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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 31  |  Issue : 1  |  Page : 110-116

In vitro evaluation of bond strength of sealers after using various irrigants and Erbium-Yttrium-Aluminum-Garnet laser irradiation on radicular dentin surface: A SEM study


1 Department of Conservative Dentistry and Endodontics, Genesis Institute of Dental Sciences and Research, Firozpur, Punjab, India
2 Department of Pedodontics and Preventive Dentistry, Dasmesh Institute of Dental Sciences and Research, Faridkot, Punjab, India

Date of Web Publication19-Jun-2019

Correspondence Address:
Dr. Prashant Monga
Department of Conservative Dentistry and Endodontics, Genesis Institute of Dental Sciences and Research, Firozpur, Punjab
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/endo.endo_9_18

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  Abstract 

Aim: The aim of this in vitro study was to evaluate and compare the push-out bond strength of Adseal and mineral trioxide aggregate (MTA) Fillapex sealer after using various irrigants and Erbium-Yttrium-Aluminum-Garnet (Er:YAG) laser irradiation on radicular dentin surface.
Materials and Methods: A total of 80 freshly extracted human permanent maxillary anterior teeth were sectioned transversally below the cemento-enamel junction. The remaining root portion was sectioned to get 4-mm thick dentin disc from coronal end of the root, with straight handpiece, and diamond disc. Root canal of specimens was prepared with bur to create space for sealer placement. Specimens were divided into eight groups of 10 samples each, as per irrigants and sealer used. In Group 1, 3, 5, and 7 specimens irrigated with distilled water, NaOCl, Ethylenediaminetetraacetic acid (EDTA), and Er:YAG laser, respectively, and obturated with Adseal sealer. In Group 2, 4, 6, and 8 irrigated with distilled water, NaOCl, EDTA, and Er:YAG laser, respectively, and obturated with MTA Fillapex sealer. After sealer setting, the force used to remove the sealer was evaluated using universal testing machine. Recorded force used to calculate the push-out bond strength in Megapascals and scanning electron microscopy examination was done for specimens.
Results: Adseal sealer had significantly higher bond strength than MTA Fillapex sealer, irrespective of irrigant used. The highest bond strength was seen in specimens irrigated with EDTA and obturated with Adseal sealer and least in specimens irrigated with distilled water and obturated with MTA Fillapex sealer.
Conclusion: Adseal sealer had significantly higher bond strength than the MTA Fillapex sealer. EDTA irrigation showed better smear layer removal, followed by Er:YAG laser irradiation, then NaOCl, least by distilled water.

Keywords: Adhesion, erbium-yttrium-aluminum-garnet laser, irrigants, sealer, smear layer


How to cite this article:
Kaur N, Bhandari S, Mahajan P, Monga P, Mahajan S, Bajaj N. In vitro evaluation of bond strength of sealers after using various irrigants and Erbium-Yttrium-Aluminum-Garnet laser irradiation on radicular dentin surface: A SEM study. Endodontology 2019;31:110-6

How to cite this URL:
Kaur N, Bhandari S, Mahajan P, Monga P, Mahajan S, Bajaj N. In vitro evaluation of bond strength of sealers after using various irrigants and Erbium-Yttrium-Aluminum-Garnet laser irradiation on radicular dentin surface: A SEM study. Endodontology [serial online] 2019 [cited 2019 Dec 7];31:110-6. Available from: http://www.endodontologyonweb.org/text.asp?2019/31/1/110/260542


  Introduction Top


The success of endodontic treatment depends on the three-dimensional obturation of root canal space with an inert material after thorough chemomechanical preparation of root canal.[1] Ideally, the obturating material should bond with radicular dentin surface to avoid any microleakage from an apical or a coronal direction which poses a clinical problem and source of failure.[2]

During mechanical instrumentation, root canals are covered by smear layer, which represent one additional interface between the obturating material and root canal walls. The absence of smear layer enables the material to enter the dentinal tubules avoiding microleakage and also helps in retention of material using mechanical interlocking.[3]

Removal of the smear layer is beneficial in obtaining disinfection. Most commonly used chemicals as irrigants are sodium hypochlorite and ethylenediaminetetraacetic acid. NaOCl has pulp tissue dissolving property and ethylenediaminetetraacetic acid (EDTA) is a demineralizing agent, which by chelating action forms an insoluble calcium chelates.[4]

Among lasers, Erbium-Yttrium-Aluminum-Garnet (Er:YAG) laser used to remove infected dentinal surfaces and the ubiquitous smear layer. Er:YAG laser irradiation exposes the orifices of the dentinal tubules, thus creating a micromechanical retention pattern which influence the adhesion of sealers.[5]

Ideally, the sealer should not shrink and bond effectively to both surrounding root canal walls and core material. A good adhesion of the sealer improves the sealing ability. Bond strength of sealers to dentin is important to maintain the integrity of the seal in both static and dynamic situations. In static circumstances, the adhesion eliminates spaces that can allow the infiltration of fluids into the sealer-dentin interface. In dynamic situations, adhesion is necessary to avoid sealer dislocation during operative procedures or masticatory function, ensuring that seal is maintained.[6],[7]

Several new root canal sealers have been developed with the property of adhesion to canal walls. One such sealer is Adseal (MetaBiomed, Korea)-epoxy resin-based sealers. It is available in the paste–paste consistency in dual syringe, having sealing property, and low solubility. Base paste consists of epoxy oligomer resin, ethylene glycol salicylate, calcium phosphate, bismuth subcarbonate, and zirconium oxide. Catalyst paste consists of poly aminobenzoate, triethanolamine, calcium phosphate, bismuth subcarbonate, zirconium oxide, and calcium oxide. The two components are combined by manually mixing the paste.[8]

Other is mineral trioxide aggregate (MTA) Fillapex (Angelus, Londrina PR, Brazil)-MTA-based sealer, which has high sealing ability and predilection toward mineralization by the formation of hard tissue. It is a new paste based sealer, consists of salicylate resin, diluting resins, natural resin, nanoparticulated resin, bismuth trioxide, and MTA. The components are mixed by self-mixing tip attached to a syringe.[7] Hence, keeping in view their sealing capacity, these two sealers, i.e., Adseal and MTA Fillapex were used to evaluate bond strength.

Therefore, Adseal sealer and MTA Fillapex sealer were tested for their adhesion to root canal after irrigation with distilled water, NaOCl, EDTA, and Er:YAG laser irradiation on the dentinal surface of root canal.


  Materials and Methods Top


A total of 80 freshly extracted human permanent maxillary anterior teeth were sectioned transversally 4 mm below the cemento-enamel junction. The remaining root portion was sectioned to get 4-mm thick dentin disc from coronal end of the root, with straight hand piece, and diamond disc. Dentin discs dimensions were measured with Vernier caliper and eighty specimens were made. Each disc was centered inside aluminum metal rings having a diameter of 16 mm and height 4 mm and secure with self-cure acrylic resin. Root canal of each specimen was prepared using a taper fissure diamond bur (Mani Inc.), to create a space for sealer placement with the dimensions as follows: larger diameter at the coronal end to be 2 mm and smaller diameter at apical end to be 1.5 mm, with a height of 4 mm.

The prepared specimens were randomly divided into eight groups of 10 samples each, according to the type of irrigant used and sealer used for obturation.

Before obturation, in each group, specimens were irrigated with irrigating solutions for 1 min and canal space was dried. Specific sealer allotted to each group was mixed according to its manufacturer's instructions and placed within the created canal space. Before the obturation of specimens, a modeling wax was attached at the apical end to prevent the over flow of sealer and was placed over the vibrator for better sealer adaptation to the root canal space.

Group 1 (n = 10) – Specimens were irrigated with distilled water and obturated with Adseal sealer

Group 2 (n = 10) – Specimens were irrigated with distilled water and obturated with MTA Fillapex sealer

Group 3 (n = 10) – Specimens were irrigated with 3% NaOCl (Septodont healthcare Pvt. Ltd, India) and obturated with Adseal sealer

Group 4 (n = 10) – Specimens were irrigated with 3% NaOCl and obturated with MTA Fillapex sealer

Group 5 (n = 10) – Specimens were irrigated with 17% EDTA (MetaBiomed® Co. Ltd, Korea) and obturated with Adseal sealer

Group 6 (n = 10) – Specimens were irrigated with 17% EDTA and obturated with MTA Fillapex sealer.

Group 7 (n = 10) – Specimens were irradiated with Er:YAG laser (Syneron dental laser) with energy of 100 mJ and frequency 10 Hz and obturated with Adseal sealer.

Group 8 (n = 10) – Specimens were irradiated with Er:YAG laser with the same energy values as group 7, and obturated with MTA Fillapex sealer.

Sealer was allowed to set for 1 week at room temperature. The push-out bond strength was evaluated using a universal testing machine by keeping specimens in an apico-coronal direction and to prevent obstruction for extrusion of sealer. The specimens were kept in prefabricated jig and the bond failure occurred by plunger moving in apico-coronal direction and the bond failure was checked by drop in force and the extrusion of the sealer into the mounting jig. The maximum failure force was recorded in Newtons (N) and that values were used to calculate the push-out bond strength in Megapascals (MPa) as per the surface area of specimens. The formula used to calculate the bond strength was as follows:[8]

MPa = N/2πrh

Where, N = the maximum load for each specimen, r = root canal radius in mm, h = the thickness of the root dentin disc in millimeters, and π =3.14.

Then, the specimens were taken for scanning electron microscopic examination, to examine the smear layer removal, and formation of sealer tags. The values were calculated and subjected to statistical analysis.


  Results Top


The results are presented in mean ± standard deviation. The one-way analysis of variance was used to compare the bond strength of Adseal and MTA Fillapex sealer. The post hoc tukey test was used to compare the bond strength of two sealers after using irrigants and Er:YAG laser irradiation on radicular dentin surface. A value of P < 0.001 was considered highly statistically significant [Table 1], [Table 2], [Table 3].
Table 1: The mean values and standard deviation among all the eight groups

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Table 2: Comparison between adseal and mineral trioxide aggregate Fillapex sealer in each irrigant

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Table 3: Comparison between irrigants and Erbium-Yttrium-Aluminum-Garnet laser irradiation in both sealers

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  Discussion Top


For the success of endodontic treatment, adaptation and adhesion of sealer to the radicular dentinal surface is an important factor. As gutta-percha does not bond to root dentin, it is used in conjunction with root canal sealer.[9] Good adhesion of sealer to dentin, reduces leakage, and also improves the fracture resistance of root canal-filled teeth.

Adhesion of sealer is affected by surface tension, surface wettability, and root canal surface cleaning. It also depends on the physical and chemical properties of the sealers, type of irrigating solution used, and presence of the smear layer. Studies have shown that sealer adhesion was increased when the smear layer was removed from the root canal.[10],[11]

Irradiation with the Er:YAG laser results in removal of the smear layer through the process of photoablation, which causes morphological alteration and dentin irregularities which influence the mechanical adhesion.[5]

Dentin surface was affected by each irrigating solution and laser application differently. Sealers and irrigating solutions both are chemicals and thus some amount of interaction between the two was expected. Whether this reaction is synergistic or antagonistic or neutral was studied, and it was found that, Adseal sealer had significantly higher push-out bond strength values than MTA Fillapex sealer in all specimens, irrespective of irrigant used [Table 1] and [Table 2].

Similar results were seen by Sagsen et al.[9] and Adl et al.[12] that epoxy resin sealer AH26 had higher push-out bond strength over the MTA Fillapex. According to Lee et al.[13] resin-based sealers had higher bond strength as compared to other sealers, as resin sealer penetrates deeper into the dentinal tubules. Vilanova et al.[11] explained the higher bond strength of the epoxy resin-based sealers was by their ability to form a covalent bond by an open epoxide ring to any exposed amino groups in collagen and contributes to long-term dimensional stability and low polymerization stresses.

In MTA Fillapex sealer, MTA is one of the ingredients and releases calcium and hydroxyl ions, which results in the formation of apatites, as comes into contact with phosphate-containing fluids.[14] Reyes-Carmona et al. reported that the apatite formed by MTA was deposited within collagen fibrils, which promotes controlled mineral nucleation on the dentin, and results in the formation of tag-like structures.[15] The reason for the low bond strength of MTA Fillapex to the dentin could be low adhesion capacity of these tag-like structures to canal walls. In contrast to results, MTA Fillapex presented an acceptable resistance to dislodgement similar to resin-based AH Plus sealer in another study.[16]

The canals were filled with sealer only, with one interface (sealer and dentin) thus making it possible to evaluate only the bond strength between the sealer and dentin rather than core material.[17] Moreover, the absence of a core material allows the root canal sealer to achieve its full expansion, which also results in higher push-out bond strength as in the study.

According to the results obtained, the presence of the smear layer had a negative effect on the adhesion values of both sealers. This was the reason for the increase in adhesion values when the smear layer was removed by EDTA, Er:YAG laser irradiation, and NaOCl irrigation in specimens, as examined in scanning electron microscopy (SEM) [Figure 1] and [Figure 2]. The specimens irrigated with distilled water irrespective of sealer used, had least amount of bond strength values, as it did not remove the smear layer [Table 3].
Figure 1: Group - 1 (Specimen irrigated with distilled water and obturated with Adseal sealer)

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Figure 2: Group - 2 (Specimen irrigated with distilled water and obturated with mineral trioxide aggregate fillapex sealer)

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The specimens obturated with Adseal sealer and irrigated with NaOCl showed lower bond strength than specimens irrigated with the EDTA. Specimens showed a significant difference between these two groups as NaOCl could remove only organic component of smear layer. It also oxidizes the component in the dentinal matrix which interferes with free-radical propagation at the resin-dentin interface which leads to lower bond strength values.[7] In SEM examination, only partial smear layer was removed by NaOCl irrigation [Figure 3] and [Figure 4].
Figure 3: Group - 3 (Specimen irrigated with NaOCl and obturated with Adseal sealer)

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Figure 4: Group - 4 (Specimen irrigated with NaOCl and obturated with mineral trioxide aggregate Fillapex sealer)

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When EDTA was used with Adseal sealer, the highest bond strength values were obtained. EDTA irrigated specimens showed the maximum removal of smear layer, thus creating open dentinal tubules and allowing better sealer penetration [Figure 5] and [Figure 6].
Figure 5: Group - 5 (Specimen irrigated with ethylenediaminetetraacetic acid and obturated with Adseal sealer)

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Figure 6: Group - 6 (Specimen irrigated with ethylenediaminetetraacetic acid and obturated with mineral trioxide aggregate Fillapex sealer)

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In the present study, the laser-treated Adseal sealer specimens showed the absence of the smear layer. The bond strength values were more than NaOCl irrigation group but less than EDTA irrigation group. Similar results were obtained by Pécora et al.[18] and Sousa-Neto et al.[19] that the Er:YAG laser application increased the bond strength of resin-based sealer.

In MTA Fillapex sealer groups, higher adhesion values were found when EDTA and NaOCl were used. When the laser was used, increased bond strength was seen; although, it was less than the NaOCl and EDTA irrigation effects. It could be possibly because MTA-based sealer is hydrophilic and requires the moisture to set. The evaporation of liquid from the dentinal tubules during laser application affects the adhesion of hydrophilic sealers.[20],[21],[22]

Ozkocak and Sonat[23] resulted that resin-based root canal sealers showed high push-out bond strength after the smear layer removal by EDTA and Er:YAG laser irradiation. In the present study, dentinal tubules were open when the smear layer was removed, but penetration did not occur in all specimens.

Saleh et al.[24] reported that all root canal sealers did not show penetration in the exposed dentinal tubules after the smear layer was removed. The bond strength was not high in all sealers that showed tubular penetration and stated that the type of irrigation should be chosen according to the different type of root canal sealer for optimal adhesion [Figure 7] and [Figure 8]. The present study results were consistent with this study, as Er:YAG laser irradiation increased the adhesion values for Adseal sealer, but did not affect much for MTA Fillapex sealer and NaOCl irrigation increased the adhesion values for MTA Fillapex but not for Adseal sealer. Hence, it was stated that different sealer requires different dentin treatment for good adhesion.
Figure 7: Group - 7 (Specimen irradiated with Erbium-Yttrium-Aluminum-Garnet and obturated with Adseal sealer)

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Figure 8: Group - 8 (Specimen irradiated with Erbium-Yttrium-Aluminum-Garnet and obturated with mineral trioxide aggregate Fillapex sealer)

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Orstavik et al.[25] in 1983 recommended the use of a universal testing machine to determine the adhesion of root canal sealers. Different parameters as microtensile, shear bond strength, and pull-out and push-out tests have been used to evaluate the bond strength. Goracci et al.[26] reported that the push-out test was more reliable and accurate to evaluate bond strength, as the fracture occurs parallel to the dentin-bonding interface and it better reflects the clinical status of the fracture.

The limitation of the present study was that fluidity, viscosity of the sealers, and obturation technique may affect the penetration depth and adhesion of sealers to root canal dentin.


  Conclusion Top


Within the limitations of this study, it was concluded Adseal-epoxy resin sealer had significantly higher bond strength than the MTA Fillapex sealer. In Adseal sealer obturated groups, the highest bond strength was seen in specimens irrigated with EDTA and least bond strength was seen in specimens irrigated with distilled water and obturated with MTA Fillapex sealer. SEM examination showed that maximum smear layer was removed by EDTA followed by Er:YAG laser and NaOCl. However, smear layer was seen in distilled water irrigated specimens. It can be stated that the type of irrigant should be chosen according to the type of root canal sealer to be used for optimal adhesion.

Acknowledgment

The authors would like to thank Genesis Institute of Dental Sciences and Research, Ferozepur, Punjab for its support.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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Sagsen B, Ustün Y, Demirbuga S, Pala K. Push-out bond strength of two new calcium silicate-based endodontic sealers to root canal dentine. Int Endod J 2011;44:1088-91.  Back to cited text no. 9
    
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11.
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18.
Pécora JD, Cussioli AL, Guerişoli DM, Marchesan MA, Sousa-Neto MD, Brugnera Júnior A, et al. Evaluation of Er: YAG laser and EDTAC on dentin adhesion of six endodontic sealers. Braz Dent J 2001;12:27-30.  Back to cited text no. 18
    
19.
Sousa-Neto MD, Marchesan MA, Pécora JD, Junior AB, Silva-Sousa YT, Saquy PC, et al. Effect of Er: YAG laser on adhesion of root canal sealers. J Endod 2002;28:185-7.  Back to cited text no. 19
    
20.
Nagas E, Uyanik MO, Eymirli A, Cehreli ZC, Vallittu PK, Lassila LV, et al. Dentin moisture conditions affect the adhesion of root canal sealers. J Endod 2012;38:240-4.  Back to cited text no. 20
    
21.
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22.
Silva EJ, Rosa TP, Herrera DR, Jacinto RC, Gomes BP, Zaia AA, et al. Evaluation of cytotoxicity and physicochemical properties of calcium silicate-based endodontic sealer MTA Fillapex. J Endod 2013;39:274-7.  Back to cited text no. 22
    
23.
Ozkocak I, Sonat B. Evaluation of effects on the adhesion of various root canal sealers after Er: YAG laser and irrigants are used on the dentin surface. J Endod 2015;41:1331-6.  Back to cited text no. 23
    
24.
Saleh IM, Ruyter IE, Haapasalo MP, Orstavik D. Adhesion of endodontic sealers: Scanning electron microscopy and energy dispersive spectroscopy. J Endod 2003;29:595-601.  Back to cited text no. 24
    
25.
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26.
Goracci C, Tavares AU, Fabianelli A, Monticelli F, Raffaelli O, Cardoso PC, et al. The adhesion between fiber posts and root canal walls: Comparison between microtensile and push-out bond strength measurements. Eur J Oral Sci 2004;112:353-61.  Back to cited text no. 26
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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