Continuous Chelation Reduces Instrumentation Time and Straightening of Double-curved Simulated Root Canals in Bovine Dentin

Adding a compatible chelator to the sodium hypochlorite (NaOCl) solution applied during instrumentation may affect shaping efficacy and canal transportation. This was studied in simulated double-curved root canals.

High-precision computer numerical control milling was used to recreate standardized S-shaped canals from a resin training block in longitudinally sectioned bovine incisor roots. These simulated root canals were instrumented chemo-mechanically at 37°C using a single-length rotary file system (ProTaper Gold). An etidronate powder (Dual Rinse HEDP) was dissolved (0.9 g per 10 mL) in a 1% NaOCl solution in the test group (n = 15), while the plain NaOCl solution was applied in the control group. Instrumentation was performed by one operator blinded to the irrigating solution. Instrumentation time was measured using a stop watch. Pre- and postoperative images were obtained by a second (blinded) investigator using a digital microscope, and super-imposed to assess canal straightening by totalizing transportation from 8 predefined locations. Data were compared between groups using Student's t-test, P < .05.

Adding the chelator, total instrumentation time was reduced to 75 ± 12 s as compared to 86 ± 14 s with plain NaOCl (P < .05). This time difference was related to the first rotary instrument in the system (S1). Canal straightening was also reduced significantly with the chelator compared to the plain 1% NaOCl solution (P < .05), while transportation at working length was similar between groups.

Under current conditions, continuous chelation expedited canal instrumentation and maintained simulated canal curvatures.