Influence of Photodynamic Therapy on Bacterial Attachment to Titanium Surface

Figure 1. An illustration of the jet impingement technique. It is used to measures shear stress required to remove a film from a solid surface—the distilled water of a known flow rate through a needle with a known nozzle diameter. An electrically operated device forces water. The diameter of the detached area can be used mathematically to calculate shear stress. Figure 2. (a and b) Two distinguished areas of detached biofilm. (a) Visually view: Central circle represents deeper penetration of the distilled water removing biofilm from the titanium substratum. Halo area represents the removal of layers of biofilm within its cohesive attachment. (b) Microscope view: The laminar nature of the biofilm appears in these images at the edge of impinged areas. Note the good diffusion of methylene blue (blue areas) under the violet color.

Figure 3. Control biofilm sample. Black (lower spectrum) represents the biofilm as is; blue (upper spectrum) represents the biofilm after water impinging. Figure 4. Treated biofilm. Black (lower spectrum) shows the treated biofilm; blue (upper spectrum) shows the same sample after water impinging.

Figure 5. Effect of photodynamic therapy (PDT) on adhesion of biofilm started from older bacteria (2 + 3 days): for these biofilms, the water jets were able to detach extensive areas (circles and halos). Figure 6. (a) Alamar Blue (AB) reduction of bacteria from treated biofilm (2 and 3 days old); (b) AB reduction of bacteria from treated biofilm of 48 hours (stationary phase). Figure 7. Visible difference in the penetration depth of distilled water between PDT treated (the left) and untreated control biofilm (right). Biofilm of 48 hours (peak stationary phase).

Scanning electron microscopy images of (a) clean, sterile titanium surface; (b) control (untreated) Streptococcus mutans biofilm; (c) central circle of detached in a control biofilm; (d) central circle of detached in a photodynamic therapy treated biofilm. Note the difference in bacterial count.