Comparative Analysis of the Chelating Capacity of Two Solutions Activated with Sonic and Ultrasonic Systems: HEBP Versus EDTA

The success of root canal treatment depends on the proper execution of each phase. However, the instrumentation and irrigation phase is especially important. During this phase, the interior of the root canal system must be removed to facilitate the next phase, obturation, achieving the most airtight seal possible, resulting in the success of the endodontic treatment. This study aimed to compare the chelating capacity and smear layer removal effectiveness of two irrigants—17% ethylenediaminetetraacetic acid (EDTA) and 9% hydroxyethylidene bisphosphonate (HEBP)—when activated using two different irrigant activation systems: sonic and ultrasonic. Additionally, the study assessed the relationship between these variables and the average diameter of dentinal tubules in the coronal, middle, and apical thirds of the root canal. A total of 105 single-rooted human teeth were decoronated and instrumented using a rotary system. Teeth were randomly assigned to four experimental groups based on the irrigant (EDTA or HEBP) and the activation method (sonic or ultrasonic). Final irrigation was performed with the corresponding protocol. Samples were analyzed using scanning electron microscopy (SEM). Smear layer removal was quantified using the Carvalho method, and dentinal tubule diameter was measured with image analysis software. Data were statistically analyzed using Kolmogorov–Smirnov and non-parametric tests, with a significance level set at α = 0.05. EDTA showed superior smear layer removal in the coronal and middle thirds, particularly when activated ultrasonically. In contrast, HEBP was more effective in the apical third, especially when used with sonic activation. There were no statistically significant differences in the overall tubule diameter between the two chelating agents; however, HEBP resulted in significantly larger tubule openings in the apical third. Activation systems played a critical role, with ultrasonic irrigation being more effective for EDTA and sonic irrigation favoring HEBP in specific canal regions. The combination of chelating agent and activation system influences both smear layer removal and dentinal tubule morphology. HEBP demonstrated promising results in the apical third with minimal structural damage, supporting its use as a viable alternative to EDTA in continuous chelation protocols.