population experiments were carried out, and Quantitative Real-time PCR was used to detect the expression level of the target strains in volunteers' oral, High-throughput sequencing technology to detect the changes in oral flora of volunteers, and judge the improvement effect of X253 lozenges on the human oral flora. The effects of X253 lozenges on the volunteers' oral odor, defecation frequency and gum bleeding was surveyed and conuted by questionnaire.
The aim of the study is to study the application of Lactobacillus rhamnosus X253 as oral probiotics by the way of a randomised, double blinded, parallel, placebo-controlled clinical trial, and to eto detect the changes in oral flora of volunteers, and judge the improvement effect of X253 lozenges on the human oral flora.