Er: YAG laser-activated 17% EDTA with side-firing tip preserves root canal dentin integrity: a micro-CT study

Purpose: The primary objective of endodontic therapy is to eliminate pathogenic biofilms from the intricate root canal system. Despite significant advancements in instrumentation and conventional irrigation, these methods often fail to adequately disinfect anatomically complex areas, leading to treatment failure. The integration of Er: YAG laser-activated irrigation (LAI) offers a promising adjunctive method to enhance disinfection through photoacoustic and cavitation effects. However, concerns regarding potential iatrogenic damage, such as a reduction in dentin thickness or microcrack formation due to thermal stress, persist. This study aimed to evaluate the safety of LAI with an Er: YAG laser using a side-firing spiral tip in combination with 17% EDTA by assessing potential structural changes in dentin thickness, canal volume, and microcrack formation, all assessed by micro-computed tomography (micro-CT) analysis. Methods: Twenty single-rooted human teeth were accessed and prepared using the ProTaper Ultimate rotary system up to the F3 size. The specimens were scanned using micro-CT before the laser treatment to obtain baseline measurements of dentin thickness and canal volume. Teeth were then treated with Er: YAG laser LAI using a side-firing spiral tip at parameters of 1.5 W, 150 mJ, and 10 Hz for 60 s, with 17% EDTA as the irrigant. After the laser treatment, a second micro-CT scan was performed. Pre- and post-treatment micro-CT data were superimposed and analyzed for changes in dentin thickness, canal volume, and the presence of microcracks. Results: The micro-CT analysis revealed no statistically significant difference between the pre- and post-treatment measurements of dentin wall thickness or canal lumen volume at the cervical, middle, and apical thirds of the root. The average change between pre- and post-treatment measurements did not exceed 0.05 mm, except for the palatal aspect in the middle part of the root. Furthermore, a careful examination of all specimens showed no evidence of microcrack formation following the LAI protocol. These findings demonstrate the safety of this protocol in preserving tooth structure. Conclusion: Our findings demonstrate that Er: YAG LAI with a side-firing spiral tip, when applied with the specific parameters tested (150 mJ, 10 Hz, 60 s), does not cause detectable structural damage to root dentin, supporting its safety profile within the context of this ex vivo study. These results suggest this protocol may be a safe adjunct for root canal disinfection, though in vivo validation and comparison with alternative activation methods are needed.