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Comparison of the efficacy of ethylene diamine tetraacetic acid and maleic acid in the removal of three calcium hydroxide intra-canal dressings: A spiral computerized tomography volumetric analysis.
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MedLine Citation:
PMID:  23349578     Owner:  NLM     Status:  PubMed-not-MEDLINE    
AIM: To assess the efficacy of 17% ethylene diamine tetra acetic acid and 7% maleic acid in the removal of 3 calcium hydroxide preparations placed as intracanal medicaments.
MATERIALS AND METHODS: The root canals of 60 single rooted premolars were prepared with a step back technique and randomly assigned into 3 experimental groups (n= 20). Group A was filled with plain calcium hydroxide mixed with distilled water in which barium sulfate was added for radio opacity, Group B was filled with Apexcal and Group C was filled with Metapex. After 7 days each group was divided into 2 sub groups (n= 10). The medicaments were retrieved with 17% EDTA (first sub group) and 7% maleic acid (second sub group). Along with the above irrigants manual and ultrasonic agitation was used. The pre and post removal volume of medicaments in root canals were measured using spiral computerized tomography. The percentage difference was calculated and statistically analyzed using Kruskal Wallis and Mann Whitney U test.
RESULTS: 17% EDTA and 7% maleic acid efficiently removed calcium hydroxide, distilled water mixture (P= 0.218) and Apexcal (P= 0.684), whereas 7% maleic acid showed better retrieval capability of Metapex than 17% EDTA (P= 0.002).
CONCLUSION: Calcium hydroxide, distilled water mixture and polyethylene glycol based calcium hydroxide were efficiently removed by 17% EDTA and 7% maleic acid. 7% maleic acid removed silicone oil based calcium hydroxide preparation better than 17% EDTA.
Mohan Thomas Nainan; Dn Nirupama; Shiny Benjamin
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Journal of conservative dentistry : JCD     Volume:  16     ISSN:  0972-0707     ISO Abbreviation:  J Conserv Dent     Publication Date:  2013 Jan 
Date Detail:
Created Date:  2013-01-25     Completed Date:  2013-01-28     Revised Date:  2013-05-30    
Medline Journal Info:
Nlm Unique ID:  101147009     Medline TA:  J Conserv Dent     Country:  India    
Other Details:
Languages:  eng     Pagination:  56-60     Citation Subset:  -    
Department of Conservative Dentistry and Endodontics, Vydehi Institute of Dental Sciences and Research Centre, Whitefield, Bangalore, India.
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Journal Information
Journal ID (nlm-ta): J Conserv Dent
Journal ID (iso-abbrev): J Conserv Dent
Journal ID (publisher-id): JCD
ISSN: 0972-0707
ISSN: 0974-5203
Publisher: Medknow Publications & Media Pvt Ltd, India
Article Information
Copyright: © Journal of Conservative Dentistry
Received Day: 29 Month: 5 Year: 2011
Revision Received Day: 06 Month: 12 Year: 2011
Accepted Day: 14 Month: 9 Year: 2012
Print publication date: Season: Jan-Feb Year: 2013
Volume: 16 Issue: 1
First Page: 56 Last Page: 60
PubMed Id: 23349578
ID: 3548348
Publisher Id: JCD-16-56
DOI: 10.4103/0972-0707.105300

Comparison of the efficacy of ethylene diamine tetraacetic acid and maleic acid in the removal of three calcium hydroxide intra-canal dressings: A spiral computerized tomography volumetric analysis
Mohan Thomas Nainanaff1
DN Nirupamaaff1
Shiny Benjaminaff1
Department of Conservative Dentistry and Endodontics, Vydehi Institute of Dental Sciences and Research Centre, Whitefield, Bangalore, India
Correspondence: Address for correspondence: Dr. Mohan Thomas Nainan, Department of Conservative Dentistry and Endodontics, Vydehi Institute of Dental Sciences and Research Centre, No. 82, EPIP Area, Whitefield, Bangalore - 66, India. E-mail:


Bacteria and their products play an important role in the initiation and perpetuation of pulpal and periapical pathology. Elimination of bacteria from root canal is normally accomplished by mechanical instrumentation in adjunct with irrigating solutions and anti-bacterial agents. Among these anti-bacterial agents, calcium hydroxide is the most commonly used and recommended for inter appointment intra-canal endodontic dressing.[1, 2]

There are 3 main types of vehicles used: (1) Water-soluble substances like water, saline, local anesthetic agent, and ringers solutions; (2) viscous vehicles like glycerin, polyethylene glycol, and propylene glycol; and (3) oil-based vehicles like olive oil, silicone oil, camphor, eugenol, metacresylate, etc.[3]

Residual calcium hydroxide on the root canal wall influences dentine bond strength and penetration of sealers into dentinal tubules. The remnants of calcium hydroxide could also react chemically with the sealer, reducing the efficiency of its properties like flow and working time.[4] Therefore, calcium hydroxide dressing has to be removed from root canals before obturation.

This can be achieved by irrigating with irrigants like sodium hypochlorite, saline or Ethylene diamine tetra acetic acid and combining the usage of hand instruments along with irrigants. Few studies have used passive ultrasonic irrigation to remove calcium hydroxide from root canal walls and were found to be effective.[58]

Maleic acid, which has been used as an acid conditioner in adhesive system, is reported to have removed smear layer, which was present in cavities prepared for adhesive dentistry. Maleic acid with concentrations of 5% and 7% can be an alternative for 17% EDTA for smear layer removal. It has anti-microbial activity against E. faecalis, is less cytotoxic than EDTA, and is effective in smear layer removal.[911]

In most of the studies done to analyze the removal of calcium hydroxide from the root canal, where it has been placed as intra-canal medicament, the technique involved sectioning the teeth longitudinally and analysis of photos of specimens with digital image processor to measure the surface area covered with calcium hydroxide. Calcium hydroxide may be lost during sectioning, which may not help in the correct evaluation of the technique.[12, 13] Three-dimensional volume analysis with spiral CT is used in the field of medicine in various applications (Thoracic and abdominal aneurysm, intracranial aneurysm etc).[14] Spiral CT volumetric analysis gives a more accurate measurement of pre-and post-removal calcium hydroxide from root canals.[15] Till now, no study has been done using maleic acid and ultrasonic passive agitation to remove calcium hydroxide from root canals. The aim of this study was to assess the efficacy of 17% EDTA and 7% maleic acid combined with sodium hypochlorite and ultrasonic agitation in removal of calcium hydroxide placed as intra-canal medicament using 3 vehicles, distilled water, polyethylene glycol, and silicone oil. The volume of calcium hydroxide removed was analyzed with spiral-computed tomography.


The calcium hydroxide formulations were selected on the basis of the vehicle used. Metapex is a commercially available product composed of calcium hydroxide, silicone oil, and iodoform (Meta Dental Corp Ltd., Elmburt). ApexCal contains calcium hydroxide and bismuth carbonate in a mixture of water, glycerin, polyethylene glycol, and auxiliary materials (Viola, Ivoclar Vivadent AG). The chemically pure 95% calcium hydroxide powder (Merck India Ltd. Mumbai) was mixed with distilled water in the ratio of 1:1 by weight, and barium sulfate was added for radio opacity.

Sixty single-rooted premolars were selected. Teeth with fractures, cracks, or any other defects were excluded. Teeth were stored in normal saline solution that was changed daily till sufficient numbers of teeth were collected. Access was prepared; working length was established 1 mm short of apical foramen. All canals were prepared by the same operator to a size 50 K file (Mani files, mani, inc Tochigi Japan) at working length using a step back technique. Irrigation was done with 5.25% sodium hypochlorite and 17% EDTA (Pulpdent Corporation 80 Okland Street Watertown MA, USA) using 5 ml disposable plastic syringe with 27 gauge needle (Endo Eze; Ultradent Products Inc. South Jordan UT, USA). After root canal preparation, a size 20 K file was passed 1 mm beyond the apex to remove any dentinal plug.[12, 15, 16] A final rinse with 10 ml normal saline was performed, and root canals were dried with paper points. The teeth were stored in normal saline in airtight bottles in between procedures.

The teeth were divided into 3 groups consisting of 20 teeth each as A, B, and C.

Group A: Pure calcium hydroxide mixture withdistilled water.

Group B: ApexCal

Group C: Metapex

In each group, the medicament was placed in the canal using lentulo spiral (Mani files, mani, inc Tochigi Japan) ensuring extrusion through the apex. Access cavities were temporarily sealed with cotton pellets and IRM (Dentsply Int Mill ford DE, USA). The teeth were stored at 37° centigrade and 100% relative humidity for 7 days. The teeth were mounted in a plastic stand using modeling wax for taking spiral CT. After CT imaging, volume of the filling material in each tooth were estimated using Siemens Emotion duo model of spiral CT with the aid of Syngo software [Figure 1].

The teeth in each group were further divided into 2 sub-groups based on the material used for removal of medicament from the root canal. 17% EDTA was used for the first sub-group (A1, B1, and C1), and 7% maleic acid (Sd Fine-Chem Ltd., Mumbai, India.) was used for the second sub-group (A2, B2, and C2).

Protocol for removing the intra-canal medicaments was

Step 1: Master apical file 6 -7 vertical motions +5 ml of 5.25% NaOCl.

Step 2: 5 ml of 17% EDTA/7% maleic acid + ultrasonic agitation

Step 3: 5 ml of NaOCl + ultrasonic agitation

Step 4: Irrigation with saline.

Ultrasonic agitation was done using 25 K ultrasonic file (Mani files, mani, inc Tochigi Japan), which was mounted on a piezoelectric handpiece (Electro Medical Systems, SA) at a power setting of 5 and was passively activated for 1 minute at 2 mm short of working length.

A second spiral CT was done, and the volume of remaining material in each tooth was estimated [Figure 1]. The removal efficacy was estimated as {(a-b) × 100/a}, where ‘a’ was volume of material packed in the root canal and ‘b’ was volume remaining after retrieval. The data obtained was statistically analyzed using Kruskal Wallis test to compare between groups. Mann Whitney U test was used for pair-wise comparison with Bonferroni corrections. The data was analyzed using statistical package for social sciences (SPSS, version 10.5).


As per Bonferroni correction for 3 group comparison, P value of less than or equal to 0.016 considered to be significant to adjust for type I error.

The removal efficiency for various groups was 94.89% (A1), 92.12% (A2), 84.55% (B1), 90.14% (B2), 65.99% (C1), and 88.65% (C2) [Table 1] [Figure 2]. Comparison of all the groups were done using Kruskal-Wallis test, and P value < 0.5 was considered significant for this. There was significant difference in retrievability among the groups (P = 0.001) when 17% EDTA was used, and no statistically significant difference among the groups (P = 0.818) when 7% maleic acid used. Mann-Whitney U test with Bonferroni corrections was carried out for pair-wise comparison between the groups, and it was evident that there was a statistically significant difference in retrievability between calcium hydroxide and Metapex group when 17% EDTA was used (P < 0.001), and there was no statistically significant difference in retrievability among the groups when 7% maleic acid was used.

17% EDTA and 7% MA showed almost equal removal efficiency for calcium hydroxide (P = 0.218) and Apexcal group (P = 0.684).

7% MA showed better removal efficiency than 17% EDTA for Metapex group (P = 0.002).

17% EDTA could remove the intra-canal medicament in group A better than in group B and C. Group B showed intermediate values (P = 0.001).

7% maleic acid removed all groups efficiently (P = 0.818).


The vehicle used to mix calcium hydroxide paste has an influencing factor in the complete retrieval of it.[5] The differences in velocity of ionic dissolution is directly related to the vehicle; the lower the viscosity, higher the ionic dissolution.[17] The aqueous vehicles promote a high degree of solubility when in contact with tissue and tissue fluids. Viscous vehicles like polyethylene glycol, propylene glycol, glycerin promote a lower solubility of the paste when compared with aqueous vehicles, probably because of their high molecular weight, which minimizes the dispersion of calcium hydroxide into the tissues.[18]

Oily vehicles are non-water soluble substances that promote the lowest solubility of the paste within the tissues, and pastes containing this kind of vehicle may remain within the root canal for a longer period than the pastes containing aqueous or viscous vehicles.[16]

The removal of calcium hydroxide has been investigated using a range of products and techniques. The most frequently described method was instrumentation of root canals with a master apical file and copious irrigation.[5, 12] Canal irregularities may be inaccessible for conventional irrigation procedures, and calcium hydroxide may remain in these extensions.[18] Passive ultrasonic irrigation is more effective in dentine debris removal from root canal walls than syringe delivery of irrigant.[8] Very few studies have been done combining manual and passive ultrasonic irrigation to remove calcium hydroxide from root canals.[14, 16, 19]

The calcium hydroxide removal efficacy of the intra-medicament can be calculated efficiently only if the amount removed can be compared with the amount filled or packed in the canal.[15] The above procedure was followed in the present study also. When retrievability of the medicaments with 17% EDTA was evaluated, the silicone oil-based medicament resisted the removal to the maximum followed by polyethylene glycol and calcium hydroxide distilled water mixture (P = 0.001). The above findings were in agreement with the studies of Lambrianidis et al., and Nandini S et al., who stated that methyl cellulose and silicone oil vehicle resisted removal from root canal because of interaction of methyl cellulose and EDTA.[5, 12, 14] The surface tension of the vehicle used in the medicament should be low to allow better penetration into inaccessible areas. The surface tension of any vehicle decreased significantly with addition of calcium hydroxide powder. Water has surface tension of 70.5 dynes/cm, which decreased to 66.5 dynes/cm with addition of calcium hydroxide.[20] Silicone oil is hydrophobic as it contains many methyl groups and has surface tension of 19 dynes/cm, which will provide better wetting and water-resistant properties.[21] Thus, in the present study, the medicament with distilled water would have been easy to remove. The surface tension value of polyethylene glycol is 43.50 dynes/cm, which is in between the values of distilled water and silicone oil.[22] The hygroscopic nature, water adsorption properties, and the surface tension values may account for the intermediate retrieval values for polyethylene glycol-based medicament in this study.

When the retrievability of the medicaments with 7% maleic acid was evaluated, the difference was not significant (P = 0.818).

In the groups where distilled water and propylene glycol were used as vehicle, 17% EDTA and 7% maleic acid showed almost same retrievable capability (P = 0.218 and P = 0.684).

In the group where silicone oil was used as vehicle, 7% maleic acid showed better retrieval capability of medicaments than 17% EDTA. Maleic acid has lesser surface tension than EDTA.[23] In this study, during initial root canal preparation, 17% EDTA and 5.25% sodium hypochlorite were used in combination for irrigation so as to remove smear layer. It is known that EDTA and sodium hypochlorite have similar surface tension levels, which are important for wetting capability and effectiveness in smear layer removal.[24, 25] This may have enhanced the effect of maleic acid. The low surface tension and acidic nature of maleic acid may have also resulted in better penetration into the dentinal tubules.


Within the limitations of this study, it could be concluded that:

  1. Silicone oil-based vehicles were more difficult to remove than polyethylene glycol and distilled water-based mixtures when 17% EDTA was used for its retrieval.
  2. Both 17% EDTA and 7% maleic acid were found to remove the aqueous-based and polyethylene glycol based-calcium hydroxide efficiently, whereas 7% maleic acid was found to perform better than 17% EDTA in removing silicone oil-based calcium hydroxide preparations.


Source of Support: Nil

Conflict of Interest: None declared.

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[Figure ID: F1]
Figure 1 

Spiral CT images of teeth filled with calcium hydroxide medicaments before and after retrieval using two reagents

[Figure ID: F2]
Figure 2 

Spiral CT images of teeth filled with calcium hydroxide medicaments before and after retrieval using two reagents

[TableWrap ID: T1] Table 1 

Comparison of removal efficiency of 17% Ethylene diamine tetra acetic acid and 7% maleic acid in 3 groups

Article Categories:
  • Original Article

Keywords: Calcium hydroxide removal, EDTA, maleic acid, sodium hypochlorite, passive ultrasonic agitation, vehicles.

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