This study was undertaken to investigate the relationship between the number of retained teeth and the masticatory ability of 60- to 70-year-old residents (82 males, 95 females, 177 total subjects) of a city in Gifu Prefecture. The masticatory ability was measured with the peanut method. The results are summarized as follows. 1) The number of retained teeth and the masticatory ability decreased with age. 2) In females, the number of retained teeth decreased more markedly with age compared to that in males. 3) The correlation between the number of retained teeth and the masticatory ability was higher in males than in females. 4) The masticatory ability was high due to the number of retained teeth. Decrease of masticatory ability resulted from the loss of retained teeth. 5) The correlation between the number of retained teeth and masticatory ability was higher in the molars and premolars than in the incisal teeth. 6) The coefficient of correlation in the premolars was the same level as in the molars between the number of teeth retained and the masticatory ability. 7) The masticatory ability decreased more in prosthetic teeth than in natural tooth dentition. 8) Eichner Index was correlated to the masticatory ability in regard to the number of retained teeth and the masticatory ability. 9) In the relation of 1 tooth to 2 teeth, the masticatory ability was higher for a large number of retained teeth than for a large number of prosthetic teeth. It was concluded that for maintaining the masticatory ability in the elderly, prevention of loss of premolar and molar teeth is an important factor.

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This study was performed for characterization of the masticatory test using chewing gum. The number of examinees was 273 male adults in Hokkaido and their age distribution was from 24 to 53 years old. The method of evaluation involved measuring the amount of sugar elution from chewing gum and chewing time during 70 strokes of mastication. We evaluated the relationships among masticatory ability, occlusal areas, occlusal force, and other factors of oral status. The results were as follows: 1. Masticatory ability was related to the number of present teeth, occlusal areas, and occlusal force, in that order. 2. The amount of sugar elution per second was thought to be more effective than the total of amount of that for the evaluation of masticatory ability. 3. This chewing gum method was suggested to be an effective way for the evaluation of masticatory function of examinees who have prosthetics such as removable partial dentures.

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Due to the revised School Health Act of 1995, the contents of the dental examination chart and dental check-up items have undergone substantial changes. Since the revised items now place considerable emphasis on health education, which has always been one of the primary goals, the dental examination is regarded as an effective measure for improving the conventional school health management, which has been heavily biased toward dental check-ups in the past. The authors conducted 3 rounds of a questionnaire by the Delphi method in 171 nurse teachers in Chiba City in order to learn of their opinions and cognition related to the method of promoting oral health education in schoolchildren and their evaluation of dental examination. As a result, responses to an item on the post-check-up activities by the nurse teachers (72.3-83.1%) indicated that their main activity is to communicate with the children's family, largely by exchanging information through health information and other newsletters. More than 50% of the nurse teachers answered that a fluoride mouthrinse system at school was unnecessary because of their lack of satisfactory knowledge or information about fluoride. This rate was stable in each: round of the survey. Concerning the disinfection of the instruments used during dental check-ups, it was indicated that a high proportion (51.8-72.8%) of the subjects had a preference for central management of disinfection and delivery of the instruments. This rate was increased from the first to the second to; the third round of the Delphi survey. The characteristic of the Delphi method in that answers reflect convergent thinking was observed in the following items: evaluation of the revised dental check-up system, introduction of 'questionable caries for observation,' frequency of dental check-ups, desirable disinfection method of dental instruments, activities of school health committee, and cooperation between the school dentist and family dentist. This phenomenon was especially obvious in the item concerning disinfection of the dental instruments.

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The purpose of this study was to determine the percentiles of remaining and sound teeth and to evaluate utilization of the percentile-curves for oral health instruction in office workers. Dental examination was performed on 3,195 males from 23 to 64 years of age and 1,909 females from 20 to 49 years of age in 1992. The 50 th percentile-value of males' remaining teeth was 27 at 40 years and 25 at 60 years. That of the females was 27 at 40 years old. The 50 th percentile-value of males' sound teeth was 15 at 40 years and 13 at 60 years. That of the females was 13 at 40 years old. The 90 th and 97 th percentile-curves of males' remaining teeth fell under 20 teeth after 55 years of age. The 75 th percentile-curve of males' and females' remaining teeth in the survey was equal to the 50 th percentile-curve drawn by the survey of the Tokyo Metropolitan Government (Oral Health Status of Adult Population in Tokyo). Oral health status of these subjects was better than that of the population in Tokyo. Substantial agreement between the oral examination and self-reported questionnaire was 44% in remaining teeth and 13% in sound teeth. This result shows that oral health professionals' advice is needed for understanding of percentile-curves of sound teeth. These results suggested that the percentile-curves of remaining teeth were not only useful indicators for assessment of the population, but also of visual utility for individual oral health instruction in office workers.

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Fluoride has been used for caries prevention in various ways, but it should be applied in an adequate and effective amount to teeth before the caries risk reaches a high level. The purpose of this study was to investigate the potential of glass ionomer cement as a means of topical fluoride application. The fluoride uptake by the enamel surface was measured in vitro. Experimental glass ionomer cement that enhances fluoride release was newly manufactured (GC Co., Tokyo). Twenty extracted caries-free human maxillary first molars were used for analysis. Windows of enamel of about 3 mm diameter were left uncovered, and the other surfaces were masked with nail varnish, and then glass ionomer cement was applied on two different sites (mesio-buccal, distobuccal). After 1 day, 1 week, 1 month, or 3 months had passed, the glass ionomer cement was mechanically removed, and the exposed enamel was sampled by dissolving it in 2μl of 0.5M perchloric acid for 60 seconds for four successive layers. The amount of fluoride and calcium in the sampled solution was determined with specific electrodes. As a result, the fluoride concentration was higher in the enamel that had been in contact with the glass ionomer cement than in that without contact. These results suggest that cement may contribute to caries prevention when used as a topical fluoride application.

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The purpose of this paper is to evaluate the caries preventive effectiveness of a school-based fluoride mouthrinsing program (FMR) as to whether it can improve the prevalence of dental caries in permanent teeth even in an era of declining dental caries prevalence. Subjects were junior high school children in a fluoride-deficient community in Wakayama Prefecture, Japan. In December 1994, 3 dentists screened the children for dental caries in permanent teeth (Kappa value=0.88-0.97), as well as plaque, calculus, and gingivitis in restricted positions of permanent dentition. The F group, in which the children had been participating in FMR in elementary school for 6 years, had a statistically lower prevalence of dental caries (n=211, 50.7% with DMF, mean DMFT=1.56) than the R group, which had less than a year of experience in participating in FMR in elementary school, as a reference group (n=144, 74.3% with DMF, mean DMFT=3.13). A univariate analysis showed that children whose plaque covered more than one third of the labial surface from the cervical portion on the central incisor of the right upper jaw (plaque grade≧1) had a statistically higher prevalence of dental caries than those with no plaque (plaque grade=0). However, multivariate logistic regression analysis failed to indicate that the plaque grade had a significant impact on the prevalence of dental caries, while the groups (the F group and R group) and year of junior high school showed a statistically significant influence on it. The plaque grade, deposition of calculus on lingual surfaces of lower anterior teeth, and gingivitis in upper and lower anterior teeth in the F group were more favorable than those in the R group, and only the plaque grade was statistically significant. In conclusion, it is disclosed that FMR has reduced the prevalence of dental caries and that the program has had preventive effectiveness for dental caries in a non-fluoridated community in an era of declining dental caries prevalence among schoolchldren.

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We developed a community-based preventive program for high-risk children with regard to the prevalence of dental caries in deciduous teeth. The program consisted mainly of topical fluoride application. The survey to evaluate the program was conducted from April 1990 through March 1994. The subjects were 1,954 children who participated in dental examinations at both 1.5 and 3.5 years of age. They were divided randomly into 2 groups (i. e, Test group and Control group) on the dental examinations at 1.5 years of age. In addition to this, each group was further divided into 2 groups with a discriminant function of screening high-risk children. In other words, the subjects were divided into 4 groups of Test-High group, Test-Low group, Control-High group, and Control-Low group. The Test-High group was recalled at intervals of 3 months, and the other 3 groups were recalled at intervals of 6 months. The Test-High group was informed of the time of next participation in the program by a postcard. The Test-High group experienced a 33.7% lower dmfs increment for 2 years (Δdmfs) than the Control-High group, with statistical significance (p<0.001). The test group experienced a 16.8% lower Δdmfs than the control group, with statistical significance (p < 0.01). There was no significant difference of Δdmfs between the Test-High group and the Test-Low group. These findings suggest that the program for high-risk children contributed to the reduction of caries incidence and that, as a result, the total amount of deciduous caries in 1.5 to 3.5-year-old children can be significantly reduced at the community level.

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The aim of this study was to assess the usefulness of image calculation for crystallo-graphic identification of enamel by High Resolution Electron Microscopy (HREM). Human sound enamel and remineralized enamel samples were observed by HREM and the obtained lattice fringes of the experimental HREM images were compared with JCPDS (Joint Committee of Powdered Diffraction Society) data and estimated possible crystals. Estimated crystals were hydroxyapatite (HAP) for sound enamel and tetracalcium diphosphate monoxide (TTCP) for remineralized enamel. Estimated crystals were calculated for HREM image simulation. Simulated images of both HAP and TTCP were completely consistent with the experimental HREM images of sound and remineralized enamel, respectively. Therefore, it is suggested that using image calculation together with HREM is a definitive method for enamel crystalloeraphic analysis.

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This cross-sectional study investigated factors related to dental caries prevalence in a low caries group. The subjects consisted of 89 schoolchildren aged 12 years. The children had participated in a fluoride mouth rinse program since 5 years of age at nursery schools. Furthermore, pit and fissure sealants were applied to teeth with sticky fissures when detected at dental check-ups twice a year. Clinical examinations were conducted to obtain data on caries prevalence (dfs and DMFS). The salivary level of mutans streptococci, the salivary level of lactobacilli, and the acid production by bacteria in the plaque were measured using Dentocult SM Strip ® , Dentocult LB Dip Slide ® , and Cariostat ® , respectively. In addition, we obtained information on gender, sum of permanent tooth surfaces sealed, toothbrushing frequency, sweet snack frequency, sweet drink frequency, use of fluoridated toothpaste, and stimulated salivary flow rate. Stepwise backward logistic multiple regression analysis was used to estimate the relationship between caries prevalence and 11 total independent variables. Furthermore, we obtained information about some reasonable linear discriminators that could identify subjects with high caries experience using the final logistic multiple regression model. Thereafter, we calculated sensitivity, specificity, and Youden's index according to the classification table. As the results of stepwise backward logistic multiple regression analysis, three variables (number of sealants, the level of Cariostat R , and frequency of sweet snacks) were selected as independent variables in the final model. The level of CariostatR showed the highest odds ratio (Odds ratio : 6.87, p=0.02). The cutpoints at which Youden's index showed the highest value, sensitivity, and specificity were 76.9% and 75.7%, respectively. According to these findings, it is safe to say that we could propose that the plaque level of Cariostat ® might be the most important variable related to caries prevalence.

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The purpose of this study is to evaluate the influence of passive immunization with egg-yolk immunoglobulin (IgY) on inhibition of streptococcal adherence. Two experiments were designed. In the first experiment for the influence of IgY on initial attachment of mutans streptococci to hydroxyapatite beads (HAp: φ0.3〜0.6mm), the amounts of bacteria were measured by spectrophotometer in four kinds of solutions : solutions of specific IgY to S. mutans MT 8148, specific IgY to S. sobrinus 6715, nonspecific IgY, and without IgY. In the second experiment for the influence of IgY on sucrose-dependent adherence of mutans streptococci to silver wire (φ0.8 mm), the amounts of bacteria were measured by spectrophotometer under the condition of sucrose-contained culture in various IgY solutions. Specific IgY to S. mutans MT 8148 prevented the initial attachment of mutans streptococci, which had similar immunity characteristics to S. mutans MT8148. On the other hand, specific IgY toS. sobrinus 6715 did not inhibit initial attachment of mutans streptococci, but inhibited sucrose-dependent adherence of mutans streptococci. It is implied that specific IgY to S. sobrinus 6715 did not bind to the serotype-specific antigen on the surface of mutans streptococci, but did to the insoluble glucan surrounding the cell surface of mutans streptococci. These results suggested the possibilities of preventing dental plaque accumulation by IgY.

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This study was undertaken to explore questionnaire research of dental behavior on the Internet. The results were analyzed regarding characteristics of the subject groups and dental behaviors, and compared with Japanese governmental statistics (the number of toothbrushing times per day, periodical dental examination, and use of oral care instruments). The results were as follows I the number of subjects as 2,637, the male-to-female ratio was about even, and the number of subjects was proportional to the area distribution, although it involved more subjects from 20 years old to 40 years old. The average of the Internet users' dental behavior as better than that of the government statistics. The results showed that we can ask questions and obtain answers with the Internet widely, easily, quickly, and at a low cost, and that Internet users tend to have better dental behavior.

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