Introduction Birth weight is associated with many health-related conditions. However, associations with dental health remain largely unknown. Infants in Russia have on average eight erupted teeth by the age of 48 weeks. We studied associations between birth weight and eruption of deciduous teeth in Arkhangelsk, Northwest Russia.

Methods Altogether, 456 randomly selected infants (51.3% were boys) at the age of 11–13 months (mean 47.8 weeks) underwent dental examination in a paediatric clinic in the city of Arkhangelsk. Data on birth weight were obtained from medical records. Mean numbers of erupted teeth by gender were compared using Mann–Whitney tests. Associations between having eight or more teeth and birth weight (in kilogrammes) were assessed by logistic regression with adjustment for gender, infant age and breastfeeding history.

Results The mean number of erupted teeth was 6.69 (95% CI 6.47 to 6.91). It was higher in boys than in girls (7.04 vs 6.32, p=0.001). Altogether, 43.6% (49.8% of boys and 37.0% of girls) of all examined children had 8 or more teeth. A positive association between birth weight and having 8 or more teeth was observed: OR 1.79 (95% CI 1.19 to 2.70). Girls were less likely to have 8 or more teeth than boys: OR 0.65 (95% CI 0.43 to 0.98).

Conclusions The mean number of erupted teeth in infants in Arkhangelsk is lower than in Russia on average. Birth weight and male gender were positively associated with the odds of having 8 teeth by the age of 48 weeks. Potential mechanisms will be discussed.