On the role of plasma proteins in bacterial adhesion to dental surfaces

Abstract: Bacterial receptors in dental pellicles could influence colonisation and subsequent plaque formation. Studies of such receptors in dental pellicles and bacterial adherence have often focused on proteins of salivary origin. We have only a limited knowledge of the receptor functions of plasma proteins reaching the pellicle via the crevicular fluid. In the present series of studies, (i) plasma proteins in pellicle formed on hydroxyapatite in vitro and on teeth in vivo and (ii) the adherence of periodontopathogenic bacteria to these pellicles were examined. The in vivo situation was examined separately on the gingival and incisal parts of teeth and at healthy and inflamed gingival margins respectively. Pellicle proteins were analysed using sodium dodecylsulphate polyacrylamide gel electrophoresis, immunoblotting and image analysis. Bacterial adherence in vitro was examined using radio-labeled bacteria and liquid scintillation. In vivo plaque samples were analysed by culturing and the PCR technique. Plasma components were readily incorporated into experimental pellicles by incubation in plasma and into natural pellicles on tooth surfaces in vivo. These components mediated the adherence of Porphyromonas gingivalis, Fusobacterium nucleatum and Actinomyces naeslundii strains in vitro and were found to a higher extent in pellicles formed at the gingival part of the tooth surface than at the incisal part. The amount of pellicle protein and the numbers of bacteria increased during gingivitis, especially on the incisal parts of the tooth surfaces. Compared with a healthy gingiva, reduced numbers of Actinomyces spp. and streptococci and increased numbers of bacteria associated with periodontitis were seen in the four-hour dental biofilms during inflammation. We conclude that plasma proteins with the ability to mediate the in vitro adherence of periodontopathogenic bacteria are important components of the in vivo pellicle, particularly at the gingival margin. In addition, more gingival crevicular fluid during gingivitis affects pellicle formation, increasing the relative amounts of plasma proteins in the pellicle and thereby modifying bacterial attachment and early dental plaque composition.