Oral probiotics are active probiotics that colonize the oral cavity and are beneficial to the host. Common probiotics in the oral cavity include Lactobacillus and Bifidobacterium. 1. Lactobacillus: Gram-positive bacteria, a group of bacteria that can break down glucose and other sugars into lactic acid. Lactobacillus metabolite acetate can kill many kinds of spoilage bacteria and pathogenic bacteria, and a proper amount of lactobacillus helps to keep the oral environment clean. 2. Bifidobacterium: Bifidobacterium is also a gram-positive bacterium, which is widely found in the human oral cavity. Bifidobacteria can also inhibit the growth of harmful bacteria in the oral cavity, preventing the gums and other parts of the body from being infected by pathogenic bacteria. Bifidobacteria can also synthesize vitamins needed by the human body to promote oral health. Probiotics in the human mouth mainly include lactobacilli and bifidobacteria, which can protect oral health, but it is still necessary to keep the mouth clean and create a microenvironment suitable for the survival of probiotics.