Streptococcus mutans biofilm changes surface-topography of resin composites

Objectives Polymerized resin composites and nonpolymerized monomers are reported to accelerate bacterial growth. Furthermore, in vivo, resin composite restorations accumulate more plaque than other restorative materials. The purpose of this study was to test the hypothesis that bacteria–composite surface interaction causes changes in surface-topography. Methods Resin composite disks were polymerized between two glass slides. Streptococcus mutans cells were brought in contact with and grown on the disks for 1 day, 1 week or 1 month. The disks were analyzed using atomic force microscopy. One-month-aged composite specimens were assayed for changes in micro-hardness and bacterial outgrowth. Results Atomic force microscopy analysis revealed a time-dependent increase in root mean square (RMS) roughness (p < 0.0001). S. mutans outgrowth was accelerated following direct contact with the surface of aged composites, with no changes in micro-hardness. Significance Our results show that S. mutans growth on resin composite increases surface roughness without affecting micro-hardness. The change in surface integrity may further accelerate biofilm accumulation.