Impact of electrode distance, axial position, and energization time on cauterization of root canal isthmuses using high-frequency current.

objectivesThis in vitro proof-of-concept study evaluated how the isthmus gap width, distance between electrodes, and duration of high-frequency electrical current application affect surface morphological changes of simulated isthmus inner surfaces. MATERIALS AND

methodsSimulated isthmus models were prepared using bovine dentin blocks immersed in Plank-Rychlo solution to create organic layers. Isthmus gap widths of 0.1, 0.2, and 0.3 mm were created. Two root canals were prepared at distances of 2 mm or 5 mm, creating six groups (n = 10 each). Root canals were filled with NaOCl, and #35 K-files served as electrodes. A high-frequency current (225 V, 520 kHz) was applied for 5 or 10 s. The demineralized surface morphology (decalcified surface) prior to HFC application served as the baseline reference for evaluating cauterization outcomes. Isthmus surfaces were analyzed using scanning electron microscopy and energy dispersive X-ray spectroscopy.

resultsHigh-frequency current application produced surface morphological changes consistent with cauterization, including exposure of dentinal tubules. Fisher's exact test showed significant differences in cauterization rates, since Group 1 showed less organic residue than Groups 4 and 5 (p < 0.05). In Groups 3 and 4, 10-s application significantly decreased organic material compared to 5-s application (p < 0.001). Ordinal logistic regression analysis confirmed that electrode distance (OR = 0.854, p < 0.0001), axial position (OR = 0.444, p < 0.0001), and energization time (OR = 3.276, p < 0.0001) were significant predictors, whereas gap width was not (p = 0.542). Coronal regions showed significantly higher cauterization rates than apical regions (91.6% [466/509] vs 68.2% [347/509]).

conclusionsWithin the limitations of this in vitro proof-of-concept study, electrode distance, axial position, and energization time significantly influenced surface morphological outcomes. Extending energization time from 5 to 10 s increased the odds of achieving higher-grade surface morphological changes by 3.3-fold. Gap width did not significantly affect the outcome. CLINICAL RELEVANCE: Electrode distance, axial position, and energization time are critical parameters for high-frequency cauterization of simulated root canal isthmuses. These proof-of-concept findings may inform future investigations into the clinical application of this technique for areas inaccessible to conventional instrumentation.