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Year : 2021  |  Volume : 24  |  Issue : 6  |  Page : 558-562
Postspace pretreatment with 17% ethylenediamine tetraacetic acid, 7% maleic acid, and 1% phytic acid on bond strength of fiber posts luted with a self-adhesive resin cement

Department of Conservative Dentistry and Endodontic, Bangalore Institute of Dental Sciences and Hospital, Bengaluru, Karnataka, India

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Date of Submission28-Sep-2021
Date of Decision07-Dec-2021
Date of Acceptance29-Dec-2021
Date of Web Publication01-Apr-2022


Context: Pretreatment of radicular dentin with chelating agents improves the bond strength of fiber-posts luted with a self-adhesive resin cement.
Aims: The aim of this study was to assess the effects of the three chelating agents as final rinse of the postspace on bond strength of fiber posts luted with a self-adhesive resin cement.
Settings and Design: This is an in vitro laboratory study.
Materials and Methods: Forty-five mandibular premolars were prepared using MTwo rotary system and irrigation was done with 2.5% sodium hypochlorite. Three groups of teeth samples were considered for postspace preparation and irrigated with different solutions: Group 1: 17% ethylenediamine tetraacetic acid (EDTA); Group 2: 7% Maleic acid; Group 3: 1% Phytic acid. This was followed by the luting the posts with RelyX U200. After a week, from each sample, 2 mm thick slices were obtained from each third of the root and subjected to push-out bond strength testing.
Statistical Analysis Used: One-way analysis of variance and Bonferroni's Post hoc analysis was used for assessing the results. The statistical significance level was set at P < 0.05.
Results: Bond strength values were improved with maleic acid and phytic acid pretreatment with slight or no significant difference between these groups. A final rinse of postspace with EDTA significantly reduced the bond strength.
Conclusions: Maleic acid (7%) pretreatment of postspace improved the adhesion of fiber posts luted with a self-adhesive resin cement.

Keywords: Bond strength; ethylenediamine tetraacetic acid; fiber post; maleic acid; phytic acid; self-adhesive resin cement

How to cite this article:
Yadav PC, Raghu R, Shetty A, Rajasekhara S. Postspace pretreatment with 17% ethylenediamine tetraacetic acid, 7% maleic acid, and 1% phytic acid on bond strength of fiber posts luted with a self-adhesive resin cement. J Conserv Dent 2021;24:558-62

How to cite this URL:
Yadav PC, Raghu R, Shetty A, Rajasekhara S. Postspace pretreatment with 17% ethylenediamine tetraacetic acid, 7% maleic acid, and 1% phytic acid on bond strength of fiber posts luted with a self-adhesive resin cement. J Conserv Dent [serial online] 2021 [cited 2023 Sep 29];24:558-62. Available from:

   Introduction Top

Teeth requiring root canal therapy presenting with significant coronal damage require posts to retain the core and the final crown [Supplementary Files].[1] While metallic posts have been traditionally popular, currently, fiber posts are preferred as they are more esthetic and can be adhesively bonded to the canal thus enhancing the longevity of postendodontic restorations. Fiber posts basically have an epoxy or methacrylate resin matrix reinforced with glass or silica fibers. They are more flexible as they have a modulus of elasticity closely mimicking that of dentin.[1],[2],[3]

Adhesive luting of fiber posts poses a greater challenge as they have to contend with the secondary smear layer (sealer and gutta-percha residues) created during postspace preparation.

Smear layer removal in endodontics is usually achieved by final irrigation using 17% Ethylenediamine tetraacetic acid (EDTA) followed by sodium hypochlorite (NaOCl). However, it has been reported that this approach may be detrimental to the adhesion of fiber posts.[4]

Presently, newer chelators like Maleic acid (7% conc.) and Phytic acid (1% conc.) are increasingly replacing EDTA as effective agents for smear layer removal.[5],[6] However, there is limited research regarding their role in the adhesion of fiber posts.

Fiber posts can be adhesively bonded to the root canals using various adhesion strategies, such as total-etch, self-etch or self-adhesive systems. While total-etch adhesives have multiple clinical steps and are highly technique sensitive, self-etch adhesives are not capable of effectively penetrating the smear layer and bonding to the underlying dentin.[7]

Self-adhesive resin cements were introduced for the first time in the year 2002. They combine the properties of glass ionomers and resin cements.[8] Unlike the other two categories, they are simple and easy to use as they contain multi-functional methacrylated phosphoric acid esters that react with the mineral phase of dentin and also infiltrate and modify the smear layer.[9] Advantages of these cements include reduced technique sensitivity, less chair-side time, decreased contamination and improved retention.[1],[6],[9] Thus, self-adhesive resins are presently the material of choice for luting fiber posts. A literature search revealed limited information regarding the role of the newer chelating agents as a final rinse on the bond strength of self-adhesive resin cements.

The aim of this study was to assess the effect of postspace pretreatment with 17% EDTA, 7% Maleic acid and 1% Phytic acid on adhesion of fiber posts luted with a self-adhesive resin cement (3M ESPE RelyX U200).

   Materials and Methods Top

The study sample included 45 extracted human mandibular premolar teeth which were stored in thymol solution (0.1%). Atraumatically extracted intact premolars with minimal root curvature and devoid of caries or restorations were included in the study. After decoronation, biomechanical preparation was done with Mtwo (VDM, Munich, Germany) NiTi rotary instrumentation up to #25 file while rinsing with 2.5% NaOCl (Chemident, Delhi, India). Obturation was done using gutta-percha/AH Plus sealer (Dentsply Maillefer, Ballaigues, Switzerland). The samples were stored at 100% humidity.

Postspace preparation was done using peeso reamer (no. 3 = 1.1 mm tip diameter) leaving 4–5 mm of gutta-percha in the apical one-third. Later, the teeth were subdivided into 3 groups for final irrigation of postspace, using 30 gauge side vented needle.

  • Group 1: 5 ml of EDTA (17%) (Prime Dental Products Pvt. Ltd, India) for 1 min (n = 15)
  • Group 2: 5 ml of maleic acid (7%) (Leo Chemicals, India) for 1 min (n = 15)
  • Group 3: 5 ml of phytic acid (1%) (Leo Chemicals, India) for 1 min (n = 15).

The surfaces of the fiber posts (3M ESPE RelyX Fiber post) were treated with silane coupling agent prior to luting them with self-adhesive resin cement (3M ESPE RelyX U200).

After storage in distilled water for a week, 2 mm thick slices were sectioned using a low speed diamond disc from coronal, middle and apical third of the postspace. The samples were subjected to push-out bond strength testing in the universal testing machine. The posts were dislodged by applying the load at a crosshead speed of 0.5 mm/min to arrive at the bond strength values (MPa). Data were analyzed using one-way analysis of variance followed by Bonferroni's post hoc test to compare the mean pushout bond strength between the regions in each study group. The level of significance was fixed at P < 0.05.

   Results Top

The mean bond strength values in EDTA group for cervical 3rd were 52.96 ± 5.25, middle 3rd was 53.56 ± 5.09 and for apical 3rd region was 32.99 ± 5.17. Thus, the multiple comparisons revealed that the mean pushout bond strength significantly decreased from cervical to apical 3rd region at P < 0.001. Bond strength values were improved with maleic acid (cervical 3rd 62.44 ± 3.21, middle 3rd 72.48 ± 5.88 and apical 3rd was 67.43 ± 5.17) and phytic acid (cervical 3rd 60.98 ± 7.24, middle 3rd 70.60 ± 8.72 and apical 3rd was 65.52 ± 3.83) pretreatment with slight or no significant difference between these groups. A final rinse of postspace with EDTA significantly reduced the bond strength [Table 1] and [Graph 1].
Table 1: Comparison of mean pushout bond strength between 3 different regions in each study group using repeated measures of ANOVA test followed by bonferroni's post hoc test

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   Discussion Top

A valuable means to evaluate the bond strength of fiber posts is the push-out bond strength test. It is considered to be highly accurate as it closely mimics the clinical situation and causes less errors during sample preparation.[7],[10] In the present study, the testing was done using 2 mm thick specimens as this has been reported to distribute stresses more homogenously.[11]

During postspace preparation, the use of peeso reamers or proprietary drills creates an additional smear layer due to the smearing of the sealer cement and gutta-percha on the canal walls. Rinsing with chelating agents has been reported to eliminate this effectively.[12]

Optimal adhesion of self-adhesive cements is based on partial removal of smear layer followed by promoting micromechanical retention. In addition, they also demonstrate a chemical reaction between the acidic monomers of the resin cement and the hydroxyapatite of the radicular dentin. Dentin pretreatment with different chelating agents has shown varying effects on the bonding of self-adhesive resin cements. While most clinicians employ EDTA as the agent of choice for postspace cleansing, it may adversely affect the bond strength of some self-adhesive resin cements.[13],[14],[15] Therefore the present research studied the role of two newer chelating agents, namely maleic and phytic acid on bond strength of a self-adhesive resin cement with EDTA being used as the control group. Final rinse was done for 1 min for all the irrigants to minimize demineralization and dentin erosion.[11]

Maleic acid is an effective smear layer removing agent at a concentration of 7% whereas increasing the concentration to 10% or more resulted in damage and demineralization of the intertubular dentin. Hence, Maleic acid in a concentration of 7% was employed in our study.[16]

Phytic acid, chemically known as inositol hexakisphosphate, is found in foods such as cereals, legumes, oilseeds, and nuts. Phytic acid etches the dentin, acts as a natural cross-linker by stabilizing the demineralized dentin matrix, and provides good resin dentin bonding. Irrigating the canals with 1% Phytic acid for 30 s to 1 min provides a clean, debris-free canal space and open dentinal tubules.[5],[17],[18] Hence, phytic acid at 1% concentration was employed in this study.

Self-adhesive resin cements are currently popular to lute the fiber postdue to their simplified clinical procedure. While their major mode of retention is micromechanical, some may demonstrate additional chemical adhesion to hydroxyapatite.[1] RelyX U200, which is the self-adhesive resin cement used in the present research, is a dual-cure cement which exhibits both modes of retention.[19],[20] It has been reported to exhibit excellent bond strength even under wet conditions.[7],[9],[21]

The present study revealed that the use of different chelating solutions as final rinse has a variable effect on bonding fiber posts to the radicular dentin. The following order was observed in the bond strength values: Maleic acid > phytic acid > EDTA.

Mean bond strength values for a maleic acid group in cervical 3rd was 62.44 ± 3.21, in middle 3rd was 72.48 ± 5.88 and in apical 3rd was 67.43 ± 5.17. For phytic acid group, the mean bond strength values in cervical 3rd were 60.98 ± 7.24, in middle 3rd was 70.60 ± 8.72 and in apical 3rd was 65.52 ± 3.83. For EDTA group the mean bond strength values in cervical 3rd were 52.96 ± 5.25, middle 3rd was 53.56 ± 5.09 and for apical 3rd region was 32.99 ± 5.17.

Numerous studies have revealed the superior performance of maleic acid as an agent to remove the smear layer. It has been reported that final irrigation with maleic acid enhances the bond strength of fiber posts as opposed to EDTA. It demonstrated an increased number of open dentinal tubules and minimal debris which promotes better adhesion of resin cement with the dentin, thus contributing to the high bond strength.[13],[14],[16],[22] Other studies have shown that maleic acid at a low concentration of 7% has reduced demineralizing effect on the dentin.[16] These findings support the results of our study.[14],[17],[22]

Shivanna demonstrated high bond strength of resin sealers to dentin after final rinse with maleic acid.[22] Ballal et al.,[13] reported that 7% maleic acid produced greater surface roughness of the root canal walls which was not the case with 17% EDTA. Furthermore, there is an increased collagen degradation seen with EDTA than with maleic acid.[17] All these additional factors may have a role in the superior performance of maleic acid in the present study.

Phytic acid is another mild chelating agent with a superior ability to deal with the smear layer than EDTA. Several mechanisms have been attributed to the high bond strength obtained after irrigation with phytic acid:

  • Mild etching effect of phytic acid without the significant depth of demineralization may facilitate better infiltration of resin monomers
  • It is a natural collagen cross-linker enhancing resin-dentin bond strength[23]
  • Interaction between phytic acid, collagen, and hydroxyapatite forms a complex structure combining collagen and calcium phytate that promotes adhesion with resin cement.[5],[17],[21]

A significant increase in bond strength of RelyX U200 has been shown after final irrigation with phytic acid as compared to EDTA in a recent research.[6] This finding also corroborates with the results of this study.

On the other hand, studies have reported that EDTA interferes with the adhesion of RelyX U200 as it creates a partial apatite-depleted substrate.[1] It has also been speculated that residual EDTA interferes with the chemical curing of RelyX U200.[24]

Comparing the bond strength at all three levels of the root canal, final rinse with EDTA demonstrated higher bond strength at the cervical third (52.96 ± 5.25) of the postspace as compared to the apical 3rd (32.99 ± 5.17). Its reduced efficacy near the bottom of the postspace has been reported by other studies. Its higher surface tension compared to maleic acid may be a factor in this regard.[17] On the other hand, both maleic acid and phytic acid demonstrated high bond strength at all levels which is similar to the results of other investigators.[14] Their superior performance could be due to better interaction with the smear layer.[16]

Overall, the bond strength of fiber posts luted with the self-adhesive resin cement showed good results when the postspace was irrigated with maleic acid and phytic acid which was not the case with EDTA. Since these results were observed under ideal laboratory conditions, they cannot be directly applied to the clinical scenario. The present study assessed the push-out bond strength 1 week after treating with the chelating agents. Long-term bond durability was not assessed. This needs to be evaluated in a future study. Although self-adhesive resin cements can simplify luting of fiber posts, further research should focus on their adhesive mechanisms and associated factors.

   Conclusions Top

The use of 7% Maleic acid as a final rinse prior to fiber postcementation using a self-adhesive cement (RelyX U200) significantly improved their adhesion.


The author would like to thank Dr. Ramya Raghu and Dr. Ashish Shetty for their significant support in completion of this project.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

   Supplementary Files Top

Sample Size Estimation

Analysis: A priori: Compute required sample size

Input: Effect size f = 0.48

α err prob = 0.05

Power (1-β err prob) = 0.80

Number of groups = 3

Output: Noncentrality parameter λ = 10.3680000

Critical F = 3.2199423

Numerator df = 2

Denominator df = 42

Total sample size = 45

Actual power = 0.8004756

The sample size has been estimated using the GPower software v.

Considering the effect size to be measured (f) at 48%, power of the study at 80% and the margin of the error at 5%, the total sample size needed is 45. Each group will consist of 15 samples. [15 x 3 groups = 45 samples].


Statistical Analysis

Statistical Package for Social Sciences [SPSS] for Windows Version 22.0 Released 2013. Armonk, NY: IBM Corp., will be used to perform statistical analyses.

Descriptive Statistics:

Descriptive analysis includes expression of push out bond strength in terms of mean & standard deviation in each study group.

Inferential Statistics:

One-way ANOVA test followed by Tukey's HSD Post hoc Analysis will be used to compare the push out bond strength between different study groups.

The level of significance [P-Value] will be set at P<0.05

And any other relevant test, if found appropriate during the time of data analysis will be dealt accordingly.

   References Top

Faria-e-Silva AL, Menezes Mde S, Silva FP, Reis GR, Moraes RR. Intra-radicular dentin treatments and retention of fiber posts with self-adhesive resin cements. Braz Oral Res 2013;27:14-9.  Back to cited text no. 1
Gu XH, Mao CY, Liang C, Wang HM, Kern M. Does endodontic post space irrigation affect smear layer removal and bonding effectiveness? Eur J Oral Sci 2009;117:597-603.  Back to cited text no. 2
Hattar S, Hatamleh MM, Sawair F, Al-Rabab'ah M. Bond strength of self-adhesive resin cements to tooth structure. Saudi Dent J 2015;27:70-4.  Back to cited text no. 3
Mazzitelli C, Monticelli F, Toledano M, Ferrari M, Osorio R. Dentin treatment effects on the bonding performance of self-adhesive resin cements. Eur J Oral Sci 2010;118:80-6.  Back to cited text no. 4
Nassar M, Hiraishi N, Tamura Y, Otsuki M, Aoki K, Tagami J. Phytic acid: An alternative root canal chelating agent. J Endod 2015;41:242-7.  Back to cited text no. 5
Muana HL, Hiraishi N, Nakajima M, Kong K, Tagami J. Effect of the dentin chelating agents Phytic acid and EDTA on degree of conversion, microhardness, and bond strength of chemical-curing self-adhesive cements. J Adhes Dent 2019;21:299-306.  Back to cited text no. 6
Özcan S, Yaman D, Aktuna S, Bala O, Nayir Y. Push-out bond strength of fiber posts luted using different adhesive resin cements. J Restor Dent 2013;1:75.  Back to cited text no. 7
Radovic I, Mazzitelli C, Chieffi N, Ferrari M. Evaluation of the adhesion of fiber posts cemented using different adhesive approaches. Eur J Oral Sci 2008;116:557-63.  Back to cited text no. 8
Aktemur Türker S, Uzunoğlu E, Yılmaz Z. Effects of dentin moisture on the push-out bond strength of a fiber post luted with different self-adhesive resin cements. Restor Dent Endod 2013;38:234-40.  Back to cited text no. 9
Ravikumar J, Bhavana V, Thatimatla C, Gajjarapu S, Reddy SG, Reddy BR. The effect of four different irrigating solutions on the shear bond strength of endodontic sealer to dentin – An in-vitro study. J Int Oral Health 2014;6:85-8.  Back to cited text no. 10
Ferracane JL, Stansbury JW, Burke FJ. Self-adhesive resin cements – Chemistry, properties and clinical considerations. J Oral Rehabil 2011;38:295-314.  Back to cited text no. 11
Coniglio I, Magni E, Goracci C, Radovic I, Carvalho CA, Grandini S, et al. Post space cleaning using a new nickel titanium endodontic drill combined with different cleaning regimens. J Endod 2008;34:83-6.  Back to cited text no. 12
Ballal NV, Kandian S, Mala K, Bhat KS, Acharya S. Comparison of the efficacy of maleic acid and ethylenediaminetetraacetic acid in smear layer removal from instrumented human root canal: A scanning electron microscopic study. J Endod 2009;35:1573-6.  Back to cited text no. 13
Kara Tuncer A, Tuncer S. Effect of different final irrigation solutions on dentinal tubule penetration depth and percentage of root canal sealer. J Endod 2012;38:860-3.  Back to cited text no. 14
Fan F, Ibrahim M, Dai P, Mao Y, He B, Wu G, et al. Effect of maleic acid on the bond strength of fibre posts to root dentine. Eur J Oral Sci 2017;125:396-402.  Back to cited text no. 15
Prabhu SG, Rahim N, Bhat KS, Mathew J. Comparison of removal of endodontic smear layer using NaOCl, EDTA, and different concentrations of maleic acid – A SEM study. Endodontology 2003;15:20-5.  Back to cited text no. 16
Kong K, Hiraishi N, Nassar M, Otsuki M, Yiu CK, Tagami J. Effect of phytic acid etchant on resin-dentin bonding: Monomer penetration and stability of dentin collagen. J Prosthodont Res 2017;61:251-8.  Back to cited text no. 17
Parčina Amižić I, Baraba A, Ionescu AC, Brambilla E, Van Ende A, Miletić I. Bond strength of individually formed and prefabricated fiber-reinforced composite posts. J Adhes Dent 2019;21:557-65.  Back to cited text no. 18
Boing TF, Gomes GM, Gomes JC, Reis A, Gomes OM. Is the bonding of self-adhesive cement sensitive to root region and curing mode? J Appl Oral Sci 2017;25:2-9.  Back to cited text no. 19
Barreto MS, Rosa RA, Seballos VG, Machado E, Valandro LF, Kaizer OB, et al. Effect of intracanal irrigants on bond strength of fiber posts cemented with a self-adhesive resin cement. Oper Dent 2016;41:e159-67.  Back to cited text no. 20
Bonchev A, Radeva E, Tsvetanova N. Fiber reinforced composite posts – A review of literature. Int J Sci Res (IJSR) 2017;6:1887-93.  Back to cited text no. 21
Shivanna V. The effect of different irrigating solutions on the push out bond strength of endodontic sealer to dentin and assessing the fracture modes: An in-vitro study. J Int Clin Dent Res Organ 2014;6:86.  Back to cited text no. 22
  [Full text]  
Nassar M, Hiraishi N, Islam MS, Romero MJ, Otsuki M, Tagami J. Effect of phytic acid as an endodontic chelator on resin adhesion to sodium hypochlorite-treated dentin. Restor Dent Endod 2020;45:e44.  Back to cited text no. 23
Husain A, Gupta S, Nikhil V, Jaiswal S. Effect of antioxidant on pull-out bond strength of fiber post bonded with self-adhesive resin luting cement. Int J Sci Res 2020;9:23-5.  Back to cited text no. 24

Correspondence Address:
Dr. Priya C Yadav
#6/44, 3rd Cross, Old Guddadahalli, Vinayakanagar, Mysore Road, Bengaluru-560 026, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jcd.jcd_489_21

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