Biofilm Accumulation on Restorations: Gap Width and Secondary Caries Association

Objectives: The aim of this study was to evaluate in situ the effect of biofilm accumulation on enamel secondary caries development next to gaps of various sizes in the presence of fluoride dentifrice. Methods: In a split-mouth, double-blind, cross-over study, 16 volunteers used an intraoral palatal device containing restored bovine enamel slabs in two phases of 14 days. Slabs were restored with composite resin (CR - Z250, 3M ESPE) or resin-modified glass ionomer (RMGI- Vitremer, 3M ESPE) with 5 gap sizes (0, 50, 100, 250 or 500 µm) and were randomly distributed in the devices. In one side of the device, biofilm was allowed to accumulate under a plastic mesh, whereas in the opposing side, regular brushing was carried out 3 times/day with a dentifrice containing 1450 µgF/g as NaF. A 20% sucrose solution was applied extra-orally 10x/day. Knoop microhardness was used to measure the enamel demineralization and the biofilm collected from the specimens was assessed for Ca, F and Pi concentration. Results: No demineralization response for increasing gap size was observed, and a higher mineral loss associated to gap presence was observed for CR (p<0.05). Mineral loss was associated to surface biofilm accumulation, and was more evident up to 60 µm from enamel outer surface (p<0.05). Higher concentrations of fluoride ion were found in biofilm formed on GI slabs (p<0.05). Conclusions: Under fluoride dentifrice use, gaps adjacent to restorations have no influence on secondary caries lesions development, but higher demineralization was found associated to biofilm accumulation on the restored surface.