Plasma polymerization technique with monomer containing thiol group on titanium implant biomaterial and examination of it's effect on bacterial adhesion

The aim of this in vitro study was to evaluate the applicability of the plasma polymerization technique with monomer containing thiol functional group on frequently used titanium implant biomaterial surfaces and the effect of the surface modification on microorganism adhesion.The study was performed using grade 4 commercial type (cp-Ti) pure titanium. Twenty discs of 4mm diameter and 1 mm height were prepared and each samples? surface was metallographically polished with a diamond paste. Ten of these samples were modified with the plasma polymerization technique under equal conditions. The remaining 10 samples of unmodified polished titanium were used as the control group. Surface roughness was determined by using atomic force microscopy. Thickness of the plasma polymerized film was measured by an ellipsometer. Contact angle measurements were performed with the sessile drop method using the OCA 20 contact angle system. Thereby, a video camera equipped with an image analyser visualizes the shape of the drop and the contact angle. The corresponding picture is saved in the computer and the contact angle is determined by software. In order to evaluate the bacterial colonization on different titanium surfaces, titanium discs were incubated in 5 ml of a suspension containing streptococcus mutans. Bacterial microcolonies were fixed in 2.5% glutaraldehyde followed by an additional fixation step in 1% Acridine Orange at room temperature for 1 hour. Quantitative analysis was performed using a fluorescence microscope. Samples were examined at 40-fold magnification and the number of microcolonies was determined on five randomly selected representative fields on each disc.The study determined that plasma polymerized sample surfaces were smoother than the uncoated sample surfaces. Also, improvements in the hydrophilic character on modified titanium were determined by the contact angle measurements. After modification with the plasma polymerization technique, thickness of the plasma polymerized film was measured as 49.4 nm. The reduction of microorganism adhesion was significant on coated surfaces.