Researchers set out to investigate whether the old saying “Gain a child, lose a tooth” has any basis in fact… and found it could do so

“Dental diseases are among the most frequent diseases globally and tooth loss imposes a substantial burden on peoples’ quality of life,” the German and Dutch researchers write.

“Non-experimental evidence suggests that individuals with more children have more missing teeth than individuals with fewer children, but until now there is no causal evidence for or against this.”

Using data from the Survey of Health, Ageing, and Retirement in Europe (with a study sample of 34,843 non-institutionalised individuals aged 50 and over from 14 European countries plus Israel), they investigated the causal relationship between the number of biological children and their parents’ number of missing natural teeth.

“Thereby, we exploited random natural variation in family size resulting from (i) the birth of multiples vs singletons, and (ii) the sex composition of the two first-born children (increased likelihood of a third child if the two first-born children have the same sex),” the researchers write in the Journal of Epidemiology & Community Health.

The SHARE survey contains information on health, educational attainment and household income of European and Israeli adults. The researchers used Wave Five, which was conducted in 2013 and included questions on the full reproductive history and number of natural teeth of 34,843 survey respondents.

The average age of the respondents in Wave 5 was 67, and they reported an average of 10 missing teeth.

Tooth loss increased with age, ranging from nearly seven fewer teeth for women in their 50s and 60s, up to 19 fewer teeth for men aged 80 and above. Higher levels of educational attainment were linked to lower risk of tooth loss among women.

The researchers applied the instrumental variables regression technique, exploiting random natural variation in a variable that is only associated with the exposure and affects the outcome only through that exposure, so mimicking a randomised controlled trial.

A third child after two of the same sex was associated with significantly more missing teeth for women, but not men, if compared with parents whose first two children were different sexes.

“Women… had an average of 4.27 (95%-CI: 1.08 to 7.46) fewer teeth than women without an additional birth whose first two children had different sexes,” they wrote.

“This study provides novel evidence for causal links between the number of children and the number of missing teeth.

“An additional birth might be detrimental to the mother’s but not the father’s oral health.”