First permanent molars function as health database dating back to before birth

Dentin forms in microscopic layers and its adequate formation depends on the presence of vitamin D. Dark streaks develop in the dentin during those periods in which the body is deprived of the nutrient, usually owing to a lack of sunlight. Prior to this study, the research team had established that such microscopic defects remain in place and can be read later. Because teeth do not decay as rapidly as body tissue and bone, they can retain such information for hundreds of years postmortem.

Prof. Megan Brickley, Canada Research Chair in Bioarchaeology of Human Disease in the Department of Anthropology at the university, explained that, combined with other data, patterns in dentin can create rich banks of knowledge about past conditions, including information about the health impacts of living in low-light environments. “It’s a living fossil of your life, starting in utero,” said Brickley. “Conceivably, it would be possible to remove the molar of anyone and compare their health to the evidence in the tooth.”

Such records begin during the original formation of teeth in the fetal stage, and now the research team has established their value for reflecting the health of the mother during pregnancy. The first permanent molars start forming in utero and retain a record of vitamin D intake dating back to the mother’s pregnancy. That record provides a critical intergenerational link that can offer valuable clues connecting maternal health to the eventual health of a child.

“We’ve been able to set out really clear evidence that there is part of the first permanent molar that records what happened in the life of the mother,” said Brickley. “This is a tool that people can use. It can be used in current health research, and in bioarcheological research.”

The researchers examined modern and archeological tooth samples, including teeth taken from two skeletons from 19^th century Quebec—one from a 3-year-old girl who had survived rickets as a toddler, and one from a young man. The girl’s undescended molar showed that her mother had suffered a vitamin D deficiency during pregnancy—a possible clue to the child’s early death. The young man’s molar also showed that his mother had suffered vitamin D deficiency, indicating the possibility of a connection between his mother’s health and his early death.

During that time, Brickley explained, social practices and weather conditions meant that pregnant women, in particular, would have had very little exposure to the sun. It only later became clear how necessary sunlight or substitute sources of vitamin D are to good health.

The study, titled “Using teeth as tools: Investigating the mother–infant dyad and developmental origins of health and disease hypothesis using vitamin D deficiency,” was published online on Nov. 11, 2019, in the American Journal of Physical Anthropology, ahead of inclusion in an issue.

 

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