Minimal invasive technique for the removal of biofilm by HIFU

Introduction: Most dental infections are typically biofilm mediated infections. E.faecalis is the primary cause for secondary pulpal and periapical infections. Studies have shown that 40%-60% of failed root canal treatment is due to the incomplete removal of E.faecalis owing to their ability to form biofilm. Current disinfection techniques are hampered due to an inefficient removal of the E.faecalis biofilm. There is a need to develop a technique which can be used for this potential clinical application. Intense ultrasound waves from High Intensity Focused Ultrasound (HIFU) create oscillating cavitations in fluids. These bubbles collapse with high-speed jets that can be utilized for various therapeutic purposes. Objectives: To study the efficacy of HIFU in removing E.faecalis biofilms. Methods: Studies were done in which the temporal effect of HIFU in biofilm removal were determined. Experiments were conducted on 4 days old E.faecalis biofilms attached to glass cover-slip and root-dentin samples. Nine cover-slips and 9 root-dentin samples were tested for each group in this study. Each experimental group was treated with HIFU at 200 kHz for either 1 or 2 minutes. Groups without HIFU treatment combined with or without mechanical removal were taken as a positive and a negative control respectively. The efficacy of HIFU on biofilm removal was investigated using confocal microscopy and Colony Formed Unit Assay (CFU). Results: The results of CFU showed 5-6 folds higher removal of biofilms in experimental groups compared to the negative control group (p<0.05). The efficacy of biofilm removal by HIFU was also confirmed by confocal microscopy images. Conclusion: HIFU could be used in removing E.faecalis biofilms efficiently. Further studies of bactericidal effect of HIFU on E.faecalis biofilms are recommended. This work was partially supported by grants from the Ministry of Education of Singapore (R224000037112)