The purpose of this study was to toothbrushing force and toothbrushing pressure are insufficient, the toothbrushing effect is unsatisfactory. However, when too strong, damage can be caused to teeth and periodontal tissue. Distinction needs to be made by defining that toothbrushing force which is a force applied overall to the brush head, and toothbrushing pressure which is pressure per unit area where the toothbrush touches the tooth directly, we calculated toothbrushing pressure from toothbrushing force. The subjects of research were 20 children aged between four and six, and 20 adults aged between 23 and 42, with no abnormality in the occlusion and periodontal tissue. By using a manual toothbrush and three types of electric toothbrush, a front and back movement type, a rolling type and a special movement type, toothbrushing force and toothbrushing pressure were measured. 1) With toothbrushing force, the manual showed the highest value for both adults and children, followed by the front and back movement type and the rolling type showed the lowest value. Meanwhile, in contrast to brushing force, the value was highest with the special movement type, followed by the front and back type, the rolling type and the manual toothbrush were close to each other. 2) Compared to adults, toothbrushing force and toothbrushing pressure were relatively low with children. 3) The fact that toothbrushing pressure can be high even when toothbrushing force is weak, indicates that in future it will be necessary to make a study by checking both toothbrushing force and toothbrushing pressure.

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In this study, we conducted an epidemiological survey of TMJ disfunction and disease using 5 anamnestic and 7 clinical items. The subjects were 1,873 students aged 12-24. The percentage of positive answers indicating symptoms was 20.4%. The main symptoms were click sounds (16.1%), restricted opening (6 .7%), and TMJ pains during jaw motion (6.l%). These positive answers were significantly more common in females than in males. The symptoms did not increase with age. Complex symptoms were more common in female students aged 18-24 than in males. 175 stubents (10.7%) had clinically observable signs. Click sounds (3.3%) and restriction of mouth opening (2.4%) were frequent. The clinically observable signs did not increase with age. The percentage of positive signs 18-24 age group was 13.5%. 458 students (24.5%) had symptoms or signs, but most of them were mild cases. Students who had complex symptoms, pain during movement of the mandible, or locking of the mouth opening were only 0.7% of the total.

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Oral health behavior, such as tooth cleaning, food intake, and social functions, is essential to one's daily life and to promote growth and development from birth to adult. The aim of this study was to assess of age characteristics of adult population in regard to oral health behavior. This survey was caried out from May to July in 1994 with a questionnaire survey for 673 adult workors aged 20 to 59 yrs in the Kanto district of Japan. The age groups were -24 yrs, 25-34 yrs, 35-44 yrs, 45-54 yrs, and 55-59 yrs. Attitudes and oral health behavior were evaluated for each age group. Statistical analysis for these data was performed with ANOVA and Chi-square test. Three items in the questionnaire (talking about oral health in one's daily life, interest in health information in newspaper colums, and the frequency of observation of one's oral health status) reflected the intensity of the interest in oral health. The interest in oral health in middle age was greater than in young adults. For the items of face and mouth apperance and chewing ability in relation to self assessment, 10-20% of the subjects under 24 yrs, and 20-30% of the 55-59-year group reported themselves relatively satisfied. In regard to the recognition of terms related to oral health, more than 50% of subjects of all age groups knew the 3 terms "dental calculus", "dental plaque", and "gum disease". These words indicated that periodontal disease was relatively well known to these adults. Tooth cleaning in young adults was more common in practice in daily life than in the middle age population. On the other hand, acceptance of dental visits and regular dental checks for young adults were less than in the middle age population. These results suggested that age was a key factor in attitudes toward oral health, and that oral health preservation also played an important role for general health promotion throughout life.

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Demineralized enamel grooves were exposed to an acid gel at pH=5 for 3 weeks after irradiation with a KrF excimer laser with a wavelength of 248 nm (total energy dose = 172 J/cm^2) or with the second harmonic wave of a Q-switched Nd : YAG laser with a wavelength of 532 nm (total energy dose=100 J/cm^2). The mineral distributions were assessed quantitatively by transversal microradiography. Compared with unlased controls, the mineral parameters, i.e., the lesion depth (l_d, μm) and the mineral loss value (ΔZ, vol%・μm) at the bottom of the grooves were not really different in the samples irradiated by either the pulsed excimer or the Nd : YAG laser, and a similar result was observed in the outer enamel surfaces near the grooves. This suggest that progression of demineralization in enamel lesions is not inhibited effectively by laser irradiation.

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This study was undertaken to discover whether retained tooth numbers according to individual lifestyles among different generations of 60 to 80-year-old persons. The subjects were 319 elderly persons living in Tokoname City and Yamaoka-cho in Japan. The subjects were surveyed using a questionnaire on past individual lifestyle and oral health condition inspected by dentists. The results are as follows. The past individual lifestyles were divided into two kinds : one had consistent or common factors, and the other not, among 80, 70, and 60-year-old generations. The common factors were being well-disciplined as children, liking sweets at the age of 20, gum swelling and tooth brushing frequency at the age of 60 in male subjects, and gum swelling at the age of 40 and 60 in females. On the other hand, the factors of bleeding from the gums at the age of 20, frequency of snack intake and having a home dentist at the age of 40 were more important for 60-and 70 year-old moles than for 80-year-old males and the factors of brushing frequency as children was more important in 80-and 70-year-old femoles than in 60-year-old females and the factors of liking sweets at the age of 60 was more important in 60-and 70-year-old females than in 80-year-old females.

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In order to identify the distribution of dust grain sizes in a dental hospital and to estimate the relationship between the distribution of dust and airborne bacteria or environmental factors, measurements were carried out in the middle-size clinics (pedodontics and orthodontics) and the large clinics (restoration and prosthetics) at Asahi University Dental Hospital for two years (1994 and 1995). We measured dust grain sizes of 0.3, 0.5, 1.0, 2.0, above 5.0μm, airborne bacteria with an SY type pinhole sampler method and Koch's dropping method, and environmental factors (temperature, humidity, air flow, and number of persons, opened windows, and functioning outlets air-conditioning). Correlation between the distribution of each dust grain size and each measured factor was analysed. The estimation of airborne bacteria colonies was performed with the environmental factors and/or dust factor by multipule regression analysis, and the effect of addition of a dust factor was evaluated. The following results were obtained : 1. Total dust (above 0.3 μm) was higher inside the clinics than outdoors, and showed a tendency to be high during working times. 2. More than 98% of dust grains were 0.3-1.0 μm, but large grains of above 5.0 μm were found at a higher rate inside the clinics than outdoors. 3. A high correlation was obtained between dust of under 2.0 μm and floating airborne bacteria, and between dust of above 2.0 μm and dropping airborne bacteria. 4. The factor of operating air-conditioning had a high negative correlation to dust factor, and it was recognized that air-conditioning decreased the dust in clinics. 5. The estimated accuracy of airborne bacteria colonies by multipule regression analysis was increased by adding the dust factor to the environmental factors. As a result, we recognize that large dust grains float in dental clinics and increasing dust volume increases the airborne bacteria. The measurement of dust is useful to estimate airborne bacteria colonies in real time, and is useful for simple air pollution monitoring.

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The effectiveness of electric toothbrushes on plaque removal was tested using dental models and artificial dental plaque. Nine electric toothbrushes presently on the market were selected for the experiment. Artificial dental plaque was applied to dental models and 10 students brushed the models with electric toothbrushes and a manual toothbrush. Although the sequence of brushing the model was fixed, the brushing time was not restricted. The time required to remove the plaque completely was measured for each toothbrush. The brushing time was compared among the electric toothbrushes and with the manual toothbrush to assess the efficacy of the electric toothbrushes. The results showed that the time required to remove the artificial plaque were equal or shorter than manual toothbrush. There were statistically significant differences among the electric toothbrushes on plaque removal. Counter-rotational movement and vibration of the bristles were more efficacious than the other types of movement in removing the artificial plaque. We showed that the types of movement but not the speed of the bristles were important factors in considering the efficaciousness of the electric toothbrushes.

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The purpose of this study was to evaluate the retention rate of pit and fissure sealant on permanent 1st molars considered at high caries risk for 6 months up to 3 years. A total of 156 pits and fissures were screened according to 4 indices ; sticky fissure, occlusal plaque level, occlusal status and age. We sealed teeth with resin in 356 primary school children (1st-3rd grades ; 6-9 years old) who had been a school-hased fluoride mouthrinsing program since the age of 4. Retention rates were 75.9-100%, 69.0-96.8% and 58.6% after 6 months, 2 years, and 3 years, respectively. Salivary contamination during operation was the major reason for failure (lower percentages described above) according to multiple regression analysis. For 22 pits and fissures where sealants dropped out, re-sealing was conducted at regular check-ups twice a year. Dental caries was observed in only 4 pits and fissures out of 156 during the survey period. These results suggested that higher retention rate could be obtained by effective cleaning and preventing salivary contamination, even for sticky fissures which were considered at high caries risk.

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The purpose of this study was to evaluate the cariogenic potential of the permanent teeth by analyzing the caries occurrence at 3 years of age and in the 6th grade of elementary school of the same subject, in a retrospective cohort study. One hundred and sixteen elementary school children in the 6th grade were chosen, whose caries data at 3 years could be obtained from the data file at the regional health center. Eight factors considered to have influence on the caries incidence of the permanent teeth were selected as explanatory variables from a questionnaire concerning life style and analyzed using Quantification Type I analysis. The multiple correlation coefficient was 0.287. When the other factor, caries attack pattern of the deciduous teeth, was added to the explanatory variables, the multiple correlation coefficient increased to 0.355. The caries attack pattern of deciduous teeth showed the strongest influence on the caries of permanent teeth (the partial correlation coefficient =0.181). No interrelation was found in other explanatory variables. These results suggest that the caries prevalence in childhood could be implicated in the caries incidence of permanent teeth.

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Fluoride prevents surface caries, but information about the prevention of fissure caries is limited. The purpose of this study was to investigate the effect of topical fluoride application on fissure caries produced in vitro. Ten artificial fissure models made of pairs of bovine enamel slices were inoculated with mutans streptococci and incubated in MSB broth at 37℃. After one week of incubation, five specimens were exposed to acidulated phosphate fluoride solution (APF, 0.9% F) for 4 minutes as the APF (+) group, and other specimens were not as the APF (-) group. A group of five specimens incubated without mutans streptococci served as controls. All theree groups were further incubated for three more weeks. After incubation, the fissuses were probed with a dental explorer and the adhesive forces due to "sticky fissures" were measured with an electric weighing system. One hundred μm sections of undemineralized enamel were obtained from each fissure block and subjected to light photography and microradiography. The depth of lost surface enamel was measured on the photographs. The surfaces of fissures after probing were examined with a scanning electron microscopy (SEM). The differences of the average adhesive forces in the APF (+), the APF (-) and the controls were not significant. However, the mean depth of lost enamel in the APF (+) group was significantly smaller than that in the APF (-) group. Breakdown of surface enamel was observed in all groups by microradiography and SEM. The results suggest that topical fluoride application significantly inhibits enamel loss in this fissure caries model and that surface enamel is destroyed by probing.

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