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Objectives <p>This 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.</p> Materials and methods <p>Simulated 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&#xa0;mm were created. Two root canals were prepared at distances of 2&#xa0;mm or 5&#xa0;mm, creating six groups (<i>n</i> = 10 each). Root canals were filled with NaOCl, and #35&#xa0;K-files served as electrodes. A high-frequency current (225&#xa0;V, 520&#xa0;kHz) was applied for 5 or 10&#xa0;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.</p> Results <p>High-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 (<i>p</i> &lt; 0.05). In Groups 3 and 4, 10-s application significantly decreased organic material compared to 5-s application (<i>p</i> &lt; 0.001). Ordinal logistic regression analysis confirmed that electrode distance (OR = 0.854, <i>p</i> &lt; 0.0001), axial position (OR = 0.444, <i>p</i> &lt; 0.0001), and energization time (OR = 3.276, <i>p</i> &lt; 0.0001) were significant predictors, whereas gap width was not (<i>p</i> = 0.542). Coronal regions showed significantly higher cauterization rates than apical regions (91.6% [466/509] vs 68.2% [347/509]).</p> Conclusions <p>Within 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&#xa0;s increased the odds of achieving higher-grade surface morphological changes by 3.3-fold. Gap width did not significantly affect the outcome.</p> Clinical relevance <p>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.</p>

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

  • 期刊论文

  • 发表日期：

    2026年6月3日

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  • Ahmed Saud Alkuwaykibi,
  • Tsutomu Sugaya,
  • Mohammed Katib Alruwaili,
  • Naoki Takahashi

摘要

Objectives

This 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 methods

Simulated 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.

Results

High-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]).

Conclusions

Within 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.