Aim of the study was to evaluate effect of root end cavity preparation either using conventional bur or ultrasonic diamond retro-tip in presence or absence of blood contamination on marginal adaptation of EndoSequence Root Repair material.

Materials and Methods: Forty four fully formed human maxillary central incisors were used ; after proper access cavity preparation, root canal instrumentation using ProTaper Universal , obturation using gutta-percha with AH plus, and apical 3mm of the roots were resected, the teeth were randomly divided into two main groups I &II of 22 samples each; root end cavities in group I were prepared using inverted cone burs and group II using ultrasonic diamond retro- tip. the group was then randomly divided into two subgroups according two blood contaminations of the root end cavities where subgroups IA and IIA the retrograde cavities were coated with fresh human blood, while subgroups IB and IIB cavities left uncontaminated. For all samples root end cavities were filled using ERRM and incubated at 37°C and 100% humidity after immersing in molds filled with heparinized blood for one week. Samples were split longitudinally and examined under SEM and size of gaps between the root-end filling materials anddentin were recorded.

Results: The highest mean gap value of ERRM was observed in subgroups IA& IB in which root end cavities were prepared using conventional bur either contaminated or not contaminated with blood than that prepared using ultrasonic diamond retro-tip in subgroups IIA&IIB, with no statistical difference between contaminated or non-contaminated cavities.