Comparison of Two Evaluation Methods of Composite Shear Bond Strength to Human Tooth Dentin: an In vitro Study

Because of importance of dentin bond، and the factors that affect improving adhesion of dentin need to be considered، The objective of this study was to comparative of shear bond strength of composite resin to human dentin in two methods in vitro. Subjects and This experimental study was performed on 40 specimens that were divided randomly into two groups (n= 20، 3rd molar teeth). Then a flat surface of dentin was created on the occlusal surface. The produced dentin level was etched by acid phosphoric 38%; then two bonding layers were placed and cured. Composites filled inside the plastic tubes on 3mm inner diameter، 2 mm height were placed on dentin surface and cured. The specimens were stored in distilled water for 24 hr. The composite shear bond strengths were measured، by universal (LMT 100)، for the first group when the tubes were still in place، while for the second group it was measured after removal of the tubes. Composite shear bond strengths were measured by universal for both groups during the presence and after the removal of the tube. Significant statistical differences between the means of shear bond strength between the first group (12. 52 ± 0. 17) MPa، and second group (10. 05 ± 0. 25) MPa (P<0. 001). Appling the force for exiting of tube prior performing of final test، could decrease the bond strength.