# Achieving Patency in Straight Canals Obturated with AH Plus Bioceramic Sealer: An Ex Vivo Study
## 4 Discussion  
In the present investigation, the efficacy of achieving patency in straight canals obturated with AH Plus Bioceramic sealer was evaluated. The study assessed the use of NaOCl and three acid solutions as an adjunct to the mechanical action of a 10 K file, in comparison to the control group (no solution). The results indicated that, although the acid solutions produced changes in the microstructure of the sealer, this effect was not related to a higher occurrence of canals with patency. Thus, among the two null hypotheses tested, only hypothesis (i) was supported by the results, suggesting no significant effect of acid-based solutions on patency rates. Hypothesis (ii), however, was not confirmed, as the microstructure of the sealer was affected. Although previous studies have investigated CSSs, including comparisons with the conventional AH Plus sealer [21; 29], one of the objectives of the present study was to determine whether some of the solvents known to be effective in retrieving CSSs could also efficiently dissolve AH Plus Bioceramic sealer. To the best of our knowledge, this is one of the first studies to specifically assess the ability of various solutions to regain patency in teeth obturated with AH Plus Bioceramic sealer. Apical patency, as defined by the American Association of Endodontists, refers to the procedure in which the apical portion of the canal is kept free of debris by recapitulating with a small file through the apical foramen [30]. In addition to other anatomical complexities within the root canal system, the apical part of the main canal is considered the \"critical zone\" due to its strategic position, which enables microorganisms to cause or maintain apical periodontitis [31]. During NSER, re-establishing patency can influence the prognosis [32]. As reported in another study [23], the time to achieve patency was measured after gutta-percha removal, simulating a short filling, with the cone intentionally left 2 mm short of the WL. This approach increased the difficulty of retreatment and allowed for a more objective assessment of sealer removal in the absence of gutta-percha. A ten-minute time limit was set to re-establish apical patency, though this may not fully reflect clinical conditions. Traditional solvents, such as chloroform, which are effective against gutta-percha and resin-based sealers, exhibit unclear action against CSSs [33]. [PERSON], et al. [33] compared the efficacy of regaining patency in teeth obturated with either AH Plus or EndoSequence BC Sealer. The samples were divided into four groups: in two groups, the gutta-percha was placed to the full WL, while in the other two, it was positioned 2 mm short. The retreatment protocol included the use of heat, chloroform, rotary files, and hand instruments. When gutta-percha extended to the WL, complete success (100%) in re-establishing WL was achieved in all groups, regardless of the sealer used. In samples where the gutta-percha was short, WL was re-established in 100% of canals filled with AH Plus, but only in 30% of those filled with EndoSequence BC Sealer. [PERSON], et al. [24] compared the efficacy of 20% hydrochloric acid (HCI), 10% FA, and chloroform as solvents for regaining patency in teeth filled with EndoSequence BC Sealer. Their results revealed that all three solvents were generally effective, but 20% HCl achieved patency significantly faster than FA and chloroform. However, scanning electron microscopy demonstrated that HCl may have caused erosion of dentinal tubules, raising concerns about its potential for structural compromise. [PERSON], et al. [21], in their micro-CT-based study, demonstrated that AH Plus resulted in substantially less residual filling material and allowed for complete re-establishment of canal patency in all samples, particularly when used with chloroform. In contrast, BC Sealer exhibited higher volumes of residual material, especially when chloroform was not used, and patency could only be regained in 14% of such cases.