High Speed Imaging of Biofilm Disruption from Smooth/Rough Surfaces

Objectives: Cavitation bubbles occurring in the cooling water generated by dental ultrasonic scalers could be a novel method of biofilm removal from tooth and dental implant surfaces. The aim of this study was to evaluate the effectiveness of biofilm removal from smooth and rough surfaces using ultrasonic cavitation.


Methods: An in vitro model system consisting of rough surfaces was prepared by performing a novel surface treatment on Thermanox coverslips (Nunc, USA). The surfaces were sandblasted for 1 minute using 250 µm sized particles. Streptococcus sanguinis (ATCC 10556) biofilm was grown on rough and smooth (unmodified) Thermanox coverslips for 4 days. After fixing and staining, biofilm removal was imaged using a high speed camera (AX200, Photron) attached to a zoom lens. Image analysis was used to calculate the area of the biofilm before and after removal.
Results: Less biofilm was removed from the sandblasted surfaces compared to the unmodified smooth surfaces. 49±8% biofilm remained on the smooth coverslips, compared to 86±20% biofilm remaining on the sandblasted coverslips (n=3) (p<0.05). The results show that using the novel surface treatment on Thermanox coverslips increased biofilm attachment, so it can be used in other biofilm studies for a more clinically relevant transparent surface. Cavitation bubbles from an ultrasonic scaler took more time to disrupt biofilm from the roughened Thermanox surfaces. Further work will be done to investigate how other parameters such as power and distance affect biofilm removal.

Conclusions: We have developed a method for calculating biofilm removal effectiveness using high speed imaging and image analysis. It was noticed that cavitation bubbles from an ultrasonic scaler took more time to disrupt biofilm from the roughened Thermanox surfaces. The surface modification and imaging techniques developed in this study will give insights into how cavitation can be optimised as a method of clinical biofilm removal.