When the body doesn’t get enough vitamin D, permanent microscopic abnormalities form in the layers of dentin to create an ongoing record that can be read like the rings of a tree even hundreds of years later, according to researchers at McMaster University. These abnormalities, the researchers say, can help anthropologists glean clues about what life was like centuries ago.
“The layers store what happens as teeth grow,” said Lori D’Ortenzio, a PhD candidate in anthropology at the university and an author of the study, which appeared in the Journal of Archeological Science. “We all know the importance of vitamin D, but until now we did not have such a clear way of measuring exactly what happened to people and when.”
For example, the discovery can provide valuable information about vitamin D deficiency, also known as rickets, which affects about 1 billion people worldwide. Most cases of rickets are caused by a lack of sun exposure with effects including pain, bone deformities, and failure to achieve or maintain adequate bone levels.
“If we can properly understand past changes in deficiency levels, we can evaluate where we currently are and move forward,” said Megan Brickley, a professor of anthropology at McMaster and the Canada Research Chair in the Bioarchaeology of Human Disease.
Typically, scientists have used bones to understand historical patterns in vitamin D deficiency. Bones are problematic sources of information, though, since bone material is constantly being remodeled in life, obscuring details of prior damage. Also, bones interact with soil and break down after death. However, dentin is not remodeled, and enamel protects it long after death, making teeth a rich source of information.
“They’re essentially fossils in your mouth,” said Bonnie Kahlon, a lab coordinator in McMaster’s anthropology department.
The researchers compared the teeth of modern-day control subjects to teeth extracted from bodies buried in rural Quebec and France in the 1700s and 1800s. Their analysis showed that one Quebec man had suffered 4 bouts of rickets in his 24 years of life, all before he was 13 years old.
Examining thin sections of the teeth under a microscope and using technology at the McMaster-based Canadian Centre for Electron Microscopy, the researchers showed that anomalies formed in the dentin layers during years when victims failed to get enough vitamin D to fully mineralize the structures that form dentin and bone.