Comparison of Microleakage between Old and New Comp osite with Two Bonding Agent Systems: An In-vitro Study

Composite restorations usually have so many complications and imperfections and it is possible to eliminate impaired region without complete replacement of the composite. Repair ability of the resin composites is a desirable property. In time of need to repair part of the restoration, the composition of preexisting composite is unknown. The aim of this study was to evaluate the microleakage between old and fresh composite with two bonding agents systems. 144 specimens of P90 (3M, Germany) and Z250xt (3M, Germany) resin composite were aged and after surface roughening with diamond bur, they were placed randomly in 8 groups. All of the specimens were covered with nail varnish except on repair surfaces. Specimens were immersed in methylene blue and after that they were sectioned. Microleakage was measured using Adobe Photoshop portable software and stereomicroscope. Data were analyzed with ANOVA test (p=0.05). G8 group (p90+single bond 2+z250XT) revealed maximum of microleakage (1.131mm) and G7 group (p90+etching+p90 bonding+ p90)showed minimum (0.325mm) (P-value=0.0001). Using acid etching and p90 primer had no effect on microleakage. Comparison of groups which were repaired with the same resin composite as preexisting composite revealed no significant difference. Some groups were detected with valuable results (P-value=0.0001). Using acid etching and p90 primer for surface treatment has no effect on microleakage. Bonding materials were used in this study has shown no difference in results. Repairing old composite restoration with composite based on different resin is not recommended