RESUMEN
The aim of the study was to examine the effect of operator experience on the quality of instrumentation of molar canals using the TF Adaptive file system (SybronEndo, Orange, CA) on a 3D-printed molar replica model. Three novice and two expert operators instrumented the root canals of three replicas each and resulting pre- and postinstrumentation 12 micron voxel size-microCT volumes of each replica were digitally registered. Relative modified canal wall surface fraction and canal transportation (1-9 mm from the apex) were calculated and analysed by anova. Instrumentation by expert operators resulted in overall higher (P = 0.002) modified wall surface fraction in the distal but not the mesial and higher (P = 0.002) combined from all canal level transportation in the mesiobuccal canals but not the mesiolingual and distal canals. Instrumentation efficiency but also transportation using the TF Adaptive file system can be higher among expert, compared to novice, operators, depending on the canal type.