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Analysis of tooth rings uncovers smoking's enduring impact, offering new clues for forensic science

Evidence of the permanent impact of smoking on people's teeth has been uncovered by researchers for the first time. Researchers from Northumbria University have discovered that smokers have telltale signs of their smoking habits ingrained deep within their teeth, which remain even after a person has quit.

Their findings, which are now in PLOS One, could help to provide new insights into forensic and historical investigations.

Teeth consist of three main hard tissues: enamel, dentin and cementum. Cementum, which covers the tooth root, develops characteristic "rings" that grow each year as we age—much like tree rings.

The research team had initially set out to see if these rings could be used to predict the age of an individual in a forensic setting, such as identifying disaster victims or for situations when an individual's DNA is not on a DNA database.

After examining a total of 88 teeth provided by both living dental patients and from archaeological remains, they were surprised to find signs of disruption in the cementum rings of some teeth, but not in others.

The disruption appeared as variations in the thickness and regularity of the rings within the teeth.

The researchers realized that these disruptions were associated with those who had identified as current or ex-smokers.

Their study revealed evidence of smoking damage in the teeth of 70% of ex-smokers and 33% of current smokers, compared to just 3% of non-smokers.

They also found that the cementum is thicker in ex-smokers. They believe this is a result of the cementum returning to its normal levels when smoking ceases, leaving 'stronger' deposits on top of the damaged rings which makes them thicker, whereas current smokers continue to have disruption to their cementum levels.

"Our research shows that it's possible to tell if someone was a smoker just by examining their teeth," said Dr. Ed Schwalbe, Associate Professor in Northumbria University's Department of Applied Sciences.

"We found that the regular annual deposition of rings was disrupted for some individuals and realized that these disruptions were associated with current or ex-smokers, but were very rare in non-smokers."

Forty-six individuals who were undergoing dental treatment requiring tooth extraction consented to take part in the study, providing 70 teeth between them along with their medical and smoking histories.

Notably, the researchers found smoking damage in one of the teeth provided by a living donor which they estimated to have occurred between the ages of 22 and 41.

On checking the information provided, they found that the donor, who was aged 58 at the time of tooth extraction, was a smoker during that period. They had begun smoking when they were 28 years old and stopped at the age of 38.

Dr. Schwalbe and Dr. Valentina Perrone worked with Dr. Sarah Inskip, UKRI Fellow at the University of Leicester's School of Archaeology and Ancient History, to sample a further 18 teeth from archaeological remains dating from 1776–1890.

Evidence of the age, biological sex and date of death was available for 13 of the 18 teeth provided.

Some of the archaeological teeth bore clear evidence of smoking activity, displaying staining and even notches from pipe smoking.

Remarkably, cementum analysis of the archaeological samples revealed that the rings within the teeth of smokers who died in the 18th and 19th centuries displayed the same signs of disruption as those from living donors who were current or ex-smokers.

The findings could prove to be especially important for forensic science and historical studies in the future, added Dr. Schwalbe.

"This could help us learn more about people's lifestyles in the past, especially in archaeological studies where patterns of tobacco use can reveal important cultural insights," he said.

"The identification of 'smoking damage' in archaeological teeth opens up further avenues to understand how the long-term consumption of tobacco in populations has affected our health through time," added Dr. Inskip, who leads the Tobacco, Health and History Project which looks at the long-term consequences of tobacco use on health between 1600–1900.

"By looking at growth rings in the teeth, we can also estimate a person's age when the tooth was removed, or when they died," said Dr. Schwalbe. "Together, this information could help identify unknown individuals—such as disaster victims or those buried in mass graves—and offer new tools for forensic and historical investigations."

Cementochronology—the study of what is more formally known as acellular extrinsic fiber cementum (AEFC)—has been widely used to estimate age at death and conditions such as pregnancy or disease, but this is believed to be the first time it has been used to predict tobacco use.

Dr. Valentina Perrone, who is now working as a Research Assistant at Leicester University, added, "We compared the cemental deposition of smokers, ex-smokers and non-smokers visually and statistically to identify irregularities that were potentially connected to smoking activity. We found that individuals with a history of smoking—whether as a current or former smoker—were significantly more likely to have disruption to their cementum than those who did not.

"Smoking is known to have a systemic impact on the body and numerous studies have highlighted the correlation between smoking, periodontitis and tooth loss. This study shows, for the first time, the biological record of smoking-related oral health damage within the dental structure."