodiphtheriticum) on the formation and progress of experimental dental caries in rats was examined.
When the enzymes were given immediately after the infection with Streptococcus mutans OMZ 176, the statistical caries score indicated that both enzymes had a significant preventive effect on the formation of dental caries in rats. The effect was especially pronounced in a combination treatment (1 unit each enzyme/g diet or ml drinking water). In observations of the tooth surfaces under a scanning electron microscope, thick plaque adhered to the enamel and the dentin of the control group, but the plaque could not be observed and the fine structure of the enamel and the dentin of the treated group (with mutanase 1 unit+dextranase 1 unit) were normal.
After experimental dental caries caused by infection with S. mutans OMZ 176 and then by Diet 2000, the rats were treated with a single or a combination dose of the two enzymes. The combination of the two enzymes (1 unit each enzyme/g diet or ml drinking water) was the most effective for the inhibition of caries progression.
From these results, the two enzymes, which have different substrate specificity, have a synergistically preventive effect on the formation and progress of dental caries in rats, suggesting the possibility of using dextranase in combination with mutanase for the prevention of human dental caries.

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Indices of dental caries experience, (percentage of individuals with DMF, mean DMFT, and percentage of teeth with DMF) have been generally employed in epidemiological studies, and previous studies have described the caries experiences of different tooth types. In this paper relationship between above the three indices and the DMFT of specific tooth types are discussed.
The materials were obtained from the data reported in THE REPORTS ON THE SURVEY OF DENTAL DISEASES (Shikashikkan Jittaichosa Hokoku) by Japanese Ministry of Health and Welfare in 1957, 1963, 1969, and 1975, Five to twenty-nine year-old subjects were studied. They were diveded five age groups, i. e. ages 5 to 9, 10 to 14, 15 to 19, 20 to 24, and 25 to 29. The three indices and the DMFT of all teeth were calculated for each age group.
Factor analysis revealed that there were three factors, which were named the“adult age factor”, “child age factor”, and “adolescent age factor”. The typical teeth in adult, child, and adolescent factors were the canines, first molars, and second molars, respectively.
Since caries of these teeth increased in the respective age factors, whenever caries preventive programs are developed, it is essential for the program to correspond to the age of the subjects.
By the multiple regression analysis, the percentage of individuals with DMF was approximately identical to the caries experience of the lower first molar because this tooth erupts earliest and has the highest caries prevalence of all permanent teeth.
The other two indices, the mean DMFT and the percentage of teeth with DMF could be estimated by the DMFT of the typical teeth, i. e. the canines, first molars and second molars in the multiple regression equations.

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To clarify the effect of tooth brushing on the prevalence of dental caries in deciduous teeth, oral examination and a questionnaire survey of tooth brushing habits were conducted on 1, 221 infants aged from 1 to 3 years old.
The data obtained were statistically analyzed and the finding were as follows.
1) No sex difference in the prevalence of dental caries was found. The mean dmft increased with age from 1 to 3 years and the value for each age group was respectively 0.53, 2.36, and 8.76 (Table 2).
2) Infants that brushed once or more daily increased with age and the proportions of those infants in 1 to 3 years of age were 45%, 59%, and 69% in ascending order (Fig. 2).
3) Regarding the relation between daily tooth brushing and caries prevalence, the group that brushed twice or more daily had more dental caries than the other groups at 1 to 2 years of age but had less dental caries than the others at 3 years of age, but these differences were not statistically significant (Table 3, 4).
4) Regarding the relation between the age at which tooth brushing commenced and the prevalence of dental caries, the group whose tooth brushing had commenced early showed less dental caries than the group whose brushing had commenced late and the difference was statistically significant in the 2-year and 3-year groups (Table 5).
5) Regarding the relation between the motivation for tooth brushing and the prevalence of dental caries, the mean dmft and dmfs in the group motivated because dental caries had occured were higher than the groups with other motivation or which did not brush, and the differences were highly significant in all age groups (Table 6).
From these findings, the reason no difference in the prevalence of dental caries between groups with and without tooth brushing habits in many epidemiological studies is thought to be that the preventive effect of daily tooth brushing in infants will be masked by highly caries-susceptible subjects that have recently joined the brushing group because of the occurrence of dental caries.

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A simple and rapid test of saliva for caries activity by Resazurin Discs was investigated. The Resazurin Disc method has a characteristic color reaction developing within 15 min at 32-37°C. The composition of Resazurin Discs was 0.0275% resazurin sodium salt, 0.2% PVA and 10% sucrose, and these were impregnated in a filter paper with 8 mm diameter. The color of these discs changed from blue to bluish violet, reddish violet, and then to red or colorless with saliva.
Experiments were demonstrated to examine the effect on color reaction of resazurin with saliva and representative strains. Resazurin Discs were highly sensitive to gram-positive microorganisms such as S. mutans, S. mitis, S. faecalis, S. aureus, L. casei and B. subtilis. The sensitivity was correlated with the number of S. mutans and Lactobacilli in saliva.
Furthermore, from the data of the spectrum analysis of color changes caused by bacterial and Salivary substrate, it was apparently shown that the visible and flurescence spectrum of resazurin coincided with the spectrum of the solution based on chemical reduction and not coincided with acid origin. These results suggested that the color reaction of saliva and bacteria was due to a chemical reaction (oxdation-reduction rate) and not to a pH effect.
The use of Resazurin Discs might be a useful caries activity test and they might also be used advantageously for a screening in dental health instruction.

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Low temperature oxygen plasma ashing has been an advantageous pretreatment method for the determination of some kinds of trace elements in biological materials, but it has not been reported as a pretreatment procedure for fluorine quantification.
We examined the suitability of a low temperature ashing system (BRANSON/IPC 1005-248 AN Low Temperature Asher) as pretreatment of biological materials (both solid and fluid samples) to assess their fluorine contents. Gas chromatography (GC) and a fluorine ionselective electrode (F electrode) were used for the analysis of the fluorine content in the materials after they were pretreated by ashing.
Using calf serum and NBS standard reference materials (orchard leaves and oyster tissue), we studied the operating conditions of the ashing apparatus and the necessity for the addit ion of some fixatives. When a known amount of NaF was added to the calf serum, a good determination reproducibility with a coefficient of variation of 0.08 and recovery rates of 85 to 90% was obtained in both cases when analysis was done by GC and F electrode without any addition of fixatives. The levels of fluorine content in NBS standard reference materials analyzed by GC after being ashed were almost equal to the NBS's noncertified values but only when fixatives were added.
Walso employed the ashing method for analyzing ionizable Fand total F in the blood plasma of rats given drinking water containing 0, 50, 100 and 200 ppm F for 10 days with the combined use of GC and the F electrode. Both ionizable and total F in the plasma were increased by increases of fluoride (NaF) in the drinking water. The ionizabletototal F ratio was found to be significantly higher in the blood plasma of those rats given drinking water containing over 50 ppm fluorine than in the control group. The total F value obtained from the same plasma sample after being ashed was generally higher in GC analysis than in F electrode measurement. The reason for this difference is unclear for the moment and further elucidation of the problem will be required

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