Influence of contemporary resin-based restorative materials on the microbial composition of in vitro biofilm microcosms.

PURPOSE: To evaluate the influence of contemporary resin-based restorative materials on saliva-derived in vitro biofilm microcosms under cariogenic challenge.

METHODS

Thirty specimens (7 mm x 1.8 mm) were fabricated from five resin-based restorative materials (n= 6 per material) according to the manufacturers' instructions: Fuji Ionomer Type II LC (GC), Filtek Supreme Ultra (3M, ESPE), Activa BioActive (Pulpdent), FIT-SA (Shofu America), SDR Flow+ (Dentsply Sirona). Hydroxyapatite (HA) discs (7 mm x 1.8 mm; HiMed Inc.) were used as controls. All specimens were UV sterilized, and biofilms were developed on the specimens using saliva from healthy donors, with and without 0.2% sucrose supplementation to mimic cariogenic challenge. After incubation, biofilm-associated cells were detached and plated onto selective agar plates to quantify total facultative anaerobes, total anaerobic bacteria, mutans streptococci, and Lactobacillus spp. Plates were incubated either under 5% CO₂ or in an anaerobic chamber. CFU counts were normalized to the specimen surface area (log¹º CFU/cm²).

RESULTS

Recoverable viable counts were significantly influenced by both material type and environmental conditions. FIT-SA and SDR Flow+ supported higher bacterial loads, particularly for mutans streptococci and Lactobacillus spp., under sucrose-enriched conditions. In contrast, Fuji maintained lower recoverable CFU under all conditions, suggesting reduced bacterial accumulation on this material in this model. Materials like FIT-SA and SDR Flow+ may promote higher recoverable biofilm-associated bacterial loads under sucrose challenge, while Fuji exhibited consistently lower CFU across conditions.

CLINICAL SIGNIFICANCE: Resin-based restorative materials marketed as bioactive supported varying levels of viable biofilm accumulation under sucrose challenge. These findings indicate that bioactive claims alone do not necessarily translate into reduced microbial burden and reinforce the need for effective disease control before definitive restorative placement, particularly in high caries-risk patients.