Effect of Surface Properties and Physisorbed Polycarboxylate on Bacterial Adhesion

Objective: A combination of laboratory models was utilized to evaluate how enamel surface properties and physisorbed polymers influence the uniformity of bacterial coverage. Methods: The influence of surface morphology and roughness on bacterial attachment was evaluated on three pellicle coated substrates (hydroxyapatite (HAP), native and polished enamel) in the presence and absence of two different polymers (Gantrez S97 and Carbopol 940). The surface roughness of the three oral hard tissue substrates with/without salivary pellicle and polycarboxylates were measured using Atomic Force Microscopy. Bacterial attachment on the three substrates was quantified using ImageJ software at 30 min, 3 h, and 24 h on both the native and polymer surface modified substrates. For each sample, 8-10 images were analyzed, and the statistical significance of the differences (p<0.05) in bacterial coverage was determined using one-way ANOVA. Results: A statistically significant difference (p<0.05) on roughness was observed between native (Ra=338±71nm) and polished enamel (Ra=14±4nm) surfaces with scan size of 50µm×50µm. For HAP and enamel, roughness decreased considerably after formation of a pellicle, while introducing a physisorbed polymer to the pellicle layer further reduced roughness. While the deposition of polymer onto HAP or enamel substrates minimally impacted surface roughness, it significantly (p<0.05) reduced the deposition of bacteria at 24 h. In addition, the polymer coated surfaces exhibited reduced bacterial coverage compared to the native surfaces over all time points and substrates measured. Conclusion: Surface roughness exhibited little effect on the initial adhesion of bacteria on pellicle coated surfaces, while modifying surface chemistry had a significant effect on bacterial adhesion. Specifically, physisorption of anionic polymers significantly reduced bacterial adhesion in comparison to native surfaces.