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The purpose of this study was to evaluate the possibility of clinical use for fluoride topical application of dilute ammonium fluoride soluion, in which fluoride concentration was 1/3 times lower than that of APF solution.Experiments were performed in vitro and in vivo using a solution of phosphoric acid-acidified NH4F (3000ppm of F-, pH 4.4) and APF (9000ppm of F-, pH 3.4). In the experiments on intact enamel, fluoride uptake, acid solubility, and morphological changes in enamel blocks following topical treatment (for 60min. at 37°C) with fluoride solutions were studied by chemical analysis, scanning electron microscopy, and electron probe X-ray microanalysis. In experiments on rats, the cariostatic effect of ammonium fluoride solution was investigated. Eighteen-day-old male Sprague-Dawley rats were infected with Streptococcus mutans GS-5 for three days and fed a cariogenic diet (Diet 2000 No. 3) during the experimental period. Experimental groups were given topical application of each fluoride solution twice a week. Caries prevalence was examined using a standardized photograph (×50) of the rat jaw, and then caries scores (caries incidence and caries extent) were calculated from these data.The fluoride uptake of NH4F-treated enamel surface was a few times higher than that of APF-treated enamel. In the electron probe X-ray microanalysis, the same results were obtained. The acid solubility test proved the acquisition of acid resistance by the enamel. SEM images showed heavy deposits of crystalline material on NH4F-treated enamel surface, whereas the deposit was homogeneous in APF-treated enamel.Both caries incidence and caries extent were clearly reduced, and significantly lower values were found in the fluoride groups than in the control group. The fluoride groups had very few serious grade lesions, whereas the control group had many collapsible lesions.It is concluded that the topical application of dilute NH4F solution leads to uptake of fluoride into the enamel surface and proves the acquisition of acid resistance by enamel in vitro, and is effective in reducing caries incidence and inhibiting caries progression in rat experimental caries in vivo. A dilute NH4F solution can be expected to have the same effect as APF in topical application for caries prevention.

The purpose of this study was to examine the prevalence of periodontal disease in an industrial population, and to evaluate the effectiveness of introducing the CPITN into the industrial dental health. The CPITN survey was performed on 126 persons aged between 20 and 64 using the WHO periodontal examination probe.Modified visible plaque index (VPI) examination and a conventional oral examination for periodontal disease were also carried out, and a questionaire about subjective periodontal symptoms was given to all subjects.From the results of the CPITN code, subjects requiring periodontal treatment (TN-II) were over 92% in all age groups. The severity of periodontal disease increased with age. There were correlations between the CPITN and the VPI, and between the CPITN and subjective symptoms.As a result, it is recognized that in this industry, nearly all subjects require treatment for periodontal disease, including dental health education. The CPITN is a simple and efficient method to evaluate the periodontal status in industrial workers.

Fluoride varnish (F-varnish) has been already used for treatment of hypersensitive dentin in clinic. In this study, F-varnish was examined in vitro the possibility of application for caries inhibition. Experiments were made in vitro of applications of F-varnish, containing 5% NaF or placebo-varnish with the intact enamel surface and fissure, for two weeks at 37°C twice a week, followed by 1, 2 or 3 weeks of washing with distilled water. Fluoride uptake and release, morphological observation, and acid solubility test on enamel blocks following treatment with F-varnish, or after washing were studied by means of electron probe microanalysis (EPMA), chemical analysis and sacanning electron microscopy (SEM).The fluoride uptake of F-varnish-treated enamel surface and fissure were increased, especially a large amount of CaF2 deposited on the outer surface layer and fissure of enamel. Although, CaF2 was released after washing for three weeks, fluoride was taken up at the depth of approximately 40μm. The acid solubility test proved that the acquisition of acid resistance was greater in F-varnish-treated enamel than in the control even after washing for three weeks. SEM of enamel surface showed that CaF2 was formed in the F-varnish-treated enamel, and clearly showed that there was an acid-resistant picture after perchloric acid-etching.Therefore, we suggest that F-varnish which applied to treat hypersensitive dentin may be effective in clinical use for caries inhibition, because the treatment time of enamel can be extended.

The purpose of this study was to examine the prevalence of periodontal disease in an industrial population, and to evaluate the effectiveness of introducing the CPITN into the industrial dental health. The CPITN survey was performed on 126 persons aged between 20 and 64 using the WHO periodontal examination probe.Modified visible plaque index (VPI) examination and a conventional oral examination for periodontal disease were also carried out, and a questionaire about subjective periodontal symptoms was given to all subjects.From the results of the CPITN code, subjects requiring periodontal treatment (TN-II) were over 92% in all age groups. The severity of periodontal disease increased with age. There were correlations between the CPITN and the VPI, and between the CPITN and subjective symptoms.As a result, it is recognized that in this industry, nearly all subjects require treatment for periodontal disease, including dental health education. The CPITN is a simple and efficient method to evaluate the periodontal status in industrial workers.