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How Mouth Bacteria Affects How Fast a Wound Will Heal

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Stockbyte via Getty Images
Stockbyte via Getty Images

Quite possibly nothing is more frustrating than accidentally chewing on your cheek. It's painful and many times seems to take forever to heal. Part of that reason is due to bacteria.

There may be billions covering the tongue, the teeth, the gums and the cheek. The number of actual species is far less, usually in the hundreds. With so many microbes present, they must play some role in wound healing. Yet, little had been done to determine what that might be.

The problem lies in trying to observe the actions inside the mouth. Without severely affecting our daily activities, the process is almost impossible. That's where laboratory models come into play. In 2013, researchers were able to develop a laboratory model to look at just how the cells of the mouth work with various species of bacteria. This opened the door to other tests including just what happens when we have an injured cheek.

Last year, this was put to the test. As expected, certain microbial species were involved; they slowed the healing process. Not surprisingly, most species were pathogenic in nature including several known to cause gingivitis. The overall effect was a reduction in healing ranging from 20 to 75 per cent. This meant with these bacteria in place, the amount of time needed for proper healing could triple. What made this result worse was the fact the bacteria didn't have to be alive in order to cause the problem. All that was needed was their corpses to cause the delay.

How dead cells could somehow disrupt the healing process was a mystery with few answers. One possible suggestion was the presence of chemicals involved in communication between bacteria. This form of crosstalk would enable other members of the species to learn of the potentially harmful conditions and to either stay away or prepare to fight.

Last month, a Belgian team of researchers provided evidence to show this indeed may be the case. Using a lab model, they were able to show how bacterial signals seem to interfere with the healing process and end up slowing it down. They also learned how this might be stopped using the help of certain good bacterial species.

The experiments were relatively straightforward. The group grew oral cells in the lab and used these as a representation of the cheek. When it was time to perform the experiments, the cheek cells were scratched to cause a laceration. In the control scenario, the wound was left to heal on its own. As for the tests, the injured cells were subjected to about a million bacteria. After 24 hours, the amount of healing was determined and then compared.

As expected, the control wounds healed about 60 per cent over the period. This is natural and would mean the scratch would be gone within three days. When bacteria were added, in most cases, the amount of healing decreased. In some cases, the level dropped to as little as 20 per cent. This meant a wound would require at least three times the length to heal completely.

But there was a surprise. In the case of a few species known to be friendly to our teeth and gums, there was the opposite effect. Both Streptococcus oralis and Streptococcus mitis increased the levels of wound healing compared to the controls.

As to why this change happened, the researchers believed it was due to a lack of nutrients for the healing cells. To prove this, they looked at the levels of glucose, the most common food source, to see if they could find any trends. Sure enough, the bacteria causing the greatest delay also took away the most glucose from the cells. On the other hand, the two bacteria with better wound healing increased the glucose concentration for the cells. They were giving up their share of the food so the wound could heal faster.

But glucose use couldn't be the only answer as dead cells also had the ability to cause delays. The authors figured chemical signals present even after death were the cause. Essentially, these signals to let other bacteria know the environment was deadly somehow were also picked up by the cheek cells. They would then slow down the healing process to deal with the unsavoury conditions.

The authors put this to the test by adding not bacteria, but the liquid medium in which they grew and died. Sure enough, several molecules halted cheek healing. As the concentration of these chemicals rose, the wound tended to be worse off. Although it wasn't a smoking gun in comparison to glucose, the authors believed it was definitely worth consideration for future treatment possibilities.

In light of the studies, there appears to be good reason to keep healthy microbes in the mouth for those moments when we accidentally abuse it. To stay prepared, the best methods are to ensure good oral hygiene is maintained including brushing and flossing. Also, try to avoid using products with triclosan. It may be useful for a few times but after as little as five exposures, it may essentially do little to help keep the pathogenic bacteria at bay.

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