Degradation in the dentin–composite interface subjected to multi-species biofilm challenges

The mechanical integrity of composite restorations challenged with multi-species oral biofilms was studied. While most studies used single-species biofilms, we used a more realistic, diverse biofilm model produced directly from plaques collected from donors with a history of early childhood caries. Biofilm growth with sucrose pulsing caused preferential degradation of the composite–dentin interface, with significant differences in bond strength reduction and failure modes depending on the composite/adhesive system used. Oral biofilms can degrade the components in dental resin-based composite restorations, thus compromising marginal integrity and leading to secondary caries. This study investigates the mechanical integrity of the dentin–composite interface challenged with multi-species oral biofilms. While most studies used single-species biofilms, the present study used a more realistic, diverse biofilm model produced directly from plaques collected from donors with a history of early childhood caries. Dentin–composite disks were made using bovine incisor roots filled with Z100TM or FiltekTM LS (3M ESPE). The disks were incubated for 72h in paired CDC biofilm reactors, using a previously published protocol. One reactor was pulsed with sucrose, and the other was not. A sterile saliva-only control group was run with sucrose pulsing. The disks were fractured under diametral compression to evaluate their interfacial bond strength. The surface deformation of the disks was mapped using digital image correlation to ascertain the fracture origin. Fracture surfaces were examined using scanning electron microscopy/energy-dispersive X-ray spectroscopy to assess demineralization and interfacial degradation. Dentin demineralization was greater under sucrose-pulsed biofilms, as the pH dropped