Permanent caries experience is associated with primary caries experience: a 7-year longitudinal study in China

The aim of this study was to evaluate the association between caries experience in primary teeth and caries experience in permanent teeth in a longitudinal study.

Teeth were examined at 5 years of age and a follow-up examination was conducted 7 years later at 12 years of age in all children from Jiading District, Shanghai, China. A total of 1885 participants were recruited in the study; 1683 students were followed up and 202 students (10.7%) were lost to follow up. Data were analyzed using the chi-square test, t-test and risk ratio.

The followed-up samples comprised 883 boys (52.5%) and 800 girls (47.5%). At initial examination, the prevalence of dental caries was 67.4% in boys and 66.5% in girls (χ² = 0.2, P = 0.70), with mean decayed, missing and filled teeth (dmft) scores of 3.5 ± 0.1 and 3.4 ± 0.1, respectively (t = 0.1, P = 0.90). At follow-up, the prevalence of dental caries was 33.9% in boys and 37.9% in girls (χ² = 2.9, P = 0.11), with mean DMFT scores in permanent teeth of 0.7 ± 0.0 and 0.8 ± 0.1, respectively (t = 1.2, P = 0.24). The group of 5-year-olds with caries had a significantly higher prevalence of caries in permanent teeth (45.5%) at 12 years of age than the group of 5-year-olds without caries (16.0%) (χ² = 141.1, P < 0.001, risk ratio = 1.5). Caries risk in permanent teeth was significantly higher with greater dmft scores (χ² for trend = 31.1, P < 0.001).

Caries in primary teeth is a major risk factor for caries in permanent teeth. The likelihood of caries in permanent teeth is higher with greater dmft scores in primary teeth.