# Achieving Patency in Straight Canals Obturated with AH Plus Bioceramic Sealer: An Ex Vivo Study
###### Abstract
Solvents are typically applied in the early stages of NSER by placing a few drops into the space created after the removal of the coronal filling [1]. Alternately, some approaches suggest flooding the canal with solvent after removing most of the remaining gutta-percha and further enlarging the canal [7]. In this context, [PERSON], et al. [16] highlighted the enhanced effectiveness of novel specific solvents (like methyl ethyl ketone/tetrachloroethylene) when combined with agitation, particularly in targeting gutta-percha and the epoxy resin-based sealer, AH Plus. Hydraulic calcium silicate-based sealers (CCSs), collectively referred to as bioceramics, have gained popularity in recent years. These materials exhibit a wide range of chemical compositions, which may influence their physical, chemical, and biological properties [17]. However, concerns regarding their solubility and retrievability remain a topic of discussion among clinicians [18]. In a recent survey, 55.5% of dentists considered that these sealers may influence the ability to re-establish apical patency during NSER [18]. CCSs are most commonly used with the single-cone obturation technique, resulting in a higher sealer-to-gutta-percha ratio compared to other techniques [17]. This approach simplifies clinical procedures while maintaining high success rates [19]. When NSER is necessary, gutta-percha can typically be removed using rotary instruments; however, the removal of CCSs can be more challenging due to their hardness [20]. Several parameters are used to assess CCS retreatability, including the ability to regain the working length (WL) and apical patency, the time required to reach the WL, and the amount of residual filling material left in the canal [20]. Studies on CCSs retreatabilityhave yielded inconsistent results. While some have demonstrated the advantages of using solvents [21], others suggest specific solvent solutions targeting sealer chemistry [22], while some report better outcomes without any solution [23]. Various solutions, including formic acid (FA), ethylenediamine tetraacetic acid (EDTA), citric acid (CA), acetic acid, carbonated water, chloroform, and hydrochloric acid, have been tested [22; 23; 24], but a definitive solvent for CCSs has yet to be identified. It is expected that the ideal solvent should be able to dissolve and remove the CCSs without causing structural damage to the dentin and perirradicular tissues. AH Plus Bioceramic (Dentsply Sirona, Charlotte, NC, USA) is a newly developed, premixed calcium silicate-based sealer available in an injectable syringe. Its composition includes zirconium dioxide, tricalcium silicate, dimethyl sulfoxide, lithium carbonate, and a thickening agent [25]. Recent studies have shown that AH Plus Bioceramic possesses key physical properties required for an effective sealer, including adequate flow, setting time, radiopacity, and a high pH, which contributes to its antibacterial activity [25]. Additionally, it exhibits significantly higher cytocompatibility and bioactive potential than AH Plus sealer, while demonstrating a cytocompatibility level comparable to Endosequence BC sealer [26]. One concern is its high solubility, which may negatively impact the quality of the obturation [22; 25]. However, research on the retreatability of this sealer remains limited. Currently, to the best of our knowledge, no study has evaluated the ability to regain patency in teeth obturated with the AH Plus Bioceramic sealer. This study aimed to compare the efficacy of different solutions in achieving patency during NSER in straight canals filled with AH Plus Bioceramic sealer and their effects on the sealer's microstructure. The null hypotheses were that (i) acid-based solutions do not significantly enhance the rate of patency achievement in teeth filled with AH Plus Bioceramic sealer and (ii) do not affect the microstructure of the sealer.