The oral cavity--a key system to understand substratum-dependent bioadhesion on solid surfaces in man.

One of the greatest challenges in life sciences and biomaterials research is adhesion of biomolecules and bacteria to solid surfaces in aqueous solutions. An example concerning everybody is biofilm formation in the oral cavity on dental materials and dental hard substances, respectively. The main characteristics typical for any bioadhesion can be observed excellently in the oral cavity. Initially, a proteinaceous layer termed pellicle is formed. It mediates the interactions between solid substrata, oral fluids and microorganisms. Numerous different materials with differing physico-chemical properties and possible impact on the acquired pellicle are present in the oral cavity such as enamel, dentine, restorative materials or dental implants. Despite the fact that in vitro studies demonstrate considerable differences of experimental pellicles formed on these materials, the in situ pellicles seem to be relatively similar and level off the different properties of the underlying substrates. However, the bacterial colonisation of pellicle-coated surfaces under in vivo conditions differs considerably. Long-range forces and detachment of biofilm layers may account for this phenomenon despite the masking effect of the pellicle. Accordingly, low-energy surfaces are desirable for restorative materials exposed to the oral cavity to minimise bacterial adhesion. The oral cavity is an easy accessible in vivo model for understanding bioadhesion and for investigation of protein-surface interactions noninvasively. For evaluation of biofilm formation on dental materials, in situ or in vivo studies are preferable.