A person's immune system may play a big role in causing their teeth to decay and their fillings to fail, a new study says.

Doctors have long placed the blame of tooth decay on bacteria alone, but research suggests that there is more to it than just microbes eating away at people's pearly whites.

Neutrophils, a type of immune cells tasked with eliminating infections in human teeth, may be doing more damage to affected sites than the bacteria they were meant to destroy.

"No one would believe that our immune system would play a part in creating cavities," said Yoav Finer, associate professor at the University of Toronto's Faculty of Dentistry. "Now we have evidence."

Oral Immune System

When the body detects bacterial infection in the teeth, it sends out neutrophils to search and destroy the nasty microbes. They often make it to the oral cavity by way of gums located round the root of teeth.

Once they find their target, they attack the infection until they eliminate it from the body. However, in their gusto to accomplish their job, they can damage their host's teeth even more than the microbes.

Finer likened it to using a sledgehammer to smash a single fly on the wall, which is pretty much how neutrophils go about destroying bacteria.

The immune cells on their own cannot cause damage to teeth. Finer said they cannot mineralize structures of the teeth since they do not produce any acids.

However, when neutrophils attack bacteria, the action results in the production of harmful acids that can demineralize teeth. Enzymes from both the immune cells and the microbes eat away at teeth, causing long-term damage and even disrupting tooth-colored fillings.

The entire destruction of people's pearly whites can happen almost instantaneously, with researchers finding damaging to dentin and tooth-colored fillings within just a few hours.

Michael Glogauer, the acting chief dentist at the Princess Margaret Cancer Centre and co-author of the study, said described the process as "a collaboration of destruction" with different kinds of motives.

Failure Of Tooth-Colored Fillings

The University of Toronto study also attempts to address why tooth-colored fillings often fail to fix tooth decay. Most patients who have undergone the procedure still develop caries within five to seven years.

The paper is the first of its kind to show how neutrophils can destroy tooth-colored fillings and damage tooth dentin. It helps establish a link between the immune cells and the decaying of teeth and the recurrence of caries.

What Is Tooth Decay?

Tooth decay is caused by a combination of bacterial infection and a buildup sugary and starchy food and drinks in the teeth, according to the National Institute of Dental and Craniofacial Research. The microbes use these substances to produce acids that can damage the enamel or hard surface of teeth.

The acids from bacteria will continue to eat away the enamel until the teeth are completely exposed. A white spot will appear in the area of the tooth where it has lost much of its minerals. This is considered the early sign of tooth decay.

Teeth can replace lost enamel using the minerals found in people's saliva and fluoride from toothpaste. However, if nothing is done to stop the decaying process, the teeth will develop permanent damage known as cavities.

The findings of the University of Toronto study are featured in the journal Acta Biomaterialia.

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