Dr Mohammad Hossein Nekoofar
Immediate Past President of Iranian Association of Endodontists
Director of International Relations, Tehran University of Medical Sciences
Honorary Senior Clinical Lecturer, Cardiff University

Effect of Acidic Environment on Dislocation Resistance of Endosequence Root Repair Material and Mineral Trioxide Aggregate

Objective: The aim of this study was to compare the effect of an acidic environment on dislocation resistance (push-out bond strength) of EndoSequence Root Repair Material (ERRM putty and ERRM paste), a new bioceramic-based material, to that of mineral tri-oxide aggregate (MTA).
Materials and Methods: One-hundred twenty root dentin slices with standardized canal spaces were divided into 6 groups (n = 20 each) and filled with tooth-colored ProRoot MTA (groups 1 and 2), ERRM putty (groups 3 and 4), or ERRM paste (groups 5 and 6). The specimens of groups 1, 3, and 5 were exposed to phosphate buffered saline (PBS) so-lution (pH=7.4) and those of groups 2, 4, and 6 were exposed to butyric acid (pH= 4.4). The specimens were then incubated for 4 days at 37°C. The push-out bond strength was then measured using a universal testing machine. Failure modes after the push-out test were examined under a light microscope at ×40 magnification. The data for dislocation resistance were analyzed using the t-test and one-way analysis of variance.
Results: In PBS environment (pH=7.4), there were no significant differences among ma-terials (P=0.30); but the mean push-out bond strength of ERRM putty was significantly higher than that of other materials in an acidic environment (P<0.001). Push-out bond strength of MTA and ERRM paste decreased after exposure to an acidic environment; whereas ERRM putty was not affected by acidic pH. The bond failure mode was predomi-nantly cohesive for all groups except for MTA in an acidic environment; which showed mixed bond failure in most of the specimens.
Conclusion: The force needed for dislocation of MTA and ERRM paste was significantly lower in samples stored in acidic pH; however, push-out bond strength of ERRM putty was not influenced by acidity.
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