![]() In contrast, the microbes in dental calculus are already calcified in place at the time of death, and don’t undergo subsequent modification. While ancient microbial DNA has also been recovered from coprolites (preserved faeces), it is thought that much of the bacterial diversity relates to changes taking place after deposition, as both internal and external microbial communities start to break down the coprolite. Instead, the DNA results from inside the tooth were completely different from the calculus, and were closer to environmental controls. If bacteria in the soil or water was penetrating the specimen and contaminating the results, the DNA sequences inside the tooth should resemble those recovered from the calculus. ![]() To test whether the microbial signal originated from the calculus alone, and not from other bacterial in the soil or water surrounding the specimen, the team analysed the microbial diversity inside the same teeth they collected calculus deposits from. This study is the first to show that DNA survives within dental calculus for long periods of time (>8 kyr), and that the DNA sequences recovered from ancient skeletons accurately relate to the oral bacteria present in the mouth of the individual during life. “We also had to develop ultra-clean laboratories at ACAD to provide a bacterial-free workspace.” "Over the past decade we tried several times to extract bacterial DNA from ancient calculus, but contaminating bacterial DNA in the enzymes and components impacted the experiments, so we had to wait for improvements in manufacturing” said Prof. Dobney and others had used microscopes to identify the range and number of bacteria present in dental calculus, and also the large amount of food preserved amongst the bacteria, it had proved impossible to accurately characterize the species present. Keith Dobney, now at the University of Aberdeen. The idea for the project - Ancient tooth decay DNA reveals effects of changing diets - came 17 years ago when Prof. Alan Cooper, direct of the University of Adelaide’s Centre for Ancient DNA, comments, “The problem is that the natural human bacterial ecosystem has been massively altered by our adoption of the farming diet, which is enormous amounts of carbohydrates, and recently, processed sugar.” However, it is important to note that oral bacteria are also an important part of health, and are equally involved in repairing damage to teeth and preventing pathogens from colonizing. For example, bacteria from dental plaque leak through the inflamed gums into the bloodstream, where they stimulate a permanent inflammation response, and are found in clumps on coronary artery walls. Importantly, dental plaque and calculus are increasingly linked to a range of systemic diseases including cardiovascular disease, premature birth, arthritis, and diabetes. Oral bacteria are inherited from your primary caregiver in early childhood, and transferred between family members later in life. ![]() RELATED | State of the oral-systemic union: 2013 RELATED | The link between periodontitis and cardiovascular disease: A brief overview It is analogous to concrete, and is composed of millions of bacterial cells calcified together with calcium phosphate which comes from the saliva. Dental calculus is the calcified plaque, or tartar, that is removed with a dental scalar during regular dentist visits.
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