Enterococcus faecalis is a bacterium frequently isolated after failed root canal therapy. This study analyzed the antibacterial and antibiofilm effects in vitro of sustained-release fillers (SRF) containing cetylpyridinium chloride (CPC) against vancomycin resistant E. faecalis. First, the solidification capability was tested by introducing liquid SRF into phosphate buffered saline, followed by 30 s of vortexing. The antimicrobial effects of SRF-CPC against static monospecies biofilms were analyzed with a metabolic assay. Inhibition of biofilm formation was tested by exposing daily refreshed E. faecalis suspensions to SRF-CPC for 9 weeks. To evaluate the effects of SRF-CPC against preformed biofilms, biofilms were grown for 1, 3 and 7 days, and then treated with SRF-CPC for 24 h. Biofilm kill time was tested by applying SRF-CPC to a 3-day-old biofilm and measuring its viability at different time points. All experiments were compared to Placebo SRFs and to untreated control biofilms. Data were analyzed with two-way ANOVA followed by Tukey’s test. Results were considered significant at P < 0.05. The liquid SRF solidified within seconds and no structural changes were observed after 30 s of vortexing at maximum speed. SRF-CPC inhibited E. faecalis biofilm formation for 7 weeks and significantly reduced its viability in weeks 8 and 9. Mature biofilms grown for 1, 3 and 7 days were destructed by SRF-CPC in less than 24 h. Fifty percent of a 3-day-old biofilm was destructed in 2 h and complete destruction occurred in less than 12 h. (P < 0.05 in all cases, compared to SRII-Placebo). SRF-CPC’s physical properties and long-lasting anti-biofilm effects make it a promising coadjuvant medication for endodontic therapy.

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.