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When do children's permanent teeth erupt? New Danish study finds answers in the genome

4 new genetic variants

4 new genetic variants that influence the timing of permanent tooth eruption were identified in a genome-wide association study of more than 5,000 Danes. Children usually get their permanent teeth between ages 6 and 14 years, but the exact timing can vary substantially between different children. It is already known that the tendency to get your permanent teeth early or late is genetically regulated. But until now, no study has shown where in the genome permanent tooth eruption is regulated.

First whole-genome association study

The study is the first genome-wide association study to examine eruption of permanent teeth. The researchers first analysed data from more than 5,000 Danish study participants and subsequently confirmed the identified genetic variants in analyses of an additional 4,000 persons from Denmark and the USA. The combined effect of the 4 variants is most pronounced in the age group 10-12 years. At this age, children with a genetically based tendency for early tooth eruption have, on average, got 3 to 4 more permanent teeth compared with other children of the same age who have a genetically based tendency for late permanent tooth eruption.

Growth and maturation

One of the identified variants is located in a genomic region known to be associated with height. The researchers therefore also examined whether the same variants play a role in other biological growth and maturation traits. Analyses of genetic variants associated with height and age at menarche showed that most of these do not play a role in tooth eruption. Rather, a separate set of genes are responsible for when in a child’s growth process the permanent teeth erupt. It is notable, however, that three of the four identified genetic variants play a role in the timing of both primary and permanent tooth eruption.

Danish National Birth Cohort (DNBC)

In the Danish part of the study, researchers at Statens Serum Institut ana-lysed data from 7,331 women participating in the Danish National Birth Cohort study. Most of these women were children in the 1970s and researchers analysed their dental data from visits at the school dentist back then. The women were furthermore examined for more than ½ million genetic variants (single nucleotide polymorphisms, SNPs) covering the whole genome. DNBC contains information on 100,000 pregnant women and their offspring, providing unique opportunities for large, basic research studies of human growth and maturation from birth, over childhood to adulthood.

Read the scientific article

Geller F, Feenstra B, Zhang H, Shaffer JF, Hansen T, Esserlind AL, Boyd H, Nøhr EA, Timpson NJ, Fatemifar G, Paternoster L, Evans DM, Weyant RJ, Levy SM, Lathrop M, Smith GD, Murray JC, Olesen J, Werge T, Marazita M, Sørensen TIA, Melbye M. Genome-wide association study identifies four loci associated with eruption of permanent teeth. PLoS Genetics 2011;7:e1002275