Abstract: Objective: To have a discussion on the effect on the acidogenicity for gene ffh of fluoride resistant streptococcus mutans (UA159-FR)after siRNA interference. Methods: UA159-FR was transformed by using electroporation and combined with targeted site of ffh gene sequence, and cultured by adding BHI, glucose, saccharose, lactose and starch with 5% saccharides into bacteria that was before interfered and after interfered respectively. PH was set to 7.5. The terminal PH was measured after 24 hours. Results: After the transfection, the result turned out to be successful. Before and after interference, there were some significant differences for transfection of fluoride resistant streptococcus mutans among different culture media of gene ffh (P<0.05).△PH of normal, glucose and lactose were significantly different before and after the interference(P<0.01); It was significant in sucrose(P<0.05) and there was no obvious difference in starch. Conclusion: The effect of siRNA interference on the acidogenicity for gene ffh of fluoride resistant streptococcus mutans is significant.

Key words: Fluoride resistant streptococcus mutans, ffh gene siRNA, Acidogenicity