Dual-species biofilm of Streptococcus mutans and Candida albicans produces subsurface caries lesions on bovine enamel

Abstract

Objectives: To develop a protocol for forming subsurface caries lesions on bovine enamel by dual-species biofilms of Streptococcus mutans and Candida albicans in vitro. Design: Biofilms were grown on bovine enamel specimens in artificial saliva (AS) for seven days. After 24 h of formation, the AS was supplemented or not with fluoride (F) using sodium fluoride (0.005 or 0.008 ppm F), and the biofilms were exposed or not to a 20 % sucrose solution (reproducing a cariogenic challenge) once/day. On the seventh day, the biofilms were harvested and had their extracellular polysaccharides (EPS) and inorganic components analyzed. The specimens were subjected to computed X-ray microtomography analysis to determine their mineral concentration. Data were compared using two-way analyses of variance, followed by Fisher's LSD or Student–Newman–Keuls tests (p < 0.05). Results: Biofilms exposed to the cariogenic challenge had significantly higher EPS concentrations than those not exposed, regardless of the presence of F. For biofilms grown with 0.008 ppm F, those exposed to the cariogenic challenge had lower F levels than those not exposed. For biofilms exposed to the cariogenic challenge, those grown with 0.008 ppm F had lower lesion depths and integrated mineral loss, and higher outer layers than those grown without F. Conclusions: The dual biofilm model assessed was able to create subsurface caries lesions in bovine enamel in vitro, which was influenced by the presence of F in the culture medium and exposure to sucrose.