An Active Attachment Biofilm Model to Develop Anti-Caries Strategies

There is a need to develop new preventive agents that target the oral microflora. For this adequate testing models are required that allow for the screening of these agents. This thesis describes a number of experiments that were performed to develop, test and utilize a biofilm model suitable for this purpose. Overall the data showed that the new biofilm model allows for the screening of potential antimicrobial compounds. The sensitivity of the model was high enough to show dose response relations both in terms of colony-forming units (CFU) counts and metabolic activity with a selected anti-microbial. Moreover the model could show the effect of compounds added to the growth medium on important metabolic output parameters such as pH and ammonium production. Shifts in the bacterial composition of the polymicrobial biofilms could be monitored. Adding a propidium monoazide (PMA) treatment step enhanced the observed effects. The concept of adding a PMA treatment step when measuring shifts in the composition of polymicrobial samples was also tested on clinical samples. Apparently a prolonged exposure to oral rinses restricted the need for the PMA treatment to show changes in bacterial composition of buccal plaque and tongue samples, whereas it still proved to be necessary when analyzing changes in saliva.