Aims: The aim of the study was to evaluate the ability of a mixture of (castor detergent and papain enzyme) MCP to remove the smear layer by using scanning electron microscope.

Materials and Methods: Samples of 45 human extracted was divided in to 3 groups (A, B, and C) n = 15 and prepared endodontically using pro taper system up to size F 3, each group was irrigated with corresponding solution 3 ml in between each file size and 5 minutes as a final irrigant as following: Group A irrigated with distilled water (control negative). Group B irrigated with 2.5% (Sodium hypo chloride) NaOCL and 17% (Ethylene di amine tetra acetic acid) EDTA (control positive). Group C irrigated with 20% castor detergent and 4% papain enzyme as a mixture (MCP). Each sample was irrigated with 15 ml of distilled water and dried with paper points. The samples were sent for SEM photograph. Each sample was evaluated at three levels (apical, middle, and cervical part of the canal)

Results: MCP solution showed partial removal of both organic and inorganic parts (dual action) of smear layer from the 3 levels of root canals, but the apical one was significantly less clean than the other two, also it has a more gentle effect of erosion than EDTA with NaOCl. EDTA with NaOCl has the ability to remove the smear layer completely from the canal, but still the apical third was significantly less clean than that of other two. It is impossible to remove the smear layer completely by NaOCl and EDTA without erosion of the inner surface of irrigated canal when EDTA was used as a final irrigant for 5 minutes.

Conclusion: solution had the ability to remove the smear layer partially at the three levels of a root canal without dentin erosion. While EDTA had the ability to remove the smear layer completely at the three levels of canal with obvious dentinal erosion. Still the apical area has mechanical and anatomical limitation in root canal irrigation.