WHY MUST HUMANS CLEAN THEIR TEETH?

When was the last time you took your pet for dental treatment?

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These days humans are expected to follow a complicated regime of twice-daily teeth cleaning, inter-dental work, plus regular trips for checkups with your dentist and hygienist in order to ensure your teeth last your lifetime.

As a species we seem prone to tooth decay, bone recession and tooth loss, more so than other species. Why is this?

This was one of the questions being looked at during the recent British Society of Periodontology conference held at Oxford.

Prof. Randolph Nesse, from the University of Arizona, looked at the problem from the angle of evolutionary biology and identified six factors that accounts for our vulnerability:

1. What we are made of and our design no longer suit our diet and current lifestyles.
2. Pathogens that attack our bodies evolve a lot more quickly than we do, so we face an ongoing war on our defences.
3. Constraints - having set off down a particular evolutionary pathway we cannot make large jumps to other forms better suited to changing circumstances.
4. Trade-offs: Some disadvantages are the by-product of adventitious mutations. e.g. back pain from walking on two legs.
5. Cost: Some genes give an early advantage only to lead to an early death later.
6. We treat symptoms and so delay dealing with causes until more damage has been done.

Prof. Nesse, pointed out that in our mouths because enamel teeth enter bone via the gingiva (gum tissue), it is little wonder that we are susceptible to gum disease. Bacteria can accumulate in pockets which form between the tooth and the gum, hiding from regular cleaning aids. This in turn causes the body to react by causing inflammation which destroys the ligaments holding the tooth in place as well as reducing bone density.

However, it is well known that some people are more susceptible to gum disease than others, a genetic component is in place. So although bacterial presence is very important in allowing periodontal disease to take hold the response of the host also plays an important role.

One factor, that is very important is the immune system. Prof. Graham Rook from UCL made the point that exposure to a wide range of microbes is essential for a healthy and strong immune system.

He pointed out that, like the brain, the immune system 'learns'; the data it uses is microbial. If it does not have enough data to work on then it malfunctions. A defective immune system can lead to overstated inflammatory responses that can cause or exacerbate all sorts of problems from gum disease to heart disease and diabetes.

With many old style infections being wiped out or prevented through hygiene practices and antibiotics, our skill in avoiding pathogens makes us more vulnerable to disease.

This is unlikely to change anytime soon, so for the meantime we are having to rely more and more on treating gum disease when signs begin to show.


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Evolution... http://www.telegraph.co.uk/