Introduction: Dental caries is a widespread chronic disease that is associated with inadequate oral hygiene and dietary habits. On dental surfaces a biofilm is formed, which later develops into caries. Caries occurs because of the formation of a biofilm in which Streptococcus mutans is predominant. The development of biofilm is influenced by many environmental factors and properties of materials. Purpose: To determine how different factors influence the development of Streptococcus mutans biofilm on different dental surfaces, which were studied. Methods: Samples of dental surfaces and few teeth were prepared. We selected materials used in dentistry: amalgam, chromium-cobalt alloy, gold, Chromasit, resin composite and ceramics. Firstly, surfaces of dental materials and teeth were studied. Surface roughness, zeta potential and contact angle of dental materials were measured. For determination of bacterial adhesion, sterile dental specimens and extracted teeth were immersed with an artificial saliva for an hour and then transferred to Petri dish; culture of Streptococcus mutans with broth was added and incubated for 10 hours. After 10 hours, the attached bacteria were fixed and the samples were examined with a scanning electron microscope. The adhered bacteria were manually counted and the results were given in percentage of the coverage of the dental surface with the bacteria. According to literature, the pH of saliva affects adhesion of Streptococcus mutans, so the fluctuation of pH in saliva was checked at volunteers and to determine if fluctuations really matter. Results: A significant higher number of bacteria was adhered to tooth surface than on other dental surfaces. The lowest number of adhered bacteria was found on amalgam surface. The pH values did not change significantly. Discussion and conclusion: It was found that Streptococcus mutans better adheres to the tooth surface than to the rest. The literature states that increasing surface roughness also increases adhesion, which was not proven in our study. It is evident from literature that development of biofilm is more influenced by the concentration of sugars in food than properties of materials. No significant changes in pH were noticed in the determination of the pH fluctuation due to the ingestion of the sugar solution. This may also be the result of the insufficiently sensitive method of pH measurement and small sample of the examined persons.