In the first stage of intraoral bioadhesion processes the formation of a pellicle layer occurs, eventually covering all surfaces of the oral cavity. The pellicle is a crucial determinant of oral biofilm formation and contains a considerable proportion of lipids. So far, the lipid composition of the in situ pellicle has not been characterized in detail, however, the importance of hydrophobic interactions for the formation of an adherent biofilm is generally acknowledged. Therefore, the requested clinical experimental study aims to examine the lipidome of the pellicle with respect to its composition, distribution and impact on physicochemical surface interactions. A special focus will be placed on the quantification and characterization of functionally relevant pellicle components by HPLC MS/MS (phospholipids, glycolipids, triglycerides, cholesterol). Furthermore different hydrophobic mouthrinses will be examined for their effect on the lipid composition and the ultrastructure of the in situ pellicle. The ultrastructure of the pellicle will be examined by transmission electron microscopy, the distribution of the lipids in the pellicle will be evaluated by immuno electronmicroscopical techniques and by mass spectrometric imaging. Finally, the primary objective of this study would be to gain a more comprehensive picture of the molecular mechanisms underlying initial bioadhesion processes and, as a result, bacterial biofilm formation with particular emphasis on the lipophilic components and hydrophobic surface interactions. The obtained results will reveal new insights about the qualitative and quantitative importance of the lipid fractions for the oral biofilm formation which, potentially, could also be transferred to bioadhesion processes in general.