Abstract
BACKGROUND: This study investigated the accuracy and reliability of apical limit control in endodontic retreatment using hybrid endodontic motors. MATERIAL AND METHODS: Thirty-six mesial canals of mandibular molars were accessed, and their apical foramina (AF) were standardized to 200 µm. Chemical-mechanical preparation was performed with WaveOne Gold instruments (#20/.07), followed by obturation with gutta-percha and AH Plus cement. After initial preparation, the teeth were divided into three groups (n = 12): Root ZX II (RZX), VDW Gold (VDW) and Tri Auto ZX2 (TRZX), all in rotary kinematics and with AF as the limit (0.0). Exposure was performed in the crown-down direction with ProTaper retreatment instruments using 2.5% NaOCl as an irrigation solution. Before using the instruments, the apexes of the teeth were immersed in alginate. With the auto-stop function activated, the hybrid instruments were calibrated to stop rotating when the desired apical limit was reached. The last instrument was fixed in the canal and a micro-computed tomography scan was performed to determine the distance between the instrument tip and the AF. Data were analyzed using the Kruskal-Wallis and Dunn tests (P<0.05). RESULTS: No significant differences were found between the RZX (0.10 mm), Gold (0.13 mm) and TRZX (0.27 mm) devices; accuracy ranged from 91.70% (RZX and VDW) to 63.63% (TRZX). TRZX had the highest number of readings besides AF. CONCLUSIONS: It was concluded that all devices studied were efficient in maintaining the apical limit of instrumentation during endodontic retreatment when taken to the AF. Key words:Endodontics, Electronic odontometry, Endodontic retreatment.