Formation of subsurface dentin lesions using a polymicrobial biofilm model.

PURPOSE: To simulate an oral demineralization environment by multiple species of bacteria by inducing subsurface dentin lesions with a polymicrobial biofilm model.
METHODS: Polymicrobial biofilms consisting of multiple species of bacteria were generated from stimulated saliva using a high-throughput active attachment model. Biofilms were grown on dentin specimens in McBain medium containing 0, 0.2 or 2.5 ppm F and on glass without fluoride for 192 hours. The medium was refreshed twice daily, after 10 and 14 hours, until 72 hours, followed by treatment for 5 minutes with 400 ppm fluoride. Specimens were recovered after 192 hours. The number of colony forming units (CFU) was measured, and integrated mineral loss (IML) was determined by transversal microradiography.
RESULTS: Mineral profiles in specimens grown with 0.2F and 2.5F revealed surface layers and initial lesions distinct from those grown with 0F. IML was significantly lower with 0.2F and 2.5F than with 0F (P < 0.05), although CFUs were similar. CFUs of biofilms grown on dentin in medium containing 0F were 10-fold higher than on glass (P < 0.05). Subsurface lesions on dentin formed consistently, with their growth progression inhibited by application of fluoride. To our knowledge, this is the first report describing the induction of subsurface dentin lesions by a polymicrobial biofilm model, and this model may be useful for studies of demineralization supporting in situ and in vivo models.