The purpose of this study was to investigate the effects of a dual-component dentifrice, which contains sodium fluoride (NaF) in one component, sodium monofluorophosphate (MFP) and calcium lactate (CaL) in the other, on fluoride uptake and on remineralization of enamel subsurface lesions in vitro. Three experimental dentifrice samples that contained following concentrations of fluoride were used in this study : NaF Dentifrice : 950 ppmF (single component), MFP dentifrice : 950 ppmF (single component) , and dual-component dentifrice : NaF 475 ppmF/total, MFP 475 ppmF and 1,500 ppmCa²total (dual component). Fluoride uptake from each of the dentifrice samples on a hydroxyapatite (Hap : as a model for human enamel) was determined. Each dentifrice was first mixed with deionized water (l : 2 slurries). HAp pellets were placed in these slurries for 5 min, washed with deionized water, and placed in 0.5 mol/l HClO_44 solutions to extract fluoride. Then, the fluoride concentrations of these solutions were determined using a F^- electrode. Remineralization ability was examined by a method as follows. Demineralized enamel blocks were treated with the slurries mentioned above for 5 min, and immersed in a remineralizing solution (2.0 mmol/l calcium, 10mmol/l phosphate, 0.025 units/ml acid phosphatase, pH 6.0). This treatment procedure was repeated twice a day. After 14 days of treatments, the enamel blocks were cut and microradiographed to measure the mineral loss value (△Z : vol%・ μm). The fluoride uptake results on HAp were 0.26±0.05 fig/cm² (Mean±SD ; Dual-component dentifrice group), 0.16±0.03 fig/cm² (NaF dentifrice group), 0.11±0.03 fig/cm² (MFP dentifrice group). The mineral loss values (AZ) were 440±148vol%・μm (Mean±SD ; Dual-component dentifrice group), 1,087±184vol%・μm (NaF dentifrice group), 1,403±312vol%・μm (MFP dentifrice group), 2,172±418vol%・μm (Baseline group). F contents and remineralization at the dual-component dentifrice group were significantly higher than at the NaF dentifrice group or MFP dentifrice group (p< 0.05). These findings suggested that the use of the dual-component dentifrice containing NaF, MFP and Ca²⁺ could be an effective approach for enhancing remineralization of enamel lesions.

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The purpose of this study was to examine the mineral ion uptake (Ca, P, and F) in human dental plaque after using a dual-component dentifrice that contained sodium fluoride (NaF) in one component and sodium monofluorophosphate (MFP) and calcium lactate (CaL) in the other, and to compare this with conventional dentifrice samples. Three dentifrice samples that contained following fluoride concentrations were used in this study :. NaF dentifrice : 950ppm F (single component), MFP dentifrice : 950ppm F (single component), dual-component dentifrice : NaF 475ppm F/total, MFP 475ppm F and 1,500 ppmCa²⁺ total (dual component) . Total concentrations of F in all of the three experimental dentifrice samples were controlled to 950ppm. Before using the dentifrice, the differences in the mineral ion concentrations in dental plaque from different sites of the dentition were examined. Two-day old plaque samples were collected from 6 male subjects (average age : 36.0 years old) in 8 different sites Cupper-anterior-buccal (UAB) and lingual (UAL), upper-posterior-buccal (UPB) and lingual (UPL) , lower-anterior-buccal (LAB) and lingual (LAL) , lower- posterior-buccal (LPB) and lingual (LPL), surface]. Two-day old plaque samples were collected, measured and set as the initial mineral ion value. Just after brushing with each of the three experimental dentifrice samples, residual plaque from the left side of the mouth was collected. Then, 6 hours after brushing, residual plaque from the right side of the mouth was also collected. Plaque samples were weighed, freeze-dried, and exposed to acid extraction using a mixed-acid extraction procedure (Margolis and Moreno, 1992). The acid extracts were analyzed for Ca and P by colorimetry and F by F^-electrode. Concentrations of Ca, P, and F were highest in the dental plaque from the LAL surface, but the differences were not statistically significant. F concentrations in dental plaque 6 hours after brushing were 0.29±0.20mg/g (mean±SD ; NaF dentifrice), 0.12±0.04mg/g (MFP dentifrice) and 0.53±0.19mg/g (dual-componentdentifrice) and statistical differences were observed (p<0.05). There were no significant differences in Ca and P uptake among dental plaques after brushing with each dentifrice. F concentration in dental plaque after brushing was highest in the case of dual-component dentifrice. The dual-component dentifrice containing NaF, MFP and Ca²⁺ enabled higher fluoride uptake in dental plaque than the conventional single component dentifrices.

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A cohort study was carried out to analyze the factors affecting dental caries incidence in 2.5-year-old children. The subjects were 71 infants and their mothers living in a town in Iwate prefecture. Infants had a dental examination and a plaque sample was removed for microbiological examination at 1 year, 1.5 years, and 2.5 years. Prior to the examination, mothers had completed a questionnaire containing questions about daily habits of dietary behavior and oral hygiene for their children, and surveys were recovered on the day of examination. To determine the mothers' experience of dental caries and the level of mutans streptococci, they underwent dental examinations and saliva was collected. The results were as follows : The dental caries prevalence rate was 21.1% and dft score was 0.93±2.50 at 2.5 years old. Logistic regression analysis was used to identify the specific nursing habits related to the incidence of dental caries. The results showed that intake of sugar-containing drinks with a feeding bottle, sharing of dishes and chop sticks with caretakers, and daily toothbrushing by caretakers at 1 year old, as well as intake of sugar-containing drinks with a feeding bottle and daily toothbrushing by caretakers at 1.5 years old were significantly correlated with the development of dental caries. The relationships between the age at mutans streptococci colonization and incidence of dental caries in infants were as follows : Compared with infants in whom mutans streptococci was first detected at 2.5 years old, infants in whom mutans streptococci was detected at 1 year old had a significantly higher incidence of dental caries. Furthermore, with respect to the relationship between early detection of mutans streptococci and nursing habits, the intake of sugar-containing drinks with a feeding bottle was a significant factor. From the results of this investigation, it is considered that the early colonization of mutans streptococci in infants is one cause of the development of dental caries and the presence of sucrose in the oral cavity may affect the early colonization of mutans streptococci in infants.

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The debris emitted as dust during grinding of teeth in a dental clinic can contain various bacteria and viruses. This dust can cause environmental pollution and exposure of dental staff to scattering pathogens in the dental clinic. Therefore, it is important to remove the dust at the point of origin. In this study, we investigated the vacuum assistant's exposure to such grinding dust. The measurement point was at the center of the lips of the vacuum assistant, and the measurement times were 0〜34 seconds and 44-78 seconds. We examined the effects of an extra-oral vacuum aspirator at three experimental positions for decreasing grinding dust exposure. As a result, in this experimental condition, no dust of more than Φ2 μm was detected. For dust ofΦ0.3-2μm, the density of small dust was higher than that of larger particles. Our findings suggested that the extraoral vacuum aspirator was an effective method for removing about 85% or more ofΦ0.3-2 μm dust produced in 0-34 seconds and 71% or more in 44-78 seconds. In comparison of the three aspirator positions, it was confirmed that the reduction of dust differed according to the position of the extra-oral vacuum aspirator. It was shown that the density of the dispersion dust measured at the vacuum assistant's lips was lower than that at the dentist's position as mesured in our former study. The position of the extra-oral vacuum aspirator with the highest effect of reducing dust in this study differed from the optimum position measured from the dentist's position. It is necessary to determine the optimum of position of the extra-oral vacuum aspirator with respect to the positions of both the dentist and the vacuum assistant for reducing dust in actual clinical settings.

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The purpose of this study was to establish a dental health guidance system that can be used at the 1.5-year-old health check-up in Onomichi. Computer software was developed to accumulate the data at 1.5-year-old and 3-year-old old health check-ups obtained by dental examination and a questionnaire. The results of 3-year-old dental examination performed the previous year and the results of a questionnaire of the same children at 1.5-year-old were utilized. The comments on the life style to improve dental health for each child was printed out as a dental health guide paper. A personal computer, a scanner, and a printer were used in the system. The 1.5-year-old dental health guidance based on the dental health guide paper of each child was started in 2000. It was shown that the system was effective and time saving. Since the data obtained at 1.5-year-old and 3-year-old dental examinations are accstored and utilized in the following year, the system can be applied even when the caries incidence of the area changes. Also it was suggested that the system could be applied to any area in Japan.

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The purpose of this study was to compare the ability to evaluate periodontal health status of second-year students in a junior high school (high school students group) with that of fourth-year dental students (dental students group) using the Development of Ability to Assess Gingival Status (DAAGS) computer program for beginners. This program was used as a computer-aided test for groups using a liquid crystal display projector. Slides for demonstration of the golden standard (G.S.) were shown to both groups for undestanding of the G.S. of the Oral Rating Index (OKI). After looking at each oral picture in 24 slides, the students of each group judged the ORI level (+ 2 to - 2) . The numbers of correct answers, reproducibility and extreme answers were calculated. According to the DAAGS criteria, the ability to evaluate periodontal health status (6 categories) of each student was assessed. The results were as follows : the mean numbers of correct answers, reproducibility and extreme answers were 9.1, 2.1 and 2.1, respectively, in the high school students group, and 10.4, 2.6 and 0.9, respectively, in the dental students group (high school students group vs. dental students group : p<0.05, p<0.05, and p< 0.001, respectively). This showed that the dental students group was superior to the high school students group in the ability to evaluate periodontal health status. In the female students, however, there were no significant differences in the three indicators between the two groups. The distribution of scores of the ability to evaluate periodontal health status was nearly normal in the high school students group, which suggested that the criteria for the beginners' course were almost valid. Furthermore, nearly half of the junior high school students reported that they took an increasing interest in gums, and about 80% of the dental students answered that this index (ORI) provides valuable information to instruct/educate youth. In summary, it was suggested that the DAAGS is worthwhile to motivate both dental students and the younger generation who enthuse over computer games.

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It is well known that perfoming continuous proper self care and receiving regular professional tooth cleaning can prevent oral diseases. However, no effective recall system is in place in private dental offices in Japan to provide regular dental prophylaxis. The purpose of this study was to establish a practical system for patients to receive regular check-ups at private dental offices in Japan. The regular check-up system was introduced at a private dental office in Hiroshima Prefecture in 1997. Four dentists and 7 dental hygienists were working in the office. The patients who agreed to receive prophylaxis every 1 to 3 months, were assigned to one of the dental hygienists. Professional tooth cleaning (PTC) was performed by the dental hygienists on the check-up patients. Charter's method using a toothbrush with extremely tapered end bristles (DENTOR SYSTEMA ) was utilized for PTC. After 6 years, the percentage of patients receiving check-ups increased to 50% of the total patients and the rate of cancellation fell as low as 2%. Each dental hygienist is currently in charge of 250 recall patients. It was shown that PTC by dental hygienists performed at regular check-ups encouraged patients to continue to visit the dental office, and also increased the number of patients visiting the dental office.

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