# Achieving Patency in Straight Canals Obturated with AH Plus Bioceramic Sealer: An Ex Vivo Study
## 4 Discussion
These studies underscore the importance of solvent selection during retreatment and suggest that the physical and chemical properties of CSSs, including their potential for dentin bonding and intratubular precipitation, may hinder their complete removal. Nevertheless, the use of chloroform has been questioned due to its cytotoxicity and carcinogenic potential, and other alternatives have been explored [7]. This study evaluated the efficacy of four different solutions (NaOCl, CA, FA, and EDTA) for achieving patency. Given that NaOCl is routinely used in endodontic procedures, it was evaluated for its ability to dissolve CSSs, to determine whether its application could affect the action of the other solutions tested. CSSs appear to be more soluble at low pH, suggesting that acids may act as solvents for these materials [34]. The selection of 10% CA was based on the study by [PERSON], et al. [35] which demonstrated that CA at concentrations of 10% can effectively dissolve hydraulic calcium silicate materials without causing adverse effects on dentin [36]. Additionally, [PERSON] and [PERSON] [22] proposed using 17% EDTA or 10% FA as a chemical adjunct to mechanical instrumentation for retreating teeth filled with TotalFill BC Sealer, while minimizing damage to the dentine structure. As in previous studies [37], our choice to use the Reciproc R25 instrument rather than the R40 was based on both clinical and methodological considerations. The R25 was primarily selected to standardize the retreatment procedure and simulate the initial stage of canal re-entry commonly encountered in clinical retreatments, where a smaller instrument is typically used to safely negotiate blockages or resistance. Furthermore, the objective of this study was specifically to evaluate the ability to regain patency in canals filled with AH Plus Bioceramic sealer, rather than to assess the overall cleanliness or extent of material removal within the root canal system. In this context, the use of an instrument such as the R25 was considered more appropriate and representative of clinical practice. The present study showed that apical patency was re-established in all five groups using a 10 K hand file. Our results corroborate previous findings [22], confirming the retreatment efficacy of CSSs used in the single-cone obturation technique in straight monor-radicular teeth. [PERSON] and [PERSON] [22] concluded that patency was achieved in the majority of cases obturated with Totalfill BC sealer, regardless of whether an adjuvant solution was used (17% EDTA or 10% FA). These findings are also consistent with those of [PERSON], et al. [23], who reported that the apical patency achievement rate, in teeth obturated with different EndoSequence BC, EdgeBioceramic, or NeoSeALERFlo sealers, was significantly higher when no solution was used, compared to 6% NaOCl, 5% acetic acid, and carbonated water. It was suggested that a possible effect of pore-liquid on the strength of CSSs could have a negative impact on their retrievability. However, contrary to our results, [PERSON]'s group concluded that retrievability decreased with the use of solutions (6% NaOCl, 5% acetic acid, and carbonated water). The differences in the solutions and sealers studied could explain the contrasting outcomes. Pre-mixed calcium silicate-based sealers have been clinically reported as successful in root canal treatment [38]. Their advantageous properties regarding antimicrobial ability and bioactivity have led to a wide consensus that they are an alternative to the standard epoxy resin sealers, namely through the single-cone technique. In the present investigation, a recently introduced pre-mixed calcium silicate-based sealer, AH Plus Bioceramic, was evaluated. As confirmed by EDS analysis, it is mainly composed of zirconium. Althoughit contains reactive tricalcium silicate, its overall calcium silicate content is comparatively lower (5-15%) than that of conventional CSSs due to the absence of di-calcium silicate in its composition [39].