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Objectives <p>To re-examine Japan’s long-term decline in permanent-tooth caries among 12-year-olds and assess its implications for population-level caries prevention beyond historically dominant systemic fluoride-centered prevention frameworks.</p> Study design <p>Ecological analysis of national surveillance data.</p> Methods <p>We assembled long-term nationwide data from Japan on caries experience in 12-year-olds. Data were derived from standardized school dental examinations with high coverage and low temporal variability. Trends were examined descriptively and interpreted in relation to historically established systemic fluoride–caries prevention frameworks, including population fluoride exposure and long-term changes in sugar availability.</p> Results <p>Japan experienced a near-continuous decline in caries among 12-year-olds over approximately 40 years, reaching a national mean DMFT of 0.53 in 2023—well below levels historically reported in populations exposed to systemic fluoride through community water fluoridation. This decline occurred without community water fluoridation and largely before the approval of high-fluoride toothpaste in 2017 and its recommendation for school-aged children in 2023. Although sugar availability declined early, caries levels continued to fall long after sugar intake stabilized.</p> Conclusions <p>Japan represents a rare natural social experiment demonstrating that sustained population-level caries reduction can occur through cumulative non-systemic fluoride pathways. These findings suggest fluoride-centered frameworks alone may not fully explain long-term population trends and support a broader multicausal approach to caries prevention. They may inform population-level oral health strategies in settings where reliance on systemic fluoride alone may be insufficient.</p>

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A 40-year decline in permanent-tooth caries among 12-year-olds in Japan in the absence of systemic fluoride-based prevention: public health implications

  • 期刊论文

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  • 发表日期：

    2026年5月18日

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  • Yoshihisa Yamashita

摘要

Objectives

To re-examine Japan’s long-term decline in permanent-tooth caries among 12-year-olds and assess its implications for population-level caries prevention beyond historically dominant systemic fluoride-centered prevention frameworks.

Study design

Ecological analysis of national surveillance data.

Methods

We assembled long-term nationwide data from Japan on caries experience in 12-year-olds. Data were derived from standardized school dental examinations with high coverage and low temporal variability. Trends were examined descriptively and interpreted in relation to historically established systemic fluoride–caries prevention frameworks, including population fluoride exposure and long-term changes in sugar availability.

Results

Japan experienced a near-continuous decline in caries among 12-year-olds over approximately 40 years, reaching a national mean DMFT of 0.53 in 2023—well below levels historically reported in populations exposed to systemic fluoride through community water fluoridation. This decline occurred without community water fluoridation and largely before the approval of high-fluoride toothpaste in 2017 and its recommendation for school-aged children in 2023. Although sugar availability declined early, caries levels continued to fall long after sugar intake stabilized.

Conclusions

Japan represents a rare natural social experiment demonstrating that sustained population-level caries reduction can occur through cumulative non-systemic fluoride pathways. These findings suggest fluoride-centered frameworks alone may not fully explain long-term population trends and support a broader multicausal approach to caries prevention. They may inform population-level oral health strategies in settings where reliance on systemic fluoride alone may be insufficient.