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Year : 2015  |  Volume : 5  |  Issue : 3  |  Page : 161-165

The effectiveness of various chelates used alone or in combination with sodium hypochlorite in the removal of calcium hydroxide from root canals

1 Department of Endodontics, Faculty of Dentistry, Hacettepe University, Ankara, Turkey
2 Department of Endodontics, BÜlent Ecevit University, Zonguldak, Turkey

Date of Web Publication26-Aug-2015

Correspondence Address:
Emel Uzunoglu
Department of Endodontics, Faculty of Dentistry, Hacettepe University, Ankara - 06100
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Source of Support: Nil., Conflict of Interest: None

DOI: 10.4103/1658-5984.163626

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Aim: To evaluate the effectiveness of various chelates used alone or in combination with sodium hypochlorite (NaOCl) in the removal of calcium hydroxide (Ca(OH)2 ) from root canals. Materials and Methods: The root canals of 72 mandibular incisors were prepared up to the ProTaper F2 file. Among these, six randomly selected teeth were used as negative and positive controls, while the root canals of the remaining 66 were filled with Ca(OH)2 paste for 1 week. Then, the experimental group specimens were divided into six groups (n = 11). The access cavities were reopened and the Ca(OH)2 paste in each group was removed using the following solutions: 2.5 mL ethylenediaminetetraacetic acid (EDTA; Group 1), 2.5 mL peracetic acid (PAA; Group 2), 2.5 mL QMix (Group 3), 2.5 mL NaOCl/2.5 mL EDTA (Group 4), 2.5 mL NaOCl/2.5 mL PAA (Group 5), and 2.5 mL NaOCl/2.5 mL QMix (Group 6). Digital photographs of longitudinally split specimens were imported into image analyzer software, and the amount of residual Ca (OH) 2 was recorded as a percentage of the overall canal surface area. The results were analyzed using Kruskal–Wallis and Conover–Dunn tests. Results: The canal walls in the positive control group were completely covered with Ca(OH) 2 compared with those in the negative control group. The lowest Ca(OH)2 removal efficiency was observed for Group 4 (P < 0.001), while Group 6 showed favorable results (P < 0.05). Conclusions: QMix combined with NaOCl can remove Ca(OH)2 from root canals as effectively as 17% EDTA and 1% PAA. The type and sequence of irrigants are more important than the total irrigant volume for effective Ca(OH) 2 removal.

Keywords: Calcium hydroxide, ethylenediamine tetraacetic acid, intracanal dressing, peracetic acid, QMix, root canal irrigation

How to cite this article:
Uzunoglu E, Turker SA, Ozcelik B. The effectiveness of various chelates used alone or in combination with sodium hypochlorite in the removal of calcium hydroxide from root canals. Saudi Endod J 2015;5:161-5

How to cite this URL:
Uzunoglu E, Turker SA, Ozcelik B. The effectiveness of various chelates used alone or in combination with sodium hypochlorite in the removal of calcium hydroxide from root canals. Saudi Endod J [serial online] 2015 [cited 2022 Aug 12];5:161-5. Available from: https://www.saudiendodj.com/text.asp?2015/5/3/161/163626

  Introduction Top

The eradication of bacteria and their byproducts from root canals is one of the primary goals of root canal treatment.[1] The elimination of all microorganisms from root canals is accomplished by mechanical instrumentation supported by various irrigating solutions and intracanal medications.[2] Calcium hydroxide (Ca(OH)2 ) is a commonly used intracanal medicament in the field of endodontics because of its antimicrobial effects and[3],[4] the ability to inhibit osteoclasts, neutralize bacterial endotoxins,[5] and induce favorable tissue repair.[6] Ca(OH)2 should be removed completely before root canal obturation because any remnants on the canal walls influence dentin bond strength[7],[8] and negatively affect the quality of the root filling and microhardness of the root canal dentin.[9][10][11] Furthermore, the remnants can react with root canal sealants and decrease their penetration into dentinal tubules,[12] flow, and working time.[13] The removal of Ca(OH)2 is commonly accomplished through several irrigants such as sodium hypochlorite (NaOCl), ethylenediaminetetraacetic acid (EDTA), peracetic acid (PAA), and citric acid alone or in combinations.[14][15][16][17] Although various irrigants and methods have been proposed for the removal of Ca(OH)2 dressings,[14][15][16][17][18] there is still no general consensus about the optimal technique. The most frequently described method for Ca(OH)2 removal from root canals is instrumentation with the master apical file (MAF) combined with copious irrigation with NaOCl and EDTA.[17] The literature shows that NaOCl alone is inadequate for Ca(OH)2 removal from root canals because of its limited ability to dissolve inorganic materials such as calcium.[14],[16],[19] On the other hand, EDTA has the ability to chelate Ca(OH)2 residues, facilitating removal by irrigation.[19] Therefore, chelates used alone or in combination with NaOCl are required for Ca(OH)2 removal.

Since its introduction in the market, PAA has been indicated for high-level disinfection and sterilization of hospital equipment and devices. Its mechanism of action involves the release of free oxygen and hydroxyl radicals that decompose in oxygen, water, and acetic acid.[20],[21] Low-concentration PAA has also been advocated as a final irrigant for smear layer removal and root canal disinfection.[20],[22] The effectiveness of 1% PAA in Ca (OH) 2 removal from root canals was recently evaluated.[15]

A novel irrigation solution, QMix 2in1 has been introduced for both smear layer removal and bacterial eradication and is a recommended chelate in addition to EDTA and PAA. It contains EDTA, chlorhexidine (CHX), a detergent, and water[23] and is used in conjunction with NaOCl. Dai et al.,[24] reported that QMix is as effective as 17% EDTA in smear layer removal. However, no current study has evaluated the Ca(OH)2 removal efficiency of QMix.

Although various irrigants and methods have been proposed for Ca(OH)2 dressing removal, there is no general consensus on the optimal technique or irrigant. This study aimed to compare the Ca(OH)2 removal efficiency of different chelates used alone or in combination with NaOCl to test the null hypothesis that there is no difference in Ca(OH)2 removal efficiency between 17% EDTA, 1% PAA, and QMix used alone or in combination with NaOCl.

  Materials and Methods Top

Seventy-two freshly extracted human mandibular incisors with single canals and straight roots were collected. All teeth were analyzed from the buccal and proximal aspects using digital radiographs to check for single canals. Following extraction, the teeth were scaled with ultrasonic instruments, washed with distilled water, and immersed in 10% formalin solution until use. To standardize the length of the specimens, the crowns of the teeth were removed and the roots were adjusted to 12 mm. The working length was established 1 mm short of the apical foramen. All canals were prepared by the same operator using the ProTaperNiTi rotary system (DentsplyMaillefer, Ballaigues, Switzerland), with the F2 file used as MAF, according to the manufacturer's instructions. During preparation, the root canals were irrigated with 2 mL of 2.5% NaOCl solution after preparation with each file. The irrigant was delivered via a 30-gauge needle placed passively into the canal without binding. After instrumentation was complete, the canals were subjected to a final rinse with 3 mL of 2.5% NaOCl, 5 mL of 17% EDTA, and 10 mL of distilled water and dried with paper points.

Next, Ca(OH) 2 (Merck, Darmstadt, Germany) and distilled water were mixed in a powder to liquid ratio of 1:1.5, and the paste was placed into each canal using a lentulo spiral up to the working length. A radiograph was obtained to confirm complete filling up to the apex. The access cavities were sealed with a temporary filling material (Cavit; 3M ESPE, St Paul, MN), and the teeth were stored for 1 week at 37°C in 100% relative humidity to simulate the clinical situation.

Sixty-six specimens were randomly assigned into six groups (n = 11). The remaining six were used as negative controls (n = 3), which did not receive a Ca (OH) 2 dressing, and positive controls (n = 3), which received a Ca (OH) 2 dressing that was not removed with the dressings from the other teeth.

The irrigant volume and application length were standardized for all groups. After removal of the temporary fillings, a #25 K file was inserted into the root canals up to the working length, and up and down strokes were used to disrupt and loosen the Ca (OH)2 dressing. Final irrigation was passively performed in each group using the following solutions:

  • Group 1: 2.5 mL of 17% EDTA (Sigma Aldrich, St Louis, MO, USA)
  • Group 2: 2.5 mL of 1% PAA (Sigma Aldrich, St Louis, MO, USA)
  • Group 3: 2.5 mL of QMix (DENTSPLY Tulsa Dental Specialties, Tulsa, OK, USA)
  • Group 4: 2.5 mL of 2.5% NaOCl + 2.5 mL of 17% EDTA
  • Group 5: 2.5 mL of 2.5% NaOCl + 2.5 mL of 1% PAA
  • Group 6: 2.5 mL of 2.5% NaOCl + 2.5 mL of QMix.

The needle tip (30-G; NaviTip; Ultradent, South Jordan, UT) used for irrigation was placed 1 mm short of the working length without binding. After the irrigation procedure, the canals were dried with paper points and longitudinal grooves were prepared on the buccal and lingual surfaces of each root using a diamond disk at a slow speed without penetrating the canal. The teeth were split along their long axis in a buccolingual direction using a hammer and chisel. The roots were divided and digital photographs were obtained. These images were imported into image analyzer software (Comef 4.3; OEG Messtechnik, Frankfurt, Germany), and the amount of residual Ca(OH)2 on the canal walls was measured in mm2 and recorded as a percentage of the overall canal surface area [Figure 1].[25] The obtained data were subjected to statistical analyses using Kruskal–Wallis and Conover–Dunn posthoctests at a 95% confidence level (P < 0.05).
Figure 1: Images of residual calcium hydroxide (Ca(OH)2) on root canal walls and the calculation of the area of residual Ca(OH)2 using an imaging program

Click here to view

  Results Top

The percentage of residual Ca(OH) 2 material on the canal walls is shown in [Table 1]. The canal walls in the positive control group were completely covered with Ca(OH) 2 compared with those in the negative control group. The lowest Ca(OH) 2 removal efficiency was observed for Group 4 (2.5% NaOCl + 17% EDTA), which showed statistically significant differences when compared with all the other groups except Group 5 (P < 0.001 for comparisons between Groups 1 and 4 and between Groups 3 and 4, P = 0.026 for comparison between Groups 2 and 4, P = 0.57 for comparison between Groups 4 and 5, and P = 0.003 for comparison between Groups 4 and 6). QMix alone (Group 3) and in combination with NaOCl (Group 6) showed better results than 17% EDTA combined with 2.5% NaOCl (Group 4). There were no significant differences among the solutions when they were used alone (P = 0.19).
Table 1: Percentage of residual CH remaining in the canal [mean and standard deviation (SD)]

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  Discussion Top

Various methods have been used to investigate the amount of Ca (OH) 2 residue on root canal walls, such as digital photography, stereomicroscopy, and scanning electron microscopy or volumetric analysis using spiral computed tomography.[14],[16],[25],[26] In the present study, the surface area measurement method was used, similar to a previous study.[25]

The literature shows that hand filing with saline or NaOCl irrigation does not eliminate Ca (OH) 2 completely from root canals;[25],[27] whereas, hand filing with EDTA irrigation allows for better removal.[16],[19] Therefore, we did not use NaOCl only for irrigation in this study. The main purpose of the present study was to evaluate the Ca(OH) 2 removal efficiency of different chelates (EDTA, PAA, and QMix), particularly QMix, used alone or in combination with NaOCl; therefore, only passive irrigation was used without any adjunctive procedure such as activation of the irrigant solution using ultrasonic devices or the EndoActivator system.[18]

The data for the present study shows that none of the irrigants completely removed the Ca(OH) 2 dressing when used alone or in combination with NaOCl, indicating no improvement in removal efficiency when combined with NaOCl. The combination of NaOCl and EDTA showed the least favorable outcome; the average amount of Ca(OH) 2

residue was 78.38%. Furthermore, NaOCl combined with EDTA was significantly less effective than EDTA alone, consistent with the finding of previous studies.[14],[25] Therefore, the null hypothesis that there is no difference in the Ca(OH) 2

removal efficiency between the tested irrigants was rejected. In contrast to these results, in a previous study,[12] EDTA irrigation followed by NaOCl irrigation resulted in complete removal of Ca(OH) 2. After NaOCl irrigation, a Ca(OH) 2 precipitate may form because of its limited ability to dissolve inorganic substances such as calcium; consequently, removal of this precipitate with subsequent irrigants can prove difficult. In previous studies, the mean values were higher when the chelates were used alone than when they were used in combination with NaOCl.[17],[28] This result was probably related to the irrigation sequence.

EDTA is a polyprotic acid in which sodium salts are noncolloidal organic agents that can form nonionic chelates with metallic ions.[29] The degradation and consequent deactivation of EDTA after its interaction with NaOCl is extremely slow; therefore, NaOCl does not compromise its clinical performance in terms of chelation, smear layer removal, and dentin softening.[29][30][31] However, in the present study, EDTA and other chelates showed lesser Ca (OH) 2 removal when used after NaOCl.

A higher concentration of PAA (2.25%) significantly decreases the mineral content of root canal dentin.[32] De-Deus et al.,[22] reported that 0.5% PAA dissolved the smear layer as effectively as 2.25% PAA and 17% EDTA. It has been shown that 1% PAA is superior to NaOCl + EDTA in Ca(OH) 2 removal.[15] Therefore, 1% PAA was used in the current study, and the results for the removal efficiency of 1% PAA were in agreement with previously published data.[15] The present study showed a better performance of PAA compared with that of NaOCl combined with EDTA.

QMix 2in1 is a good endodontic irrigant for smear layer removal with antimicrobial agents. It is composed of EDTA, CHX, and a surfactant;[23],[24] and has been designed for use as a final rinse for 60–90 s in place of 17% EDTA. QMix is a clear, ready-to-use solution that requires no chair-side mixing. This one-step final rinse is supposed to combine the antimicrobial and substantivity properties of CHX with the smear layer removal properties of EDTA. Previous studies reported that QMix was as effective as 17% EDTA in smear layer removal.[23],[24] Taneja et al.,[32] reported that QMix and 17% EDTA caused similar calcium ion loss. The present study revealed that QMix and its combination with NaOCl was as effective as 17% EDTA and 1% PAA in Ca(OH) 2 removal from root canals. This could be attributed to its composition. The combination of a chelating agent and detergent apparently improved the efficacy of QMix in calcium ion elimination. To the best of our knowledge, this is thefirst study to evaluate the effectiveness of QMix in Ca (OH) 2 removal from root canals. Further investigations are required to support our findings.

  Conclusions Top

This study revealed that QMix and its combination with NaOCl can remove Ca(OH) 2

from root canals as effectively as 17% EDTA and 1% PAA. Furthermore, the type and sequence of irrigants are more important than the total irrigant volume for the successful removal of Ca(OH) 2 from root canals.

  References Top

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