RESUMEN
Contamination leads to decreased bond strength causing failure of restorative treatments. The present study evaluated micro-shear bond strength of composite-composite after saliva contamination and searched for the best method to maintain primary bond strength. In this in-vitro trial, specimens made by Z100 composite resin were divided into 7 groups each containing 15 samples and were prepared as follows: Group 1- Control [no contamination], Group 2: Saliva+air drying, Group 3- Saliva+rinsing+ air drying, Group 4- Saliva+ rinsing+ air drying+ etching, Group 5- Saliva+ rinsing+ air drying+ etching+ bonding, Group 6- Saliva+ alcohol, and Group 7- Saliva+ 0.5 mm removal of composite+ rinsing + air drying. Z100 composite was added through tiny tubes [0.7x1 mm] to the prepared surfaces and cured. The microshear bond strength was then determined. Data were analyzed using ANOVA and Tukey's multiple comparison tests. Mean and standard deviation of the microshear bond strength was 23.0 +/- 3.60 MPa in group 1, 11.71 +/- 2.49 MPa in group 2, 17.60 +/- 4.25 MPa in group 3, 21.84 +/- 6.34 MPa in group 4, 21.25 +/- 7.58 MPa in group 5, 21.65 +/- 5.53 MPa in group 6 and 17.34 +/- 5.95 MPa in group 7. Differences between groups 1 and 2 [P<0.0001], 2 and 4 [P<0.0001], 2 and 5 [P<0.001] and 2 and 6 [P<0.0001] were statistically significant. The results of this study showed that air drying of the surface after saliva contamination decreased microshear bond strength significantly. All cleansing methods increased bond strength of the specimens up to thatof the control group