Aim: The purpose of this study was to assess smear layer removal following canal preparation with single file (One Shape file) and multiple file system (Protaper Universal files).
Methodology: Sixteen freshly extracted mandibular molars were tested and divided into two experimental groups (n=8): group 1, cleaning and shaping was done using One Shape file (8 canals); and group 2, cleaning and shaping was done using a kit of Protaper Universal Files till file F2 (8 canals). Two grooves were prepared on the lingual and buccal surfaces of the instrumented roots by disc to facilitate vertical splitting with a chisel after canal instrumentation. The presence of smear layer was evaluated under SEM in the apical, middle and coronal thirds of the canals. Blind evaluation was done by two trained evaluators and scores were complied separately. Data were then collected, tabulated and statistically analyzed.
Results: Smear layer scores showed no statistically significant difference either in comparison between the two systems or between different root levels in each group.
Conclusions: Under the condition of the current study, both rotary systems failed to remove smear layer at different root canal levels using saline only as an irrigant.