The C shaped configuration of root canal is one of the most important anatomical variations of the canal. It was first documented by Cooke and Cox in 1979. The prevalence of C shaped root canal reported to ranges from 2.7% to 44.5% in mandibular second molars. Failure of Hertwig's epithelial root sheath to fuse on to the buccal or lingual root surface may be the main cause of this configuration. This type canal configuration consists a single ribbon shaped orifice instead of several discrete orifices and the orifice looks like 180° arc starts from mesio lingual line angle to and sweeps...