694 In vitro Biofilm-Associated Enamel Demineralization Under Distinct Sugar Exposure

Friday, March 23, 2012: 10:45 a.m. - 12:15 p.m.
Presentation Type: Oral Session
R.A. ARTHUR, R.A. WAEISS, A. HARA, F. LIPPERT, and D. ZERO, Preventive and Community Dentistry, Indiana University School of Dentistry, Indianapolis, IN
The development of microbial biofilm models to study carious lesions initiation and progression are needed to mimic in vivo caries under laboratory conditions.

Objectives: This study aimed to develop a microbial 4-species-consortia biofilm model to study enamel caries lesion development under constant and intermittent sugar exposure.

Methods: Biofilms were grown on the surface of 16 cm2 salivary-pellicle-coated enamel specimens with known Vickers surface hardness. Mixed-species suspensions were inoculated in 2.5-ml-wells containing enamel specimen and media supplemented with sucrose (S). In a constant sugar exposure design (CE), biofilms were grown in media supplemented with 0.25% S which was replaced once a day. An intermittent design (IE) exposed biofilms to media containing 5% S three-times a day. During the remaining time the biofilms were incubated in artificial saliva solution (containing 0.02 ppm fluoride) representing demin-remin cycles. Loosely adherent cells were removed by shear forces in both designs. The acidogenic potential of biofilms was checked daily by measuring the pH of the culture. Counts of viable cells on biofilms were assessed after 4 and 5 days of biofilm formation for CE and IE designs, respectively. Enamel specimens (n=6/group) were evaluated regarding percentage of surface microhardness change (%SMC) and carious lesion depth (LD) via transmitted light microscopy. Experiments were conducted in duplicate.

Results: Counts of viable cells of S. mutans, S. salivarius, S. sanguinis and L. casei ranged from 104 to 106 CFU/cm2 in both designs with S. sanguinis found only in biofilms formed under IE. S. mutans and L. casei were the most prevalent strains in biofilms of both designs. %SMC was -78.4±2.5 and -61.0±9.6 and LD (µm) was 78.1±9.3 and 34.8±3.6 (mean±se) for CE and IE, respectively.

Conclusions: This new biofilm consortia is a promising approach to study the multi-factorial aspects of carious lesion initiation and progression under distinct sugar exposure regimens.

Keywords: Biofilm, Cariology, Demineralization, Enamel and Microbiology