By Dr. Mehmood Asghar
Apart from their primary role in chewing and speech, human teeth provide a wealth of valuable information. For centuries, human teeth have been used for various diagnostic and therapeutic purposes: for forensic identification (Shahin et al., 2013), to diagnose underlying medical conditions (Aoyama et al., 2021), and to understand human diet patterns (O'Sullivan et al., 1998).
While most of these efforts were previously geared towards diagnosing underlying or future medical issues, little information was available on the effect of mental disorders and adversity on the growth trends of primary teeth.
Recently, a groundbreaking investigation revealed a fascinating finding: a correlation exists between pre- and peri-term psychological stress in pregnant mothers and the thickness of the neonatal lines in the baby’s teeth.
This research was led by Erin C. Dunn, ScD, MPH, a social and psychiatric epidemiologist, an investigator in the Psychiatric and Neurodevelopmental Genetics Unit of the Massachusetts General Hospital (MGH), and associate professor of psychiatry at Harvard Medical School. Dunn primarily investigates the timing of early-age adversities in children on their mental well-being and development.
Tooth Development is Affected by Physical and Psychological Factors
During her research, Dunn was intrigued that anthropologists used teeth from previous eras to learn about their lifestyles and habits. Armed with this information, Dunn developed a hypothesis that the width of neonatal lines (NNL) in primary teeth may indicate psychological stress or adversities experienced by the mother during pregnancy – when the teeth are still in the developmental stages.
“Teeth create a permanent record of different kinds of life experiences,” Dunn notes. Exposure to physical stressors such as poor nutrition, disease, or mental illness tends to affect the composition and physical properties of the enamel and dentine and result in the appearance of stress lines (Sabel et al., 2008). These stress lines are similar to the rings that mark the age of trees. Just like the tree rings vary depending on the climatic conditions, NNL may also vary according to the environmental experiences of babies in-utero. Typically, thicker NNL indicates stressful conditions.
Avon Longitudinal Study of Parents and Children Study Provides Insight
To test their hypothesis, Dunn and co-lead authors – who were associated with the Psychiatric and Neurodevelopmental Genetics Unit at the time of the study, Rebecca V. Mountain, Ph.D., a research fellow and Yiwen Zhu, MS, a data analyst – collected 70 naturally exfoliated primary canines collected from the Avon Longitudinal Study of Parents and Children (ALSPAC) Study. Out of these 70 children, 34 were male, 94% were white, and 57% were born full-term to mothers of child-bearing age.
The scientists measured the width of the NNL at the enamel-dentine junction (EDJ) using a microscope. Additionally, the mothers were asked to fill out questionnaires during and after pregnancy concerned with four factors that influenced child development: stressful prenatal periods, history of maternal psychological issues, neighborhood quality, and availability and level of social support.
The Ground-breaking Findings
The findings of this study were published recently published in JAMA Network Open (Mountain et al., 2021). Following the adjustment of the results for known factors that can influence NLL width – such as iron supplementation during pregnancy, gestational age, and maternal obesity – several interesting findings were revealed. First, children born to mothers who self-reported lifetime history of depression had 3.4 μm wider mean NLL at the enamel dentine junction (EDJ) than those whose mothers were not exposed (p < 0.01). Secondly, children whose mothers had a lifetime history of psychiatric problems had a 2.7 μm wider mean NLL at the EDJ than those whose mothers did not have any psychiatric illness (p < 0.03). Furthermore, children whose mothers experienced pregnancy-related depression or anxiety at 32 weeks of gestation had 2.7 μm wider NLL at the EDJ than children of mothers who did not have any history of mental illness during pregnancy (p < 0.02).
According to the US Centers for Disease Control and Prevention (CDC), early diagnosis of mental health problems in children and their families can go a long way in improving their quality of life. However, there's currently no systematic approach available to detect children at risk of developing psychological disorders. Although much information is not currently available to explain the link between NLL width and maternal history of mental disorders, this study paves the way for future research to develop, and to standardize tools that allow dental and healthcare professionals to identify children who could develop mental health disorders in the future based on the pattern and width of the NLL.
Dunn believes that her future research to identify the causative link between the growth lines and maternal psychological disorders could be vital in identifying at-risk children and to prevent the onset of pediatric mental diseases right from an early age - unlike the conventional approach to treat these issues after they appear later in life.
Aoyama, N., Fujii, T., Kida, S., Nozawa, I., Taniguchi, K., Fujiwara, M., Iwane, T., Tamaki, K., & Minabe, M. (2021). Association of periodontal status, number of teeth, and obesity: A cross-sectional study in Japan. Journal of Clinical Medicine, 10(2), 208.
Mountain, R. V., Zhu, Y., Pickett, O. R., Lussier, A. A., Goldstein, J. M., Roffman, J. L., Bidlack, F. B., & Dunn, E. C. (2021). Association of maternal stress and social support during pregnancy with growth marks in children’s primary tooth enamel. JAMA Network Open, 4(11), e2129129-e2129129.
O'Sullivan, E. A., J. Curzon, M. E., Roberts, G. J., Milla, P. J., & Stringer, M. D. (1998). Gastroesophageal reflux in children and its relationship to erosion of primary and permanent teeth. European journal of oral sciences, 106(3), 765-769.
Sabel, N., Johansson, C., Kühnisch, J., Robertson, A., Steiniger, F., Norén, J. G., Klingberg, G., & Nietzsche, S. (2008). Neonatal lines in the enamel of primary teeth—a morphological and scanning electron microscopic investigation. Archives of Oral Biology, 53(10), 954-963.
Shahin, K. A., Chatra, L., & Shenai, P. (2013). Dental and craniofacial imaging in forensics. Journal of Forensic Radiology and Imaging, 1(2), 56-62.
Author: Dr. Mehmood Asghar is a dentist by profession and an Assistant Professor of Dental Biomaterials at the National University of Medical Sciences, Pakistan. Dr. Asghar received his undergraduate and postgraduate dental qualifications from the National University of Science and Technology (NUST), Pakistan. He is also currently pursuing a Ph.D. in Restorative Dentistry from Universiti Malaya, Malaysia. Apart from his hectic clinical and research activities, Dr. Asghar likes to write evidence-based, informative articles for dental professionals and patients. Dr. Asghar has published several articles in international, peer-reviewed journals.