Effect of calcium hydroxide and four irrigation regimens on instrumented and uninstrumented canal wall topography

The topography of instrumented and uninstrumented canal walls exposed to ca lcium hydroxide and four different irrigation regimens was observed by scan ning electron microscopy. After chemomechanical debridement, one tooth in e ach matched pair was medicated with calcium hydroxide. One week later, the teeth were irrigated and split longitudinally for evaluation. When no calci um hydroxide was used, predentin and pulpal debris covered the dentinal tub ules of the uninstrumented surfaces in specimens irrigated with water or ED TA, but was absent on uninstrumented surfaces in specimens irrigated with N aOCl or NaOCl and EDTA. A typical smear layer was absent in instrumented sp ecimens irrigated with NaOCl and EDTA, but covered the dentinal tubules of the instrumented surfaces of the EDTA irrigated specimens (partially) and t he water or NaOCl irrigated specimens (completely). Calcospherites or their remnants were seen on the uninstrumented canal walls of specimens irrigate d with NaOCl or NaOCl and EDTA, respectively; Calcium hydroxide use did not alter the surface topography in specimens irrigated with water, EDTA, or N aOCl, but seemed to erode the intertubular dentin in specimens irrigated wi th NaOCl and EDTA. All irrigants seemed to effectively remove most of the c alcium hydroxide.