Biofilms are groups of microorganisms that stick together and form a layer on the surface of the teeth. Dental caries (tooth decay) is a polymicrobial disease caused by these biofilms. It develops due to several factors, including diet, poor oral hygiene, and the combined action of bacteria present in a sticky layer on the tooth surface.
Researchers from Aarhus University in Denmark have now found that arginine, an amino acid naturally present in saliva, may neutralize the harmful effects produced by these bacteria on the surface of the teeth and alter the composition of biofilm and its matrix structure.
Arginine is an amino acid that is naturally present in saliva and many dietary proteins.
Arginine works through the ADS pathway ( arginine deaminase system), a metabolic process used by certain oral bacteria to convert arginine into alkali, helping raise pH levels in dental plaque.
As we know, tooth decay is caused by the acidic environment created by the bacteria in the biofilm. But some beneficial bacteria take arginine from the saliva or oral care formulations like toothpaste and metabolize via Arginine deaminase to produce alkali which counteracts the effects of acid produced by bacteria.
The study included 12 participants who were provided with specialized splints to collect dental biofilms from both sides of the jaw. The participants were asked to dip the specially designed splints into sugar solution for 5 minutes, then dip one side of the splint into distilled water (as placebo) and other side of the splint into arginine for 30 minutes. This procedure was repeated three times a day with arginine applied to the same side.
According to Sebastian Schlafer, Professor at the Department of Dentistry and Oral Health, Aarhus University, Denmark, this experimental setup allowed researchers to observe real-time biofilm responses to arginine exposure.
However, researchers note this was a small experimental study with only 12 participants and short exposure periods using an experimental biofilm model, and that larger clinical trials are needed before translating these findings broadly into preventive dentistry.
Alter the pH level from acidic to basic through ADS pathway
Alters the carbohydrate structure of biofilm
causes microbial shift
pH effects:
Oral microorganisms with the arginine deiminase system (ADS) metabolize arginine to yield ornithine, carbon dioxide, and ammonia. This ammonia elevates pH levels in dental biofilms and counteracts the activity of acid producing microorganisms and thereby protects the dental tissue from demineralization.
Researchers used a special sensitive dye called C-SNARF, a fluorescent indicator that changes color based on acidity, allowing precise measurement of pH inside biofilms, to assess acidity in different areas of the biofilm. Biofilm exposed to arginine showed higher pH values at 10 and 35 minutes after exposure to sugar.
Microbial Changes:
To determine the composition of the biofilm, researchers used a technique called 16S rRNA gene sequencing, a genetic method that identifies bacteria by analyzing their ribosomal RNA signatures, and found that arginine alters bacterial biofilm composition by reducing the proportion of microorganisms that exhibit low ADS activity, such as the mitis or oralis group of streptococci, while increasing the proportion of high ADS activity microorganisms, such as S. parasanguinis and S. gordonii, along with shifts away from cariogenic species including Streptococcus mutans.This shift thereby may reduce cariogenic activity.
The major portion of the biofilm consists of two carbohydrate components: fucose- and galactose-based carbohydrates, which are sugar molecules forming part of the sticky framework that holds biofilms together. These form acidic pockets that trap harmful acids. The researchers used fluorescent labeled lectins, proteins that bind to these carbohydrates, and found that arginine reduces the amount of fucose-based carbohydrates and induces a structural shift in galactose-based ones, making them less abundant near the biofilm base and more concentrated toward the top.
Researchers suggest that adding arginine to oral care formulations like toothpaste and gels may help reduce cariogenic activity and shows preventive potential against tooth decay.
It is also considered safe to use as it is present naturally in the body and in dietary proteins.
Arginine stands out as the most researched and effective amino acid for caries prevention through its unique arginine deiminase system (ADS) pathway. Other amino acids like lysine and glutamine show only limited preclinical promise.
Lysine demonstrates some ability to inhibit Streptococcus mutans biofilm formation in laboratory studies but lacks human clinical trials or commercial applications. Similarly, glutamine offers weak pH buffering in animal models without significant caries reduction evidence in humans
Yumi C. Del Rey, Pernille D. Rikvold, Marie B. Lund, Eero J. Raittio, Andreas Schramm, Rikke L. Meyer, Sebastian Schlafer. “Arginine modulates the pH, microbial composition, and matrix architecture of biofilms from caries-active patients”. International Journal of Oral Science, November 2025.Accessed January 27,2026.https://www.nature.com/articles/s41368-025-00404-5
Sahar Assar,Mathilde Frost Kristensen,Yumi Chokyu Del Rey , Marie Braad Lund, Eero Juhani Raittio ,Andreas Schramm ,Rikke Louise Meyer ,Sebastian Schlafer.”Microscale analysis of the effect of arginine on oral biofilms”.J Dent ,sept 2025.Accessed January27,2026.https://pubmed.ncbi.nlm.nih.gov/40449826/
