|Year : 2016 | Volume
| Issue : 1 | Page : 32-37
Comparative evaluation of push-out bond strength of resin-based sealer and mineral trioxide aggregate-based sealer after using normal saline and 2% chlorhexidine as a final irrigant: In vitro study
Pooja Ravindrakumar Gupta, Shalini D Aggarwal, Shirin P Kshirsagar, Karan Bhargava, Vinay Rai, Monika Chawla
Department of Conservative Dentistry and Endodontics, Dr. D. Y. Patil Dental College, Dr. D.Y. Patil Vidyapeeth, Pimpri, Pune, Maharashtra, India
|Date of Web Publication||21-Jun-2016|
Pooja Ravindrakumar Gupta
C/53, Ayojan Nagar, Devsar, Bilimora, Gujarat
Source of Support: None, Conflict of Interest: None
Aim: The aim of this study was to compare the push-out bond strengths of a resin-based sealer and a mineral trioxide aggregate (MTA)-based sealer after using normal saline and 2% chlorhexidine (CHX) as the final irrigant.
Materials and Methods: Fifty percent of the samples were irrigated with 2% CHX, and other 50% samples were irrigated with normal saline as the final irrigant. Each set of twenty samples was then further split into groups based on the sealer used. For Group 1 - AH Plus® (Dentsply, Maillefer, Ballaigues, Switzerland), a resin-based sealer was used after using normal saline as the final irrigant (n = 10). In Group 2 an MTA-based sealer was used after using normal saline as the final irrigant (n = 10). In Group 3, AH Plus® (Dentsply, Maillefer, Ballaigues, Switzerland) was used after using 2% CHX as the final irrigant (n = 10). In Group 4, an MTA-based sealer was used after using 2% CHX as the final irrigant (n = 10). After obturation, all the samples were cut perpendicular to their long axis to obtain slices of 3mm each from the coronal and middle third. The discs were then subjected to assess the push-out bond strength by using the Universal Testing Machine.
Results: AH Plus® (Dentsply, Maillefer, Ballaigues, Switzerland) showed a significant higher push-out bond strength as compared to the MTA-based sealer after using both saline and 2% CHX. The highest Push-Out Bond Strength was seen with AH Plus® (Dentsply, Maillefer, Ballaigues, Switzerland) after using 2% CHX.
Conclusion: AH Plus® (Dentsply, Maillefer, Ballaigues, Switzerland) after using CHX as the final irrigant has shown the best result among all the groups.
Keywords: Final irrigants; mineral trioxide aggregate based sealer; push-out bond strength; resin-based sealer.
|How to cite this article:|
Gupta PR, Aggarwal SD, Kshirsagar SP, Bhargava K, Rai V, Chawla M. Comparative evaluation of push-out bond strength of resin-based sealer and mineral trioxide aggregate-based sealer after using normal saline and 2% chlorhexidine as a final irrigant: In vitro study. Endodontology 2016;28:32-7
|How to cite this URL:|
Gupta PR, Aggarwal SD, Kshirsagar SP, Bhargava K, Rai V, Chawla M. Comparative evaluation of push-out bond strength of resin-based sealer and mineral trioxide aggregate-based sealer after using normal saline and 2% chlorhexidine as a final irrigant: In vitro study. Endodontology [serial online] 2016 [cited 2019 Nov 12];28:32-7. Available from: http://www.endodontologyonweb.org/text.asp?2016/28/1/32/184337
| Introduction|| |
Effective cleaning and shaping of the root canal, as well as the creation of an apical seal, is the essential goal for successful endodontic treatment. Different irrigants and obturation techniques are being used for the same purpose. To effectively clean the canals 5.25% sodium hypochlorite (NaOCl), 17% ethylene diamine tetra-acetic acid (EDTA) and 2% chlorhexidine (CHX) are required to be used in tandem or in combinations thereof. NaOCl is effective at dissolving organic tissue and is antimicrobial. However, there is a safety concern if NaOCl is extruded out of the root canal apex and into the periapical tissues. CHX has comparable antibacterial efficacy to NaOCl and has the advantage of having substantivity. However, CHX lacks the tissue dissolution capabilities of NaOCl. Hence, CHX cannot replace NaOCl but can be a supplemental and also the final irrigation step after NaOCl and EDTA irrigation because of its property of substantivity.  EDTA acts as a chelating agent and helps to remove the smear layer, thus opening up dentinal tubules.
In obturation procedures, sealers are used to attain an impervious seal between the core materials and root canal walls.  Endodontic sealers with adhesive properties have been developed to have better-sealing abilities than ZOE-based sealers, by incorporation of resin monomers into the sealer. The adhesion of resin to dentin occurs by forming a hybrid layer.
Collagenolytic factors such as matrix metalloproteinases (MMPs) have been found in sound radicular dentin which can lead to collagen degradation, loss of structural integrity, and subsequently reduced bond strengths.  CHX is able to increase the durability of resin-dentin bonds by being able to contribute to the dentin matrix preservation by being a potent inhibitor of enzymes related to the endogenous proteolytic activity of dentin, such as MMPs and cysteine cathepsins.
Using fluid transport models, some authors reported leakage with AH Plus® (Dentsply, Maillefer, Ballaigues, Switzerland) and gutta-percha.  Leakage can be reduced by using a material that adapts well to the root canal walls and does not shrink on setting. Mineral trioxide aggregate (MTA) Fillapex® (Angelus, Brazil) is a new paste-paste MTA-based root canal sealer with a high sealing capacity and it can also promote regeneration of cementum, according to the manufacturers.
Chemical irrigants used during root canal preparation may alter the chemical composition of the dentin surface as well as the interaction between the dentin and the resin-based sealer.  There is no study comparing push-out bond strengths of MTA-based sealers (MTA Fillapex® Angelus, Brazil) and resin-based sealers (AH Plus® Dentsply, Maillefer, Ballaigues, Switzerland) after using normal saline or 2% CHX as the final irrigant. Therefore, this study aimed to evaluate the push-out bond strengths of MTA-based sealer (MTA Fillapex® Angelus, Brazil) and resin-based sealer (AH Plus® Dentsply, Maillefer, Ballaigues, Switzerland) after using normal saline or 2% CHX as a final irrigant.
| Materials and Methods|| |
Forty extracted mandibular premolars having root curvatures within 5° were selected for this study. All the teeth were autoclaved and stored in normal saline. Teeth were then marked at the level of cementoenamel junction and were decoronated with a diamond disk. Canal patency was established by inserting a No-10 K-file and the working length was measured using a 15-K file. All samples were then instrumented with rotary ProTaper Universal System (PTUS™, Dentsply, Maillefer, Ballaigues, Switzerland) up to size F2.
The canals were then copiously irrigated with 5 ml of 5.25% NaOCl (Photon, Rahul Photographic Company, India) during instrumentation and then were rinsed with 5 ml of 17% EDTA (Desmear, Stedman Pharmaceuticals, India) to effectively remove the smear layer. All the forty samples were irrigated with 5 ml of saline. Twenty samples were further irrigated with 5 ml of 2% CHX as the final irrigant. All the samples were then dried with tapered paper points. Each set of twenty samples was then further split into groups of ten each and either a resin-based sealer or an MTA-based sealer was used [Figure 1] and [Figure 2]. According to the sealer and final irrigation used as mentioned above, all samples were thusly divided into four groups with ten samples each:
- Group 1: AH Plus® (Dentsply, Maillefer, Ballaigues, Switzerland) sealer after using saline as a final irrigant
- Group 2: MTA-based sealer after using Saline as a final irrigant
- Group 3: AH Plus® (Dentsply, Maillefer, Ballaigues, Switzerland) sealer after using 2% CHX (Asep-Rc, Stedman Pharmaceuticals, India) as a final irrigant
- Group 4: MTA-based sealer after using 2% CHX (Asep-Rc, Stedman Pharmaceuticals, India) as a final irrigant.
The canals were obturated using single-cone obturation protocol using the sealer of the respective group [Figure 3]. All the samples were then stored in distilled water at 37°C for 24 h. All the samples were cut perpendicular to their long axis to obtain slices of 3 mm each, from the coronal and middle third, using a slow-speed diamond saw with lubrication. The exact dimension of each disc was measured with an electronic digital caliper to be within the range of 1 0.04 mm. All the discs were then mounted in acrylic blocks [Figure 4]. The discs were then subjected to assess the push-out bond strength by using the universal testing machine. Statistical analysis was then done using Kruskal-Wallis test [Figure 5], Student's unpaired t-test, and one-way ANOVA test [Figure 6].
|Figure 5: Determination of push-out bond strength under universal testing machine|
Click here to view
| Results|| |
- Among both the sealers AH Plus® (Dentsply, Maillefer, Ballaigues, Switzerland) and MTA Fillapex® (Angelus, Brazil) AH Plus® (Dentsply, Maillefer, Ballaigues, Switzerland) showed a significant higher push-out bond strength after using both normal saline and CHX (P < 0.001)
- After using CHX as the final irrigant AH Plus® (Dentsply, Maillefer, Ballaigues, Switzerland) showed the highest push-out bond strength among all the groups
- Push-out bond strength after using CHX was found to be significantly higher than normal saline for both AH Plus® (Dentsply, Maillefer, Ballaigues, Switzerland) and MTA Fillapex® (Angelus, Brazil) (P < 0.05)
- MTA Fillapex® (Angelus, Brazil) showed poor bond strength after using both normal saline and CHX compared to AH Plus® (Dentsply, Maillefer, Ballaigues, Switzerland).
Comparison of mean values of push-out bond strength (MPa) at coronal and middle in Group I, II, III, and IV (n = 10).
| Discussion|| |
Three-dimensional obturation of the root canal is essential to ensure that the canal is completely sealed with the obturating material in order to prevent reinfection. Root canal sealer along with an obturating material helps to achieve a three-dimensional obturation thereby providing a monobloc effect, where obturating material, sealer, and root dentin all together act as a single unit.
Bond strength testing has become a popular method for determining the effectiveness of adhesion between endodontic materials and tooth structure. Among the various tests used to measure bond strength are microtensile strength test, shear bond strength test, and push-out bond strength test. Goracci et al.  reported that the push-out test is more reliable than other tests, and the push-out method better reflects the clinical status of the fracture to determine the bond strength of root canal sealer. This test has been used by many researchers to determine the bond strength.
The push-out test design has several advantages over the other tests. This test design makes it easy to align samples for testing and is less sensitive to small variations among specimens and to the variations in stress distribution during load application. The model has been shown to be effective and reproducible and this method allows root canal sealers to be evaluated even when bond strengths are low.  Bond strength is recorded in megapascals (MPa). For root canal sealers push-out bond strength determines the strength of adhesion of the sealer-dentin interface. Higher push-out bond strength indicates that higher amount of load is required to fracture the sealer dentin interface. Thus, indicating that the bond is stable and lesser likely to undergo dissolution.
Epoxy resin-based sealer, AH Plus® is successfully and commonly used for root canal treatment from more than a decade. Many studies have shown good bond strength values with this sealer. On the other hand, AH Plus® leakage studies have shown that leakage occurs between the sealer dentin interface which can lead to root canal failure and also it is incapable of producing hydroxyapatite-like layer and to induce cementogenesis. Moreover, it does not provide antimicrobial behavior and is not capable to heal the lesion.
MTA Fillapex® is an endodontic sealer based on MTA developed by Angelus (Londrina, Brazil), 2010. It is a paste-paste system containing Portland cement, bismuth oxide, and dehydrated calcium sulfate. The biological advantages of MTA-based sealers are the induction of new tissue formation including root cementum and the induction of healing of lesion. It is also engineered to penetrate into lateral canals and is highly radiopaque and provides a constant release of calcium ions maintaining a high pH which elicits antibacterial effects. MTA-based sealers were introduced with the idea of sealer that contains superior physical and biological properties.
Sealers and irrigating solutions are both chemicals and thus some amount of interaction between the two categories is to be expected. Whether this reaction is synergistic or antagonistic or does not affect each other in either way is what the chief objective of this study was.
NaOCl, the most commonly used irrigant in endodontics, has many desirable qualities but is not able to remove the smear layer. Thus, 17% EDTA is used for this purpose, which opens up the dentinal tubules. This allows for better penetration of irrigants into the dentinal tubules. CHX is a broad spectrum bactericidal irrigant which is highly active against Enterococcus Faecalis. It also has the advantage of substantivity. Carrilho et al.  evaluated the effect of CHX on bond strength of resin-based sealers and found that there was a significantly better preservation of bond strength with CHX. It acts as an MMP inhibitor and prevents collagen disintegration, thus allowing better penetration of resin sealers into the collagen meshwork. All interactions of irrigants should be prevented by using normal saline in between as they form different precipitates which interfere with bonding.
In this study, AH Plus® was the best performer, showing the highest values of push-out bond strength in the coronal one-third after CHX was used as the final irrigant. This could be because CHX itself increases the bond strength of resin-based sealer and also more number of dentinal tubules is present in the coronal third. More the dentinal tubules present, more will be the resin penetration and resin tag formation, which leads to higher bond strength of sealer.
Push-out bond strength of AH Plus® is much higher than MTA Fillapex® after using either normal saline or CHX as the final irrigant. The probable reasons of higher push-out bond strength for AH Plus® could be the formation of a covalent bond by an open epoxide ring to any exposed amino groups in collagen, very low shrinkage while setting, long-term dimensional stability, inherent volumetric expansion of AH Plus® may have contributed to the superior bond strength of AH Plus® .
There was no statistically significant difference to be found between the push-out bond strength values of AH Plus® after using either CHX or saline as the final irrigant in the coronal one-third. This pattern was replicated when results were evaluated for the middle one-third segment when AH Plus® was used as a sealer.
When MTA-based sealer was used it showed a significantly higher bond strength in the middle one-third as opposed to be coronal one-third, both after the use of normal saline and 2% CHX. A comparison of the push-out bond strength (intergroup) shows that irrespective of the root canal segment or the final irrigant used, AH Plus® showed higher values across the board.
Results can vary because of the presence of smear layer. The protocol of smear layer removal would also have been aggressively followed to improve the results. Removal of smear layer allows better penetration of resin-based sealer and improves the bond strength. It has been reported that EDTA decalcified dentine to a depth of 20-30 μm in 5 min.  Many studies have shown that paste-type chelating agents, while having a lubricating effect, do not remove the smear layer effectively when compared to liquid EDTA.  Thus, an aqueous form of EDTA should be used.
According to Torabinejad, MTA should not interact with EDTA because it interferes with the setting of MTA. Thus, complete removal of EDTA is necessary from the canal. However, Torabinejad has concluded from various studies that presence of smear layer does not affect the setting property of MTA or MTA-based sealers. 
Sagsen et al. did a study to compare the push-out bond strength of iRoot SP, MTA Fillapex, and AH Plus endodontic sealers to root canal dentine and they concluded that the iRoot SP and AH plus had significantly higher bond strength values than the MTA Fillapex (P < 0.05).  Similar study was done by Sonmez et al. (2012) where they evaluated push-out bond strength of MTA Fillapex and compared it with ProRoot MTA and AH Plus. They concluded the results as follows: ProRoot MTA > AH Plus > MTA Fillapex. Statistically significant differences were found among all groups.  Mandava et al. (2014) did a study to evaluate and compare the effect of two resin sealers AH plus (Dentsply, Germany) and MetaSEAL (Parkell, USA) and an MTA sealer MTA Fillapex (Angeles, Brazil) on the fracture resistance of endodontically treated teeth. They concluded that AH Plus showed better fracture resistance among the sealer groups. Statistically, no significant difference was found between MetaSEAL and Fillapex groups. 
The results obtained in this study are concurrent with the conclusions of the authors mentioned above.
In this study, to accurately determine the bond strength of MTA Fillapex® (Angelus, Brazil) canal could have been completely filled with sealer in order to reduce the interfaces. This will lead to primary monobloc formation. The use of gutta-percha with MTA sealer leads to secondary monobloc formation. In this case during push-out test, it is difficult to determine that fracture occurs at sealer-dentin interface or gutta-percha sealer interface. Thus, with monobloc formation accurate determination of fracture at sealer-dentin interface can be done. If above-mentioned criteria would have been followed then results could have been better with MTA Fillapex® (Angelus, Brazil).
| Conclusion|| |
Within the limitations of this study, the conclusions drawn from this study are as follows:
- Among both the sealers AH Plus® (Dentsply, Maillefer, Ballaigues, Switzerland) and MTA Fillapex® (Angelus, Brazil), AH Plus® (Dentsply, Maillefer, Ballaigues, Switzerland) have shown better results after using both normal saline and CHX
- MTA Fillapex® (Angelus, Brazil) has shown poorer bond strengths after using either normal saline or CHX
- Push-out bond strength after using CHX is higher than normal saline for both the groups when either AH Plus® (Dentsply, Maillefer, Ballaigues, Switzerland) or MTA Fillapex® (Angelus, Brazil) was used as a sealer
- Push-out bond strengths after using normal saline were found to be lower than CHX when either sealer was used
- AH Plus® (Dentsply, Maillefer, Ballaigues, Switzerland) sealer after using CHX has shown the best results among all groups.
MTA Fillapex® (Angelus, Brazil) root canal sealer had low adhesion strength to root dentine. Further studies are required to check the efficacy of MTA-based sealer with different irrigants.
Routine use of CHX as the last irrigant just before the insertion of a sealer into the root canal system may lead to significant increase in longevity of root canal treatment.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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