Those culture conditions do not simulate the conditions of biofilm formation and growth in the oral cavity. In the mouth the salivary flow over the coating is persistent, applies significant shear forces, and supplies sustained nutrition to the bacteria. This may accelerate bacterial metabolism, growth and biofilm formation. Others showed that the formation and growth of Escherichia coli biofilm on surfaces in a drip flow bioreactor was twice that obtained in a shaker, assessed by both CFU amounts and carbohydrate and protein concentrations. This indicates that biofilm grown in the drip flow bioreactor system will be more similar to the in vivo conditions and present a greater challenge to the antimicrobial peptide coatings than standard culture conditions. In this report, coatings with the antimicrobial peptide GL13K were tested in a drip-flow reactor against Streptococcus gordonii, a primary colonizer on oral surfaces that provides attachment for the subsequent pathogenic biofilm formation by P. gingivalis. Adherence of P. gingivalis to surfaces in the developed biofilm depends on deposition of S. gordonii cells on the salivary pellicle at the colonized surface. If S. gordonii is not present in the biofilm, only a few P. gingivalis cells are able to attach on the surface and as a result they are easier to detach and remove from the compromised surface. Notably, S. gordonii has been found in the microbiota of bacterial colonization immediately after installation of oral implants as well as on locations associated with dental peri-implantitis. Therefore, strategies that prevent S. gordonii adhesion on the surface compromise the biofilm formation, and therefore can minimize the risk of developing periimplantitis. The GL13K peptide coatings prevented S. gordonii biofilm formation on titanium disks and exerted unique effects on the mechanical integrity of the bacteria cell wall. After enzymatic digestion of the cell wall, the protoplast can be stabilized in an osmotic condition in which cell lysis does not occur. However, it is noteworthy that the cell membrane in bacteria visualized in Figure 5-F, -G show localized morphological disturbances that may indicate their compromised function. Approximately 10% of bacteria on GL13K coated surfaces exhibited cell wall rupture. This is an underestimated number because bacteria that ruptured in parts of the cells that are hidden to the FE-SEM view can not be counted and others were washed away during the rinsing and preparation of the samples for SEM visualization. Nevertheless, the bactericidal effects of the GL13K coatings –measured by CFU and visualized in the Live/Dead WZ4002 fluorescence staining images was notably higher than a mere 10%. This suggests that the cell wall rupture is a relevant associated phenomenon but not the only cause for the bacterial death. The interaction of antimicrobial peptides with bacterial cell membranes has been studied extensively and typically leads to pore formation through one of several proposed mechanisms.