Effect of curing time on biofilm formation of different nanofilled resins

The aim of this in vitro study was to evaluate the effect of curing time on roughness, bagnability and bacterial biofilm formation of different nanofilled resins. 48 pressed round 2mm-thick disks of each tested composite were prepared (n=12). Group 1: Admira Fusion X-Tra (Voco, Germany); Group 2: Filtek Bulk Fill Posterior (3M, USA); Group 3: SDR (Dentsply, Germany); Group 4: Grandioso Flow (Voco, Germany). Before light curing with the same multiLED light, sample of each group were divided in 2 subgroup according to the curing toime (10 s and 80s). All prepared samples were stored in a drying oven at 37°C for 24 h. The upper surface was then serially tested to obtain superficial roughness (Ra), surface free energy and chemical constitution through EDX analysis. Then, samples were sterilized and stored in a bioreactor to simulate adhesion and biofilm formation by Streptococcus Mutans. The biofilm was then evaluated and quantified through a confocal laser microscopy after dead/alive coloration. Statistical analyses was performed with ANOVA test and significance was set for p<0.05. The ANOVA test showed that curing time significantly affected the biofilm formation over composite surfaces (p=0.0001). Within tested composites, group 2 showed the less formation of biofilm after 10 second of polymerization. The curing time of nanofilled composites seems a fundamental step to limitate biofilm formation over surface materials. Further studies are necessary to evaluate how aging process affect biofilm formation.