A three-year-old children's health examination at health center S in Kagawa Prefecture was performed from April 1992 to March 1993. The results focussed on the relation between oral findings and pre-/post-natal conditions (children's gestational age, birth conditions, and others) as follows ; 1. Dental caries prevalence rate was 62 percent. This prevalence rate was higher than that of the same age standard level of nation-wide dental caries investigation of Japan in 1993. 2. As for the existence of dental caries, df/d tooth score in number and the susceptible types to dental caries of deciduous teeth, children with a birth weight <2500g showed significantly better results than those &ge;2500g. 3. The children born under abnormal delivery conditions showed significantly fewer tooth caries (df/d tooth score) than those born under normal conditions. 4. The children born at a gestational age of <37 weeks showed significantly fewer tooth caries (df/d tooth score) than those with gestational age &ge;42 weeks. 5. The children born to mothers in abnormal pregnant conditions showed a significantly higher occurrence of malocclusion than those born to mothers in normal conditions of pregnancy.

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This study compared the denture satisfaction and masticatory function of wearers of insurance-provided dentures and wearers of other dentures. A total of 263 subjects were interviewed, followed by clinical evaluation and measurement of masticatory function : biting pressure, biting force, occlusal contact area and peanuts comminution. 100 subjects from the 2 groups, matched according to sex, age, and the number of remaining teeth were selected and divided into two well-balanced groups. Statistical analysis showed no significant differences in denture satisfaction and masticatory function between the two groups. The mean period of use of other dentures (9.7yrs) was significantly longer than that of insurance-provided dentures (5.3yrs). Both groups reported difficulties in chewing tough or hard food. It was concluded that two types of dentures are similar in denture satisfaction and masticatory function, but not in durability.

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With the rapid increase in the aging of the population, dental health care for the aged is becoming increasingly important. However, the actual status of dental diseases of the bed-ridden aged has not been well clarified. The purpose of this study was to investigate the actual status of dental diseases of the bed ridden aged and to clarify the reason why, in spite of equal need for treatment, that the demand for the treatment differs. The investigation was made on 86 bed ridden aged persons at home, who agreed to cooperate, from among 187 persons (65-85 years old) who benefit from the home visiting services with guidance offered by Nakano Ward, Tokyo. We conducted the investigation together with the Nakano Ward Health Sevice Serction staff members in charge of home visiting services with guidance, and a dentist in charge of examinations. Interviews with the aged persons and nurses were carried out at their homes. The objects of the investigation were physical conditions, actual status of home care, eating habits, sense of dental health, actual receipt of dental treatment, demand for dental health services, and intraoral examination. As a result, the following points were clarified. 1. There is a tendency for less demand amongst those who are less independent in their daily life. 2. There is no demand among those who have no family dentist. 3. There is no demand among those who do not with to receive any guidance as to dental health. 4. There is no demand among bed ridden aged persons who have never been advised by nurse to receive dental treatment.

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This study was designed to do comparative research on caries-preventive effect between a low-fluoride dentifrice and conventional fluoride dentifrices. For 180 minutes, bovine permanent tooth enamel was treated with NaF dentifrice (100 ppmF^- ; NaF group). SnF_2 dentifrice (1,000 ppmF^- ; SnF_2 group) and MFP dentifrice (1.000 ppmF^- ; MFP group). We measured the amount of fluoride penetrating into the enamel, performed an acid resistance test and observed the enamel surface by SEM after treatment with each dentifrice and after the acid resistance test. We found that, in the NaF group, the amount of fluoride penetrating into the enamel was significantly less than in the SnF_2 group and was not significantly different from in the MFP group. We recognized that the fluoride penetrated deep into the enamel in the NaF group too. In the acid resistance test, we found a tendency for a small quantity of phosphorus to dissolve into an acetate buffer in the SnF_2 group. The NaF group showed significantly smaller solubility than the control group, and the NaF group had the same acid resistance as the MFP group. In the SEM observations, after treatment with dentifrice, many adhesive particles were seen on the enamel surface in all fluoride groups. In the NaF group, after acid resistance test, we also recognized some adhesive particles on the enamel. These findings showed that the effect of the NaF dentifrice (100 ppmF^-) was similar to that of the MFP dentifrice (1,000ppmF^-), and suggested that the NaF dentifrice (100 ppmF^-) was useful for caries prevention.

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We surveyed a consciousness regarding toothbrushing in 97 first year and 123 fifth year students and obtained the following results. 1. The number of times for toothbrushing in the two groups : the majority of the first year students (18.6%) answered "two times a day" and the fifth year students (47.2%) answered "more than three times". 2. The majority answer for toothbrushing time in the first year students (37.1 %) was "2 to 3 minutes" and the maiority in the fifth year students (54.5 %) was "over 3 minutes". 3. Most of the first year students answered that they use "1/3〜l/2" dentifrice on the toothbrush and most of the fifth year students answered "about 1/2". 4. In the two groups, most students answered that using less dentifrice makes brushing more satisfactory because a lot of foam does not mean that toothbrusing is done properly. 5. Students in both groups did not specify the main reason for choosing a dentifrice. The second reason given was to prevent dental caries and periodontal disease. 6. Some students do not use dentifrice, but we could not identify the reason in this study.

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The remineralization of root surfaces was investigated microradiographically in vitro using thin sections of root samples with or without cementum. Samples with cementum and with exposed dentin were prepared from extracted human premolars. They were demineralized in a 0.1M lactic acid gel (pH=5) for 2 w and sectioned to the thickness of about 100 μm. The sections were subsequently coated with nail varnish except for the demineralized surfaces and were remineralized in 20 mM Hepes (pH=7) with 1ppm F^- containing 1.5mM Ca^<2+> and 0.9 mM phosphate for 8 days. During the remineralization period, the sections were microradiographed repeatedly at days 0, 1, 2, 4, and 8 under wet conditions. After demineralization (day 0), the lesion depth values l_d and the mineral loss values ΔZ were roughly the same, 108 μm and 2,660 vol% ・ μm, respectively, indicating no difference between the samples with and without cementum. If we consider remineralization the subsurface mineral loss values ΔZ' (vol% ・ μm) were not different significantly between samples with and without cementum up to day 8. In contrast, the width of hyper-remineralization layer l_a (μm) and the mineral accumulation value ΔZa (vol% ・ μm) indicated that the hyper-remineralization occurs more rapidly and in large amounts in dentine compared with the samples with cementum present. Correspondingly, the maximum level of mineral V_<max> was significantly higher (p<0.05) in the dentine samples (74 vol%) than in the samples with cementum (38 vol%) at day 2. In contrast, the subsurface lesion width l' (μm) in the cementum covered samples was lower by 12 % (day 4) and by 26 % (day 8) with respect to the dentine samples, respectively. The results suggest that demineralization in root surfaces is most likely independent of the cementum layer, while (hyper-) remineralization process is strongly influenced by absence and presence of cementum.

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In the present study, an intraoral fluoride releasing device (IFRD) was embedded in a removable oral appliance and placed in a human oral cavity. Its effects on salivary, plaque, and urinary fluoride levels were studied for 30 days including prior to, during, and after-application in three cycles. Unstimulated saliva samples were collected on rising, at noon, and before dinner. Plaque samples were collected at noon from six different areas of the mouth and daily urine samples were collected, on specified days. The removable appliance, in which two IFRDs were embedded, was produced in a form of partial denture for a missing lower left first moler. The mean fluoride release from the IFRD, before the experiment, was 0.31±0. 13 mgF/day. The salivary fluoride concentrations, 0.018±0.005ppm before the experiment, were elevated by the IFRD 52, 27, and 23 times, respectively, at rising, at noon, and before dinner. The appliance in the study provided a constant fluoride supply (0.2 to 0.5 ppm) by the IFRD. After the IFRD was removed, the salivary fluoride concentration dropped immediately to 0.038±0.018 ppm on the evening of the day. Fluoride contents in the plaque were increased in five areas about l.5 to 2.2 times except in lower incisor region, after being inserted. After the IFRD was removed, the fluoride decreased slowly in the five areas, except in the lower left molar region. Urinary fluoride excretion and volume on a specified day did not change during the time of the experiment. These results suggest that use of the IFRD was maintained fluoride in the oral cavity. The presence of fluoride in the oral cavity may prevent demineralization of the enamel and contribute to the remineralization of initial lesions. Thus, a good possibility for clinical application of the IFRD is indicated.

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To encourage smoking-cessation counseling by oral health team, we surveyed the smoking habits and attitudes of 213 students at three dental schools in West Japan with a self-administered questionnaire. The percentage of smoking was 34%. About 80% of the smokers started smoking in their university days. Many smokers (70%) had already made serious attempts to quit but their reasons for not smoking were personal and there were few social reasons. Most considered smoking harmful to health with lower rates in smokers, but there was important ignorance about tobacco as a major cause of specific diseases. Many students (70%) were concerned with advising patients whom they knew to have smoking-related disease, but few accepted a preventive role in advising patients. Most lacked confidence in their counseling skills and there was little knowledge of public health measures for smoking control, although many students (70%) considered that health worker should receive smoking-cessation counseling training. These attitudes towards smoking were similar in the three schools. These results provide important challenge to dental education regarding smoking and health consequences, and regarding counseling strategies of smoking cessation.

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The purpose of this study was to investigate the relationship between infant feeding methods and development of deciduous dentition. Occlusal conditions and interdental spaces were examined in a total of 678 children, of an average age of three years and five months. The occlusal conditions were classified into six types based the relationship between upper and lower incisors : normal, edge to edge, deep overbite, maxillary protrusion, open bite, and mandibular protrusion. Interdental space was examined at each contact point and classified into three types : spaced, closed, and crowded. Before the examination of the children, the parents filled out a questionnaire included questions relating to the method and duration of infant feeding and finger sucking habits. The subjects were grouped according to their feeding methods from birth to five months of age as follows : breast-fed only, bottle-fed only, and both. We compared the breast-fed group (n= 248) with the bottle-fed group (n=113), and obtained the following results. 1. Although there was no significant difference in the occlusal conditions between the two groups, the incidence of open bite and maxillary protrusion were slightly higher in the bottle-fed group in relation to finger sucking habits 2. In maxillary deciduous dentition, only the incisor region showed slight difference in the condition of the interdental spaces, and there were no significant differences in the number of interdental spaces and the condition of crowding between the two groups. 3. In mandibular deciduous dentition, the breast-Led group showed lower prevalence of interdental spaces, higher incidence rate of children having smaller number of the spaces, larger number of crowded teeth, and series of crowded teeth, compared to the bottle-fed group. Therefore, concenrning mandibular deciduous dentition, the results suggested that the breast-fed group had more children who had not enough space for dentition than the bottle-fed group. But the degree of difference was not remarkable. These results led to the conclusion that there was no critical relationship between infant feeding methods and development of deciduous dentition.

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The purpose of this study was to investigate the effect of a topical application of Ag(NH_3)_2F for the prevention of interproximal surface caries in primary molars. Two hundred and eighty-three 3-year-old children whose primary molars had intact proximal surfaces were selected for this program after their parents' permission was obtained. The interproximal surfaces of the primary molars were treated with 38% Ag(NH_3)_2F for one minute using dental floss at randomly selected test sides. The treatments were done twice in children at ages of 3 and 3.5 years ; and 184 of them were followed up for 18 months until the age of 4.5 years. For the children of ages of 3 and 4.5 years, questionnaires on toothbrushing and snacking habits were administered to their parents and the results were analyzed together with the rates of caries incidence and the preventive effects of Ag(NH_3)_2F. The results were as follows : 1. The percentage effectiveness of prevention for interproximal caries (including C_0) was 41.0 % for maxillary molars and 37.9% for mandibular molars. These two percentages were statistically significant by McNemar's x^2 analysis. The percentage effectiveness of interproximal caries with cavities was 50.0% for maxillary molars and 54.2% for mandibular molars. In this case, only the latter was statistically significant. 2. The children who ate sweet snacks often at the age of 3 years had double the relative risk of those who ate sweets less frequently. In the former, the percentage effectiveness was high (38.5 %) and the topical application of Ag(NH_3)_2F was very effective in prevening interproximal surfact caries. 3. At the age of 3 years, the relative risk of the children who had dental caries (except for interproximal surfaces of molars) was 1.5 times higher than the relative risk of the caries-free children. On the other hand, the percentage effectiveness for the former was 15.4%, which was low as compared with 41.5% for the latter. The topical application of Ag(NH_3)_2F was not very effective in prevening interproximal surface caries in the children with carious teeth at the age of 3 years. 4. According to the questionnaire of the children at the age of 4.5 years, those who used toothpaste for less than 1 year had about double the relative risk as compared with those who used toothpaste for 1 year and more. The percentage effectiveness of the children who used toothpaste for 1 year and more was 46.2%, which was higher than the 27.8% of those who used toothpaset for less than 1 year. Futhermore, the relative risk of the children who did not brush their teeth every day was 1.3 times higher than the risk of those who brushed every day. The percentage effectiveness of the children who brushed every day was 37.0%, which was higher than the 21.3% of those who did not. The results indicated that toothbrushing and the usage of toothpaste played an important role in increasing the effectiveness of the topical applications of Ag (NH_3)_2F.

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