The aim of the study was to assess the possibility of penetration of Escherichia coli bacteria into the dentinal tubules of the samples and determine the antimicrobial efficacy after 5 and 20 min exposition of 3% H2O2 (groups I and II) and 1 and 5 min exposition of 3% NaOCl (groups III and IV) for surface disinfection of bovine teeth. The samples were subjected to inoculation with E. coli suspension. The quality of disinfection was assessed with the three methods. The surface disinfection of samples proved to be effective only in groups II and IV. In the cultures of all dissolutions of dentinal chips suspensions in groups I, III and V there was a growth of E. coli in the form of a continuous pitch. In the group II a growth of Escherichia coli was revealed only in the initial dissolution in the quantity 1,8x101 CFU/ml, whereas in the group IV the growth was nil. Quantitative estimation of bacterial penetration using the method of maximum dissolutions revealed similar quantity of bacteria as in the group II as well as in the calculation of CFU. The application of 3% solution of H2O2 with the exposition of 20 minutes secures the qualitative surface disinfection of teeth without destruction of bacteria inside dental tubules and that allows to discover viable bacteria inside dentinal tubules.