Objectives: To measure the effect of 0.5M citric acid on the shear bond strengths of five classes of endodontic sealers (CH=calcium hydroxide, ER=epoxy resin, GI=glass ionomer, ZO=zinc oxide eugenol, UD=urethane dimethacrylate) when interfaced with surfaces of 5.25% NaOCl-treated dentin. A second objective was to measure the shear bond strengths of these sealers to 5.25% NaOCl-treated gutta percha. Methods: Cylinders (n=10 per treatment group) of each sealer were applied to three surfaces treated with 5.25% NaOCl [GP=gutta percha, C=bovine dentin (control) and TX=bovine dentin treated with 0.5M citric acid]. The cylinders were sheared from the surfaces using an Instron testing machine at a crosshead rate of 1.27 mm/min. The shear stress data for each sealer were subjected to a General Linear Models analysis and a post hoc Tukey comparison test (a=0.05). Results: The means, standard deviations and Tukey NSD groupings (*) are as follows:

	CH	ER	GI	UD	ZO
C (MPa)	0.21 ± 0.15*	3.16 ± 1.41	0.19 ± 0.20*	0.11 ± 0.11	0.02 ± 0.02*
TX (MPa)	0.09 ± 0.07*	6.75 ± 0.40	0.11 ± 0.04*	0.03 ± 0.03*	0.01 ± 0.01*
GP (MPa)	1.03 ± 0.17	2.07 ± 0.23	2.05 ± 0.34	0.01 ± 0.01*	0.53 ± 0.10

Conclusions: For CH, GI and ZO, the use of 0.5M citric acid produced no statistically significant differences in bond strengths from the control. For UD, the bond strength of the control group was statistically higher than those of TX and GP. For ER, bond strengths were statistically different from each other and ranked from high to low: TX, C, GP. This research was funded by the J. Dean Robertson Society of the University of Oklahoma College of Dentistry.

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