The objectives of the present study were to clarify the presence or absence of dental decay with some salivary factors possibly responsible for development of decay and, further, to attempt to understand better the relationship between both by using a comparability test and multivariate analysis. The dental status of 198 infants, ranging in age from 1.5 to 3 years was examined. We collected the data of four factors, i, e., salivary pH, salivary buffer capacity, Cario-stat^<[○!R]>, and the df tooth number. The infants were categorized as either having caries or not. Evaluation of the respective salivary factors as a screening test showed that combining the bacterial test and another factor gave better validity over the single test. Using a linear function (discri-minant function) developed from the combination of the salivary pH, the salivary buffer capacity, and bacterial factor (Cariostat^<[○!R]>), we found that the character level of each infant could be plotted in one dimension. The difference in the distribution of discriminant function values between infants with caries and without caries was statistically significant (p<0.05). Using this discriminant function score, infant with a negative score should have a caries risk 3.5 times greater than that of infants with positive functional scores. This means that it is possible to diagnose correctly which children would have a caries-prone oral environment.

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This study was conducted with a questionnaire given to 673 adults workers aged 20 to 59 yrs in the Kanto district of Japan. Age specific surveys were done in 10-yrs groups -24 yrs, 25-34 yrs, 35-44 yrs, 45-54 yrs and 55-59 yrs, and then the lfe-style and health habits of these adults were evaluated with age characteristics. Statistical analysis for these data was performed with ANOVA and Chi-square test. The results were as follows : 1. In the questionnaire item "having some hobby", 30.5 % of the subjects in the 25-34 yrs, age group, and 33.5 % in the 35-44 yr age goup answered "yes". In the item of "having leisure time", 25.7 % in the 25-34 yr, group and 33.5 % in the 35-44 yr group answered "yes". These two age groups had a lower rate than other age groups for these two items. In the item "having reliable friends", 32.3 % in the 35-44 yr group answered "yes". In the item "eating supper with one's family ", 36.5 % in the 25-34 yr group answered "yes". This indicates that these two age groups, 25-34 yrs and 35-44 yrs, have less time to spare in daily life and less social support in comparison with other age groups. 2. In regard to occupational environment, overtime workers were 43.1 % in the 25-34 yr. group. That was the highest rate in all age groups, and in the middle age and older groups, there were fewer overtime workers. In the item "having stress in daily life", 52.8 % of the subjects in the under 24 yr group answered "yes", and 29.1 % in the 55-59 yr group. In the item of "having satisfaction in one's work", the older group showed a higher rate than younger groups. 3. In subjective health status, the rate of subjects who feel health was 71.3 % for 25-34 yrs, 67.7 % for 35-44 yrs, and 69.1 % for 55-59 yrs. Thus 60-70 % of all the persons in this survey feel health in their daily life, and there were no differences among age groups in this item. 4. In regard to heath habits, in the item "eating breakfast every day", 36.1 % answered "yes" in the under 24 yr group, and 65.5 % in the 55-59 yr group. In the item "regularly medical check-up", 2.8 % answered "yes" in the under 24 yr group and 29.1 % in the 55-59 yr group. In these two items, there is a tendency for older subjects to have more check-up than younger subjects. In contrast, the items "smoking", "drinking", "exercise", "weight control", "getting enough sleep", "avoid eating between meals" and "stress" received positive answers from 10-31 % of each age group. 5. The score of health habits, composed of the 9 items "smoking", "drinking", "exercise", "weight control", "getting enough sleep", "eating bteakfast", "avoid eating between meals", "regular medical check-up" and "stress", was 2.1±1.9 for the under 24yr group, and 3.0±2.1 for the 55-59 yr group. The score of health habits in the older group was significantly higher than in the younger group (p<0.05).

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The The aim of this study was to determine the buffering action of saliva on demineralization potential of sucrose and sorbitol solutions. A modified enamel demineralization device was fixed on the buccal surface of the mandibular first molar. Volunteers (n=8) wore the device for 4 days without brushing to accumulate plaque on the enamel surface. After 4 days, the device was removed and each test solution or test solution+saliva were directly applied to plaque in vitro. As test solutions, 10 % sucrose and 10 % sorbitol were used. Thin enamel sections (100 μm) were evaluated for the degree of demineralization by microradiography. The buffering action on the degree of demineralization was marked. But when applied to saliva, the difference between the sorbitol+saliva group and the control group was not statistically significant. The difference between the 10 % sucrose group, the 10 % sorbitol group and the 10 % sucrose+saliva applied group, the 10 % sorbitol+saliva applied group was statistically significant (p<0.01). This investigation suggested that the decrease of demineralization, when applied to saliva, was due to the buffering action of saliva.

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Recently, methods of examination for TMJ disfunction and diseases in youth have become necessary. In this study, we investigated clinical functions and disorders of TMJ such as the maximal mouth opening, TMJ pain, masticatory muscle pain, the smoothness, the deviation of mandible, click sounds and locking at mouth opening, and pain of TMJ when the mandible was in motion or stationary. The inter and intra-differences among three examiners were studied regarding these eight items. Although there were wide differences regarding the smoothness of mouth opening, there was strong apreement regarding the other seven items among the three examiners. From these results, the item about smoothenss of mouth opening seemed to be unsuitable, but the other seven items were good for the inspection of TMJ. In addition, in order to eliminate errors, the criteria for these items must be decided upon among the examiners before inspection of TMJ.

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In order to estimate the relationships between malocclusion indices and dental caries or periodontal disease indices, an epidemiological study of 140 dental college students by oral examination and model impression of the dental arch was undertaken. A stepwise multiple regression analysis was used to find the various indices of dental malocclusion and oral hygiene that have an influence on dental caries and periodontal diseases. These analyses were used to develop models which are useful in explaining caries indices of DFS and PDFS, periodnntal diseases indices of PMA, PI and BOP, as dependent variables, and the dental malocclusion indices of ALD, NMT, HLD, OFI, CRD and DAI, and oral hygiene indices of DI, CI and PCR, as independent variables. These variables were divided into full mouth, maxilla, mandible, anterior of maxilla, and mandible for calculating by the multiple regression analysis. The results of the analysis were as follows : 1) The relationship of malocclusion indices and oral hygiene indices to dental caries indicated that the independent variables (DFS, PDFS multiple correlation coefficient R=.436, .256 p<0.01) associated with the dependent variables, which were ALD, NMT in the full mouth, showed a high significant partial correlation coefficient. On the other hand, oral hygiene indices were not related to dental caries. 2) The relationship of malocclusion indices and oral hygiene indices to periodontal diseases indicated that the independent variables (PMA, PI, BOP multiple correlation coefficient R=.621, .671, .624 p<0.001) associated with the dependent variables, which were NMT and all oral hygiene indices, especially CI, in full mouth, showed a high significant partial correlation coefficient. In addition, in the case of anterior mandible, CRD has a strong influence on the periodontal diseases and showed a high multiple correlation coefficient and a high significant partial correlation coefficient. 3) The relationship of malocclusion to oral hygiene indicated that malocclusion indices were hardly associated with oral hygiene indices.

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The purpose of this study was to devise a method to screen infants and preschool children for teeth predisposed to caries using Cariostat^<[○!R]>, a commercially available test for susceptibility to caries. The subjects were 80 infants and preschool children of both sexes residing in Minoo City, Osaka Prefecture, Japan, who were annually checked on their first and four successive birthdays for their subclinical and clinically evident dental caries at Minoo Dental Healh Center from 1989 onward. The following are the findings. 1. The prevalence rate of clinically evident dental caries and the dmft index at 5 years of age were 30.0 % and 1.25, respectively. 2. Both the number of children having any tooth requiring close periodic observation (children with CO teeth) and the average number of such teeth peaked at 4 years of age. 3. A full 2-year comparative follow-up of 2-year-olds having CO teeth against those without CO teeth or decayed teeth revealed that the former had a higher caries prevalence rate at 5 years of age. 4. Observations in terms of Cariostat^<[○!R]> revealed that caries-free 2-year-olds, who showed increased Cariostat^<[○!R]> values at 3 years of age, showed dmft indexes larger than in any other Cariostat^<[○!R]> value group. These children were found to have a caries prevalence rate of 73.3 % when were 5 years of age. In conclusion, we propose that the presence of pre-caries teeth at the age of 3 and the age-de-pendent transition of Cariostat^<[○!R]> value in a period from 2 to 3 years of age might be used as a predictor of caries appearing at 5 years of age.

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Several studies have reported that aqua oxidizing water (AOW) obtained from conventional tap water by adding a small amount of NaCl has strong bactericidal effects. Some studies have also suggested that AOW is useful in dental practice. It is very important to confirm the safety of AOW for oral soft tissues. The aim of this study was to investigate the bactericidal effects and to clarify the cytotoxity to human adult gingival cells of AOW. S. mutans and E. coli were used for the bactericidal test. The cytotoxity of AOW was estimated by measuring the DNA synthesis of gingival fibroblasts and keratinocytes exposed to AOW, and by measuring the release of LDH activity into the medium from these cells after AOW treatment Undiluted AOW was effective against the two strains tested, and the same effect was observed with 20% AOW (5-fold dilution) treatment for 30 sec. Undiluted AOW strongly inhibited the DNA synthesis of both kinds of gingival cells. The activity of DNA synthesis of gingival cells treated with 20% AOW for 30 sec. was similar to that of cells treated with conventional tap water, There were no differenses of activity of LDH release between 20% AOW treated cells and conventional tap water treated cells. These results suggest that 20% AOW which has bactericidal activity and is not toxic to gingival cells may be useful for dental clinical application.

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The present study was to determine the surface of enamel subsurface lesions ultrastructurally, chemically and thermodynamically by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (ESCA), and the contact angle method. Enamel specimens (3 mm in diameter) were prepared from extracted, caries-free human incisors using a diamond core drill. The surface of enamel specimens was polished with the standard methods. The subsurface lesions were produced by immersing in demineralizing solution for O, 2, 4, 8 and 24 hours at 37℃. The demineralizing solution (pH5.0) was prepared from 0.1M lactic acid, 0.2% calbopol, and 50% saturated hydroxyapatite. The AFM images showed that crystal interspaces were the pathways of acid attack at the surface of subsurface lesions. The AFM crystal images detected remineralized crystals at the parts of the surface of subsurface lesions after demineralization for 4 hours. The remineralized crystals were square and significantly different from the enamel crystals of the controls. These remineralized crystals and crystal interspaces increased at the surface of subsurface lesion with increasing demineralizing periods. Judging from the crystal structure, the remineralized crystals could be brushite. The results of ESCA analysis indicated that Ca/P atomic ratio increased at the surface of subsurface lesions as compared with the controls. The increase of Ca/P atomic ratio depended on the decrease of the P contents at the surface of subsurface lesion. The contact angles of the surface of subsurface lesions were lower than those of the controls. These results indicated that the remineralized crystals were produced on the surface of subsurface lesions. The presence of the remineralized crystals on the surface of subsurface enamel lesion could alter the characterizations of the enamel surface.

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A cariostatic effect of phosphoric acid-acidified ammonium fluoride solution on artificial caries lesion formation was reported previously. The purpose of the present study was to examine the mode of action of this solution on emanel. Intact human enamel was immersed and stirred in three kinds of solution at 37℃ for 1 hour. The three solutions were as follows : (1) phosphoric acidacidified ammmonium fluoride solution - NH_4F group, 900ppmF^-, pH4.5 ; (2) acidulated phosphate fluoride solution - APF group, 900ppmF^-, pH4.5 ; (3) deionized water - control group. Artificial caries lesions were formed with demineralizing solution according to Moreno (1974), consisting of 50 % synthetic hydroxyapatite saturated lactate buffer (pH4.5). Distribution of phosphorus, calcium, and fluoride in enamel were determined with line analysis by EPMA, and state analysis was performed to identify the reaction products in fluoride treated enamel. The enamel surface contained 17.5% F in the NH_4F group, and 14% F in the APF group. The fluoride penetrated deeper into the enamel in the NH_4F group. Only Ca and F were detected in fluoride-treated superflcial enamel by magnified analysis. Ca and F were also detected in the crystal deposits, and a large ammount of calcium fluoride was seen in the NH_4F group and APF group. The state analysis with EPMA showed that the reaction products were calcium fluoride and fluorapatite, and the volume of reaction products was large in the APF group. In state analysis with EPMA, fluorapatite was detected in the caries lesions, and the volume of fluorapatite was high in the fluoride groups. In conclusion, ammonium fluoride solution acted by producing calcium fluoride and fluorapatite on the enamel surface. Then calcium fluoride was released slowly into the demineralizing solution, and reacted with calcium and phosphorus in solution to produce fluorapatite. The greater formation of calcium fluoride and fluorapatite in the NH_4F group and APF group had a higher cariostatic effect than control group.

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