Researchers at Northumbria University have found the first solid evidence that smoking leaves permanent marks deep in the teeth, even after smokers have quit.
The findings, published in the journal PLOS One, could open new avenues for forensic and historical research.
Teeth are made up of three main hard tissues: enamel, dentin and cementum. Cementum covers the roots of teeth and forms “rings” over time as they age, similar to tree rings. These cementum rings provide a unique perspective on physiological changes throughout an individual’s life.
The researchers initially hoped to use these cementum rings to predict an individual’s age and help forensics, such as identifying disaster victims or individuals with missing DNA information.
However, after analyzing a total of 88 teeth from modern dental patients and historical archaeological sites, the research team unexpectedly found that some of the teeth had abnormal damage to the cementum rings, and these abnormalities were closely related to smoking behavior.
The study showed that 70% of ex-smokers and 33% of current smokers had cementum damage in their teeth, compared to only 3% of non-smokers.
These damages manifested as changes in the thickness and regularity of cementum rings, reflecting that smoking leaves a permanent biological mark deep in the teeth.
More interestingly, the study also found that cementum deposits were thicker in ex-smokers than in smokers. The researchers speculate that this is because the cementum recovery process after quitting smoking forms denser deposits in the damaged area, increasing the overall thickness. For current smokers, cementum development remains disturbed.
In this study, 46 patients who underwent tooth extraction volunteered 70 tooth samples, accompanied by detailed medical and smoking histories.
One case was particularly convincing: the researchers detected cementum damage in the teeth of a 58-year-old patient that could be traced back to the age of 22 to 41.
Further verification revealed that the patient started smoking at the age of 28 and quit at the age of 38, which coincided with the time period of damage in the tooth.
The research also involved the analysis of 18 archaeological teeth excavated between 1776 and 1890 in collaboration with Dr. Sarah Inskip of the University of Leicester.
Thirteen of these teeth confirmed the age, sex and time of death of the deceased. Some teeth also showed obvious signs of tobacco use, such as stains and gaps left by pipe smoking.
Surprisingly, the cementum destruction characteristics of these 19th-century smokers’ teeth are very similar to those of modern smokers or former smokers. This provides valuable clues to the lifestyle, cultural background and health of historical populations.
Dr. Schwalbe pointed out that this discovery is of great significance for forensic investigations and historical research. He said: “These data help us better understand the living habits of past populations, especially the potential health effects of tobacco use.”
Dr. Inskip added: “The discovery of smoking damage in archaeological teeth provides us with a new path to study the long-term effects of tobacco on human health between 1600 and 1900.”
Dr. Schwalbe also emphasized that the annual ring characteristics of cementum can not only infer an individual’s smoking history, but also be used to estimate age, which helps to identify unidentified dead, such as victims of disasters or nameless people in ancient tombs.
The method used in this study is called “cementum chronology”, and its more formal academic name is “cell-free extrafibrous cementum (AEFC) analysis”.
Although this technology has been used to estimate the age of death or reflect physiological states such as pregnancy and disease in the past, this is the first time it has been used to identify smoking behavior.
Dr. Perrone, a research assistant currently working at the University of Leicester, added: “We compared the cementum deposition characteristics of smokers, ex-smokers and non-smokers through visual observation and statistical methods, and found that people with a history of smoking – whether they have quit smoking or not – are more likely to have abnormal cementum structure than never smokers.”
This study provides us with a new perspective on the impact of smoking on oral health, and for the first time records the profound impact of smoking on health in tooth tissue. Through the “biological rings” of teeth, scientists are gradually revealing the hidden evidence of tobacco’s long-term damage to the human body.
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