The effect of smear layer removal on the push-out bond strength of two calcium silicate-based endodontic sealers (ENDOSEAL MTA and Sure-Seal Root) to root canal dentin

Abstract

Introduction: One of the main goals of root canal treatment is to achieve a tight seal to prevent the penetration of microorganisms to the root canal system. Smear layer removal prior to obturation is a controversial issue, based on the majority of reports, the bond strength to root dentin decreases in the presence of smear layer. Several studies have been done to compare the bond strength of calcium silicate based sealers in comparison to conventional resin based sealers that have shown different results, therefore the aim of this study is to determine the effect of smear layer removal on the push-out bond strength between different calcium silicate based sealers (EndoSeal MTA and SureSeal Root) and dentin in comparison with that between epoxy resin sealer (AH-plus) and dentin.

Method & Material: 93 mandibular premolars with straight roots without curvature are used. The length of the teeth are standardized to 21mm by trimming the crowns. After determining the working length, the cleaning and shaping of the canals is done using the rotary system. After preparation teeth are randomly divided into 3 major groups: Group A: the smear layer is removed by irrigation with 5mL of 17% EDTA and 5mL 5.25% NaOCl and the final irrigation is done with distilled water. Group B: smear layer is removed by 17% EDTA and 5.25% NaOCl with ultrasonic activation and the final irrigation is done with distilled water. Group C: smear layer preserved. (control group) Groups A, B and C are divided into 3 subgroups according to the sealer type: SureSeal Root sealer in subgroup A1, B1, C1, Endoseal MTA sealer in subgroup A2, B2, C2 and subgroup A3. B3, C3 AH plus resin sealer is used. The root canals are obturated with single cone technique using F3 gutta-percha. After obturation, push-out bond strength test is performed, each root sectioned at a slow speed using a water cooled diamond disk approximately 2 mm thick from middle region. The push-out test is performed using universal testing machine by applying a continuous load to the apical side of each slice. The failure modes are analyzed under a stereomicroscope at 30x magnification. Data will be analyzed with the two way analysis of variance. Statistical significance was defined at 0.05. Statistical analysis are performed using SPSS 17 software.

Results:

Based on the results of two-way analysis of variance, it was observed that: The interaction between the type of sealer and the method used to remove the smear was significant. In NaOCl + EDTA group, the lowest and highest bond strength were related to ENDOSEAL MTA and AH Plus sealers, respectively, while in the samples prepared by ultrasonic activation, the lowest and highest bond strength were related to AH Plus and ENDOSEAL MTA sealers, respectively. On the other hand, in the control group, the lowest and highest bond strength were related to AH Plus and Sure-Seal Root sealers, respectively.

Conclusion: The ultrasonic activation to remove smear layer had no effect on the push-out bond strength of calcium silicate based sealers and the AH Plus. The effect of smear layer removal by combining sodium hypochlorite and EDTA solutions on the push-out bond strength of calcium-based silicate sealer is different, so that the effect on the Sure-Seal Root bond strength is negligible but reduces the ENDOSEAL MTA bond strength. Removal of smear layer by combining sodium hypochlorite solutions and EDTA increases the bond of AH Plus resin sealer to dentin.