Div. of Preventive Dentistry

Professor　 OGAWA Hiroshi

face

Our Education

Preventive Dentistry
Public Health

Our Research

1) Epidemiological studies
Several epidemiological studies on oral diseases, including intervention studies to prevent caries, have been conducted on a school-wide basis since 1970. These studies have achieved positive results in model areas by increasing the rate of caries-free children aged 11～12 years to 90% and reducing the average number of carious teeth to 0.1. The data from these studies along with the results of laboratory studies on oral bacteria were collected and analyzed to identify the cause of dental caries in children at high risk in whom caries development could not be prevented by the basic caries prevention program.
The World Health Organization (WHO) Oral Health Country/Area Profile Program has been monitoring the epidemiological characteristics of periodontal disease in different nations since 1989. Based on the concept of periodontal health derived from a study by the Global Network, new methods for screening and monitoring periodontal diseases need to be developed. Furthermore, the WHO Global InfoBase needs to be further developed by collecting the basic data necessary for health policy planning.
The Niigata Elderly Study, a longitudinal study conducted since 1998, is investigating the relationships between oral and general health and disease development and progression. Additionally, more than 150 research papers have been published.
Furthermore, we have conducted basic epidemiological studies on the relationship between the development of oral disease and lifestyle in collaboration with dental schools and health ministries in Myanmar, Thailand, and Indonesia to develop an oral health policy. These studies are part of the activities of the WHO Collaborating Centre for Translation of Oral Health Science (JPN-75).

2) Clinical studies
We conducted clinical intervention studies in collaboration with the Department of Internal Medicine to investigate the effects of periodontal treatment using antimicrobials on the improvement of insulin resistance in patients with diabetes and confirmed a significant increase in serum adiponectin concentrations.
We developed a simple gas chromatograph specifically designed for the halitosis test. The effectiveness of this device was confirmed by our clinical studies. Simple gas chromatographs are currently available on the dental market worldwide because of their convenience for chairside use in private practice. Additionally, oral rinses and sprays containing zinc chloride have been found to be effective in treating halitosis in cross-matching research. Clinical studies have shown that proteases of plant origin are effective in controlling the tongue coat, thereby preventing halitosis. Further clinical studies using proteases with different profiles are needed to introduce proteases into the nursing care setting for older adults.
In preventive dentistry, individual health management plays an important role in caries prevention in children, root caries prevention in older adults, and periodontal disease prevention in adults. Therefore, developing programs for the assessment, prediction, and maintenance of disease risk are major themes for future studies. We need to collect further clinical data to achieve these goals.

3) Basic research
We are conducting basic research to develop a caries activity test that focuses on the glucan-synthesizing ability of Streptococcus mutans, a common cariogenic bacterium. Its glucan-synthesizing ability has been confirmed to vary depending on the strain. Thus, assessing the insoluble glucan-synthesizing ability of S. mutans within the mouth is more effective than performing the conventional caries activity test for screening children at high risk of caries whose caries cannot be prevented by basic caries prevention programs. We are currently analyzing the gtfB gene, which codes for the insoluble glucan synthesis of S. mutans, to investigate how the insoluble glucan-synthesizing ability corresponds to the base sequences in different strains.

Clinical Fields

1) Professional mechanical tooth cleaning
Thorough cleaning of the tooth surface by a dentist or dental hygienist is called professional mechanical tooth cleaning. Using specialized equipment and fluoride abrasives, we clean and polish all tooth surfaces, focusing on calculus and plaque left over from brushing. This creates an oral environment that is less prone to tooth decay and periodontal disease. Additionally, we provide instructions on how to choose a proper toothbrush, hold the brush, apply the bristles, move the brush, apply appropriate force, and use interdental brushes and dental floss for proper toothbrushing.
2) Fluoride application
Fluoride application prevents tooth decay by increasing the resistance to such decay. This is achieved through the acquisition of acid resistance, improvement of crystallinity, and promotion of remineralization. Fluoride can be applied systemically (fluoride ingested orally acts on the enamel during tooth formation) and topically (fluoride acts directly on the tooth surface). In our department, we perform the following fluoride applications:
a) Fluoride mouthwash (prevents decay of permanent teeth)
b) Fluoride gel application (prevents decay of deciduous teeth and permanent tooth roots)
c) Fluoride-containing toothpaste (prevents decay of all teeth)
The safety of fluoride has been scientifically proven.
3) Measurement of halitosis using gas chromatography
Volatile sulfur compounds, including hydrogen sulfide, methyl mercaptan, and dimethyl sulfide, are the causative agents of halitosis and can be quantitatively evaluated using gas chromatography. A gas chromatograph is a precision instrument that separates chemical substances in exhaled breath and measures volatile sulfur compounds, making it possible to accurately measure which substances are present and their amounts. Additionally, a dentist with specialized knowledge can qualitatively evaluate halitosis using a sensory test. Because a large amount of volatile sulfur compounds are produced from the tongue moss that accumulates on the tongue, we provide guidance on how to clean the tongue to properly remove the tongue moss.

Our Website

https://www5.dent.niigata-u.ac.jp/~prevent/japanese/index.html

Our Citizenship

In 2007, the WHO designated the Department of Oral Health Science, Division of Preventive Dentistry, Niigata University Graduate School of Medical and Dental Sciences as a WHO Collaborating Centre for Translation of Oral Health Science. The terms for reference of the center are as follows: 1) Assisting the WHO in strengthening the oral health information system. 2) Supporting the WHO in integrating the oral health component into the WHO Healthy Ageing policy documents. 3) Assisting the WHO in promoting oral health through primary prevention. 40 Assisting the WHO in supporting the Member States in implementing the phase-down use of a dental amalgam within the framework of the Minamata Convention on Mercury.

Research Figures

Back to index