Comprehensive analysis of bacterial flora of a biofilm model in initial caries-inducing environment.

Purpose: To analyze changes in pH and bacterial flora with duration of culture and timing of sugar supply using a polymicrobial biofilm model.

Methods: The biofilm was prepared using the method of Exterkate et al. Stimulated saliva from an adult was collected on a glass slide and added to unbuffered McBain medium containing 0.2% sucrose and cultivated under anaerobic conditions for 10 hours. Cultivation continued anaerobically in saliva-free medium refreshed twice daily, with or without sucrose, in five groups: in the Control and Groups A and C, with 0.2% sucrose for 96, 192 and 288 hours, respectively; in Groups B and E, with 0.2% sucrose for 96 hours then, respectively, without for 96 and 192 hours; in Group D, with 0.2% sucrose for 96 hours, without for 96 hours, then with for 96 hours. The pH of all spent medium was measured. Total bacteria counts were determined by Q-PCR. The bacterial composition was determined by next-generation sequencing of 16S rDNA.

Results: The pH of spent medium depended on the presence or absence of sucrose. Total bacteria counts were higher in A, C and D than the other groups, and markedly lower in Group E. Principal components analysis and cluster analysis showed wider variation of bacterial flora of the biofilm in Groups B, D and E than other groups.

Clinical Significance: Inspection of bacterial flora of a biofilm model of the initial caries-inducing environment may lead to the development of materials and procedures for the prevention of dental caries.