High-Intensity Focused Ultrasound Versus Airflow® in Debriding Ti-Attached S. mutans Biofilms

INTRODUCTION AND AIMS: Effective management of biofilm-associated peri-implantitis requires the eradication of microbial biofilms to control disease progression and preserve implant osseointegration. However, achieving complete biofilm removal remains a challenge. High-intensity focused ultrasound (HIFU) is an emerging technology offering non-ionizing radiation, no extraneous materials, and minimal residuals or aerosols. This in vitro study compared the effectiveness of HIFU and a commercial air-pressured abrasive method (Airflow®) in removing Streptococcus mutans biofilms attached to Titanium (Ti) discs.

METHODS: Bacterial biofilms were grown on 36 pairs of machined (M) and roughened (R) Ti discs for 10 days. Biofilms in the test group (12 pairs) were treated with the optimized HIFU for 2 min in a water medium and the residual biofilms were examined using two imaging methods, confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), and three quantitative methods including crystal violet (CV), 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) and flow cytometry (FCM) assays for biomass, bacterial viability, and live/dead bacterial counts respectively. The data from the test and the control samples (untreated and Airflow® treated) were subjected to ANOVA followed by post-hoc Tukey's test to determine the statistical differences between the groups.

RESULTS: Except the MTT data from M discs, the findings showed that both HIFU and Airflow® methods achieved similar levels of bacterial debridement, removing over 99% of bacteria in FCM assays (99.8 ± 0.16% versus 99.3 ± 0.49% for M discs, 99.96 ± 0.02% versus 99.5 ± 0.37% in for R discs). Complete biofilm removal was noted in HIFU-treated samples compared to the Airflow® in SEM images.

CONCLUSION AND CLINICAL RELEVANCE: Our findings indicate that both novel HIFU and traditional Airflow® methods were equally effective in removing the S. mutans biofilms from titanium disc surfaces. Further research is needed to explore the clinical application of HIFU in managing peri-implantitis.