Development of small-scale water fluoridation equipment.

PURPOSE: A water fluoridation program launched in the United States in 1945 has become a worldwide application for caries prevention. Although such a program is important in Japan, water fluoridation in large communities has not been established. This study aimed to develop safe small-scale water fluoride equipment that can be easily used to carry out water fluoridation programs in areas with children in long-term care facilities, and in developing countries without water supply facilities. METHODS: Batch-type NaF addition adjustment equipment was manufactured as small-scale water fluoride equipment. The fluoride concentration of the adjusted water with this equipment was measured using an ion meter and a fluoride composite electrode. All 51 water quality standards set by the Ministry of Health, Labour, and Welfare of Japan were tested. RESULTS: The fluoride ion concentration of the adjusted water was 0.7 mg/L and it was constant and stable. The adjusted water conformed to the water quality standard values of the Japanese Water Supply Law. CONCLUSION: Water produced with small-scale water fluoridation equipment had a fluoride concentration of 0.7 mg/L, which is the recommended concentration for caries prevention. The fluoride concentration was stable.

Anti-demineralization effect of desensitizer containing copolymer and sodium fluoride on root dentin - a transverse microradiographic study.

Objective: To evaluate anti-demineralization effects of dentin desensitizer containing sodium fluoride and methacrylate-co-p-styrene sulfonic acid (MS polymer) on root dentin using transverse microradiography (TMR). Material and methods: Twenty-four dentin specimens were divided into four groups: MSO (no fluoride), MSF (3000 ppm F), FJL (9000 ppm F), and Control. In MSO and MSF, each desensitizer was rubbed into the dentin surfaces for 10 s then left for 20 s. In FJL, paste containing 9000 ppm F was applied onto the surface for 30 s. All specimens, including the Controls, were rinsed with deionized water, dried and an area of their surface exposed to pH 5.0 acidic solution, refreshed every 24 h, for 4 days. Sections 300-µm-thick were assessed by TMR. Mineral profiles and integrated mineral loss (IML) of lesions were analyzed by dedicated software. IML was analyzed with one-way ANOVA and Tukey's test. Results: MSF and FJL specimens showed high mineral volume % at the surface and in lesions, and significantly lower IML than the other groups (p < .05). Conclusion: Dentin desensitizer containing 3000 ppm fluoride and MS polymer has the same anti-demineralization effect as does a fluoride paste containing 9000 ppm F.

Micromolar sodium fluoride mediates anti-osteoclastogenesis in Porphyromonas gingivalis-induced alveolar bone loss.

Osteoclasts are bone-specific multinucleated cells generated by the differentiation of monocyte/macrophage lineage precursors. Regulation of osteoclast differentiation is considered an effective therapeutic approach to the treatment of bone-lytic diseases. Periodontitis is an inflammatory disease characterized by extensive bone resorption. In this study, we investigated the effects of sodium fluoride (NaF) on osteoclastogenesis induced by Porphyromonas gingivalis, an important colonizer of the oral cavity that has been implicated in periodontitis. NaF strongly inhibited the P. gingivalis-induced alveolar bone loss. That effect was accompanied by decreased levels of cathepsin K, interleukin (IL)-1ß, matrix metalloproteinase 9 (MMP9), and tartrate-resistant acid phosphatase, which were up-regulated during P. gingivalis-induced osteoclastogenesis. Consistent with the in vivo anti-osteoclastogenic effect, NaF inhibited osteoclast formation caused by the differentiation factor RANKL (receptor activator of nuclear factor κB ligand) and macrophage colony-stimulating factor (M-CSF). The RANKL-stimulated induction of the transcription factor nuclear factor of activated T cells (NFAT) c1 was also abrogated by NaF. Taken together, our data demonstrate that NaF inhibits RANKL-induced osteoclastogenesis by reducing the induction of NFATc1, ultimately leading to the suppressed expression of cathepsin K and MMP9. The in vivo effect of NaF on the inhibition of P. gingivalis-induced osteoclastogenesis strengthens the potential usefulness of NaF for treating periodontal diseases.

Correlation of dental health behavior with health awareness and subjective symptoms in a rural population in Japan.

The aim of this study was to determine the association of dental health behavior with health awareness, oral condition, and subjective symptoms in Japan. The present study included 1699 individuals who underwent dental checkups at the public health center of Miura City. All those who underwent dental checkups were asked to fill out a questionnaire. The correlation between having a regular dentist and each of the other items was analyzed. Undergoing regular checkups was significantly related to having a regular dentist. To analyze the correlation of dental health behavior with Subjective symptoms and Health awareness, structured equation modeling was performed following factor analysis. As a result, only the regression weight between dental health behavior and health awareness was found to be statistically significant. The present survey indicates that dental health behavior was significantly related to Health awareness but not to Subjective symptoms.

Fluoride-treated bio-resorbable synthetic nonceramic [corrected] hydroxyapatite promotes proliferation and differentiation of human osteoblastic MG-63 cells.

When resorbable hydroxyapatite (HA) granules, which are used as a bone supplement material, were treated in neutral 4% sodium fluoride (NaF) solution, formation of a reactant resembling calcium fluoride was observed on the surface of the granules. Immediate and slow release of fluoride from fluoridated HA (HA+F) granules was observed after immersion in culture fluid, and the concentration increased over time to 1.25 ± 0.05 ppm F at 0.5 hours, 1.57 ± 0.12 ppm F at 24 hours, and 1.73 ± 0.15 ppm F at 48 hours. On invasion assay, migration of human osteoblast-like MG-63 cells exposed to the released fluoride was confirmed in comparison to the cells incubated with a nonfluoridated control sample (P < .01). In addition, fluoride added to the medium increased MG-63 cell proliferation in a manner dependent on fluoride concentrations up to 2.0 ppm (P < .05). At 5.0 ppm, however, fluoride significantly inhibited cell proliferation (P < .005). Activity of the osteogenic differentiation marker, alkaline phosphatase (ALP), also increased with fluoride after exposure for 1 week, increasing significantly at 1.0 ppm (P < .05). The promotion of MG-63 cell migration and proliferation, as well as increased ALP activity, suggested that fluoride released from the surface of resorbable HA granules, which were fluoridated by prior treatment with neutral 4% NaF solution, can provide a superb method to supply fluoride and promote osteogenic cell differentiation.

Relationship between Duration of Fluoride Exposure in School-Based Fluoride Mouthrinsing and Effects on Prevention and Control of Dental Caries.

The objective of this paper was to assess the effects of school-based fluoride mouthrinsing (S-FMR: weekly using 0.2% NaF solution) in two groups of school children with different periods of exposure to S-FMR in elementary school. Subjects were the S-FMR group consisted of 599 children, participated for six years. The control group consisted of 282 children, participated for less than one year in the sixth year of elementary school. From the results of the present survey, the caries reduction rate of S-FMR in the permanent teeth was 36.6% for DMFT and 42.8% for DMFS, and person rates with DMF, DMFT, DMFS, and CO (questionable caries under observation) were inhibited in both boys and girls. Girls in the control group showed clearly higher values for all parameters of dental caries because of earlier teeth eruption; however, no gender differences were observed in the S-FMR group. As caries prevalence in the first molars accounted for about 85% regardless of participation to S-FMR, and first molar caries were more common in the mandible than in the maxilla, consideration should be given to preventive measures against pit-and-fissure-caries in addition to S-FMR.

IL-1ß-mediated up-regulation of DEC1 in human gingiva cells via the Akt pathway.

Growing evidence indicates that inflammation is a contributing factor leading to cancer development. However, pathways involved in this progression are not well understood. The involvement of DEC1 in cancer prompted us to examine whether pro-inflammatory cytokine interleukin-1ß (IL-1ß) induces the expression of DEC1 in oral inflammation. We found that IL-1ß up-regulated DEC1 and hypoxia-inducible factor-1α (HIF-1α) protein and elevated the HIF-1α-responsive gene vascular endothelial growth factor (VEGF) expression in human primary gingival cells. HIF-1α and DEC1 immunoreactivity were significantly higher in the cases of gingival inflammation. We demonstrate that IL-1ß up-regulates DEC1 and HIF-1α protein through a classical inflammatory signaling pathway involving Akt. Our data strongly suggest that PI-3K-Akt is an upstream participant in IL-1ß-mediated DEC1 and HIF-1α induction. This is supported by the following data: (1) IL-1ß induces 473 serine phosphorylation of Akt; (2) IL-1ß-mediated Akt activation occurs in a PI-3K-dependent manner, and specific inhibition of PI-3K prevents Akt phosphorylation; and (3) inhibition of Akt prevents IL-1ß-mediated DEC1 and HIF-1α induction. Taken together, these results suggest that DEC1 is one of the important transcription factors in inflammation.

Involvement of HMGB1 and RAGE in IL-1ß-induced gingival inflammation.

OBJECTIVE: Extracellularly released high mobility group box 1 (HMGB1) protein behaves as a cytokine, promotes inflammation and participates in the pathogenesis of several disorders in peripheral organs. The role of HMGB1 and receptor for advanced glycation end products (RAGE) expressed in gingival inflammatory tissues was explored. METHODS: Real time PCR was applied to assay HMGB1 and RAGE mRNA expression in gingival epithelial and fibroblast cells induced by interleukin-1ß (IL-1ß). A highly selective inhibitor of inducible nitric oxide (iNOS) was employed. ELISA was done for measurement of HMGB1 concentrations in cell culture media of gingival epithelial and fibroblast cells. Immunohistochemistry was performed to analyse the expression and sub-cellular localization of HMGB1, together with RAGE, in specimens obtained from patients with chronic inflammation. RESULTS: A time-dependent response of HMGB1 and RAGE expression in gingival cells to IL-1ß induction was observed. IL-1ß promotes HMGB1 production in human gingival epithelial cells in a nitric oxide-dependent manner. HMGB1 and RAGE appeared highly expressed in gingival inflammatory tissues. CONCLUSION: These results demonstrate that HMGB1 and RAGE are abundantly expressed in gingiva and promptly released during gingival inflammation. We suggest a role for HMGB1/RAGE/iNOS signalling on inflamed gingival epithelial cells.

Fluoride Retention following the Professional Topical Application of 2% Neutral Sodium Fluoride Foam.

The objective of the present research was to determine the appropriate amount of fluoride to use professional topical application and the residual amounts of fluoride in the oral cavity using a 2% neutral sodium fluoride (NaF) foam with a dedicated tray. Using dentition study models, a method for determining the appropriate amount of NaF foam was investigated. In eight adult subjects, the appropriate amount of NaF foam, the concentration of fluoride in the saliva following professional topical application, and the amount of residual fluoride in the oral cavity following professional topical application was examined. The results indicated that the appropriate amount of NaF foam was approximately 0.8 g, the amount of residual fluoride in the oral cavity was approximately 25% of the amount of foam used.

Low concentration fluoride stimulates cell motility of epithelial cells in vitro.

Oral mucosal tissue can serve as a long-term fluoride reservoir following topical application and retain a small amount of fluoride in oral environment for prevention of dental caries. The aim of this study was to determine the effect of low level sodium fluoride (NaF) on the proliferation and migration of epithelial cells in vitro. Human primary gingival epithelial cells and human epidermal HaCaT keratinocytes were used. Cultured epithelial cells, treated with various concentrations of NaF ranging from 5 microM to 500 microM, were investigated by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt (MTS) assay, wound healing assay, invasion assay and quantitative real-time PCR. MTS assay revealed that fluoride added to human gingival epithelial cells elevated cell proliferation at a concentration of 5 microM or more. The wound healing assay and invasion assay confirmed this observation. Quantitative real-time PCR revealed that low concentration of NaF up-regulated fibronectin mRNA expression in fluoride-treated cells compared with controls. These results suggest that a low concentration of NaF is able to induce cell proliferation, migration, and matrix production in epithelial cells. Our results provide new information on epithelial cell adhesion and may thus aid in the understanding of periodontal physiology.

Study of the clinical usefulness of a dental drug system for selective reduction of mutans streptococci using a case series.

The aim of this study was to evaluate the clinical efficacy and safety of a dental drug delivery system (3DS) for the selective reduction of mutans streptococci. Twenty patients with high levels of mutans streptococci in saliva participated. The efficacy of 0.2% chlorhexidine (CHX) delivered by 3DS in reducing the salivary levels of mutans streptococci compared with total streptococci and lactobacilli was investigated. Each subject was treated by professional mechanical tooth cleaning (PMTC) and subsequently individual trays with CHX for 5 min. Salivary bacterial samples were taken at the baseline and weeks 1-12. A significant reduction in the colony count of mutans streptococci was observed during the first 4 weeks compared with the baseline count, while no significant decrease in the count of total streptococci or lactobacilli was found during 12 weeks. In particular, the proportion of mutans streptococci in total streptococci remained low after 12 weeks. Our results indicate that the new 3DS used in combination with PMTC appears to be a promising intraoral drug delivery system which, when used with a low CHX concentration selectively, effectively reduces mutans streptococci in the oral cavity with no adverse effects.

Nondestructive testing in human teeth using a leaky Lamb wave device.

A Lamb wave interdigital transducer mounted on a layered substrate composed of two plates, a thin piezoelectric ceramic plate and an acrylic plate, operating at a liquid-solid boundary, is investigated for ultrasonic nondestructive testing of the layer thickness in human teeth. A higher-order mode having a phase velocity higher than the longitudinal wave velocity in the human teeth can be used for nondestructive testing. In the combination of the two layers, the fourth mode of leaky Lamb wave is most favorable for a frequency-controllable radiation angle of an ultrasound beam into a water layer as an acoustic coupler. In the configuration of an acoustic delay line, the layer-thickness measurement in vivo, evaluated from the time interval between two reflected ultrasound echoes, is successfully realized under a thin water layer as the acoustic coupler.

Screening of periodontitis with salivary enzyme tests.

The purpose of this study was to determine the usefulness of salivary biochemical markers for the screening of periodontal disease and examine the agreement between the results of saliva enzyme tests and those of probing depth. The present study included a total of 187 subjects who underwent annual medical check-ups at the Comprehensive Health Care Center, Honjo, Saitama Prefecture, Japan. Periodontal pocket probing was performed with a WHO probe, and various enzymes and biochemical parameters in saliva were measured. For lactate dehydrogenase (LDH), the proportions of the five isoenzymes were calculated. To decide the cut-off point for each enzymatic activity, receiver operating characteristic curves (ROC curves) were constructed and the points of minimum difference between sensitivity and specificity were decided. Among the biochemical markers tested, salivary LDH level had the highest sensitivity and specificity (sensitivity 0.66, specificity 0.67), while salivary levels of aspartate aminotransferase (AST) and blood urea nitrogen (BUN) also had sensitivity and specificity above 0.60. Among the LDH isoenzymes, LDH4 and LDH5 dominated in whole saliva samples. Salivary LDH may be a feasible and useful parameter for the screening of periodontal disease, while salivary AST and BUN also appear to be potentially useful for this purpose.

Correlation between patient satisfaction and dental clinic credibility in regular dental check-ups in Japan.

The aim of this study was to investigate the relationship between dental clinic credibility and patient satisfaction with regular dental check-ups, to compare the level of satisfaction of patients who had regular check-ups with those who did not, and to identify factors associated with regular dental checkups. Thirty-nine private dental clinics in 17 prefectures throughout Japan participated in this study. A total of 9024 questionnaires were distributed to the patients at these clinics, and patients returned the questionnaires using a pre-paid envelope (response rate 56.8%). The questionnaires consisted of items related to patient demographics and 11 items concerning the level of patient satisfaction with the dental clinic. Using multiple logistic regression analysis, the strongest correlation was found between dental clinic credibility in regular checkups and the technical competence of the dentist. The responses to those items concerning making an appointment, and the cleanliness and neatness of the waiting room were different between patients who had regular check-ups and those who did not. To investigate the factors that encourage regular dental check-ups, correlation of factors with regular check up experience were analyzed. Multivariate-adjusted odds ratios indicated a strong association between regular dental check ups and both the technical competence of the dental hygienist and the cost of treatment.