2025 Volume 67 Issue 4 Pages 181-185
Purpose: This study aimed to evaluate the removal efficiency of three different intracanal medicaments using either single-syringe irrigation (S-SI) or multiple ultrasonic-activated irrigation (M-UAI).
Methods: Forty-two extracted human mandibular premolars were prepared to a size of 30/0.06 taper and randomly assigned to two irrigation groups: S-SI and M-UAI. Each group was subdivided based on the intracanal medicament used: Calcipex II (calcium hydroxide-based; CP), Calfee paste (calcium hydroxide-based; CF), or Bio-C Temp (calcium silicate-based; BT) (n = 7 each). After 1 week of storage under 100% humidity at 37°C, the samples underwent removal using either S-SI (1.5 mL sodium hypochlorite, 30 s) or M-UAI (1.5 mL, sequentially: 17% ethylenediaminetetraacetic acid, distilled water, 6% sodium hypochlorite, and distilled water, with 30-s activation for each). Residual intracanal medicament volume was assessed using micro-computed tomography. Statistical analysis was performed using the Kruskal-Wallis test and Mann-Whitney U test (α = 0.05).
Results: In S-SI, CF was removed more effectively than CP. In M-UAI, CF and CP showed similar rates, whereas BT had a significantly lower removal rate.
Conclusion: Removal efficiency varied among medicaments. CF demonstrated superior removability under both S-SI and M-UAI protocols compared with CP and BT.
The primary goal of root canal therapy is to effectively manage intracanal infections by eradicating microorganisms, toxins, by-products, and infected dentin through chemo-mechanical disinfection followed by proper root canal obturation [1]. However, the intricate morphology of the root canal system presents considerable obstacles to thorough cleaning and disinfection, with existing evidence indicating that even following biomechanical preparation, complete disinfection of fully shaped canals remains clinically insufficient [2,3]. Hence, interappointment intracanal medication has been utilized for several decades to further augment the microbial reduction effects [4]. Furthermore, intracanal medication serves as a physical barrier, inhibiting reinfection of the root canal and limiting nutrient availability to any residual bacteria [5].
Calcium hydroxide (CH) has been one of the most widely used intracanal medicaments in endodontics over the decades, primarily due to its potent antibacterial properties and tissue-dissolving capabilities, which have established it as the preferred choice for intracanal medicament, a practice well-supported by the literature [3,6]. Currently, a diverse range of commercially available intracanal CH medicaments is used in clinical practice, each varying in composition and CH concentration [7]. Calcipex II (Nippon Shika Yakuhin, Shimonoseki, Japan) is a premixed, water-based CH paste commonly employed as a temporary intracanal dressing during root canal treatment. Its antimicrobial activity is attributed to its high pH (approximately 12) and favorable flow characteristics. Calcipex II is composed of 24% CH, 24% barium sulfate (as a radiopacifier), and 52% other constituents, including purified water and thickening agents. Calfee Paste (GC Showa Yakuhin, Tokyo, Japan) is a recently introduced water-based CH paste (Table 1). According to the manufacturer, Calfee Paste is composed of 36% CH and contains an amphipathic polymer expected to enhance the removability of the paste due to its water-absorbing properties.
Moreover, recent advancements and promising results associated with calcium silicate-based intracanal medicaments have introduced new perspectives to enhance root canal disinfection between treatment sessions [8]. Bio-C Temp (Angelus, Paraná, Brazil) was the first calcium silicate-based intracanal medicament, composed of calcium silicates combined with calcium tungstate and titanium oxide radiopacifiers, along with calcium aluminate, calcium oxide, and a base resin [9]. A previous study showed that Bio-C Temp released Ca2+ and OH− similar to CH-based intracanal medicaments [10]. It has been introduced as a novel intracanal medicament in endodontic procedures or retreatments, management of root resorption, and treatment of immature teeth [11].
While CH has long been acknowledged for its therapeutic benefits, concerns remain regarding its complete removal from root canals. Inadequate removal of the intracanal dressing prior to obturation may significantly contribute to treatment failure [12], since any remaining CH may interfere with the proper sealing of the root canal filling, potentially resulting in apical leakage [13]. Similarly, concerns have been raised that exposure to CH for more than 5 weeks leads to a reduction in the mechanical properties of root dentin [14]. Consequently, it is imperative that the intracanal dressing be thoroughly removed before the root canal filling procedure to ensure optimal sealing and treatment success. Various devices and techniques have been examined; however, to date, no method has proven capable of fully eliminating intracanal dressings from root canals [15].
The conventional syringe irrigation technique (SI) remains the most widely used approach in clinical scenarios. However, its effectiveness has been questioned, especially regarding its inability to reach complex root canal anatomies [16], irregularities [17], and the apical third of the canal [16,18]. Accordingly, ultrasonic-activated irrigation (UAI) has been introduced to overcome the limitations associated with SI techniques [19]. UAI facilitates the transmission of acoustic energy from an oscillating file to the irrigation solution within the root canals [20].
Recent studies employing micro-computed tomography (micro-CT) to assess intracanal CH medicament removal have shown that it facilitates a more dependable three-dimensional quantitative analysis, providing enhanced sensitivity compared to sectioning methods [16,21]. While studies have investigated the removal of CH-based medicaments in comparison with calcium silicate-based alternatives [8,11], the available literature on this topic remains limited. Given the critical importance of complete CH removal prior to root canal obturation, this study aimed to determine and compare the removal efficacy of three different intracanal medicaments using micro-CT imaging. The focus was on (i) the single-SI (S-SI) technique, simulating the initial cleaning following temporary seal removal, and (ii) multiple UAI (M-UAI) techniques, corresponding to the final thorough cleaning. The null hypothesis tested was that the intracanal medicaments would exhibit comparable removal efficiency, irrespective of the irrigation technique (S-SI or M-UAI) employed.
| Materials | Composition | Manufacturer/ Lot No. |
|---|---|---|
| Calcipex II | calcium hydroxide, barium sulphate, purified water, thickening agents | Nippon Shika Yakuhin, Shimonoseki, Japan/ P5U |
| Calfee Paste | calcium hydroxide, barium sulphate, purified water, others | GC Showa Yakuhin, Tokyo, Japan/2303151 |
| BioC Temp | tricalcium silicate, dicalcium silicate, tricalcium aluminate, calcium oxide, base resin, calcium tungstate, polyethylene glycol, titanium oxide | Angelus, Paraná, Brazil/ 66700 |
The present research was approved by the ethics committee at Institute of Science Tokyo (No. D2023-029).
Sample size calculationThe required sample size of at least seven per group was determined based on the data from a preliminary study using G*Power 3.1.9 software (Heinrich-Heine-Universität Düsseldorf, Germany). Parameters were set at α of 0.05, β of 0.75, and an effect size of 0.7.
Specimen selectionA total of 42 single-rooted premolar teeth with fully formed apices were included in the study. None of the teeth showed signs of root caries, fractures, cracks, resorption (internal or external), or calcification. Each root was radiographed in mesiodistal and buccolingual projections to assess the root canal anatomy, with curvatures of <10°. All teeth were pre-scanned using a micro-computed tomography system (InspeXio SMX-100CT Plus, Shimadzu, Kyoto, Japan) at a resolution of 0.03 mm, with 70 kV and 100 µA. The scanning procedure employed a 1-mm thick aluminum filter, a 360° rotation with a 0.5° step, five-frame averaging, and a field of view of 25.5 × 25.5 × 23.9 mm (XYZ), resulting in a scan time of approximately 360 s per specimen. Three-dimensional models were reconstructed using fixed volume settings in Amira 3D software (version 2023.2; Visage Imaging GmbH, Berlin, Germany), with the region of interest defined from the cementoenamel junction to the root apex. Following the verification of the initial geometric anatomy, the canals were allocated to one of six test groups. Kruskal-Wallis and Dunn’s tests indicated that the geometric parameters did not differ significantly among the test groups (P > 0.05).
Specimen preparationRoot canal preparation was initiated by creating an access cavity. A size 10 K-file (Zipperer, Munich, Germany) was inserted into the canals, extending 1 mm beyond the apical foramen to establish patency. The working length was determined by subtracting 1 mm from the measured value. Preparation was completed using nickel-titanium rotary files (Vortex Blue, Dentsply Tulsa Dental, Tulsa, OK, USA) following the manufacturer’s instructions until a size 30/0.06 taper reached the full working length. The root canal was irrigated with 2 mL of 6% sodium hypochlorite (NaOCl) solution (JP Dental Antiformin, Nippon Shika Yakuhin, Shimonoseki, Japan) after each instrument throughout the preparation. The irrigant was delivered via a 3 mL syringe and a 27 G needle (Nipro, Osaka, Japan), which was inserted up to the working length. The final irrigation sequence was completed using 5 mL of 17% ethylenediaminetetraacetic acid (EDTA) followed by 5 mL of distilled water.
Intracanal medicament paste was carefully injected into each canal using the syringe and needle provided with the product, until the paste exited through the apex. The samples were subsequently assessed with micro-CT to verify full canal obturation. The access cavities were sealed with temporary restorative material (Caviton EX, GC, Tokyo, Japan), and the apices were sealed with utility wax to establish an effective seal. The specimens were subsequently stored in an oven at 37°C with 100% relative humidity for 7 days. Following this, the specimens were randomly distributed into one of two experimental groups based on the intracanal medicament paste removal technique: the single-syringe irrigation group (S-SI) and the multiple ultrasonic-activated irrigation group (M-UAI). Each group was further subdivided into three subgroups (n = 7) according to the specific intracanal medicament paste used: Calcipex II (CP), Calfee paste (CF), or Bio-C Temp (BT).
Removal of intracanal medicament pasteFollowing the removal of the temporary restoration, a #10 K file was carefully advanced to the working length to facilitate the removal of intracanal medicament paste. For the S-SI group, a 3-mL syringe and a 27G needle (Nipro) were used, with 1.5 mL of 6% NaOCl irrigated for 30 s. The needle tip was positioned 1 mm short of the working length, and irrigation was performed using a gentle up-and-down motion with a 4 mm amplitude. For the M-UAI group, ultrasonic activation was performed using a #10/0.02 stainless steel tip (U-file; Pierce, Tokyo, Japan) connected to an ultrasonic unit (ENAC 11W; Osada, Tokyo, Japan). The root canals were irrigated with 1.5 mL of each irrigant and activated for 30 s in the following sequence: 17% EDTA, distilled water, 6% NaOCl (applied twice), and distilled water. The tip was positioned 1 mm from the working length and activated at 30 kHz and 3.6 W with a power setting of 3.
Micro-CT measurements and analysisThe specimens were scanned using a micro-CT device both before and after the removal of the intracanal medicament paste, following the same acquisition parameters as those used in the preoperative phase. Prior to scanning, the utility wax used to seal the apex was carefully removed to prevent interference with image quality. The volume of intracanal medicament paste before and after irrigation was measured in mm³ using Amira imaging software (Visage Imaging GmbH). The intracanal medicament removal rate was calculated using the following formula: [(intracanal medicament volume before irrigation – intracanal medicament volume after irrigation) × 100] / intracanal medicament volume before irrigation.
Statistical analysisThe normality of data was evaluated using the Shapiro-Wilk test. Based on the distribution, statistical comparisons between the groups were conducted using the Kruskal-Wallis test and the Mann-Whitney U test with Bonferroni correction, with an overall significance threshold was set at 5%. Statistical software (SPSS Statistics version 26.0; IBM, Armonk, NY, USA) was used for all the analysis.
Figs. 1 and 2 show representative micro-CT images of teeth with intracanal medicament before irrigation, after irrigation, and after superimposition under different irrigation protocols. Figs. 3 and 4 present the median, minimum, and maximum values of the removal rate of different intracanal medicaments within the root canals, as evaluated using the two irrigation methods.
In the S-SI technique, the CF group exhibited a significantly higher removal rate of intracanal medicament compared to the CP group (P < 0.05). The removal rate of the BT group was between that of the CP group and the CF group with no significant differences (P > 0.05).
In the M-UAI technique, a significantly lower removal rate of intracanal medicament was found in the BT group compared to the other groups (P < 0.05). There was no significant difference observed between the CP and CF groups (P > 0.05).
Scale bar = 1 mm.
Scale bar = 1 mm.
Different lowercase letters indicate significant differences between the groups (P < 0.05), based on the Kruskal-Wallis test followed by post hoc Mann-Whitney U tests with Bonferroni correction. CP: Calcipex II; CF: Calfee Paste; BT: Bio-C Temp.
Different uppercase letters indicate a significant difference between the groups (P < 0.05), according to the Kruskal-Wallis test and post hoc Mann-Whitney U tests with Bonferroni correction. CP: Calcipex II; CF: Calfee Paste; BT: Bio-C Temp.
The initial finding of this study demonstrated that the CF group exhibited superior removability from the root canal compared to the CP group when a single-irrigation technique (S-SI) was employed. This method is typically the first procedure that most clinicians would employ after removing the temporary filling. This suggests that the CF paste was more efficiently removed in a single irrigation cycle, resulting in the partial rejection of the null hypothesis. However, the adjunctive use of UAI further facilitated intracanal medicament removal, with no significant difference observed between the CF and CP paste groups, both of which showed comparable and improved reductions in intracanal medicament. Conversely, the BT group demonstrated notably lower removal rate even after multiple UAI applications.
Comparative data on using CF as an intracanal medicament are still scarce. A previous study compared the removal efficiency of intracanal CH medicaments within 3 mm of the root apex using three different irrigation methods [22]. The study found that the residual volume of the prototype CF, prior to its commercial launch, was significantly smaller than that of CP. These results were consistent with the present findings using the S-SI technique. The thickening agent in the CF likely contributed to the enhanced removability of the intracanal CH medicament. CP uses titanium oxide or aluminum oxide as thickening agents [22], whereas CF employs an amphipathic polymer , which becomes hydrated upon exposure to irrigants. Since titanium oxide and aluminum oxide powders are poorly soluble in water, their removal from the root canal is more difficult compared to the water-absorbing agent used in CF [22].
However, no significant difference was observed between the CF and CP groups with the M-UAI technique, although the CF group exhibited slightly higher removability. UAI is thought to promote the circulation of root canal fluids throughout the canal system, facilitating the dilution and displacement of residual intracanal CH medicament, which contributes to its removal [23]. Furthermore, a combination of 17% EDTA and NaOCl has been recommended to enhance the removal of residual CH more effectively than using NaOCl alone [24]. Given that previous studies have identified the combination of EDTA and NaOCl as the most effective clinical irrigation protocol, the present study modified this methodology to optimize the removal efficiency of intracanal CH medicament [25,26].
The suboptimal performance of the BT dressing may be attributed to its material composition, specifically the formation of a poorly soluble calcium silicate hydrate residue as a byproduct of the hydration reaction of calcium silicate [27]. Furthermore, some studies have suggested that the effectiveness of ultrasonic irrigation may be diminished when applied to CH using viscous vehicles [11], such as those used in BT [28]. Recent investigations have assessed BT’s biocompatibility, antibacterial efficacy, and physicochemical properties [9,11,15,29]. A previous study reported a reduced residual volume of calcium silicate-based medicaments in comparison to those based on CH [8]. This discrepancy with current findings may be ascribed to the varying methodologies employed. Nevertheless, drawing robust conclusions regarding its efficacy as an intracanal medicament remains challenging, considering the limited body of literature on BT, a calcium silicate-based medicament. Future research should explore the extent of BT material remaining in contact with the dentin following the application of various additional removal protocols.
Thorough elimination of CH medicament from the root canal is essential for optimal adhesion and sealing of the endodontic sealer [31]. A prevailing opinion exists that the majority of CH dressings ought to be extracted from the root canal prior to obturation, as they may hinder penetration, flow, and setting of the sealer, ultimately compromising the root canal seal [30,32]. Additionally, concerns have been raised that exposure to CH reduces the mechanical properties of root dentin [14]. Numerous studies have underscored the challenges associated with removing intracanal CH medicaments from the root canal system using various irrigation techniques, with findings suggesting varying degrees of removability across different methods [16,31,33,34,35]. UAI has become a fundamental focus in contemporary endodontic research and is widely regarded as the gold standard for endodontic therapy [34,36]. A comprehensive review of in vitro investigations has presented compelling evidence supporting UAI as an effective approach for removing CH from root canals facilitated by cavitation and acoustic transmission [19].
In the current study, S-SI was performed to evaluate the initial removal of the intracanal medicament paste, while M-UAI was employed as the final irrigation technique. In routine clinical practice, immediate and complete removal of intracanal medicaments following the removal of temporary fillings is not typically prioritized during root canal irrigation. Instead, the initial removal is performed during the first SI, followed by root canal treatment, during which any remaining intracanal medicament is further eliminated. Final irrigation is then conducted to ensure the complete removal of the intracanal medicament. This approach demonstrates clinical relevance, as SI allows for early removal of the intracanal medicament, making this experimental system applicable to practical treatment protocols.
The remaining amount of CH medicament within the root canals can be assessed utilizing a range of methods, including scanning electron microscopy [16,37], surface area measurements [38], stereomicroscopic imaging or scoring systems [34], and confocal laser scanning microscopy [39]. However, the accuracy of these analyses has been questioned due to their reliance on subjective evaluation, which may introduce examiner bias, as well as the potential underestimation of residual CH medicament resulting from the limitations inherent in two-dimensional imaging and sectioning methods. Volumetric analysis using spiral or micro-CT has more recently been employed, offering more precise information compared to surface area measurements [16,21]. Given its advantages, such as high-resolution 3D volume analysis and nondestructive evaluation, the present study employed micro-CT to quantitatively assess the residual amounts of CH.
The current study has several limitations that should be acknowledged. First, its scope was restricted to single-rooted teeth with straight root canals, which excluded the exploration of various root canal configurations and anatomical irregularities. Consequently, the results may not be directly applicable to teeth exhibiting variations such as curved or irregular root canals. Furthermore, this study focused solely on evaluating the removability of CH medicaments without examining how residual medicaments might influence the properties and performance of endodontic sealers. To enhance the clinical relevance of the present findings, future investigations should incorporate a broader sample encompassing diverse tooth types and root canal geometries and explore the potential impact of residual intracanal medicaments on subsequent treatment outcomes.
Despite the inherent limitations of this study, a notable strength lies in the selection of human teeth and the use of micro-CT to assess the root canal anatomy. This method enables precise matching of specimens based on key anatomical parameters, ensuring consistent distribution across groups and providing a robust and reliable baseline for comparison among experimental groups [40]. Based on the current findings, although nearly all CF and CP medicaments were removed after multiple UAIs, further research is required to optimize the additional irrigation protocols for the effective removal of BT medicament. The current laboratory setup demonstrated that CP exhibited favorable results compared to the other intracanal medicament pastes, particularly when using the S-SI technique. However, none of the intracanal medicament pastes ensured complete removability, regardless of whether the S-SI or M-UAI techniques were employed.
CH: calcium hydroxide; micro-CT: micro-computed tomography; CP: Calcipex; CF: Calfee Paste; BT: Bio-C Temp; NaOCl: sodium hypochlorite; EDTA: ethylenediaminetetraacetic acid; SI: syringe irrigation; UAI: ultrasonic-activated irrigation; S-SI: single-syringe irrigation; M-UAI: multiple ultrasonic-activated irrigation
Ethical approval for this research was obtained from the ethics committee of Tokyo Medical and Dental University (No. D 2023-029).
The authors explicitly declared that there are no conflicts of interest in relation to this article.
This research was supported, in part, by a Grant-in-Aid for Scientific Research C from the Japan Society for the Promotion of Science (No. 20K09935ZA, to W.S.).
PYAM: Investigation, data curation, formal analysis, writing—original draft, and visualization. SW: Conceptualization, methodology, validation, funding acquisition, writing—review and editing, and project administration. TO: Conceptualization, methodology, writing—review and editing, and supervision. All authors have reviewed and approved the final version of the manuscript.
1)PYAM: phu.endo@tmd.ac.jp, https://orcid.org/0009-0006-7074-2490
1)SW*: s.watanabe.endo@tmd.ac.jp, https://orcid.org/0000-0002-2053-9201
1,2)TO: t.okiji.endo@tmd.ac.jp, https://orcid.org/0000-0002-9791-4508
The authors thank all the staff from the Research Core Center of Tokyo Medical and Dental University for providing equipment and technical support for micro-CT.
The datasets generated during the current study are available from the corresponding author on reasonable request.
