Canal Blockage and Debris Extrusion with Eight Preparation Techniques

The objective of this study was to assess and compare canal blockages and apical extrusion of dentin debris during canal shaping with eight preparation techniques. A total of 208 canals in extracted human teeth were prepared by one operator using one type of file. The techniques included were standardized, stepback with reaming, stepback with circumferential filing, stepback with anticurvature filing, double-flare, stepdown, crown-down pressureless, and balanced force. Records were kept of the number of canals that became permanently blocked with debris at some stage during preparation. Dentin debris extruded apically was collected in preweighed containers and the dry weight of debris determined to 10(-5) g precision. Blockages varied significantly among techniques (p < 0.001) and occurred most frequently in canals prepared with the stepback techniques with anticurvature (n = 19) and circumferential filing (n = 16) and least in the balanced force technique (n = 0). Apical extrusion occurred in 169 of the 208 roots, but there were no significant differences in the incidence of extrusion among techniques. The weight of extruded dentin did vary significantly among techniques (p < 0.05), with most extrusion occurring with the stepback techniques with circumferential (0.71 mg) and anticurvature (0.69 mg) filing and the least extrusion with the balanced force (0.38 mg) and crown-down pressureless (0.46 mg) techniques. Under the conditions of this study, it is concluded that techniques involving a filing (linear) motion caused significantly more blockages and extruded significantly more apical dentin debris.