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ORIGINAL ARTICLE  
Year : 2013  |  Volume : 16  |  Issue : 3  |  Page : 238-242
An in vitro comparison of bond strengths of Gutta-percha/AH Plus, Resilon/Epiphany self-etch and EndoREZ obturation system to intraradicular dentin using a push-out test design


Department of Conservative Dentistry and Endodontics, KLEVK Institute of Dental Sciences, Belgaum, Karnataka, India

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Date of Submission22-Oct-2012
Date of Decision05-Jan-2013
Date of Acceptance11-Jan-2013
Date of Web Publication4-May-2013
 

   Abstract 

Aim: To evaluate and compare the push-out bond strengths of three obturation materials; Gutta-percha/AH Plus, Resilon/Epiphany self-etch (SE) and EndoREZ obturation system to intraradicular dentin.
Materials and Methods: Sixty single-canal anterior teeth were prepared and assigned to experimental groups (n = 20), designated as Group I: Gutta-percha/AH Plus, Group II: Resilon/Epiphany SE and Group III: EndoREZ sealer/EndoREZ points.After obturation, each tooth was prepared for push-out assessment with root slices of 2 mm thickness using universal testing machine.
Statistical Analysis: Two way analysis of variance and Scheffe's test.
Results: Gutta-percha/AH Plus root fillings showed significantly highest bond strength. Also, root segment location did not have a significant influence on bond strength.
Conclusion: The adhesiveness quality to root dentin promoted by newer methacrylate resin-based obturation systems like Resilon/Epihany SE and EndoREZ is compromised even when teeth with simple anatomic features were obturated under well-monitored laboratory conditions.

Keywords: AH Plus; EndoREZ; epiphany; push-out bond strength; resilon

How to cite this article:
Patil A S, Dodwad K P, Patil A A. An in vitro comparison of bond strengths of Gutta-percha/AH Plus, Resilon/Epiphany self-etch and EndoREZ obturation system to intraradicular dentin using a push-out test design. J Conserv Dent 2013;16:238-42

How to cite this URL:
Patil A S, Dodwad K P, Patil A A. An in vitro comparison of bond strengths of Gutta-percha/AH Plus, Resilon/Epiphany self-etch and EndoREZ obturation system to intraradicular dentin using a push-out test design. J Conserv Dent [serial online] 2013 [cited 2019 Aug 25];16:238-42. Available from: http://www.jcd.org.in/text.asp?2013/16/3/238/111323

   Introduction Top


The success of endodontic treatment includes three essential elements, viz. thorough debridement, disinfection and a complete three dimensional obturation. [1],[2] The objective of three-dimensional obturation is to completely seal the canal system from any bacterial ingress from oral cavity and periradicular tissues. [3],[4] Additionally, the obturating materials seal within the canal system any irritants that are not removed during chemomechanical preparation. [5],[6]

Gutta-percha has been considered as the "gold standard" filling material and for many years has been used as a core material with zinc oxide eugenolbased or Ca(OH) 2 based sealers. [4],[7],[8] However, leakage and recontamination of the root-canal system continue to cause post-treatment complications. [5]

Recently endodontic sealers have been developed to improve the sealing and bonding to root dentin. [9] One such epoxy-resin based sealer is AH Plus (DentsPly, Mailleffer) that has been extensively used because of its good handling characteristics and the potential for better wettability of dentin and gutta-percha surfaces. [10]

Manufacturers have further incorporated adhesive dentistry in endodontics by introducing obturation systems with a specific focus on obtaining a "monoblock" in which the core material, sealer and root canal dentin form a single cohesive unit. The introduction of Resilon (Resilon Research, North Branford, Conn.) offers the promise of adhesion to root dentin. Resilon is a thermoplastic synthetic resin material that is based on polymers of polyester and contains difunctional methacrylate resin, bioactive glass and radiopaque fillers. [11] It can couple to a variety of dentin adhesives and resin-type sealers, including Epiphany. [9],[12] Recently, Epiphanyself-etch (SE) was introduced with the promise of optimizing the clinical performance with a simplified application procedure. [13] Another is the EndoREZ (Ultradent, South Jordan, UT) system that establishes a bond between a methacrylate resin-coated gutta-percha core material and a urethane dimethacrylate-based sealer. [14],[15],[16]

An improved bond and the creation of a monoblock root canal obturation are claimed to be the main advantages of these materials. [5] Thus the present in-vitro study is an attempt to evaluate and compare the push-out bond strength of gutta-percha/AH Plus, Resilon/Epiphany SE and gutta-percha/EndoREZ to dentin. The null hypothesis tested was that there are no differences in the bond strength between obturation groups tested.


   Materials and Methods Top


Sample selection and specimen preparation

Sixty extracted single-rooted, single-canal anterior teeth were collected and stored in 0.1%thymol solution until use. The teeth were decoronated at cementoenamel junction (CEJ) with diamond disc and standardized to 10mm + 1 mm length. Working length was established by placing #15 stainless steel K-file into the canal until it was seen at the apical foramen and then subtracting 1 mm. Cleaning and shaping was done by using 0.06 taper K3NiTi rotary instruments in a gear reduction handpiece (Rotary Master, J.MORITA, USA) upto size #40.

The canals were irrigated with 3% sodium hypochlorite during instrumentation with a final rinse of 17% ethylene diamine tetraacetic acid. The canals were dried with sterile paper points, and specimenwere then randomly assigned into three experimental groups of 20 teeth each based on the obturation material used.

Canal filling

In Group I, AH Plus sealer was mixed on a paper pad and applied to the root canal walls using a lentulospiral. Pre-fitted #40/0.06 tapergutta-percha cone was coated with AH Plus sealer and pumped a few times. The cone was removed, re-coated with sealer, and then inserted upto the working length. In Group II, Epiphany SE sealer was dispensed into the canal using intra-oral tips supplied with the system. Then, a pre-fitted #40/0.06 taper Resilon cone was inserted upto the working length. In Group III, EndoREZ sealer was dispensed into the canal through NaviTip and then a pre-fitted #40/.06 taper EndoREZ cone was placed in the canal as in Group II.

All the samples were coronally sealed with Cavit TM - G. They were then wrapped in moist gauze piece and stored in incubator at 37°C for 2 weeks.

Push-out assessment

Each root was horizontally sectioned into approximately 2 mm thick slices. The apical most 3 mm portion was discarded. Any sample containing non-circular filling material was also discarded. Overall, this produced three slices per specimen; coronal, middle and apical. The order of slices as well as each slice's apical side was identified. Thickness of each slice was measured with a digital caliper and recorded. Then, each slice was placed under a micrometer microscope where the diameter of each obturation site was measured and recorded. This measurement and thickness measurements were used to calculate the bonded area of the filling material.

On the coronal side of the slices, the larger diameter was measured to select a support jig with a hole large enough to provide clearance for the obturating material when it will be dislodged from the tooth slices. On the apical side of the slices, the smallest diameter was measured to select a punch to be used to supply load with that side, making sure that the punch would not contact the dentin around the obturating material, causing a crack and erroneous results. Thus, 0.5 mm diameter plunger was prepared. Each specimen was subjected to push-out test using Universal testing machine where the plunger moved in an apical to coronal direction at a crosshead] speed of 1 mm/min, which resulted in displacement of filling material. The universal testing machine gave the debonding force for individual specimen.

The push-out bond strength was calculated using the formula:

Debond stress (MPa) = Debonding force (N)/Area (mm 2 )

Where debonding force is the maximum force before debonding and area is the average value of the perimeter times the thickness.

This was done for all specimen.The data obtained was subjected to two way analysis of variance and Scheffe's test.


   Results Top


The mean push-out bond strength for each group were as follows: Group I (Gutta-Percha/AH Plus): 1.49 + 0.16MPa, Group II (Resilon/Epiphany SE): 0.95 + 0.13MPa and Group III (EndoREZobturation system): 0.56 + 0.15MPa [Table 1].Group I shows significantly highest bond strength whereas Group III showed the lowest bond strength. [Table 2] lists the group-by-location push-out bond strength values. The interactions between different groups was found to be significant (P < 0.05) while the group-by-location interaction was not found to be significant (P > 0.05). Same is also shown by means of graphs [Figure 1] and [Figure 2].
Figure 1: Mean bond strength for the three groups

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Figure 2: Mean bond strength at different locations within a group for three groups

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Table 1: Mean and standard deviation values of bond strength in MegaPascal for different groups

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Table 2: Mean and standard deviation values of bond strength in MegaPascal at different locations within each group for the three groups

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   Discussion Top


As a consequence of the current results, the null hypothesis was rejected.The bond strength of root canal sealers to dentin is important for maintaining the integrity of the seal in root canal filling. [17],[18] Although sealers can form close adhesion to the root canal wall, none is able to bond to gutta-percha; leaving a gap through which bacteria may pass. [9] An improved bond and creation of monoblockare considered to be the main advantages of Resilon/EpihanySE and EndoREZ oburation system. These properties should be reflected by improvements in interfacial strength between root-filling material and intraradicular dentin, which may be evaluated using thin-slice push-out tests. [19]

In this study, 60 single-rooted, single-canal anterior teeth were used, which were decoronated at CEJ and standardized to 10mm + 1 mm length to serve as stable and equivocal reference for all measurements. [10] Cleaning and shaping was carried out with 0.06 taper K3 till an apical size of 40. K3 has positive rake angle that provides for more effective cutting surface. Its three radial lands reduce friction on the canal wall and promote debris removal. Also its asymmetrical flutes provide superior canal tracking and eliminate transportation thus preventing the file from screwing into the canal. [20] Thus, K3 rotary NiTi files were used in the present study.

The canals were irrigated with 3% NaOCl and a final rinse of 17% EDTA. Sodium hypochlorite was not used as the final irrigating solution since it is an oxidizing agent that leads to oxidation of some component of the dentin matrix. Furthermore, oxygen has been shown to inhibit polymerization of resins, thus leading to reduced resin bond strengths. [21],[22] For obturation, single matched-cone technique was used. This passive-fit single-cone obturation protocol, without any type of condensation, was used to maintain experimental consistency among all groups. [10] Though manufacturers of Resilon/Epiphany SE and EndoREZ recommend light curing of coronal aspect for 40 s; but it was not done since then only the most coronal portion would likely be influenced by light activation.

Samples were then incubated for 2 weeks at 37°C to simulate clinical conditions and allow the sealer to set. [12] Each specimen was horizontally sectioned into approximately 2 mm thick slices. Apical 3 mm section was rejected due to small size of the filling material. Furthermore, samples with non-circular filling material were discarded as it would result in non-uniform stress distributions during testing and thus inaccurate measurements. This resulted in variance of sample size per group, which was accounted for during statistical analysis. When instrumentation was done with 0.06 taper K3 rotary NiTi files to an International organization for standardization size 40, apical diameter of canal at working length was 0.4 mm. The root section obtained after discarding apical 3 mm had an apical diameter 0.58 mm. Thus, a 0.5 mm diameter cylindrical plunger was used. The universal testing machine gave the debonding force for individual specimen. The push-out bond strength was then calculated using the formula:

Debond stress (MPa) = Debonding force (N)/Area (mm 2 ) [5],[14],[18]

In the present study, Group I (Gutta-percha/AH Plus) showed highest bond strength, which was greater than both Group II (Resilon/Epiphany SE) and Group III (EndoREZobturation system). Group II (Resilon/Epiphany SE) showed lower bond strength compared to Group I (Gutta-percha/AH Plus) but higher than Group III (EndoREZobturation system). The group-by-location interaction was not found to be significant.

The results of the present study correlate well with that of other studies [14],[18],[19],[20],[23] who also used push-out test design and found higher bond strengths in teeth obturated with gutta-percha and AH Plus sealer compared with those filled with Resilon/Epiphany or EndoREZ obturation system. A plausible explanation for the significantly lower bond strengths detected in the groups containing methacrylate resin-based sealer is the effect of cavity configuration factor (C-factor). C-factor is found to be extremely high in long, narrow root canals. In these situations, there is very limited unbonded surface area to provide relief from the stresses created by polymerization shrinkage. It is likely that the bond between sealer core and sealer dentin is not adequate enough to resist this debilitating stress that develops during polymerization resulting in gap formation. [13]

Despite using the similar methodology, the results of Resilon/Epiphany SE group in the present study did not correspond well with that of Skidmore et al. [2] who found a significantly higher mean bond strength to root dentin in the Resilon/Epiphany (1.51 + 1.22MPa) compared with gutta-percha/Kerr extended working time (0.66 + 0.39MPa).

A potential factor that may have accounted for this dissimilarity includes the difference in obturation technique. The use of single-cone obturation in the present study results in a greater sealer thickness when compared with warm vertical compaction used in their study. This can negatively influence the sealing ability of the root canal filling except when using AH Plus sealer. This phenomenon, along with its inherent volumetric expansion, may have contributed to the superior bond strength found with this epoxy resin-based sealer in the present study. [13]

Research on EndoREZ obturation system disclosed good hydrophilic properties, thus helping create long resin tags in radicular dentin. However, these tags appeared unbonded and exhibited insufficient adhesive strength to resist polymerization shrinkage, resulting in gap formation between sealer and canal wall. This may help explain the very low bond strength inthis group in the present study. [13]


   Conclusion Top


The results of the present study challenge the claim of "monoblock" formation by the new resin-based sealers. The adhesiveness quality to root dentin promoted by both resin-based sealers is compromised even when teeth with simple anatomic features were obturated under well-monitored laboratory conditions. The higher push-out bond strength found in the gutta-percha/AH Plus root fillings reiterate the fact that the era of conventional nonbonding root filling has not yet come to an end.

 
   References Top

1.Seltzer S, Bender IB. Cognitive dissonance in endodontics. J Endod 2003;29:714-9.  Back to cited text no. 1
    
2.Schilder H. Filling root canals in three dimensions. Dent Clin North Am 1967;11:723-44.  Back to cited text no. 2
    
3.Kandaswamy D, Venkateshbabu N, Arathi G, Roohi R, Anand S. Effects of various final irrigants on the shear bond strength of resin-based sealer to dentin. J Conserv Dent 2011;14:40-2.  Back to cited text no. 3
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4.Kumar N, Aggarwal V, Singla M, Gupta R. Effect of various endodontic solutions on punch out strength of resilon under cyclic loading. J Conserv Dent 2011;14:366-9.  Back to cited text no. 4
[PUBMED]  Medknow Journal  
5.Lance J. Skidmore, David W. Berzins, James K. Bahcall. An in vitro comparison of the intraradicular dentin bond strength of resilon and gutta-percha. J Endod 2006;32:963-6.  Back to cited text no. 5
    
6.Torabinejad M, Ung B, Kettering JD. In vitro bacterial penetration of coronally unsealed endodontically treated teeth. J Endod1990; 16:566-9.  Back to cited text no. 6
    
7.Stratton RK, Apicella MJ, Mines P. A fluid filtration comparison of gutta-percha versus Resilon, a new soft resin endodontic obturation system. J Endod 2006;32:642-5.  Back to cited text no. 7
    
8.Bouillaguet S, Wataha JC, Tay FR, Brackett MG, Lockwood PE. Initial invitro biological response to contemporary endodontic sealers. J Endod 2006; 32:989-92.  Back to cited text no. 8
    
9.Teixeira FB, Teixeira EC, Thompson JY, Trope M. Fracture resistance of roots endodontically treated with a new resin filling material. J Am Dent Assoc 2004; 135:646-52.  Back to cited text no. 9
    
10.Versiani MA, Carvalho-Junior JR, Padilha MI, Lacey S, Pascon EA, Sousa-Neto MD. A comparative study of physicochemical properties of AH Plus and Epiphany root canal sealants. Int Endod J 2006; 39:464-71.  Back to cited text no. 10
    
11.Baba SM, Grover SI, Tyagi V. Fracture resistance of teeth obturated with Guttapercha and Resilon: An in vitro study. J Conserv Dent 2010; 13:61-4.  Back to cited text no. 11
[PUBMED]  Medknow Journal  
12.Venturi M, Breschi L. Evaluation of apical filling after warm vertical gutta-percha compaction using different procedures. J Endod 2004; 30:436-40.  Back to cited text no. 12
    
13.De-Deus G, Di Giorgi K, Fidel S, Fidel RA, Paciornik S. Push-out bond strength of Resilon/Epiphany and Resilon/Epiphany self-etch to root dentin. J Endod 2009; 35:1048-50.  Back to cited text no. 13
    
14.Matthew A. Fisher, David W. Berzins, James K. Bahcall. An in vitro comparison of bond strength of various obturation materials to root canal dentin using a push-out test design. J Endod 2007;33:856-8.  Back to cited text no. 14
    
15.Doyle MD, Loushine RJ, Agee KA, Gillespie WT, Weller RN, Pashley DH, et al. Improving the performance of EndoRez root canal sealer with a dual-cured two-step self-etch adhesive. I. Adhesive strength to dentin. J Endod 2006; 32:766-70.  Back to cited text no. 15
    
16.Gillespie WT, Loushine RJ, Weller RN, Mazzoni A, Doyle MD, Waller JL, et al. Improving the performance of EndoREZ root canal sealer with a dual-cured two-step self-etch adhesive. II. Apical and coronal seal. J Endod 2006; 32:771-5.  Back to cited text no. 16
    
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18.Ungor M, Onay EO, Orucoglu H. Push-out bond strengths: The Epiphany-Resilon endodontic obturation system compared with different pairings of Epiphany, resilon, AH Plus and gutta-percha. Int Endod J 2006;39:643-7.  Back to cited text no. 18
    
19.Gesi A, Raffaelli O, Goracci C, Pashley DH, Tay FR, Ferrari M. Interfacial strength of resilon and gutta-percha to intraradicular dentin. J Endod 2005;31:809-13.  Back to cited text no. 19
    
20.Mounce RE. The K3 rotary nickel-titaniumsystem. Den Clin of North Am 2004;48:137-58.  Back to cited text no. 20
    
21.Morris MD, Lee KW, Agee KA, Bouillaguet S, Pashley DH. Effects of sodium hypochlorite and RC-prep on bond strengths of resin cement to endodontic surfaces. J Endod 2001;27:753-7.  Back to cited text no. 21
    
22.Ari H, Yaºar E, Belli S. Effects of NaOCl on bond strengths of resin cements to root canal dentin. J Endod 2003;29:248-51.  Back to cited text no. 22
    
23.Sly MM, Moore BK, Platt JA, Brown CE. Push-out bond strength of a new endodontic obturation system (Resilon/Epiphany). J Endod 2007; 33:160-2.  Back to cited text no. 23
    

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Correspondence Address:
A Sanjana Patil
A-14/10, Staff Quarters, JNMC Campus, Nehru Nagar, Belgaum, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0972-0707.111323

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    Figures

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    Tables

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