Effects of surface properties of polymer-based restorative materials on early adhesion of Streptococcus mutans in vitro

ObjectiveWe investigated the effects of the surface properties of polymer-based restorative materials on early adhesion of Streptococcus mutans (UA159) in vitro.MethodsFour direct polymer-based restorative materials, including a nanoparticle restorative (Filtek™ Z350, 3 M ESPE, USA), a nano hybrid universal restorative (Filtek™ Z250 XT, 3 M ESPE, USA), a low shrink posterior restorative (Filtek™ P90, 3 M ESPE, USA) and a polymer-based pre-reacted glass ionomer (Beautifil II, Shofu, Japan), were selected. After polishing under different conditions, surface morphology was examined using scanning electron microscopy. Surface roughness (SR), water contact angle (CAW) and surface free energy (SFE) were determined by profilometry and the sessile drop method. Early adhesion of S. mutans was investigated using confocal laser scanning microscopy. The area occupied by adherent bacteria (A%) was calculated with COMSTAT2 software. The correlations between A% and SR, CAW, and SFE were analyzed by linear regression using SPSS 20.0 software at a significance level of 0.05.ResultsThe value of A% was strongly correlated with SR (r = 0.893, P < 0.01) for surface roughness (Ra) of 0.02-0.80 μm, whereas a weaker correlation was obtained between A% and SR when Ra ≤ 0.20 μm (r = 0.643, P < 0.01). On super smooth surfaces (0.02 μm ≤ Ra ≤ 0.06 μm), SR did not influence early bacterial adhesion (r = 0.001, P > 0.05), a medium positive correlation between A% and SFE was obtained (r = 0.426, P < 0.01), and no correlation between A% and CAW was found (r = −0.028, P > 0.05)ConclusionsEarly adhesion of S. mutans on direct polymer-based restorative materials was mainly affected by SR. SFE influenced early adhesion of S. mutans on super smooth surfaces, while hydrophobicity did not.