This natural amino acid can help stop cavities before they start

Researchers found that arginine, an amino acid found naturally in saliva, plays an important role in reducing tooth decay. Some beneficial bacteria use the arginine deaminase system (ADS) to convert arginine into alkaline compounds that help combat harmful acids. When more arginine is available, these protective bacteria tend to grow more easily, while acid-producing bacteria struggle to grow. Previous laboratory studies conducted outside the human body have also indicated that arginine can alter the overall composition of dental biofilms.

Human intraoral arginine test

To confirm whether these effects also occur in real mouths, a research team led by Post.doc. Yumi C conducted. Del Rey and Professor Sebastian Schlafer at Aarhus University in Denmark conducted a clinical study. Their findings were published in International Journal of Oral Sciences.

The study included 12 participants with active tooth decay. Each person received custom-made dentures, which allowed the researchers to collect healthy dental biofilm from both sides of the jaw. Participants were asked to immerse the dentures in a sugar solution for 5 minutes, immediately followed by either distilled water (as a placebo) or arginine for 30 minutes. One treatment was applied to one side of the mouth, and the other treatment was applied to the other side. This routine was repeated three times daily, always applying the arginine to the same side.

“The aim was to study the effect of arginine treatment on the acidity, bacterial type and carbohydrate matrix of biofilms in patients with active caries,” explains Sebastian Schlafer, professor at the Department of Dentistry and Oral Health. After 4 days, once the biofilm has fully formed, the dentures are removed for a detailed examination.

Arginine reduces acidity levels after exposure to sugar

To measure acidity within biofilms, the researchers used a pH-sensitive dye known as C-SNARF-4. This dye allowed them to evaluate acidity in different regions of the biofilm. Biofilms that received arginine treatment showed significantly higher pH levels, meaning lower acidity, after 10 and 35 minutes of sugar exposure.

“Our results revealed differences in the acidity of biofilms, with those treated with arginine being significantly more protective against acidification caused by sugar metabolism,” says first author Yumi C. del Rey.

Changes in the structure of the biofilm and glycolytic components

The team also examined the structural components of biofilms using fluorescently labeled lectins, which are proteins that bind to specific carbohydrates. Two main components of carbohydrates have been studied: fucose and galactose. These sugars make up a large part of dental biofilms and are thought to contribute to the formation of “acid pockets” that trap harmful acids.

Biofilms exposed to arginine showed an overall reduction in fucose-based carbohydrates, which may reduce their ability to cause damage. The researchers also observed a structural shift in the biofilms. Galactose-containing carbohydrates became less abundant near the base of the biofilm and more concentrated toward the top, suggesting reorganization that may limit acid accumulation near tooth surfaces.

Changing the balance of oral bacteria

To determine which bacteria were present, the researchers analyzed bacterial DNA using 16S rRNA gene sequencing. Biofilms treated with either arginine or placebo were largely dominated by Streptococcus and Veillonella species. However, treatment with arginine resulted in a significant reduction in the streptococcal population associated with stomatitis/stomatitis. These bacteria produce acid but are poor at producing alkali.

At the same time, arginine slightly increased the presence of streptococci that are better at metabolizing arginine. This shift helped raise the pH levels within the biofilms. Together, the results show that arginine made dental biofilms less harmful by lowering acidity, changing carbohydrate composition, and reshaping the microbial community.

A safe and promising strategy against tooth decay

Tooth decay affects people of all ages around the world. Researchers suggest that adding arginine to products such as toothpaste or mouthwash could help protect people who are particularly susceptible to cavities. Because arginine is a naturally occurring amino acid produced by the body and found in many food proteins, it is considered safe and may be appropriate for use in children.