Human papillomavirus (HPV) infection is a major risk factor for cervical cancer, and may also be associated with the development of oropharyngeal cancer and prognosis of affected patients. However, the causal relationship between HPV infection and oral cancer has not been fully elucidated. In this review, we examined recent results of epidemiologic and basic research studies to elucidate risk factors associated with oral HPV infection, HPV prevalence in oral cancer patients, and the characteristics of the molecular mechanism of HPV-positive oral cancer. We found that HPV DNA was positive in 4.0-32.0% of oral cancer cases, with HPV16 being a common high-risk type found in oral cancer specimens. Also, the rate of HPV16-positivity was higher in epithelial dysplasia lesion and oral squamous cell carcinoma samples compared with normal epithelial tissues, suggesting that HPV16 is involved in oral cancer development. A low percentage of oral cancer cases showed E6 and E7 mRNA-positivity, and the positive rates of E6 and E7 mRNA were lower than those of HPV DNA; thus, we suggest that molecular mechanisms independent of stable E6 and E7 expression may be involved in the malignant transformation of HPV-related oral cancer (i.e., oral cancer caused by oral HPV infection). Although HPV16-positive oral cancers were associated with a better prognosis compared with HPV16-negative oral cancers, it remains unclear whether HPV-related oral cancers are associated with a better prognosis. Since oral HPV infection is associated with poor oral hygiene, oral health care and smoking cessation may play significant roles in its prevention. For the development of evidence-based prevention strategies for the treatment of HPV-related oral cancer, it is necessary to clarify the significance of the existence and role of HPV in HPV DNA-positive oral cancer. It is strongly anticipated that the results of basic and clinical studies of oral HPV infection will be presented in the near future.

It was recently reported that dental care management not only reduces the economic burden caused by dental diseases, but also helps to prevent the deterioration of lifestyle-related diseases. This study was aimed to comprehensively survey the findings to date on how the oral health status and dental health service utilization are associated with dental and medical expenditures. Investigation focused on: (1) association of the oral health status with dental and medical expenses, and (2) association of the utilization of dental health services with dental and medical expenses. An initial combination of electronic-database and hand searches yielded 32 relevant reports, which were then intensively reviewed.

(1) Many studies revealed that patients with 20 or more teeth incur lower dental costs, and those with more remaining teeth incur lower medical costs. In addition, there were reports that the presence of dental disease, primarily periodontal disease, is associated with higher dental and medical expenses.

(2) There were reports that participating in regular preventive visits to a dental clinic or dental check-ups is associated with lower dental and medical costs.

The results of this study reveal that dental and medical expenditures are particularly associated with the number of remaining teeth, and with participation in dental health activity such as regular preventive dental visits. Caries and periodontal disease are the leading causes of tooth loss: the present findings suggest that continuing regular dental check-ups from a young age focused on the prevention of such dental diseases could make a consistent contribution to controlling costs of not only dental care but also general medical care.

The oral health of elderly people is not only important in the maintenance of solid nutrition and articulation but also for their quality of life (QOL). The presence of ≥20 teeth is one of the criteria in the maintenance of the oral function and general health. In 2015, the Ministry of Health, Labour and Welfare of Japan announced the guideline called “Healthy Diet”, which supports the longevity of Japanese people. We examined the association between the presence of ≥20 teeth and healthy diet among 75-year-old people. This study included 338 people aged 75 years who participated in the Niigata Elderly Study (2003), in which oral examination, medical checkup, and a brief-type self-administered diet history questionnaire (BDHQ) survey had been carried out. A healthy dietary pattern was defined according to Japan’s healthy diet guideline. The healthy diet assumes that one meal consists of three main dishes: grain dish, fish or meat dish, and vegetable dish. For each dish, there are lower and upper limits on the amount of food consumed per meal. For this reason, we set the per-day lower limit as equal to three times the lower limit for a meal. In this study, the sufficiency group satisfied all three dish divisions (i.e., those who achieved a healthy dietary pattern), and the insufficiency group did not meet at least one dish division. The association between the presence of ≥20 teeth and a healthy dietary pattern was evaluated using multivariable logistic regression. As a result, individuals with ≥20 teeth had significantly higher odds of having a healthy dietary pattern (adjusted odds ratio, 1.7; 95% confidence interval: 1.1–2.6). In conclusion, our results suggest that there is a relationship between the presence of ≥20 teeth and meal patterns in elderly people.

We used the 4th version of an original chart prepared in 2008 to assess the health condition of the temporomandibular joint (TMJ) in order to study the dental health of students.

The purpose of this study was to identify factors associated with subjective symptoms of temporomandibular disorders (TMD), as their identification would be important for establishing specific contents of a health guidance program. This chart incorporates several questions about TMD, the TMJ, and factors influencing TMD awareness (occlusion, lifestyle, and stress). The time period of the study was 2008-2014, and the subjects were 391 prefectural 3rd grade junior high school students (208 males and 183 females) in Saitama Prefecture, because students in junior high school usually encounter marked stress.

We considered subjective symptoms using this chart. At first, we divided the students into two groups based on the presence or absence of subjective symptoms of TMD. Then, these two groups were compared by 3 kinds of factor: the number of factors, and physical and mental factors measured using the visual analog scale (VAS).

The study revealed that their subjective symptoms were significantly different (p<0.05) with respect to lifestyle. There were significant differences in the number of influencing factors between the two groups (p<0.05). The VAS score showed a correlation between physical and mental factors. The group with symptoms showed a lower VAS score, and their physical score was significantly lower (p<0.05).

Therefore, these results suggest that the perceived subjective symptoms of TMD were mainly affected by lifestyle; however, the number of influencing factors was also involved. In the students with symptoms, a weak relationship between physical and mental factors was suggested.

Abstract in Japaneses