A continuous culture biofilm model of cariogenic responses

Aims: To validate an in vitro model for the analysis of physiological and e cological responses to sugar challenge in bacterial populations, and subseq uent changes in enamel mineralization. Methods and Results: A seven-organism bacterial consortium was grown in a b iofilm mode on enamel and hydroxyapatite (HA) surfaces in a continuous cult ure system and exposed to repeated sucrose challenges. This produced 'pH-cy cling' conditions within the system. Populations on HA surfaces were enumer ated. Changes in relative proportions of the different populations, and in the total viable count, were observed, between different treatments. Micror adiography of the enamel sections showed increasing demineralization with i ncreasing sucrose concentration. The lesions formed were similar to 'white- spot' lesions found in vivo. Differences in the quality of biofilms formed were also observed using Confocal Laser Scanning Microscopy. Conclusions: An in vitro model has been validated for the analysis of both physiological and ecological responses to sucrose challenges in bacterial p opulations, and subsequent changes in enamel mineralization. Significance and Impact of the Study: This model should facilitate the stud y of changes in bacterial populations in response to application of putativ e anticaries agents and concomitant changes in enamel mineralization.