Tooth decay is one of the most common health problems worldwide. It begins when bacteria in the mouth break down sugars from the food we eat.
This process produces acids that slowly damage the outer surface of the teeth, known as enamel. These bacteria don’t work alone—they live in thick, sticky layers called dental biofilms, which cling to the teeth and speed up acid damage.
New research shows that a naturally occurring amino acid called arginine, which is already found in saliva, may help prevent this process. Arginine seems to support certain “good” bacteria in the mouth that can fight harmful acid and make the biofilms less dangerous.
Inside the body, some helpful bacteria use a system called ADS (arginine deiminase system) to turn arginine into alkaline compounds. These compounds help neutralize acid.
When arginine is present in larger amounts, these beneficial bacteria grow better, while the acid-producing bacteria struggle. Earlier lab studies had shown that arginine could change the way dental biofilms develop—but these studies were done outside the human body.
To test what happens in real mouths, scientists at Aarhus University in Denmark designed a clinical study. Led by Postdoctoral researcher Yumi C. Del Rey and Professor Sebastian Schlafer, the team studied 12 volunteers who had active tooth decay. Each person received special dentures that collected dental biofilms from each side of the jaw.
Participants were told to dip the dentures into a sugary solution for five minutes, followed by either distilled water (used as a placebo) or an arginine solution for 30 minutes. One side of the mouth always received the arginine, while the other side received the placebo. This routine was repeated three times a day over four days.
The researchers then removed the dentures and carefully examined the biofilms. Using a special dye that changes color with acidity, they found that the biofilms treated with arginine were less acidic after sugar exposure—both at 10 minutes and 35 minutes afterward. In simple terms, arginine made the biofilms less harmful to the teeth.
The team also studied the sugary components of the biofilms using special markers. These sugars, including fucose and galactose, are thought to form “acid pockets” that trap damaging acids.
In the arginine-treated biofilms, levels of fucose were lower. Galactose sugars were pushed toward the top of the biofilm, away from the tooth surface. This change in structure might help reduce damage to teeth.
Another part of the study looked at what kinds of bacteria were present. The biofilms were mostly made up of Streptococcus and Veillonella bacteria. However, arginine treatment lowered the amount of one group of acid-producing streptococci (mitis/oralis group) and slightly increased bacteria that are better at using arginine to make alkaline compounds.
Together, these changes show that arginine can make dental biofilms less acidic and less harmful. It changes the makeup of sugars in the biofilm and encourages healthier bacteria to grow.
This is good news for dental care. Tooth decay affects people of all ages, and arginine could offer a safe and natural way to fight it.
Because arginine is already found in many foods and produced by the body, it’s considered safe even for children. The researchers suggest it could be added to toothpaste or mouth rinses to help protect people who are more likely to get cavities.
If you care about tooth health, please read studies about an important causes of tooth decay and gum disease, and common tooth disease that may increase risks of dementia.
For more health information, please see recent studies about mouthwash that may increase your tooth damage, and results showing this diet could help treat gum disease.
The study is published in the International Journal of Oral Science.
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