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Background/purpose: The aim of the this study was to compare the amount of debris apically extruded during endodontic retreatment using two rotary nickel–titanium (NiTi) instruments (K3 and R-Endo) and Hedström files. Materials and methods: Forty-five extracted human mandibular premolar teeth were used in this study. Root canals of the teeth were filled before being randomly assigned to three groups. In group 1, gutta-percha was removed with K3 (SybronEndo, West Collins, CA, USA) rotary NiTi instruments. In group 2, gutta-percha was removed with R-Endo (Micro-Mega, Besançon, France) rotary NiTi instruments. In group 3, gutta-percha was removed using Hedström files (Dentsply Maillefer, Ballaigues, Switzerland). Debris extruded from the apical foramen was collected into Eppendorf tubes. The liquid inside the tubes was dried, and the debris in each group was weighed and compared. Data were statistically analyzed using one-way analysis of variance, and Kruskal–Wallis test and Mann–Whitney U test. Results: Although all retreatment techniques resulted in apical extrusion, groups 1 and 2 produced significantly less apical extrusion than group 3 (P0.05). Conclusion: All retreatment techniques produced extruded debris during endodontic retreatment; however, both rotary NiTi systems were associated with less apical extrusion than manual instrumentation with Hedström files.

Background/purpose: Endodontic treatment success depends on treatment of all root canals, but the implementation status is affected by various factors. We examined whether the fee payment change affected the extra root canal endodontic treatment (EXRCT) in adult teeth in the National Health Insurance (NHI) system of Taiwan since 2008. The effect of hospital level, sex, and age on EXRCT was also examined. Materials and methods: Two longitudinal health insurance databases for 2005 and 2010 were used. Excluding third molars and endodontic retreatment, the EXRCT rate in permanent dentition were compared for different tooth positions, hospital levels, sex and age between 2005 and 2010. Results: In total, 80,995 teeth in 2005 and 76,018 in 2010 underwent root canal filling. The rate of EXRCT increased markedly from 2005 to 2010, particularly for the upper first molar (1.84% to 3.18%), lower first premolar (3.45% to 4.58%), lower first molar (12.4% to 18%), and lower second molar (0.95% to 1.87%). The difference between 2005 and 2010 remained statistically significant after adjustment for hospital level, sex, and age. The lower second molar had the highest adjusted odds ratio for the difference between 2005 and 2010 (1.99; CI: 1.49–2.66), followed by the upper first molar (1.91; CI: 1.55–2.35), lower first molar (1.60; CI: 1.47–1.75), and lower first premolar (1.38; CI: 1.11–1.72). Conclusion: The payment change of Taiwan NHI seems to encourage the use of EXRCT in molars. Hospital level, sex, and age also affected the rate of EXRCT.