Statistical models for evaluating the penetrating ability of endodontic instruments

An in vitro study was conducted to evaluate the penetrating ability of hand instruments (No. 10 K-file and "Pathfinder") and an automated device with a No. 08 (Canal Finder System) file in 270 extracted curved and narrow molar roots. The roots were randomly allocated to six groups, each one corresponding to a different permutation of the three instruments. The experiment was performed in three sequential stages, and Stages II and III were undertaken only in roots where no apical penetration was achieved in the previous stage(s). Statistical models were designed to fit the resulting clinical data. The No. 08 Canal Finder System and No. 10 K-file proved to be similar in their penetrating ability in Stage I (with estimated probabilities of 71.1% and 68.8%, respectively). The No. 08 Canal Finder was found to be the most efficient in Stage II and especially in Stage III, with a probability of penetration of 20.7%, compared with 9.8% for the "Pathfinder" and 7.4% for the No. 10 K-file.