Adhesion of sealer cements to dentin with and without the smear layer

The influence of a smear layer on the adhesion ofsealer cements to dentin was assessed in recently extracted human anterior teeth. A total of 120 samples was tested, 40 per sealer; 20 each with and without the smear layer. The teeth were split longitudinally, and the internal surfaces were ground flat. One-half of each tooth was left with the smear layer intact, while the other half had the smear removed by washing for 3 min with 17% EDTA followed by 5.25% NaOCl. Evidence of the ability to remove the smear layer was verified by scanning electron microscopy. Using a specially designed jig, the sealer was placed into a 4-mm wide × 4-mm deep well which was then set onto the tooth at a 90-degree angle and allowed to set for 7 days in 100% humidity at 37°C. This set-up was then placed into a mounting jig which was designed for the Instron Universal Testing Machine so that only a tensile load was applied without shearing or applying preloading forces. The set-up was subjected to a tensile load at a crosshead speed of 1 mm per min. The results show significant differences (p