In vitro evaluation of residual bis-gma released after polimerisation of different band cements

The aim of this study is to evaluate the amount of released Bis-GMA from two different compomer resins, which are used to bond orthodontic bands, at two different times (10 minutes and 24 hours) and after thermocycling (24th hour after 5000 cycles) by using the High Pressure Liquid Chromatography (HPLC) analysis. For this purpose two experimental groups were formed; Group 1: light-cure compomer resin cement (Ultra Band Lok, Reliance Orthodontic Products, Itasca, USA) and Group 2: dual-cure compomer resin cement (Opal Band Cement, Ultradent Products, South Jordan, USA). For each group, rectangular seramic blocks (Sirona Dental Systems, Bensheim, Germany) were used to prepare 10 upper right first molar teeth samples by using CAD-CAM technique. Two different compomer resins were used for the cementation of molar bands (#39.5, M.I.B. Dental, Malmaison, France) and then polymerized by a high intensity LED curing unit (VALO, Ultradent, South Jordan, USA), following manufacturers' instructions. At two different times (10 minutes and 24 hours) and after thermocycling (24th hour after 5000 cycles) the amount of residuel Bis-GMA were analysed by using HPLC. All data were analyzed statistically. "Independent t test" and "U test" were used for statistical analysis. To compare the average of multiple measurements of the same group, "Wilcoxon Signed Rank test" was used. In all groups, amount of residual Bis-GMA increased with time. The maximum release of Bis-GMA was found in the "Opal Band Cement" group both At the first 10 minutes (p<0.0001) and at the end of 24 hours. At the end of 10 minutes and 24 hours the difference of released amount of Bis-GMA was not statistically significant between two groups (p>0.05). As a result, the highest amount of Bis-GMA release in both groups was found at 10 minutes, but the released amount of Bis-GMA between 10 minutes and 24 hours in both groups were lower than the first 10 minutes. After thermocycling no release was detected in any group. Thus, within the limits of the present study, both resins being tested can be suggested as safe, in terms of long-term monomer release. Key words: Bis-GMA, orthodontic band, compomer, High Power Liquid Chromatography (HPLC)