Abstract: ABSTRACT Objective: To explore the influence of Sonodynamic therapy( SDT) produced by ultrasound( US) combined with the sensitizer hematoporphyrin monomethyl ether( HMME) on biological activity and membrane structured of dental plaque bacterial biofilm. Methods: Collecting bacterial samples from patients with periodontitis and incubate at 37 ℃, anaerobic( 85% N2, 10% CO2, 5% H2). Groupsing: 1. HMME minimum inhibitory concentration: HMME with concentration 0 ?/ml, 10 ?/ml, 20 ?/ml, 30 ?/ml, 40 ?/ml, 50 ?/ml, 60 ?/ml is divided into 7 groups; 2. SDT efficacy: Control groups, HMME groups( 50 ?/ml, minimum inhibitory concentration), US groups, SDT groups. Detection: The minimum inhibitory concentration of HMME in the dental plaque at the ultrasonic intensity of 3 W/cm2 and the time of 5 min; colony-forming units( CFU) of dental plaque under SDT; plate count method was used to detect the survival rate of bacteria; the activity of plaque bacterial biofilm; the change of morphological structure. Results: 1. When the intensity of ultrasound is 3 W/cm2, 5 min, the minimum inhibitory concentration of HMME as a sound sensitizer is 50 ?/ml, and the dose-effect relationship is significant (P<0.05). 2. In the comparison of bacterial biofilm survival rate, the SDT groups were much lower than the other groups (P<0.05). 3. Compared with the morphology of the plaque bacteria in the Control groups which is clear, the bacteria is concentrated and the tubular structure is intact, the plaque bacteria in the SDT groups are damaged, scattered, and the structure is no longer complete. 4. Compared with Control groups, HMME groups and US groups, the plaque bacterial biofilm in SDT groups had a larger proportion of dead bacteria. Conclusions: SDT has a certain bacteriostatic effect on plaque bacterial biofilm. During the process of bacteriostasis, the proportion of dead bacteria increases, and the structure of bacterial biofilm is destroyed, resulting in a killing effect.

Key words: Plaque bacterial biofilm, Sonodynamic therapy, Hematoporphyrin monomethyl ether, Biofilm structure