who met inclusion criteria, will receive an identical X253 Probiotic lozenge Supplement looking and tasting placebo.

who met inclusion criteria, will receive an identical X253 Probiotic lozenge(containing active L.r X253).

who met inclusion criteria, will receive an identical X253 Probiotic lozenge(containing inactive L.r X253).

Every two weeks, all volunteers were given the number of probiotic lozenges to be used within two weeks. Edible method: 3 times a day, 1 tablet every time (0.8g/tablet). Put the tablet in the mouth and keep it in the mouth for at least 2-3 minutes before swallowing. Take it once every 30 minutes after breakfast, lunch and dinner. Do not brush your teeth, eat foods, or rinse your mouth within half an hour of consumption. Maintain oral hygiene according to the original habits during consumption, and do not use fluoride toothpaste during consumption.

In a sterile operating table, place the collected dental floss in a 180μL lysozyme (20mg/mL) water bath, use a DNA extraction kit (Tiangen Biotechnology Co., Ltd.) to extract the DNA in the oral sample, and store the DNA sample at -20°C. Quantitative Real-time PCR (Tiangen Biotechnology Co., Ltd.) was performed for the Porphyromonas gingivalis(P.g), Streptococcus mutans(S.m), Streptococcus gordonii(S.g), and Bifidobacterium(Bif) contained in the DNA of the tartar sample. The experiment results at 0 weeks were used as the control, and the relative quantitative method which is named 2-∆∆ct method was used to calculate the gene expression level of the target bacteria in the 2th week.

In a sterile operating table, place the collected dental floss in a 180μL lysozyme (20mg/mL) water bath, use a DNA extraction kit (Tiangen Biotechnology Co., Ltd.) to extract the DNA in the oral sample, and store the DNA sample at -20°C. Quantitative Real-time PCR (Tiangen Biotechnology Co., Ltd.) was performed for the Porphyromonas gingivalis(P.g), Streptococcus mutans(S.m), Streptococcus gordonii(S.g), and Bifidobacterium(Bif) contained in the DNA of the tartar sample. The experiment results at 0 weeks were used as the control, and the relative quantitative method which is named 2-∆∆ct method was used to calculate the gene expression level of the target bacteria in the 4th week.

Design a questionnaire about the improvement of oral problems, and distribute it to the volunteers every week, then collect and organize the data.