We have been conducting several epidemiological studies of oral diseases including an intervention study on a school-wide basis to prevent caries since 1970. This study showed positive results in achieving a rate of 90% caries-free children aged 11-12 years in the model area, and reducing the average number of carious teeth to 0.1 since 1996. We are currently collecting and analyzing data along with a basic study on oral bacteria to elucidate the cause of children at a high risk of dental caries in whom caries development could not be prevented by the basic caries prevention program.

The Global Network led by the WHO headquarters has been revealing the epidemiological characteristics of periodontal disease in different nationalities and ethnic groups since 1989. Based on the concept regarding the periodontal tissue health obtained from the study by Global Network, new periodontal screening and monitoring methods are aimed to be developed as well as the management of WHO Global Info by collecting basic data necessary for health policy planning.

Previous epidemiological studies have revealed that halitosis, which attracts public attention, is often caused by problems in the mouth. We focus on the fact that true halitosis associated with periodontal disease is caused by volatile sulphur compounds (VSC), and have been evaluating the pathological condition of periodontal disease by measuring the VSC level, and performing an epidemiological study to predict periodontal disease progression.

The relationships between oral and general health, and the development and progression of disease have been elucidated by a cohort study in the elderly in Niigata (Niigata elderly study) since 1998. The analysis requires an appreciable period due to the large amount of data.

We are also working on joint research with Michigan University (United States) (Periodontal disease and systemic illness), Newcastle University (United Kingdom) (Oral health and nutrition), and London University (Oral cancer and precancerous lesion), and basic epidemiological studies including the relationship between the development of oral disease and lifestyle with dental schools and health ministries in Myanmar, Sri Lanka, Cambodia, and Laos to develop an oral health policy. These studies are part of WHO Collaborating Centre activities.

We have performed a clinical intervention study with the Department of Internal Medicine regarding the influence of periodontal treatment using antimicrobials on the improvement of insulin resistance in diabetic patients, and confirmed a significant increase in serum adiponectin concentrations in diabetic patients.

We were involved in the development of simple gas chromatography specifically designed for the halitosis test. The effectiveness of the device was confirmed by many clinical studies. Simple gas chromatograph are available on the dental market worldwide due to their convenient use chairside in private practice. Oral rinses and sprays containing zinc chloride have been found to be effective for halitosis treatment in cross-matching. Clinical studies showed that plant-origin protease is effective for tongue coat control, preventing halitosis as a result. A clinical study has been performed using protease in different profiles to introduce protease into the nursing-care scene for the elderly.

Individual health controls in clinical preventive dentistry including caries prevention in children, root caries prevention in the elderly, and prevention of periodontal disease in adults are also important. Assessment, prediction, and maintenance program construction of the disease risk are major themes for future study. We need to collect clinical data consistently to achieve these goals.

We have been conducting basic research to develop a caries activity test focused on the glucan-synthesizing ability of Streptococcus mutans, a common cariogenic bacterium. It has been confirmed that the glucan-synthesizing ability varies depending on the strain. It is more effective to assess the insoluble glucan-synthesizing ability of S. mutans in the mouth than the conventional caries activity test for the screening of children with a high caries risk whose caries cannot be prevented by basic caries prevention programs. We are currently analyzing the gtfB gene coding for the insoluble glucan synthesis of S. mutans to investigate the insoluble glucan-synthesizing ability corresponding to the base sequences in different strains.