Microbeam x-ray diffraction analysis of dental calculus.

The crystalline components of human dental calculus were investigated using microbeam x-ray diffraction analysis. Hydroxyapatite and octacalcium phosphate were most frequently found in that portion having porous and zonal structure. In the portion of the homogeneous illustration showing high calcification, whitlockite is a main component. Brushite was unexpectedly rare, and no calcite was detected in any portion of human dental calculus. The mechanism of the formation of dental calculus being considered in this paper is that octacalcium phosphate or brushite is formed during the initial stage of calcification of dental plaque, and is gradually hydrolyzed and transformed into hydroxyapatite and/or whitlockite.

The status of fluoride mouthrinse programmes in Japan: a national survey.

The purpose of this investigation was to determine the current status of fluoride mouthrinse programmes throughout Japan. Data collection and analysis took place in 1992. The focus of this study was on schools that were participating in the rinse programme at the time of the survey. Questionnaires were sent by mail to 49 dentist-members of the Association for the Promotion of Fluoride Use in Japan. These members gathered information from the schools and, when necessary, also from local government offices. Starting with a single prefecture in 1970, the rinse programme increased to 32 out of 47 prefectures by 1992. The total number of schools using fluoride mouthrinse was 1,183 (nursery schools and kindergartens 48 per cent, primary schools 46 per cent, and secondary schools 6 per cent). In nursery schools and kindergartens, 60 per cent of the participating schools adopted the daily method using 0.05 per cent NaF solution. In primary and secondary schools, 78 per cent adopted the weekly method using 0.2 per cent NaF solution. The costs for the rinse regimen were paid for by public funds of the prefectural and municipal governments in 71 per cent of the schools. Fifty-four per cent of the schools which first initiated the rinse programmes in their districts identified dentists and dental associations as the most influential in programme acceptance and implementation. Although the number of fluoride rinse programmes is increasing, it is still modest. These results suggest that cooperation between dental organisations, dental schools and prefectural governments can play very important roles in implementing school based rinse programmes.

ESR on the hydroxyl ion vacancies in the apatites.

Heating biological apatites and synthetic apatites in the stream of inert gas saturated with heavy water vapor, introduces OD ions which substitute for the hydroxyl (OH) ions and partially for the OH vacancies, depending on the heating time and the gas flow rate. This has been verified by ESR and partially by IR. Deuteration gives no serious alterations of the a-axis dimension or of the PO4 bands in the IR spectra. These findings have been interpreted as suggesting that the OH ions diffuse out and the OD ions diffuse in through specific pathways, and the diffusing ions interact permanently with none of the other ions in the apatite structure. Heating in dry inert gas results in the formation of hydroxyl ion vacancies. The ESR spectra of these samples in the g = 2.06 region have been interpreted in terms of O-2 and O-. The shortening of the a-axis dimension in this case has been accounted for based on the loss of structurally incorporated H2O and the loss of the OH ions on the hexad axis.

[The effect of ammonium fluoride solution at various concentrations on enamel].

The fluoride concentrations of ammonium fluoride solution (NH4F,pH 4.4), which has the same effect on enamel powder as conventional APF solution, were studied. Human enamel powder (200 mesh passed) was treated with solutions of NH4F (1,000 ppmF-, 3,000 ppmF-, 5,000 ppmF-, 7,000 ppmF-, 9,000 ppmF-, pH 4.4) and APF (9,000 ppmF-, pH 3.4) for 5 min. at 37 degrees C. Some of the specimen was washed with 1MKOH solution for 48 hours. Fluoride uptake by enamel powder was analyzed by means of chemical analysis and reaction products identified using X-ray diffractometry. The fluoride uptake of 5,000 ppmF- of NH4F-treated enamel was the same as that of APF-treated enamel. X-ray diffractometry showed that CaF2 was formed in the experimental groups. CaF2 with high crystallinity was formed in the NH4F-treated enamel, and the peak height of X-ray diffraction pattern of CaF2 in 3,000 ppmF- of NH4F-treated enamel was the same as that of APF-treated enamel. In conclusion, the ammonium fluoride solution of 3,000-5,000 ppmF- had a similar effect on enamel powder as conventional APF solution.

[Cohort study on cariostatic effect of 100ppmF- fluoride mouthrinsing].

The cariostatic effect of fluoride mouthrinsing with dilute fluoride solution in the school dental health programs was examined. The subjects were 138 children (75 of boys and 63 of girls) who carried out fluoride mouthrinsing with solution of 100 ppmF- for 6 years and 105 children (65 of boys and 40 of girls) who had no fluoride mouthrinsing were analysed by cohort study from 1983 to 1989. The cariostatic effect was evaluated by DMFT index and DMF rate for each tooth type in each erupted school grade. The increment of DMFT index was less than that of the control group. There was a clear cariostatic effect with the advance in the school grade. DMF rate for each tooth type of 1 in 2nd grade and 2 in 3rd grade students showed a statistically significant difference. Both that of upper and lower first molars in 1st and 2nd grade also showed the same result as that of upper incisors. In conclusion, a high cariostatic effect was obtained by introducing the use of fluoride mouthrinsing with a solution of 100ppmF- to the school dental health program, and the observation of DMF rate for each tooth type classified with each erupted school grade was a useful method to evaluate the cariostatic effect of fluoride mouthrinsing.