Is the third molar erupting at a younger age than before?

The aim of this study was to update the much-cited knowledge, published over half a century ago, of the age of eruption of the third molar in the Finnish population.

The study followed a retrospective and cross-sectional protocol and included 710 digital panoramic radiographs of patients (49.3% men, 50.7% women) aged 15-23 years visiting the public oral health care services of the City of Helsinki in 2015. Age and sex of the subjects were recorded. The radiographs were examined for inclination of the third molars in both jaws and vertically located teeth were further classified into four stages of eruption: (A) in bone, (B) alveolar emergence, (C) gingival emergence, and (D) complete emergence. Statistics included chi-squared, Mann-Whitney U, and median tests.

Of altogether 2502 third molars, 53.0% (n = 1325) were in vertical position. The median age of gingival emergence (stage C) of the third molar varied between 19.8 and 20.8 years, and the median age of reaching the occlusal level (stage D) between 20.8 and 21.8 years depending on sex and the jaw.

The median ages for the third molar to pierce the gum were lower than reported over half a century ago.