The following is the second post of a guest blog series written by researchers in the Dunn Lab at Massachusetts General Hospital. Read the first post.

In this second post, we highlight a new paper e-published in the journal Biological Psychiatry. If you did not get a chance to read it earlier, you can check out our first post highlighting members of Dunn Lab’s Team Tooth here.

In the post below, Becky Mountain, a post-doc in the lab, summarizes the main takeaways from this work.

Exposure to early life adversity, such as growing up in poverty, witnessing violence, or having a parent with mental illness, is a primary determinant of health. Though not all children who experience early life adversity will go on to have mental health problems, these exposures have been shown to about double a person’s risk for mental health disorders, such as depression and anxiety. Unfortunately, these types of adversities are common, estimated to affect nearly half of all youth in the United States.

Recent research by our group and others has suggested that the timing of when these adversities occur matters. In other words, there appear to be “sensitive periods” during development when the brain is more plastic  and thus when exposure to adversity may have more potent and long-lasting impacts.

However, current tools to measure these adverse exposures are limited; they often rely heavily on personal memories of very early life events or parental reports. Scientists and mental health professionals are in urgent need of new objective tools that can help to identify individuals who have been exposed to early life adversities, particularly psychosocial stressors, as well as when those exposures occurred.  With this information, professionals would be better equipped to identify people at greater risk for subsequent mental health disorders.

In our recent publication, entitled “Teeth as Potential New Tools to Measure Early-Life Adversity and Subsequent Mental Health Risk: An Interdisciplinary Review and Conceptual Model”, we propose that teeth, may be just such a tool.

Specifically, we highlight the major features of teeth that make them ideal tools or biomarkers for psychiatry and related fields:

1. Teeth Develop During Known “Sensitive Periods” in Development

Most humans have two sets of teeth: 20 primary or “baby” teeth and 32 secondary or permanent teeth. Our primary teeth begin forming as early as 7 weeks in utero.  Our permanent teeth are typically completely formed by late adolescence or early adulthood.

This development corresponds with sensitive periods of brain formation, including rapid brain growth during the prenatal period.

2. Teeth Leave a Permanent Record of Their Incremental Formation, Just Like the Rings of a Tree

Our teeth develop incrementally in consistent layers on an approximately daily and weekly basis that correspond to the body’s natural biorhythms. This leaves behind incremental lines or “growth marks” that can be measured microscopically. 

3. Human Teeth Preserve Biological Memories of the Existence and Timing of Past Physiological Stressors

Previous research has shown that physiological disruptions during development, including severe illness and malnutrition, can result in macroscopic level defects in a tooth’s enamel (the hard, white outer surface of the tooth). These exposures can also cause disrupted or accentuated growth marks, also known as “stress lines,” in the enamel of an individual’s teeth. These stress lines can potentially be dated in primary teeth  to the week or even day of the disruption.

4. Human Teeth May Also Preserve Biological Memories of the Existence of and Timing of Past Psychosocial Stressors

There is also some promising new evidence, primarily from research with primates, that suggests teeth may also capture psychosocial stressors. For example, several studies have found stress lines in primate teeth corresponding to stressful events in the primates life, including separation from their mother or larger social group.  

5. Teeth Are Spontaneously Shed or Routinely Removed Across the First Two Decades of Life, Making Them Potentially Ideal Tools to Guide Primary Prevention Efforts in Psychiatry

Our primary teeth are naturally shed beginning around 6 years of age and are replaced by the permanent teeth. Children and adolescents often have primary or permanent teeth extracted as part of orthodontic work.  And the third molars or “wisdom teeth” are commonly removed during late adolescence. These represent multiple of windows of opportunity to potentially identify at risk individuals and introduce intervention programs before the typical onset of depression symptoms and other mental health disorders.

Based on these features of teeth, we developed the TEETH (Teeth Encoding Experiences to Transform Health) Conceptual Model to explain how early life exposure to psychosocial stress becomes embedded in teeth and could be used as predictive biomarkers of future psychiatric risk. There are three basic tenets of the TEETH Conceptual Model:

• Tenet 1: Early life adversity may be associated with disrupted processes involved in brain and tooth development.
• Tenet 2: Developmental disruptions during tooth formation may produce time-resolved biological imprints that can be objectively captured.
• Tenet 3: Disrupted developmental processes may predict mental health risk.

To fully investigate teeth as a biomarker of psychosocial stress exposure and future mental health risk, further research is needed in several areas. We need to better understand what teeth capture in terms of the type of exposures, when or under what conditions do they capture it, how they capture it (or what the underlying mechanisms are), and the logistical and feasibility issues for implementing wide-scale collection of teeth for clinical research.  

If teeth can be validated as an objective biomarker of early life exposure to psychosocial stress and a predictive tool to identify those at greatest risk for future mental health issues, teeth could transform diagnostics and prevention. We could potentially direct at-risk individuals to targeted intervention programs years before the typical onset of symptoms using a tool many people throw away or hide in a drawer. 

We hope this post has you excited about the potential of teeth as biomarkers. Have any thoughts on this you want to share?  Find us on Twitter @ErinDunnScd!

About the Mass General Research Institute
Research at Massachusetts General Hospital is interwoven through more than 30 different departments, centers and institutes. Our research includes fundamental, lab-based science; clinical trials to test new drugs, devices and diagnostic tools; and community and population-based research to improve health outcomes across populations and eliminate disparities in care.
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