The shortage of dental hygienists is a problem in Japanese dental clinics. We examined the reasons for dental hygienist turnover based on the occupational stress model, which is an important concept in the field of occupational health, and analyzed the differences in perceptions between dental hygienists and dentists. In this cross-sectional study, a mail-based questionnaire survey was conducted in 2017, sent to 1,334 dental hygienists and 1,185 dentists in Miyagi Prefecture. The questions were based on six stress models. The differences between the answers of the dental hygienists and dentists were analyzed using the chi-square test. Among 313 dental hygienists (response rate: 23.5%) and 213 dentists (response rate: 18.0%), we used the data of 303 and 174 respondents, respectively, with no missing values. The major reasons for the turnover of dental hygienists were “personality conflict issues (78.2%),” “long working hours (68.6%),” and “low salary (58.4%).” However, dentists were significantly less likely to think that these were the causes for hygienists leaving their jobs; most dentists considered “maternity leave” as the main reason. Regarding personality conflict issues, most dental hygienists answered that the director dentist was the cause. In contrast, dentists thought that staff were the cause of the problem. Regarding working hours, both hygienists and dentists answered that “long working hours” was a problem. However, in addition, hygienists also considered the difficulty of taking paid leave and overtime work as problems. Most dental hygienists who were unemployed wanted to return to work part-time, and many wanted to avoid working afternoon hours. There was a large difference of opinion between dentists and dental hygienists in terms of recognizing workplace problems in relation to reasons for job turnover. Recognizing and resolving these issues in dental practices may lead to more suitable work environments for dental hygienists.

 In this study, we examined factors related to the shape of the toothpaste tube nozzle and associated properties, in order to clarify the appropriate amount of fluoride-containing toothpaste. The opening of the nozzle and weight per 1 cm smear of 31 types of dentist-prescribed fluoride toothpastes were measured. Smeared weights were measured by 6 examiners, subsequently, the average values were taken as weight per 1cm, and the coefficient of variation (CV) and sampling error (%) were determined. To assess statistical dispersion of the weights, one-way analysis of variance and Bonferroni correction for multiple comparisons were performed, and the results of successive comparisons of each dentifrice were taken as significant differences. Furthermore, single correlation and multiple regression analyses were performed on the nozzle opening, standard weight, smeared weight, specific gravity, viscosity, coefficient of variation, sampling error (%), significant difference in each dentifrice, and relevance. As a result of the single correlation analysis, the standard and smeared weights, nozzle opening and specific gravity, smeared weight and specific gravity, smeared weight and viscosity, viscosity and coefficient of variation, standard weight and sampling error (%), smeared weight and sampling error (%), viscosity and sampling error (%), coefficient of variation and sampling error (%), standard weight and specific gravity, standard weight and viscosity, and standard weight and significant difference showed a correlation (p<0.05). Multiple regression analysis data demonstrated that the nozzle opening, specific gravity, coefficient of variation, and viscosity showed significant correlations (p<0.05).

 Therefore, in order to use an appropriate amount of fluoride toothpaste, it is necessary to specify the standard weight pertaining to 1cm of smear.

 Erythritol, a sugar alcohol, is used in a wide range of foods as an artificial sweetener, as well as in dentifrices and mouthrinses due to its potential caries-reducing properties. We previously showed that erythritol altered the metabolism of Porphyromonas gingivalis, a major periodontal pathogen, and reduced its abundance in dual-species biofilms with oral streptococci. In this study, we focused on volatile sulfur compounds (VSCs) responsible for oral malodor, and investigated the effects of erythritol on the VSC-producing capabilities of P. gingivalis and another periodontal pathogen, Treponema denticola.

 Prior to the VSC production assay, the inhibitory effect of erythritol on P. gingivalis planktonic growth was tested in 3-fold diluted trypticase soy broth (dTSB) with or without 0.5, 1, 5, or 10% erythritol, respectively. In the VSC production assay, P. gingivalis and T. denticola were cultured in respective liquid media with or without 5-10% erythritol in ventilated flasks sealed with silicone plugs, and were incubated under anaerobic conditions without shaking for 18 and 48 h, respectively. Following homogenization by pumping, the headspace air above a certain distance from the surface of bacterial culture was collected in a gas-tight syringe, and gas chromatography was applied to determine the levels of VSCs (hydrogen sulfide, methyl mercaptan, dimethyl sulfide, and dimethyl disulfide). A comparison of VSC levels was performed using one-way analysis of variance with post-hoc paired comparisons conducted with Dunnett’s test.

 In dTSB, erythritol had a moderate inhibitory effect on P. gingivalis planktonic growth. Meanwhile, erythritol showed significant concentration-dependent inhibitory effects on methyl mercaptan and dimethyl disulfide produced by P. gingivalis, and the inhibition rates of 5% erythritol were 29.0 and 90.1% and those of 10% erythritol were 72.0 and 98.4%, respectively. Hydrogen sulfide and dimethyl sulfide, which the bacterium produces only at relatively low concentrations, were not detected at all in the presence of 10% erythritol. On the other hand, erythritol did not significantly affect the VSC-producing capability of T. denticola. These results indicate that erythritol inhibits the planktonic growth and production of VSCs by P. gingivalis in a species-specific manner, and may help to improve periodontitis-associated oral malodor.

 According to the 2016 Japanese National Health and Nutrition Survey, 52.9% of people over 20 years of age attend dental checkups in the past year. The goal of the Second Health Japan 21 is to increase this rate to over 65%, but this goal has yet to be achieved. This study enrolled 366 people (183 males, 183 females; average age: 64.6 years) who underwent dental examinations in Osaki, Soo District, Kagoshima Prefecture during 2016–17. Exploratory factor analysis was performed to identify factors leading to regular checkups by family dentists. From the results of a self-completed questionnaire and dental examination, we extracted combinations of factors using decision tree analysis, a data mining method, and evaluated their effects using the χ²-test. This showed that oral hygiene treatment within a year, sex, and use of interdental cleaning adjuncts were three important factors influencing the decision to attend regular dental checkups. This suggests that dentists should instruct patients to visit a dental office for oral hygiene treatment at least once a year and to use interdental cleaning tools at least 3 days a week to improve the rate of dental checkups. Encouraging men to undergo regular dental checkups was suggested to be more effective.

Abstract in Japaneses