Bond strength between cements and metals used for endodontic posts

Abstract

Objectives. Adhesive cements used with metal endodontic posts may decrease fracture in non-vital teeth. Results from studies that evaluate cements for post retention by pulling posts out of extracted teeth are difficult to interpret owing to the number of interfaces where fracture might occur. The objective of this study was to isolate the metal/cement interface for tensile bond strength testing and microscopic observation. Methods. Three metals and seven cement treatments were examined for bond strength by using a truncated cone tensile test. The bond strength data were analyzed by a two-way ANOVA and Scheffé's multiple comparison test at p=0.05. Specimens were examined at 50× magnification to determine the failure mode and with scanning electron microscopy (500×) to observe the surfaces after debonding. Results. Significant differences in tensile bond strengths were found among cements compared within two of the metal groups. One of the metal groups had no significant differences among cement bonds. When comparing within cement treatment groups, two groups had significant differences in bond strength among the metals. Microscopic observations revealed adhesive, cohesive and mixed failure modes that varied with cement treatment and metal combination. The interaction between metal and cement was a critical determinant of the strength and characteristic fracture mode of the bond achieved. Significance. Some of the cement treatments performed better (i.e., higher bond strength) with some metals than with others. Other cements had similar bond strengths with all three metals. Because of this interaction, careful consideration of the materials combination should help to maximize the bond at the metal/cement interface.