Ex vivo comparative analysis of retrievability among four calcium silicate-based sealers for regaining apical patency

Article information

Restor Dent Endod. 2025;.rde.2026.51.e3

Publication date (electronic) : 2025 December 8

doi : https://doi.org/10.5395/rde.2026.51.e3

Darian Shomali¹, Timothy Kirkpatrick², Sang Won Kwak³, , Hyeon-Cheol Kim^3,, Ji Wook Jeong^2,

¹Department of Endodontics, School of Dentistry, UT Health San Antonio, San Antonio, TX, USA

²Department of Endodontics, School of Dentistry, University of Texas Health Science Center at Houston, Houston, TX, USA

³Department of Conservative Dentistry and Dental Research Institute, Pusan National University School of Dentistry, Yangsan, Korea

Citation: Shomlai D, Kirkpatrick T, Kwak SW, Kim HC, Jeong JW. Ex vivo comparative analysis of retrievability among four calcium silicate-based sealers for regaining apical patency. Restor Dent Endod 2026;51(1):e3.

^*Correspondence to Hyeon-Cheol Kim, DDS, MS, PhD Department of Conservative Dentistry and Dental Research Institute, Pusan National University School of Dentistry, 20 Geumo-ro, Mulgeum-eup, Yangsan 50612, Korea Email: golddent@pusan.ac.kr

^*Ji Wook Jeong, DMD, MSD Department of Endodontics, School of Dentistry, The University of Texas Health Science Center at Houston, 7500 Cambridge Street, Suite 6400, Houston, TX 77054, USA Email: Ji.wook.jeong@uth.tmc.edu

Hyeon-Cheol Kim and Ji Wook Jeong contributed equally to this work as co-corresponding authors.

Received 2025 July 2; Revised 2025 July 25; Accepted 2025 August 12.

Abstract

INTRODUCTION

Nonsurgical endodontic retreatment is typically the first choice of treatment when an endodontic treatment fails. The goal of retreatment is to remove all the existing obturation materials from the previous root canal treatment, disinfect the entire root canal system through proper cleaning and shaping, and then obturate the canals. The success rate of retreatment shows a similar success rate in comparison to initial nonsurgical endodontic therapy [1]. Root canal obturations with short fills greater than 2 mm have been shown to have a lower success rate compared to fills within 2 mm of the apex [2]. By extending working length, cleaning and obturating to the apical foramen is a major contributing factor in determining the success of retreatment. Instrumenting the root canal mechanically and chemically the root canal to its full length directly increased the success of treatment [3,4].

Calcium silicate-based sealers (CSS) or bioceramic sealers are being used around the world today. Advantages associated with these sealers include biocompatibility with surrounding tissue and osteoconductivity, the presence of calcium phosphate, which results in a chemical composition that is similar to tooth and bone, and an improvement in dentin-to-sealer bonding [5–7]. There are a few outcome studies that show favorable results from the treatment of CSS using both warm vertical and single cone techniques [8–10], while multiple brands of bioceramic sealers have been released in the market around the world.

Retrievability is a desirable property for any root canal sealers and achieving apical patency through the adequate removal of previous root canal contents increases the survivability of the tooth [11]. While bioceramic sealers have many advantages, it is important to note that the literature on the retrievability of bioceramic sealers is not consistent [12]. Some studies have shown that conventional retreatment techniques may not effectively remove CSS [12,13]. Other studies have indicated that there is similar efficacy in retreatment for both bioceramic sealers compared to traditional sealers [14]. Moreover, it was reported that CSS was likely to be extruded through the apical foramen [15,16].

Sodium hypochlorite (NaOCl, 0.5%–6%) is a primary liquid used to clean and irrigate root canals in nonsurgical root canal treatment due to its tissue-dissolving and antibacterial efficacy [17]. In addition, NaOCl can dissolve traditional root canal sealers such as calcium hydroxide-, polyketone-, zinc oxide eugenol-, and epoxy resin-based sealers [18]. Therefore, NaOCl can be used as a solution to simultaneously remove root canal sealers and disinfect root canals in nonsurgical retreatment. However, this conventional retreatment technique using NaOCl did not considerably remove the bioceramic sealer and regain apical patency during retreatment [12]. Moreover, in the case of short obturation with a bioceramic sealer in the study, the regaining patency rate was only 30% [12]. However, only one type of CSS was used in this previous study [12].

Interestingly, a study showed that the retrievability of different brands of CSS significantly varied [19]. Therefore, clinicians need to predict the retrievability of different brands of CSS before they execute the retreatment procedure. However, in this previous study, the sample design was extremely focused on the penetrability of the sealers for regaining apical patency, and a 2 mm length of thick sealer set in the apex was tested. For this reason, the sample design might not be realistic enough to prove the retrievability of the sealers in everyday retreatment cases and the results might not reflect the clinician’s decision.

This study aimed to evaluate the retrievability of four different brands of CSS in a straight root canal with a short obturation model.

METHODS

Root canal preparation and obturation

All teeth were decoronated to create a standardized length of 12 mm (Figure 1A). The teeth were then randomly divided into four experimental groups (n = 34) and one negative control group (n = 17). The sample size (experimental group and negative control) was determined based on our previously published study with similar experimental designs and outcomes assessing apical patency [19].

Figure 1.

Schematic design of the tooth sample. (A) A decoronated tooth with a single untreated canal (red). (B) Shaped canal (blue) by instrumentation up to 35/.04, 2 mm short of the working length. (C) Injecting BC sealer (grey) into the canal. (D) A 35/.04 gutta-percha cone was placed into the sealer-filled canal.

The experimental groups were based on which calcium silicate sealer was used: NeoSEALER Flo (NEO; Avalon Biomed, Houston, TX, USA), Ceraseal (CS; Meta Biomed, Colmar, PA, USA), Endosequence BC Sealer (BC; Brasseler USA, Savannah, GA, USA), AH Plus Bioceramic (AHB; Dentsply Sirona, Charlotte, NC, USA).

After working length was established with a 10/.02 K file, apical patency was achieved and confirmed by visualizing the file exiting the apical foramen. Each canal was instrumented to a 15/.02 K file at working length. The teeth were then instrumented 2 mm short of the working length using Vortex Blue nickel-titanium rotary instruments (Dentsply Tulsa Dental, Tulsa, OK, USA) to a master apical size 35/.04 taper (Figure 1B). A 35/.04 gutta-percha cone (GP) was placed, and a radiograph was taken to confirm the fit (Figures 2A and 2C). Throughout instrumentation, each canal was irrigated with 6 mL of 6% NaOCl after each file was used, followed by 3 mL of 17% ethylenediaminetetraacetic acid for 1 minute. All root canals were irrigated using 30-gauge irrigation needles (Max-I-Probe or Prorinse, Dentsply Tulsa Dental) and dried with paper points. The minimum waste tip from each sealer in its respective group was then inserted into the coronal third of each canal and ensured the sealer would travel through the apical foramen (Figure 1C). The sealer was placed in the canal until it could be seen extruding from the apical foramen. Using a single cone technique, each canal was obturated with a 35/.04 GP cone and the sealer (Figure 1D). Radiographs were also taken to confirm that the apical 2 mm had sufficient sealer (Figure 2B). If the remaining 2 mm of the canal was poorly obturated with voids, the tooth sample was excluded from its group (Figure 2D). Each sample was placed in an Eppendorf tube containing a wet sponge soaked in Hanks’ balanced salt solution (HBSS), ensuring only the root tip was in contact with the sponge. All tubes were positioned in stabilizing stands to maintain sample orientation. The teeth were stored at 37°C in 100% humidity in HBSS for 7 days.

Figure 2.

Representative examples of the accepted and rejected fillings. (A, B) Accepted samples: radiographs with a master cone (A) and with the cone and sealer (B). (C, D) Rejected samples: radiographs with a master cone (C) and with the cone and sealer (D), showing a large void in the apical 2 mm (white arrow).

Endodontic retreatment

The teeth were retreated one week later. Retreatment was performed using hand files, with irrigation using 6% NaOCl. GP was removed using a stepwise technique starting with a size 30 H file to engage and extract the bulk of the material, followed by size 25 and/or 20 H files until complete removal of GP. Successful retreatment was measured by regaining apical patency with the 10/.02 or 15/.02 K file. No solvent was used for softening the root canal filling.

Failure was defined as the inability to advance further apically and achieve apical patency within a ten-minute period. The timing began immediately after the complete removal of GP and continued until the initiation of attempts to regain patency. Postoperative radiographs were taken regardless of success or failure (Figure 3).

Figure 3.

Representative radiographic images of the experimental groups with achieved apical patency (upper row) and with failed apical patency (lower row). Left: after obturation. Right: after retreatment. (A) NeoSEALERFlo (Avalon Biomed, Houston, TX, USA). (B) Ceraseal (Meta Biomed, Colmar, PA, USA). (C) Endosequence BC Sealer (Brasseler USA, Savannah, GA, USA). (D) AH Plus Bioceramic (Dentsply Sirona, Charlotte, NC, USA).

RESULTS

The success rates for regaining apical patency were 79.4% (NEO), 69.7% (AHB), 50.0% (BC), and 37.0% (CS) (Figure 4). NEO showed the highest regaining apical patency rate, while CS showed the lowest patency. The patency rate was significantly different between NEO and CS (p < 0.01). According to Tukey contrast test, the difference in patency rates between CS and AHB is marginally significant (p = 0.056).

Figure 4.

Apical patency success rate (%) among NeoSEALER Flo (NEO; Avalon Biomed, Houston, TX, USA), Ceraseal (CS; Meta Biomed, Colmar, PA, USA), Endosequence BC Sealer (BC; Brasseler USA, Savannah, GA, USA), and AH Plus Bioceramic (AHB; Dentsply Sirona, Charlotte, NC, USA) groups. Tukey contrast test reveals a marginally significant difference in patency rates between CS and AHB (p = 0.055). ^*p < 0.01.

DISCUSSION

An ex vivo sample design was used in this study to assess the retrievability of four different CSS in the unshaped canal of the apex (Figure 1). Radiographs were taken before and after the obturation to ensure that the apical 2 mm was full of sealer without voids (Figure 2B). Thus, the samples could be standardized with the sealers in the 2 mm of root canals from the apices to strictly assess the retrievability of the CSS without the additional factor of voids in the sealer.

Apical patency was achieved in this study with rates ranging from 37% to 79%. The results of 50% (BC) and 79% (NEO) in this study are similarly patterned to those of the previous study, which showed 64% (BC) and 100% (NEO) [19]. Also, the texture of NEO was soft when it was removed from the root canal with a hand file, while the texture of CS or BC was hard. Based on the results of this study, clinicians should be careful when attempting to regain apical patency into CS or BC during retreatment, trying carefully not to create a ledge or transport the canal. It could be useful to measure the softness of CSS set for predicting retrievability in the future.

The brands of bioceramic sealers have similar but variable chemical compositions and setting properties (Table 1). The chemical compositions of the sealers in our study are as follows. NEO consists of tricalcium silicate (<25%), calcium aluminate (<25%), dicalcium silicate (<10%), grossite (<6%), tricalcium aluminate (5%), and radiopacifiers [20]. AH Plus consists of zirconium dioxide (50%–75%), tricalcium silicate (5%–15%), dimethyl sulfoxide (10%–30%), lithium carbonate (<0.5%), and a thickening agent [20,21]. CS consists of tricalcium silicate (20%–30%), dicalcium silicate (1%–10%), and tricalcium aluminate (1%–10%), along with a radiopacifier and thickening agents [20]. BC consists of zirconium oxide, calcium silicates, calcium phosphate monobasic, calcium hydroxide filler, and thickening agents (Table 1) [22]. Furthermore, NEO and AH Plus have shown a higher volume of open pores within the sealer upon setting when compared to CS [20].

Table 1.

Chemical composition of root canal calcium silicate sealers

The variability in chemical composition among the different brands of CSSs could also play a role in the softness of the sealers. At this point, it is unknown how each type of calcium silicate and its percentage within the sealer has an impact on setting softness. However, it is known that NEO has a higher volume of open pores within the sealer upon setting, which could explain the softer composition of the sealer [20].

The authors suggest five potential causes for the formation of pores in CSS after root canal filling. First, since CSS is set via hydration [23], its setting reaction can release water vapor or trap air as calcium silicates react with water to form calcium silicate hydrate and calcium hydroxide. Second, inconsistent mixing can lead to voids or air entrapment. Third, if the canal is excessively dried, CSS may set incompletely or exhibit delayed setting [23]. Fourth, CSS secondarily generates a hydroxyapatite crystalline structure [24], which may not compact tightly. Fifth, the handling of CSS during placement can also introduce voids. Further research is needed to better understand how the setting mechanism of CSS affects the micro- and macro-structure of each sealer.

Different canal types and sample designs can lead to variations in the success rates of patency. The success rate of patency for BC in straight canals was 50% in this study, while the patency rate for BC in the previous study was 30% in mesiobuccal canals of mandibular molars [12]. In the previous study, the regaining patency rate for BC was 64% in straight root canals [19]. In the present study, the tooth samples with voids of BC were thoroughly evaluated (Figure 2D). Ten samples with voids were discarded: 7, 2, and one sample in CS, BC, and AHB, respectively. Excluding these factors might contribute to the different success rates of regaining patency. The success rates were likely higher if those samples with voids had been included.

There have been suggestions to utilize solvents or solutions for the dissolution of CSS. A promising report was published that the regaining patency for BC in straight canals with short fills was achieved, ranging from 93% to 100% with the solvents of chloroform, formic acid, or hydrochloric acid [25]. This is not consistent with the results of the present study, indicating a 50% patency rate for BC in straight canals with short fills. Because NaOCl irrigation is generally used to disinfect root canals, 6% NaOCl was, in this present study, used to irrigate and remove the canal fillings until apical patency was regained. However, the authors in the present study did not use acids while standardizing the samples (Figure 1) and screening the teeth samples by radiographs (Figure 2B and 2D). Ten-minute time frame of this study design could affect the results. In addition, the short fills by 2 mm in this study could reduce the patency rate compared to the short fills by 1.5 mm in the previous study [25]. For those reasons, we suggest that the retrievability of CSS with different methods by ex vivo needs to be tested and compared using standardized teeth samples.

The period of storage after obturation can affect the rate of regaining apical patency. The samples in this study were obturated with CSS and stored in an incubator for 7 days. Clinically, it is not common to retreat a case that has been obturated recently. Theoretically, CSS may be more difficult to regain apical patency after many years due to the additional calcification that may occur in the canal. An ex vivo study reported that retreating the teeth containing CSS a year after obturation was more challenging than the case after a month [26]. For this reason, the patency rate of the present study might be overestimated compared to the retreatment cases on the chair side.

To reduce the bias of the tooth samples, only straight roots were selected in this study. Therefore, GP was removed with fewer morphological changes in the canal walls. However, it is common for clinicians to touch and modify the canal wall with files during the removal of GP, possibly resulting in ledge, zip, or transportation, especially when removing GP in curved canals. Those morphological changes are considerable factors in reducing the success rates of retreatment [27]. Therefore, the patency rates of the present study should be conservatively applied for retreatment cases when clinicians remove GP in short fills with curved canals containing CSS.

Given the significant variation in retrievability among different CSS, it is important for clinicians to document the specific sealer used at the time of root canal obturation. In retreatment scenarios, knowing which CSS was previously applied can help practitioners anticipate the difficulty of removal and select appropriate techniques and solvents. This information may be especially valuable when patients are referred or when retreatment is performed by a different provider. Therefore, in addition to the obturation technique, recording the brand and type of CSS in the patient’s chart should be considered a standard part of endodontic documentation.

CONCLUSIONS

The tested CSSs showed significantly different retrievability in terms of regaining apical patency. Upon endodontic retreatment, the retrievability of NEO was significantly higher than CS. In retreatment cases, identifying the type of CSS previously used is essential, as it significantly influences the ease and success of retreatment.

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