# Achieving Patency in Straight Canals Obturated with AH Plus Bioceramic Sealer: An Ex Vivo Study
###### Abstract  
This study compared the efficacy of different solutions in achieving patency in teeth filled with AH Plus Bioceramic sealer. Eighty-five premolars with a straight canal were prepared. After sealer placement, a master gutta-percha cone was introduced 2 mm short of the working length. The teeth were stored at 37 \({}^{\circ}\)C and 100% humidity for five weeks before retreatment. Filling materials were removed up to the gutta-percha cone's length. The canals were then randomly assigned to groups: G1 (control, no solution), G2 (5.25% NaOCl), G3 (17% EDTA), G4 (10% citric acid), and G5 (10% formic acid). The apical patency was attempted with a 10 K file within a period of 10 min, by a blinded operator. Additionally, sealer samples were immersed in the solutions, followed by scanning electron microscopy analysis. The Kruskal-Wallis test was used for statistical analysis. Patency was achieved in all canals except one in the control and one in the NaOCl groups. No significant differences were found in the time required to achieve patency. Acid solutions had a greater impact on the sealer's structural integrity, and a decalifying effect of EDTA and citric acid was registered. Apical patency in straight canals obturated with AH Plus Bioceramic sealer was consistently achieved regardless of the solution used. calcium silicate-based sealers; endodontics; apical patency; retreatment; root canal sealers; solvents +
Footnote †: journal: Applied Sciences  
0000-0001-8858-7885-3  
pancy may be influenced by factors such as the instrument design, the age of the root canal filling, the obturation technique, the type of sealer used, and the canal anatomy [1]. Despite advancements in technology, achieving complete removal of the previously placed obturation remains challenging [5; 6]. Techniques for removing filling materials include rotary files, ultrasonic instruments, heat, lasers, hand files, and solvent solutions [5; 7]. Although a combination of these methods is often required, the introduction of retreatment rotary systems has greatly enhanced the process, leading some clinicians to overlook the use of solvent solutions [5; 7]. Nevertheless, the effectiveness of combining solvents for filling removal remains controversial [5; 8; 9]. Some authors suggest that this approach can help reduce complications, particularly when the filling material has hardened over time or in cases involving thin and curved canals [1]. However, other studies argue that solvents should be reserved for situations where reaching the working length is challenging (e.g., in curved canals), as they may slow down the retreatment process and contribute to the accumulation of filling remnants on canal walls and within dentinal tubules [10; 11; 12]. Chloroform has historically been regarded as the most effective agent for softening gutta-percha due to its strong solvency properties [13]. However, concerns regarding its cytotoxicity and potential carcinogenicity have led to limitations on its clinical use. Consequently, alternatives such as orange oil have gained interest for their lower toxicity, although they typically exhibit slower and less effective softening capabilities compared to chloroform [14]. Traditionally, these chemical agents have been used indiscriminately for both gutta-percha and sealer removal. More recently, specialized formulations have been developed to selectively target specific types of sealers. For example, EndoSolv E (a tetrachloroethylene-based solution) is tailored for zinc oxide-eugenol sealers, while EndoSolv R (containing formamide and phenyl ethylic alcohol) is intended for resin-based sealers. Both products, previously manufactured by Septodont, have now been replaced by a newer version--EndoSolv--which is indicated for use with both types of sealers. Additionally, combined solutions such as \"methyl ethyl ketone + tetrachloroethylene\" and \"methyl ethyl ketone + orange oil\" have been proposed as dual-action options capable of softening both gutta-percha and resin sealers simultaneously [7; 15].