Sediment layers in rock or tree rings can hold clues to what the environment was like at different times in the past – and the same idea may even apply to your own teeth. Scientists at New York University have found that the material that makes up tooth roots preserves a lifelong record of stresses on the body, such as childbirth, illness, and even prison time.
While most of a tooth doesn’t grow once it’s popped up in your jaw, the tissue around the roots do. Known as cementum, this stuff regularly adds new layers after the tooth surfaces. And for this study, the researchers investigated the hypothesis that major physiological events would leave their mark in these layers.
To test the idea, the team examined 47 teeth from 15 different people, between the ages of 25 and 69. The life histories of all of these people were known, including things like whether they’d given birth, had major illnesses or even moved from rural to urban areas. Crucially, they also knew what ages these events had occurred.
The researchers then used a range of imaging techniques to study the rings of cementum in the roots of their teeth, and determine what ages different rings correspond to. And sure enough, rings of different colors appeared to correspond to the ages that people underwent major biological events.
For example, the team noticed a distinct line in one sample that corresponded to 17.6 years of age in the patient. When the researchers checked the file, they found that the patient had moved from a rural environment to a city at the age of 18. Other rings in other teeth occurred around the same time as their owners were experiencing childbirth, menopause, systemic illnesses, and in one case, even being incarcerated.
“A tooth is not a static and dead portion of the skeleton,” says Paola Cerrito, lead author of the study. “It continuously adjusts and responds to physiological processes. Just like tree rings, we can look at ‘tooth rings’: continuously growing layers of tissue on the dental root surface. These rings are a faithful archive of an individual's physiological experiences and stressors from pregnancies and illnesses to incarcerations and menopause that all leave a distinctive permanent mark.”
That said, the researchers caution that it’s not an exact science. The timing can be off by a few years, and it can really only be tested when the patient’s history is comprehensively known. There’s also no telling what specific event occurred just by looking at a ring. That means that scientists can’t, for example, look at a mark on an unknown tooth and determine that its owner gave birth at the age of 25.
Still, it’s an intriguing discovery that improves our understanding of our own physiology.
The research was published in the journal Scientific Reports.
Source: New York University
