The aim of the present study was to investigate the dental plaque formed on natural teeth surfaces by optic and confocal laser scanning microscopy (CLSM), to quantify the microbial density by viable cell counts, to identify the recovered microbial strains, the antibiotic susceptibility testing and their pathogenicity features (i.e. adherence and invasion capacity on HeLa cells, adherence on prostetic substrata used in oral medicine by original experimental models, production of extracellular enzymes and exotoxins). results: The CLSM revealed a very complex and highly organized architecture of dental plaque. The direct optic examination of Gram-stained smears revealed a great diversity of morphological types (82.5% of cases), with comparative levels of microbial densities. 50% of recovered microbial strains exhibited ability to adhere to three different polimeric inert substrata used in oral medicine, but reduced adherence and invasion capacity of HeLa cells and scared expression of soluble enzymatic factors.