Methods: : 90 composite blocks (2X2X8 mm, Z100- 3M, ESPE) were prepared and divided into six groups. Specimen of group 1 was not contaminated (control group), for other specimens the surface was contaminated with blood then rinsed and dried. Group 2 got only this treatment and the remaining blocks treated as follows; group3,acid etch (phosphoric acid- Ivoclar Vivadent), group4,acid etch and bond (margin bond, Coltene), group5 ethyl alcohol , and group6, removal of 0.5mm of outer surface of composite. Composite cylinders (0.7 X 1mm) were placed on the prepared surfaces and cured. Micro -shear bond strength was measured using microtensile tester (Bisco Inc.USA). Data were analyzed by ANOVA and Tukey multiple comparison tests.
Results: : The average value of bond strength was 23±3.60 MPa for group 1, 17.89±6.52 MPa for group2, 19.40±6.08 MPa for group3, 20.20±5.72 MPa for group4, 20.01±6.83 MPa for group5 and 19.10±6.20 MPa for group6. There was no significant difference between groups.
Conclusions: All of the decontamination methods in this study could increase the bond strength of composite to composite interface to the level of the control group.