Your mouth is home to hundreds of species of bacteria, living together in what's known as the oral microbiome. Understanding it helps explain why oral probiotics are marketed the way they are.
Most oral bacteria are harmless or even beneficial, existing in balance with each other. Problems tend to arise when that balance shifts toward bacteria associated with plaque, decay or gum inflammation.
The theory behind oral probiotics is introducing beneficial strains that can help compete with less desirable bacteria, potentially supporting a healthier balance over time.
The oral microbiome is influenced by diet, hygiene habits, saliva composition and genetics. A probiotic supplement is one input among many, not a standalone solution.