June 2006

Objective: In an effort to promote adequate development of the masticatory system and prevent dental diseases, the Oral Health Promotion Project (OHPP), which focuses on diet, was started in 1984. The intervention was carried out over eight years and then followed up for a further nine years, in a district with no regular dental service, on Miyako Island, Okinawa, Japan. The aims of this study were to evaluate the project’s effect on dental caries and masticatory function. Research design: Longitudinal data on the complete deciduous dentitions(IIA) at age 4 (n=163) and on the permanent dentition (IVA) at age 13-15 (n=112) were compared to control age-matched groups , aged 4 (n=105) and aged 13-15 (n=70). The control data were collected from a neighbouring district. Instructions on diet were gradually introduced to those in charge of the subjects’ food regimes. Results: Mothers reported that children born after the OHPP was begun took less snacks and caloric drinks (p<0.001) and more fibre-rich food (p<0.05) than those who born before the start of the project. The number of carious teeth decreased significantly among subjects born after the start of the project. The masticatory function was summarized in one factor using chewing performance, bite force, muscle activity duration time (using EMG) and mean amplitude of muscle activity. The factor score was higher for those born after 1984 than for those born in 1981-1983 and for those in the control district (GLM, p<0.001). Conclusion: It is suggested that OHPP can promote the masticatory function and prevent dental caries, but that it would be crucial to begin intervention soon after birth. Key words: Breast feeding, dental caries, dentition, development, diet, electromyography, mastication, masticatory function, oral health