The naturally occurring amino acid arginine makes cavity-prone dental plaque less acidic after sugar intake. Digest
Dental cavities form when bacteria living on teeth repeatedly turn sugar into acid, lowering the local pH and, over time, leading to mineral loss in the tooth. Scientists have suspected that some nutrients might help counter this process, but it has been unclear whether they can make dental plaque less harmful by changing how it behaves rather than simply removing bacteria.
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The study involved ten adults with active tooth decay, each wearing a custom lower-jaw splint that held small glass surfaces with a texture similar to enamel (the protective outer covering of teeth), where plaque could grow for four days. Three times per day, the growing plaque was briefly exposed to sucrose (common table sugar), then treated on one side with the amino acid arginine and on the other side with water as a control. This split-mouth design allowed each person to serve as their own comparison. Once the plaque matured, researchers examined how acidic it became after a sugar challenge, which bacteria were present, and how the plaque's sticky carbohydrate matrix was organized.
- Plaque grown with or without arginine contained similar core bacteria, mainly Streptococcus and Veillonella, which are typically found in young dental plaque.
- After exposure to sucrose, arginine-treated plaque stayed less acidic than untreated plaque, indicating better resistance to acid buildup.
- Arginine reduced matrix material rich in fucose, a sugar commonly found in saliva that helps plaque stick together.
- Galactose-containing parts of the matrix were not reduced overall, but arginine shifted where they were found, with less accumulation near the tooth surface and more in the outer layers of the plaque.
- Overall, arginine did not dramatically change which bacteria were present, and people differed widely in how their plaque responded. Arginine exposure was linked to lower levels of the mitis–oralis group of streptococci, a group of bacteria known to produce acid, while some bacteria that can use arginine showed a slight but not statistically reliable increase.
- People differed widely in how much arginine helped limit acid buildup, and these differences could not be clearly explained by which bacteria were present or by measured features of the plaque's sticky matrix.
Arginine may work through several overlapping processes. Some oral bacteria can break down arginine using the arginine deiminase system, a metabolic pathway that produces ammonia, which helps neutralize acid. At the same time, arginine appears to reshape the plaque's sticky matrix, which may influence how acids spread within the plaque during sugar exposure. These effects could make plaque less damaging during periods of sugar exposure.
Taken as a whole, the results point toward a new strategy that focuses on making dental plaque less damaging rather than eliminating it. Future studies will need to test whether these short-term, microscale pH improvements translate into meaningful protection against cavities over longer periods and in everyday oral care settings.