Overdenture abutment teeth are susceptible to periodontal disease or dental caries because of poor oral hygiene. Very little is known about the effects of the shape of the abutment teeth on plaque control. To study this, we made a simulator whose basic structure was a cantilever made from a phosphor bronze square bar with strain gages. Device-1 could detect lateral and vertical forces applied to the bristles of a toothbrush. Device-2 could detect lateral and vertical forces exerted on an abutment tooth model. Device-2 could change the tooth model which was a column with a taper angle of 0°,10°,20°,30°, and 40° and a height of 0.5, 1.0, 1.5, and 2.0 mm, respectively. The measured error of both devices was less than 5%. Ten subjects, 22 to 45 years (average : 34 years) contributed to this experiment. Brushing forces were continuously monitored with a signal processor 7T-18A (Nippon-denki-sanei, Ltd.) and transferred to a Macintosh (Apple Computer, Inc.) during brushing of the model with the Bass' method by the subjects. The results of experiment showed that the forces exerted on the tooth model significantly increased, but not the forces exerted on the toothbrush, when the height of the tooth model increased or the taper angle decreased. Brushing force differed significantly among individuals. To detect the cervical area of tooth with a toothbrush for removal of dental plaque, the abutment tooth may have to be at least 1.5mm in height and should have a small or no taper angle.

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Dental Checker^[○!R](KAITEC Co., Tokyo) is a computer program for assessing dental health knowledge, attitudes, behavior, life environment, willingness and disease symptoms. In this paper the interest was focused on analyzing answers to the 60 questions of the Dental Checker. Answers were obtained from 77,440 Japanese adults. The results were as follows. 1. More than two third of those surveyed (68.8%) answered that they did not know the total number of an adult's teeth. About half of the subjects believed that a toothpaste with fluoride was effective in preventing periodontitis (49.2%). 2. Most of those surveyed (90.9%) felt that "periodontitis is a serious disease." More than half of the subjects (53.3%) reported a belief that they may eventually require false teeth. 3. Nearly half reported that they "clean their teeth before going to bed no matter how tired they are"(45.8%), and that they "renew their toothbrush at least once a month" (45.1%). Furthermore, 78.0 percent of the subjects answered that they did not feel comfortable brushing their teeth without toothpaste. On the other hand, less than 3 percent reported regular flossing. The majority (81.3%) reported not using dental floss at all. 4. The most frequent oral symptoms were bleeding gums and food impaction between teeth (72.9% and 70.6% respectively). Far behind food impaction between teeth were enlarged spaces between teeth (46.9%), and reduced chewing ability (37.6%). However, 44.9% of the respondents agreed with the statement that they are too busy to go to the dentist. 5. More than half of the subjects wished for the highest level of dental treatment even if it was expensive (53.8%). On the other hand, the percentage of those "going to see the dentist regularly" was only 4.7 nercent. It can therefore be recommended that the ongoing oral health education should strive to provide employees with proper information about oral health, and with the appropriate items such as dental floss for cleaning spaces between teeth.

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The aim of this study was to assess the validity of self-reported number of missing teeth. Subjective tooth loss was determined by respondents' reports of the number of missing teeth. The validity of respondents' report was assessed by comparing the reported number to the number determined by actual clinical examination. The results were as follows. 1. The actual number of missing teeth was significantly associated with age (r=0.397, n=145 ; p<0.001), but could not be estimated by age. 2 . Reported and actual number of missing teeth had a nearly curvilinear relationship represented by a quadratic function (R=0.832, n=137 ; p<0.001). A slight tendency towards underreporting of tooth loss was found for individuals with a moderate level of missing teeth. 3. The disagreement between the clinical examination and the self-assessment depended on age group, but not on gender. The validity of self-reported number of missing teeth was high in this adult group. The results suggest that the self-reporting of tooth loss may be useful for the promotion of the 8020 movement proposed by the Ministry of Health and Welfare's Study Group on Dental Health Measures for Adults.

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A new toothbrushing technique named the Toothpick method was compared with the Bass method in respect to the gingival massage effect. Twenty-four male students with experimental gingivitis participated. After 14-day plaque accumulation (day 0), two quadrants of all the subjects were brushed professionally using the Toothpick method. The 2 remaining quadrants were given professional toothbrushing using the Bass method followed by professional flossing. After staining the dental plaque, trained dentists brushed the quadrants by the assigned methods once daily for the following 21 days. The students suspended their own oral hygiene procedures during the experiment. Blind examiners assessed the clinical and cytological parameters. On day 21, the percentage of sites with bleeding on probing was significantly lower in the quadrants brushed using the Toothpick method than those using the other procedure. The percentage of highly keratinized cells of gingival papillary epithelium increased significantly in the quadrants brushed with the Toothpick method. The time for the Toothpick method was shorter than that for the Bass method and flossing. It was concluded that the Toothpick method may provide added benefits resulting from gingival massage in a short time.

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The aim of this study was to improve the working conditions of dental hygienists in municipalities in Chiba Prefecture. This survey was carried out with a questionnaire for 25 municipalities where dental hygienists worked. Items of the questionnaire about mothers' classes which were carried out in the 25 municipalities from April 1995 to March 1996, were as follows : (1)grasping of community character, (2)establishing of goals, (3)planning and budget, (4)enforcement, (5)analysis, and (6)evaluation. We investigated whether these activities were participated in by dental hygienists. Municipalities in which (1)grasping of community character, (2)establishing of goals, (3)planningand budget, (4)enforcement, (5)analysis, and (6)evaluation were carried out, used dental hygienists for these activities.

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The purpose of this dental survey was to clarify the characteristics of oral health conditions in Nagasaki and Yamagata Prefectures in Japan and to use the results to benefit oral health plans. The number of subjects for the oral examination and the questionnaire were 4,253 and 6,122, respectively. The average number of permanent tooth in persons 50 years old and above in Nagasaki was significant less than in Yamagata. The average in remote places such as isolated islands in Nagasaki and isolated places among mountains in Yamagata was less than that in other districts in each prefecture. DMFT-indices in 12 year olds of Nagasaki, Yamagata and Japan as a whole were 5.62, 4.42, and 3.64, respectively. The main persons taking care of preschool children in the daytime were nursery teachers (39.6%), mothers (35.5%) and grandparents (10.1%)in Nagasaki and mothers (33.3%), grandparents (33.3%) and nursery teachers (28.8%) in Yamagata. About 90% of guardians of these infants regarded tooth brushing as an important method for dental caries prevention and the rate of those who selected fluoride application or periodic oral checks were only 10〜15% and 30%, respectively. Only 26〜36% of adults received sufficient explanation for their own periodontal treatments from their dentists. Twenty to thirty-eight percentage of adults desired their dentists to check their oral health periodically and to give them more information and advice on their oral health.

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Professional topical fluoride application is an effective caries preventive measure performed by dentists or dental hygienists. However, the decreasing availability of the application trays which have been widely used and transferring of responsibility for the dental health care program for mothers and children to municipalities may affect the professional topical fluoride program at health centers. To clarify the situations and problems concerning the professional topical fluoride programs, a questionnaire was sent to health centers throughout the country. There sults provide an important basis for the future plans regarding the professional topical fluoride program. In the middle of January, 1993, we sent the questionnaire by mail to 946 health centers who were asked to send back the responses within 2 months. We received responses from 77.6% of the health centers that had received the questionnaire, of which 43.7% were conducting the program at the time of the survey. 3.2% had discontinued the program, and 53.0% had never undertaken the program. Of the health centers that were conducting the program. 59.0% were using acidulated phosphate fluoride solutions, 30.7% sodium fluoride solution, and 24.2% acidulated phosphate fluoride gel. For application of fluoride, the complicated paint on technique was most commonly used (78.2%), follwed by the iontophoresis technique (30.5%), the tray technique (7.8%), and the toothbrush technique (4.9%). The health centers that were actively conducting educational campaigns on the program or health instructions on the use of fluoride had been performing larger-scale applications over longer time periods than others. The reasons for discontinuation of the program were loss of dental experts (22.7%), lack of time(18.2%), transfer of the program to the dental association (18.2%), changes to other preventive measures (13.6%), discontinuation of the budget (9.1%), transfer of the program to the municipalities (9.1%), and failure to prove the preventive effect (9.1%). The reasons for not undertaking the program were lack of sufficient equipment, personnel, or time (39.2%), lack of budgets (20.9%), because the municipalities were conducting on the program (21.2%), because the dental association were conducting on the program (8.0%), presence of opposition movements (6.4%), because these health centers placed emphasis on educational programs or health instruction on subjects other than use of fluoride (6.1%), and lack of conviction regarding the preventive effect (5.5%).

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It is important to improve dietary habits to prevent dental caries. To estimate sugar intake for evaluating caries risk is very valuable to prevent dental caries. Questionnaires are used for estimating sugar intake, but this is not an objective method. We investigated sucrase activity in saliva to estimate sugar intake. Sucrase is produced by bacteria in saliva. Our intention was to estimate sugar intake objectively by analysis of sucrase activity in saliva. Subjects were 65 males and 107 females. We investigated methods of measuring sucrase activity and the relationship between the activity and sugar intake. The results were as follows : 1. Sucrase activity was measured by adding 100 mg of sucrose to 1ml of whole saliva and incubating it at 37℃ for about 90 minutes. 2. Comparing fresh and preserved saliva samples, sucrase activity was not significantly different. 3. Frequent habitual use of sugar had significant correlation to sucrase activity. 4. Using factor analysis, sucrase activity was separated from bacterial factors and host factors and it seems to be a diet factor.

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There are five deciduous dental caries types in 18-month-old children ; types O_1, O_2,A, B, C, and type O which indicates children with no dental caries. The purpose of this study was to investigate the possibility of the distinction between types O_1 and O_2 as a screening criterion to choose high-risk children. First we used a questionnaire to get information on present screening conditions. The health department of 44 municipalities in Tokyo replied (Response rate : 80%). The following results were obtained. 1. 19 municipalities (43.2%) had their own criteria for screening types O_1 and O_2. 2. In 22 municipalities (40.0%) type O_2 accounted for more than 80% of all the caries types in 18-month-old children in 1994. 3. There was no significant correlation between the occurrence of type O_2 and the caries prevalence increase from 18-month-old to 3-year-old children in municipalities. Those results suggested that it is necessary to develop a new screening criterion for type O. Therefore we planned a second project to investigate the risk factors related to the increase indental caries between 18 months and 3 years. The subjects were 630 3-year-old children in 1995 (330 in city S of Tokyo and 300 in city I of Hokkaido). The factors we used were "breast or bottle feeding at night," "frequency of eating sweet food," "frequency of drinking sweet beverages," "tooth brushing with guardians' help," and "plaque score on the labial surfaces of the upper incisors." The following results were obtained. 4. The factors of "eating sweet foods every day" (p<0.01) and "breast or bottle feeding at night"(p<0.05) were related significantly to the caries increase. 5. The factor of "drinking sweet beverages every day" showed a similar tendency. 6. The habit of "tooth brushing with guardians' help" and "plaque score" were not significant risk factors for caries increase. From these results, it was concluded that the factors of "breast or bottle feeding at night," "eating sweet foods every day" and "drinking sweet beverages every day" were the risk factors for caries incidence and that it would be preferable to introduce these three factors as a new screening criteria for O_2 types in 18-month-old children.

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Two or more sites to which the environmental factors such as flow of saliva and foods, plaque accumulation, or enamel wear are required to determine the time-dependent changes of fluoride concentration in enamel surface through the post-eruptive maturation in young permanent teeth. Therefore we measured the fluoride concentrations using the micro-sampling technique at mesio-labial and disto-labial sites in enamel surfaces of 15 permanent lower central incisors extracted for reasons of severe periodontitis. We determined the mean fluoride concentration curves at two different sites in labial enamel surface of matured permanent lower central incisors, and found that there were no significant differences between the fluoride concentrations at these two sites at any depth from 1.0 to 20.0μm. These results suggest that difference between the influences of the environmental factors affecting the mesio-labial and disto-labial sites in enamel surfaces of permanent lower central incisors is negligible.

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The purpose of this study was to judge whether the influence of dental health plans in municipalities on decline in caries prevalences in deciduous teeth of infants and promotion of dental health knowledge and behavior of mothers are stronger than the influence of community characteristics or not. Fifteen factors concerning community characteristics and eight factors concerning dental health plans in each municipality considered to have influence on the caries prevalence in 3-year-olds and the dental health knowledge and behavior of the mothers of 4 or 5-year-olds in Shizuoka Prefecture were selected as explanatory variables and analyzed using multiple regression analysis. A lower prevalence of caries was found in infants living in cities where families were larger and a higher proportion of mothers did not work. The health plans in municipalities, such as dentists and dental hygienists engaged in the health division, dental health congresses, dental health plans, evaluation of dental health activities for pregnant women and infants, dental health activities for pregnant women, health education by dentists or dental hygienists for the mothers of 1.5-year-olds, dental health activities for infants other than 1.5-year-olds, and fluoride applications did not have any influence on decline in the caries prevalence in deciduous teeth. Better dental health knowledge and behavior was found in mothers living in a municipality with more dental health activities for pregnant women, more health centers per capita, and more health nurses per caoita. We suggest that two plans in municipalities, namely dental health activities for pregnant women and fluoride applications, promote dental health knowledge and behavior in mothers. These results suggest that the influence of some dental health plans in municipalities on promotion of dental health knowledge and behavior of mothers are stronger than the influence of community characteristics, but that the influence of all plans on decline in caries prevalence indeciduous teeth of infants are weaker than the influence of community characteristics.

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