Abstract
Biofilm formation in the oral cavity is postulated to cause oral diseases such as dental caries, periodontal diseases, and peri-implantitis etc. Recently, an artificial mouth system (AMS) was developed to study oral biofilm formation on dental materials in vitro by simulating the human oral environment. The purpose of this study was to monitor the biofilm formation on titanium (Ti) and hydroxyapatite (HA) using AMS and to evaluate the biofilm morphology by scanning electron microscopy (SEM). As bacterial strains, Streptococcus mutans (S.mutans) and Streptococcus sobrinus (S. sobrinus) were employed. The number of bacterial cells on each specimen was evaluated after 5 and 18 hours assays. The number of S. mutans cells after 18 hours was significantly higher than after 5 hours (p<0.05). No significant differences existed between Ti and HA specimens for both S. mutans and S. sobrinus cells in each assay period. The 18 hours assay specimens provided a significantly higher amount of water-insoluble glucan (WIG) by S. mutans than 5 hours specimens (p<0.05). There were no significant differences between Ti and HA in the amount of WIG in each assay period. On SEM observation, biofilm formation of S. mutants and S. sobrinus was recognized on the HA specimen surface and no distinct differences were recognized. Higher magnification observation revealed the formation of pores with a diameter of approximately 5µm. This was due to the pH decrease during biofilm formation. Ti surface could not be influenced by the decrease of pH. This was confirmed by acid etching of HA and Ti. Pores were also formed by acid etching on enamel but not on Ti. It is suggested that the formation of such pores is related with caries formation. In conclusion, biofilm formation on HA and Ti could be monitored using AMS.
