Cohort study on incidence of coronal and root caries in Japanese adults.

The purpose of this study was to investigate the incidence of coronal and root caries in participants aged 20-59 years in Japan. The participants comprised 118 men and 23 women undergoing a re-examination 5 years after an initial examination. Lesions were classified as gingival recession, decayed root caries, or filled surfaces. The rates of incidence of coronal caries over the 5 years were 87% in women aged 20-29 years, 77% in men aged 20-29 years, 62% in men aged 30-39 years, 64% in men aged 40-49 years, and 60% in men aged 50-59 years. The rates for those observed to be at risk for the incidence of root caries were 25% for women aged 20-29 years, 16% for men aged 20-29 years, 11% for men aged 30-39 years, 43% for men aged 40-49 years, and 35% for men aged 50-59 years. The distribution for the number of new coronal and root caries lesions was 68.8% and 24.1%, respectively. Univariate logistic regression analyses for new coronal caries revealed that the risk factors were age group at baseline (OR=0.702, p=0.0440), number of coronal decayed and filled surfaces at baseline (OR=2.893, p=0.0107), and number of sound teeth at baseline (OR=3.381, p=0.0013). Moreover, univariate logistic regression analyses for new root caries revealed that the risk factors were age group at baseline (OR=1.787, p=0.0039), presence or absence of gingival recession at baseline (OR=3.288, p=0.0062), and presence or absence of root decayed and filled surfaces at baseline (OR=11.00, p<0.0001). It was concluded from these results that the target of caries prevention in adults should not only be focused on root surfaces, especially in those aged 40 years or over, but also on the coronal surfaces of the dentition in those in their twenties.