Both the chronological order and geographical (spatial) orientation must be considered in epidemiological studies. However, objective statistical evaluation for the latter purpose has only recently come into widespread use. In most studies on the geographical distribution of dental caries, geographical information has been evaluated in a subjective manner. In this study, therefore, we conducted before-and-after analyses of the regional clustering of caries in three-year-old children in the wards, cities, towns, and villages of Kanagawa Prefecture between 1981 and 2006. Principal component analysis without rotation was applied to evaluate the eight indices, including dmf-rate% and dmft index, between 1981 and 2006. Two principal components (COMP1 and COMP2) were extracted (total cumulative variance=92.85%). Factor loading suggested that COMP1 was related to the trend of dmf-rate% and dmft during the 25-year period, and COMP2 was related to the caries prevalence in 2006. Regional disparities of caries indices and relevant socioeconomic indicators were evaluated based on the coefficient of variation (CV) and Gini coefficient In addition, regional clustering was verified employing global Moran's I test (g-MIT) and global Geary's C test (g-GCT), which are statistical measures of spatial autocorrelation. The Spatial Data Analysis Machine (SDAM) developed by Tsukuba University was used to calculate g-MIT and g-GCT. This analysis showed that, over the 25-year period, regional disparity and regional clustering of dmf-rate% was significant, whereas only regional clustering was significant for dmft. Stepwise multiple regression analysis revealed that the natural population increase was highly significant as a socioeconomic indicator related to regional clustering. Finally, wards, cities, towns, and villages which should be given special attention in terms of the dental health policy were identified using the hot/cold spot pattern analysis of the Local Indicators of Spatial Association (LISA) statistic from the viewpoint of spatial epidemiology.

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The objective of the present study was to elucidate the relationship between the burden of tooth-brushing assistance experienced by staff at facilities for intellectually disabled individuals and their personal factors, as well as factors related to tooth-brushing assistance. An anonymous self-reported questionnaire survey was conducted involving 527 staff at 27 facilities that agreed to cooperate among the 43 facilities for intellectually disabled individuals in one prefecture in the Tokai region. A total of 393 valid responses (74.6%) were obtained and analyzed. After performing univariate analysis regarding the relationships between the burden of tooth-brushing assistance and each variable, logistic regression analysis was conducted using variables showing significant relationships as independent variables and the presence or absence of the burden of tooth-brushing assistance as the dependent variable. The results showed that the following factors were each significantly related to the burden of tooth-brushing assistance: gender, gingival swelling in the resident, frequency of brushing the buccal side, inability of the resident to open their mouth, difficulty with the tooth-brushing posture, and difficulty completing tooth-brushing assistance on time. The odds ratio of the burden of tooth-brushing assistance was 2.31 for men relative to women, 2.96 for staff providing assistance to residents with relative to those providing assistance to residents without gingival swelling, 2.45 for staff who rarely relative to those who frequently brush the buccal side, 2.61 for staff who have difficulty getting residents to open their mouths relative to those who do not, 1.99 for staff who have difficulty with the tooth-brushing posture relative to those who do not, and 1.85 for staff who have trouble completing tooth-brushing assistance on time relative to those who do not. These findings suggest that, in order to alleviate the burden of tooth-brushing assistance among staff at facilities for intellectually disabled individuals, it is necessary to investigate measures such as support for improving the tooth-brushing assistance skills of male staff, the use of PCR for identifying sites requiring tooth-brushing assistance, training in methods of tooth-brushing assistance corresponding to the oral condition of residents, and the use of electric toothbrushes to facilitate faster tooth-brushing assistance.

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Background: The present study evaluated the concurrent and predictive validity of a self-reported masticatory function questionnaire on comparison with the objective masticatory function estimated using the total number of teeth, posterior teeth, and functional tooth units (FTUs), defined as pairs of opposing teeth. Methods: The subjects comprised 1,091 males and 1,577 females, aged from 40 to 75 years. Oral examinations were conducted in dental clinics. Information on the chewing ability was collected from a self-administered questionnaire using the key indicator "Can you bite tightly with your back teeth and dentures?" Analysis of covariance was used to calculate the adjusted mean number of total teeth, posterior teeth, and FTUs by age group and the self-reported function. Results: In all age groups, subjects who could only bite on one side or could not bite on either side had fewer teeth over-all and fewer posterior teeth than those who could bite on both sides. The numbers of FTUs decreased with the self-reported masticatory function in all age groups. In all age groups, those subjects who could only bite on one side or could not bite on either side had fewer FTUs than those who could bite on both sides. Conclusion: This study confirms that assessing the masticatory function employing a self-administered questionnaire is useful on the masticatory function screening of adults within the age range of 40 to 75 years.

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Epithelial stem cells play an important role in maintaining the homeostasis of tissues including the gingiva. Hydrogen sulfide (H₂S), the main cause of physiological halitosis, is also one of the causes of periodontal conditions, and it activates the apoptotic process initiating periodontitis. The aim of this study was to determine if H₂S causes apoptosis in human gingival epithelial stem cells. Human gingival epithelial stem cells were magnetically separated using α₆β₄, integrin and a keratinocyte proliferation marker, CD71. The isolated cell fractions were analyzed immunocytochemically for expression of the stem cell markers p63 and cytokeratin 19 and the differentiation markers cytokeratin 10 and involucrin. The cells were incubated with 50ng/mL of H₂S in 5% CO₂ air for 24 and 48h. To detect apoptosis, the cells were double-stained with Annexin V and 7-AAD, and analyzed using flow cytometry. Membrane depolarization, cytochrome C-release into the cytosol, and caspase-9 and -3 were assessed using flow cytometry or ELISA assays. The isolated cells were positive for cytokeratin 19 and p63, whereas they were negative for both cytokeratin 10 and involucrin. Apoptotic cells significantly increased to 27.30±2.0 and 37.30±1.91% at each time point, rescpectively (both p<0.01), whereas necrotic or late apoptotic cells comprised less than 16%. Clear mitochondrial membrane depolarization was detected, and cytochrome C-release was markedly increased (0.18±0 vs. 0.26±0.01ng/mL at 24h, and 0.17±0 vs. 0.46±0.05ng/mL at 48h; p<0.01). Active caspase-9 was significantly increased (1.38±0.66 vs. 6.35±1.26ng/mL at 24h, and 1.38±0.66 vs. 12.49±0.92ng/mL at 48h; p<0.01), and caspase-3 was also increased (0.20±0 vs. 0.73±0.20ng/mL at 24h, and 0.20±0 vs. 1.23±0.26ng/mL at 48h; p<0.01). It was concluded that H₂S may induce apoptosis in human gingival epithelial stem cells via caspase-9 and -3 pathways.

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This study investigated the factors commonly associated with subjective symptoms of oral dryness and thirst, such as dry mouth, stickiness of the oral mucosa and difficulty in swallowing, in junior and senior high school girls. The subjects were 143 junior high school girls and 854 senior high school girls (total: 997). Results of multiple logistic regression showed that 1) factors significantly associated with subjective symptoms of stickiness of oral mucosa were stuffy nose, mouth breathing and stress, and 2) factors significantly associated with subjective symptoms of difficulty in swallowing were age, skipping meals, eating fast foods, drinking water or tea when eating a meal, stuffy nose and stress. The results of this study showed that stuffy nose and stress, but not dietary habits, were common factors associated with subjective symptoms of dry mouth, stickiness of oral mucosa and difficulty in swallowing.

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