Four species of enteric rods mainly coaggregated with Actinomyces and Candida in a strain-specific manner. Enterobacter cloacae showed the highest reactivity with the oral microorganisms, followed by Serratia marcescens, Escherichia coli and Klebsiella pneumoniae in this order. The coaggregation reactions were mediated by heat-labile components on the cell surface of enteric rods. The addition of mannose reversed some of the coaggregation reactions but did not influence the others, indicating that the reactions include mannose-sensitive and mannose-resistant adhesins on the enteric rods. Twelve out of 20 enteric strains were also aggregated by human whole saliva. Coaggregation with indigenous oral microorganisms and aggregation mediated by saliva potentially promote the colonization of pathogenic enteric rods in the oral cavity.

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Water is used in dental treatment with high frequency. Since this is supplied to patients through air turbine and air-water syringes, quality of the water is important. The purpose of this study was to examine the bacterial contamination, and measure the number of bacteria and the residual chlorine concentration in the water from air-water syringes on Monday, which is the first working day of the week. The number of bacteria was measured using standard agar (37°C, 48 hours). The residual chlorine concentration was measured by DPD method (510nm). The relation between the number of bacteria, the predictive value of displacement need, and the water supply system was also investigated. The results were as follows:
1) The first 10ml water which was taken before clinical application had 2.6-57.5×10³ CFU/ml. The number of bacteria was reduced with the amount of water displacement.
2) Residual chlorine in the first 10ml water could not be found under the limits of the detective procedure. Only one of ten samples after 210ml displacement cleared the guideline of quality after 210ml displacement.
3) The predictive value of displacement need was 50-434ml. The average of direct water supply was 278ml and indirect water supply was 332ml.
4) There was no significant difference between the number of bacteria and the predictive value of displacement need according to the difference of water supply system.
5) Nine kinds of bacteria were found in the samples and all of them were non glucose fermentive gram-negative bacteria.

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The aim of the present study was to elucidate the role of masticatory ability in maintaining the quality of life in the elderly.
Masticatory ability was evaluated by the test jelly method and self-assessment. The life-related factors assessed were grip strength, quickness and equilibrium as physical activities, and the TMIG Index of Competence that was designed to measure Instrumental Self-maintenance, Intellectual Competence and Social Role as high-level competence.
The results were the following.
1) The group who kept their masticatory ability also retained grip strength and quickness. Regarding equilibrium, there was no relation to masticatory ability; this might be due to the fact that most subjects in this study had the stable mandibular position because of prosthetic treatments.
2) Keeping the masticatory ability was related to performing Social Role in the TMIG Index of Competence. This result might indicate that masticatory ability takes part in maintaining the social contacts which affect mental and physical health of the elderly.

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The effect of a fluoride slow-releasing device (FRD) on early caries lesion in human root dentine was studied using an intraoral device.
A total of 21 adults aged 22-25 years old were subjected to the use of fluoride slow-releasing sealant (Teethmate-F, Kuraray) as an FRD in this study. A total of 42 demineralized root dentine samples with or without sealant were mounted on the buccal surfaces of the upper first molars of subjects. After 7 days, samples were removed from oral cavities and were ground to the thickness of 120μm for microradiography. For lesion area in all microradiographs, lesion depth (Ld; μm) and mineral loss (ΔZa; ETa·μm) were measured by videodensitometry. Baseline data was also obtained from areas covered with acid resistant varnish before intraoral experiments.
Mean Ld values were 55.7±4.3μm (±S.D.) at baseline, 58.2±10.7μm for the specimens with sealant (FRD group) and 65.3±15.5μm for specimens without sealant (control group). Mean values of ΔZa were 3, 670±527 ETa·μm at baseline, 4, 733±1, 355 ETa·μm for the FRD group, and 5, 569±1, 490 ETa·μm for the control group. Statistically significant differences (p<0.05) were detected only between baseline and the control group for both measurements. Most of the samples in the FRD group, however, had lower ΔZa than those in the control group and remineralization was observed in some specimens in the FRD group. These findings suggest that FRD has possibility to inhibit progression of early caries lesions on root surfaces.

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Masticatory functions must be considered from infant to the aged because of their importance in eating functions. Especially, improvement of eating functions is desired for aged and handicapped persons from the viewpoint of quality of life.
Therefore, we carried out the oral examination, measurement, and analysis of masticatory performance and occlusal relationship from the point of view of the establishment of masticatory ability in the developing child.
Subjects of our investigation were 513 elementary school children (249 males, 264 females) and 387 junior high school children (193 males, 194 females) in Saitama Prefecture, Japan.
In the oral examination, we counted the current number of teeth, both deciduous and permanent.
Caries conditions were assessed by the criteria of WHO and represented as DMF and df.
The measurement of masticatory ability was carried out by the screening method employing dried peanuts.
Masticatory performance was calculated by the following formula:
Masticatory performance (%)
=Lost weight/Original weight×100
Occlusal conditions were evaluated by accumulated biting force (kg), average biting force (kg/mm2), and occlusal contact area (mm2).
The results obtained were as follows:
1) Masticatory ability tended to be lower among fifth or sixth graders in elementary school.
2) Accumulated biting force and occlusal contact area tended to increase with the school grade, although they were lower for fifth or sixth graders in elementary school.
3) The data suggested that the masticatory ability was related to the number of present teeth, biting force, and occlusal contact area. Our study suggests that the development of masticatory ability should be considered in giving guidance on eating habits to school-aged children.

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In recent years, a remarkable decline in the prevalence of dental caries has been observed in most industrialized countries. The purpose of this study was to examine the changes in caries prevalence among Japanese adolescents. A total of 1387 male students aged 15 to 19 years at a vocational high school in Sendai were examined for both DMFT indices and DMFS indices once yearly from 1975 to 1991. Because irregular yearly variations in those indices among the same age groups were observed, the data were first analyzed by using Chebyshev's orthogonal polynomials. Thus quadratic regression curves with statistical significances were obtained, suggesting that the caries prevalence was increasing and then decreasing for most age groups during the period of this study. Secondly, mean DMFS indices were calculated by the method of 3-year moving average to smooth the year variation. The mean 3-year DMFS numbers (3-DMFS) in the same age groups showed yearly staggered peaks: in 1979 for the 15-year-olds, 1980 for 16-year-olds, 1981 for 17-year-olds, 1982 for 18-year-olds and 1983 for 19-year-olds. After each peak, a statistically significant decrease in caries prevalence was observed in 15- to 18-year-old groups. The 3-DMFS numbers decreased from those at their peak years to those at 1990 as follows: from 13.91 to 11.08 for 15-year-olds, 16.85 to 13.21 for 16-year-olds, 19.17 to 15.26 for 17-year-olds, and 21.02 to 17.97 for 18-year-olds.
The prevalence of dental caries for each age group was also determined by analysis of the separate DS, MS, and FS indices from 1976 to 1990. Significant decreases in DS and MS indices, and significant increases in FS index were observed for all age groups.
Based on the review of both domestic and international trends in caries prevalence in relation to those indicated by this study, a more remarkable decline in caries prevalence among Japanese adolescents is expected to occur in the near future, if the public awareness of oral health is further promoted and various preventive measures with fluoride are more extensively implemented for the reduction of dental caries.

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Of the four levels of salivary mutans streptococci (classes 0-3 by “Strip mutans” test) in primary schoolchildren, class 3 (>10⁶CFU/m^l saliva) was designated as a high caries risk group in our previous report (J. Dent. Hlth., 44; 211, 1994). Data obtained in a one-year longitudinal survey of caries increment in permanent dentition were analysed to find the correlation between salivary levels of mutans streptococci and caries incidence. A total of 198 primary schoolchildren (3rd grade: 104 children, 6th grade: 94 children) was followed up over one year, but 26 subjects without full caries data were excluded for further statistical analyses. Mean caries increments (ΔDT and ΔDMFT) by the salivary levels of mutans streptococci (classes 0-3) were computed from the caries data obtained at both baseline and follow-up examinations. For the 3rd grade schoolchildren, mean numbers of DMFT of class 3 at both baseline and reexamination were statistically higher (p<0.05) than those of classes 0-2. In the 6th grade, similar trends were found between class 3 and class 0 or class 1. ΔDMFT of the 6th grade children in the class 3 mutans streptococci was significantly higher than that of class 0 (P<0.05), while no definite difference in the 3rd grade was found (p=0.10). The results of the present study showed that high levels of mutans streptococci in saliva were associated with high caries incidence and that class 3 was an indicator in selecting a high caries risk group among primary schoolchildren.

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