The evaluation of fluoride release-recharge, surface roughness and antibacterial properties of multi-walled carbon nanotube reinforced glass ionomer cements

The aim of this study was to evaluate the fluoride release and recharge properties, surface roughness (Ra) as well as antibacterial properties of glass ionomer cements (GIC) reinforced with different ratios of multi-walled carbon nanotubes (MWCNT). Experimental groups of the study were formed according to the amount of MWCNT incorporated (G1: 1 wt%, G2: 2 wt%, G3: 3 wt%, respectively.). Unmodified Ionofil U was assigned as the control group (G0). Initial and after-recharge cumulative fluoride release of groups were recorded at 24 h, 48 h, 72 h, 7 days,15 days and 28 days. Ra values were recorded using a profilometer and a SEM imaging was performed. The antibacterial effects on S. mutans were analyzed by direct contact test with optical density values recorded using a spectrophotometer. Statistical evaluations were done with NCSS 2007. Repeated measures ANOVA in repeated measures of multiple groups, Newman Keuls multiple comparison test in subgroup comparisons, one-way ANOVA in group comparisons and Tukey multiple comparison test in subgroup comparisons were used. G3 released the highest amount of fluoride whereas the lowest was released from G0 (p<0.05). After fluoride recharge, G3 showed the highest amount of fluoride release and G0 showed the lowest at the end of 28 days (p<0.05). No statistically significant differences were found between the Ra values (p>0.05). SEM imaging demonstrated a relatively homogenious surface in G0. G2 and G3 revealed significantly increased antibacterial effects compared to G0 (p<0,05). MWCNT incorporation improved the fluoride release, recharge and antibacterial properties of the conventional GIC yet, did not cause any significant deterioration on the surface properties. Further studies are required to benefit from the promising CNT technology in the field of pediatric dentistry. Key words: Multi-walled carbon nanotubes, glass ionomer cements, fluoride release and recharge, surface roughness, direct contact test, antibacterial properties, SEM