The aims of the present study were to investigate relationships between various factors which could affect toothbrushing behavior in schoolchildren, and to use the findings for development of an education program for gingivitis prevention. Toothbrushing behavior and knowledge, attitude toward toothbrushing, cognitive-behavioral factors and oral-health status were surveyed in 81 fifth grade children of an elemental school in Fukuoka City. Although 93.3% children reported daily toothbrushing, gingival inflammation was found in 85.1% of the subjects. Gingival inflammation was significantly correlated with plaque accumulation (r=0.515, p=0.0001). However, neither of these correlated with factors of toothbrushing behavior (p>0.05). Self-esteem, a cognitive-behavioral factor, was significantly associated with 5 items in the questionnaire regarding toothbrushing behavior, while self-management skills showed significant correlation with 8 items (p<0.05). The factor analysis revealed two factors which could explain the background of toothbrushing. Self-management skills showed high factorloading (0.526, 0.716) in both factors, while self-esteem contributed to one factor. These findings indicated that gingival inflammation was derived from poor skills in removing plaque, and suggested that self-management skills could be related to the establishment of daily toothbrushing. Self-management skills may be considered in the development of an education program for gingivitis prevention.

View full abstract

The aim of this study was to determine the variation in buffer capacity in dental plaque from different areas of the dentition that may be related to the caries status of associated tooth surfaces. Two-day plaque samples were collected from 8 different sites of 10 adult subjects living in Hokkaido ; upper-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). Wet plaque samples were weighed and 25 mmol/L KCl were added to give a final concentration of 10mg/ml. The samples were dispersed with sonication and vortex mixing. A small stir bar was added to the suspension. A micro pH electrode was then applied and the pH was determined. The suspension was then titrated with 10mM-HCl to pH 3.0. Titration curves were expressed by the 3 rd order polynomial (y : pH, x : volume of acid added). Statistical analyses among 8 different sites were carried out using the ANOVA and Scheffe's test. The highest pH without acid was LAL (7.33±0.37 SD) and the lowest were LPB (6.61±0.25 SD) and UAB (6.62±0.40 SD) with statistical significances (p<0.0001). Significant differences were seen in the volume of acid added from pH 6.5 to 5.5, as well as from pH 5.5 to 3.0. Plaque associated with the LAL, which is very prone to saliva and less prone to caries, had the significantly highest volume of acid added in pH 6.5-5.5 (102.10±23.63 SE nmolH^+/mg plaque, p<0.01) and in pH 5.5-3.0 (435.32±77.25 SE nmolH^+/mg plaque, p<0.01), respectively. Compared to the other sites, LAL will maintain a higher pH and be more likely to precipitate some constituents affecting the plaque buffer capacity due to rapid salivary clearance. On the other hand, plaque in UAB seems to be the most caries susceptible because of the lowest buffer capacity, when examined, of any under-critical pH area. The results indicated that site-specific plaque buffer capacity which may reflect the differences in exposure to saliva, has been shown to be a possible cause of differences in local cariostatic challenge.

View full abstract

In Japan, it has not been demonstrated how many children carry out a fluoride mouth rinsing (FMR) program at home because of the lack of any national survey. To overcome this problem we conducted a nationwide questionnaire survey of Japanese dentists. The study population was 3, 026 dentists who were systematically selected from the membership list of the Japan Dental Association. We prepared a structured questionnaire about instruction in FMR at the subject's dental clinic. The outcome measures we adopted in this mail survey were the rate of dentists who adopted the instruction in FMR program, and the numbers of children who were instructed in an FMR program at their dental clinic. After calculating summary statistics of these outcome measures, we estimated the numbers of children carrying out an FMR program at home on a nationwide basis. The response rate was 61.5% (1, 862/3, 026). The rate of dentists who adopted the instruction in FMR program was 19.9% (95% CI : 18.1%-21.7%). The average numbers of children who were instructed in an FMR program within a year was 28.0 (SD : 48.4, 95% CI : 19.6-36.4). The estimatd numbers of children carrying out an FMR program at home in Japan was 347, 000 by using the average value of the sample. By using the value of 95% CI of the sample, estimates were from 221, 000 to 493, 000. This is the first study which demonstrated the status of FMR programs at home on a nationwide scale in Japan. This national survey should be continued by solving several problems which were identified in this study.

View full abstract

Although there has been a wide range of reports on the average number of teeth and the average dental expenses of elderly people in each municipality in Japan, no report describing the relation between the average number of teeth and the average dental expenses was found. On the basis of previous studies, we proposed a hypothesis that the average dental expenses of elderly people is high in the municipalities where the average number of teeth in elderly people was high, due to the high rate of dental treatment in elderly people and we performed an ecological study in order to check this hypothesis. Stepwise regression analysis was performed using a criterion variable : the average dental expenses of the elderly people insured by national health insurance in May 1999, and explanatory variables : the average number of teeth in elderly people, the number of dentists in clinics or hospitals per a population of 100, 000, the population density, the ratio of aging population, the ratio of employees engaged in primary industry, the ratio of employees engaged in tertiary industry and the average amount of a residents' tax, and a weighting variable : the number of the elderly people insured by national health insurance, for each of the 62 municipalities in Shizuoka prefecture. The result was as follows. Population density and the average number of teeth in elderly people were selected for analysis. Because the average number of teeth in elderly people was statistically significant (p<0.01) in analysis when the other variables describing characteristics of a municipality were controlled, it was found that the average dental expenses of elderly people was high in the municipalities where the average number of teeth in elderly people was high. After that, a path analysis was performed on the basis of the model that the average dental expenses of elderly people is influenced by the rate of dental treatment, the average number of days of dental care per patient, and the average dental expenses per elderly patient per day in each municipality. The rate of dental treatment, the average number of days of dental care per patient and the average dental expenses per elderly patient per day is each influenced by population density and the average number of teeth in elderly people for each municipality. The result was as follows. The relation between the rate of dental treatment and the average dental expenses, and the relation between the average number of teeth and the rate of dental treatment was shown. Subsequently, it was found that the average rate of dental treatment was high in the municipalities where the average number of teeth was high, and that the average dental expenses of elderly people was high in the municipalities where the average rate of dental treatment was high. We were able to successfully confirm our hypothesis.

View full abstract

The purpose of this study is to investigate the remineralization process with QLF (quantitative light-induced fluorescence ; Inspektor Research Systems, The Netherlands) method on artificial enamel lesions. 30 human enamel specimens (4mm in diameter) were mounted on an acrylic rod and polished. Lesions (low demineralization and high demineralization) were formed in specimens by immersion for 12 and 48 hours respectively in demineralizing solution (Lactic acid ; 100mM, CaCl_2 ; 3mM, KH_2PO_4 ; 10mM, NaCl ; 100mM, pH 4.5). Lesion severity in the two groups were measured by the QLF method. QLF is a method to quantify the severity of incipient caries lesions in the smooth tooth surface without affecting the tooth. It is based on the decrease in the intensity of Enamel-Dentin auto-fluorescence as lesions are formed. The specimens were immersed for 15 days in remineralizing solution (CaCl_2 ; 1.5mM, KH_2PO_4 ; 5mM, NaCl ; 100mM, casein ; 20ppm, NaNO_3 ; 0.2%, sodium fluoride, pH 6.5) which contained 0, 0.1 and 1ppm fluoride (renewed every 3 days). The surface images of the specimens were recorded with QLF on days 3, 6, 9, 12 and 15 during the remineralizing process, and the remineralization rate was calculated from the variations in the fluorescence intensity. A high remineralization rate was observed in the 1 ppm F group (low demineralized specimens ; 89%, high demineralized specimens ; 52%). For the low demineralized specimens, the remineralization rate at 1 ppm F was higher than the rates at 0 and 0.1ppm F. In contrast, the high demineralized specimens showed no significant difference between the remineralization rates in each of the 0, 0.1 and 1 ppm F groups. The remineralization rate at 0ppm F was not different from 0.1ppm F in both the low and high demineralized specimens. It was concluded that the 1 ppm fluoride ion works as an accelerator of remineralization in relatively low demineralized enamel lesions in this in vitro study.

View full abstract

Titanium and its alloys are frequently used as biomaterials in orthopedics and dentistry, but titanium ions are released from the implants as a result of corrosion. However, the effects of titanium ions on the cell function of osteoblasts remain poorly undestood. The aim of the present study was to investigate the effect of potassium titanium oxalate (TiK) on the proliferation of, and alkaline phosphatase (ALP) activity in osteoblastic MC3T3-E1 cells. The addition of 0.01mM TiK did not inhibit proliferation, but remarkable inhibition was seen at TiK concentrations above 0.1mM. When TiK was added to the medium, crystalloids were formed. The proliferation of cells in a medium from which the crystalloids had been removed by filtration was inhibited, but the activity was less than that in the presence of crystalloids. TiK concentrations above 0.1mM inhibited the ALP activity of cells. However, TiK did not affect the activity of ALP extracted from the cells. No morphological changes of cells treated with 0.1mM TiK for 24 hrs were observed. Our findings suggest that high concentrations of TiK may affect the proliferation and differentiation of osteoblasts, and titanium ions play an important role in this mechanism.

View full abstract