|Year : 2019 | Volume
| Issue : 1 | Page : 57-62
A comparative evaluation of the push-out bond strength of a resin-based sealer (AH Plus™) when two different intermediate irrigants are used, with and without a root canal brush: In vitro study
Ishan Ahmed, Shalini Devindernath Aggarwal, Anita Sanap, Vinay Rai, Swapnil Khadtare, Poorva Kurtarkar
Department of Conservative Dentistry, Dr. D.Y. Patil Dental College and Hospital, Dr. D. Y. Patil Vidyapeeth, Pimpri, Pune, Maharashtra, India
|Date of Web Publication||19-Jun-2019|
Dr. Shalini Devindernath Aggarwal
Department of Conservative Dentistry and Endodontics, Dr. D. Y. Patil Dental College and Hospital, Pimpri, Pune - 411 018, Maharashtra
Source of Support: None, Conflict of Interest: None
Aims: The aim of this study was to evaluate and compare the push-out bond strength (POBS) of a resin-based sealer (AH Plus™) when 95% isopropyl alcohol (IA) or 10% citric acid (CA) was used as an intermediate irrigant, with and without a Canal Brush™.
Settings and Design: In vitro laboratory study.
Subjects and Methods: After due processing, thirty human teeth were split into three main groups. As per the grouping, either 95% IA or 10% CA was used as intermediate irrigants. The control group used no intermediate irrigant. Each of these three groups was further split into two subgroups, each containing five samples. All the samples were subjected to cleaning and shaping with ProTaper rotary files (PTUN) up to size F2 using NaOCl and saline as the irrigants. The canals were then irrigated with 5.25% NaOCl during instrumentation and then were rinsed with an intermediate irrigant (either 95% IA or 10% CA) as per the specifications of that particular group. All the samples were then irrigated with Chlorhexidine Gluconate (CHX) as the final irrigant and one subgroup from each main group was further cleansed with a canal brush. The discs were then subjected to assess the POBS using the universal testing machine.
Statistical Analysis Used: Statistical analysis was done using Tukey-Kramer's multiple comparison test, Student's unpaired t-test, and one-way ANOVA test.
Results: The combined usage of CA with Canal Brush™ gave the highest (statistically significant) POBS value. The worst performers were the two subgroups in which no intermediate irrigant was used. The usage of IA and CA as intermediate irrigants did not lead to statistically significant results when no canal brush was used.
Conclusions: Within the limitations of this study, it was concluded that the use of CA and IA with canal brush significantly increased the POBS of the resin-based sealer.
Keywords: Canal brush, citric acid, intermediate irrigants, isopropyl alcohol, parachloroaniline, push out bond strength
|How to cite this article:|
Ahmed I, Aggarwal SD, Sanap A, Rai V, Khadtare S, Kurtarkar P. A comparative evaluation of the push-out bond strength of a resin-based sealer (AH Plus™) when two different intermediate irrigants are used, with and without a root canal brush: In vitro study. Endodontology 2019;31:57-62
|How to cite this URL:|
Ahmed I, Aggarwal SD, Sanap A, Rai V, Khadtare S, Kurtarkar P. A comparative evaluation of the push-out bond strength of a resin-based sealer (AH Plus™) when two different intermediate irrigants are used, with and without a root canal brush: In vitro study. Endodontology [serial online] 2019 [cited 2020 Jan 29];31:57-62. Available from: http://www.endodontologyonweb.org/text.asp?2019/31/1/57/260534
| Introduction|| |
The success of endodontic treatment depends on the eradication of microbes from the root canal system and prevention of reinfection. To achieve this, effective irrigation is of utmost importance. No single irrigant can serve this function completely. Optimal irrigation can be achieved using two or more irrigants, in a specific sequence, to achieve safe and effective irrigation.
Sodium hypochlorite (NaOCl) is a potent antimicrobial agent, killing most bacteria instantly on direct contact. NaOCl is the only root-canal irrigant that dissolves necrotic and vital organic tissue. This tissue dissolving property of NaOCl makes it one of the most preferred irrigant till date. Several authors recommend irrigation of the root canal system in a protocol where NaOCl is followed by the usage of CHX as an irrigant. Depending on its concentration, chlorhexidine gluconate (CHX) can have both bacteriostatic and bactericidal effect. The uptake of CHX onto teeth is reversible. This reversible reaction of uptake and release of CHX leads to substantive antimicrobial activity and is referred to as “substantivity.”
It was, however, found that the presence of NaOCl in the root canal and then irrigation with CHX will produce an orange-brown color precipitate, called para chloroaniline (PCA). This precipitate could interfere with the bonding of sealer and its bond strength. Adhesion in the root canal system is one of the most important factors that will decide the long-term success or failure of an endodontic treatment.
Ree and Schwartz (2010) in their seminal paper have described the limitations of bonding within the root canal system and have concluded that in addition to the root canal geometry which is unfavorable, the effect of irrigants and their interactions leads to compromised adhesion of root canal sealers in the root canal system., The rationale of this study is to evaluate the push-out bond strength (POBS) obtained after these variables are used.
| Subjects and Methods|| |
Roots with single canals were taken for this study. Radiographs were taken to check the canal curvature and roots having canal curvature more than 5° were discarded. Thirty teeth with root curvature within 5° were selected for this study. All teeth were autoclaved for disinfection. Teeth were decoronated at the cemento-enamel junction (CEJ) with a diamond disk, and roots were then randomly allocated to the respective groups. Sectioning of the decoronated roots was done 2 mm away from the CEJ and slices of 4 mm thickness were prepared. All samples were then subjected to cleaning and shaping with ProTaper rotary files (PTUN) up to size F2 using NaOCl and saline as the irrigants. The canals were irrigated with 5.25% NaOCl during instrumentation and then were rinsed with an intermediate irrigant (95% isopropyl alcohol [IA] or 10% citric acid [CA]). All samples were irrigated with CHX as a final irrigant with or without canal brush. Ten samples were irrigated with 95% IA as an intermediate irrigant with or without the CanalBrush™ and another 10 samples were irrigated with 10% CA as an intermediate irrigant with or without the canal brush. All the samples were then dried with paper points. In the groups where canal brushes were used, it was used without drying the slice of dentin irrigated with CHX and was used for a period of 30 s, at 250 rpm, and 1.5 torque settings in an X-Smart Plus machine from Dentsply. According to the Intermediate irrigant and the use of root canal brushes as mentioned above, all samples were divided into six groups:
- Group 1a: 5.25% NaOC) and 2% chlorhexidine/CHX were used without the use of the intermediate irrigants and with the canal brush (n = 5). Group 1b: 5.25% NaOCl and 2% Chlorhexidine/CHX were used without the use of the intermediate irrigants but without the canal brush (n = 5). Group 2a: 95% IA as an intermediate irrigant with canal brush (n = 5)
- Group 2b: 95% IA as an intermediate irrigant without the canal brush (n = 5)
- Group 3a: 10% CA as an intermediate irrigant with canal brush (n = 5)
- Group 3b: 10% CA as an intermediate irrigant without root canal brush (n = 5).
AH Plus® (Dentsply, Maillefer, Ballaigues, Switzerland) was then used to fill the root canal space completely. All the samples were then stored in the humidor at 37°C for 24 h. Each sample was observed with loupes under ×4 magnification for any signs of physical deformation such as cracks and fissures. Any samples showing signs of physical deformation were immediately discarded. The exact thickness of each disk was measured with a digital caliper to be within the range of 4 ± 0.2 mm.
The area under load was calculated by:
Area = ½ × (circumference of coronal aspect + circumference of apical aspect) × thickness.
The push-out value in MPa was calculated from force (N) divided by area in mm2. The disks were then subjected to assess the POBS using the universal testing machine loaded with a 0.45 mm diameter stainless steel plunger, at a speed of 0.5 mm/min until bond failure occurred.
Statistical analysis was done using Tukey-Kramer's multiple comparison test, Student's unpaired t-test, and one-way ANOVA test.
| Results|| |
The results obtained at the end of this study showed without a doubt that the usage of a canal brush at the end of an irrigation protocol which includes both NaOCl and CHX, led to a statistically significant improvement in the POBS of the sealer [Figure 1].
|Figure 1: Mean push-out bond strength values in MPa and mean load values in N|
Click here to view
The group that performed the best was the one in which 10% CA was used as an intermediate irrigant along with a canal brush at the end of the irrigation protocol. The POBS of this group was higher than that seen in any of the other subgroups [Figure 1].
The group that did the next best was the one in which IA was used along with a canal brush. The subgroups not using the canal brush were found to be poorer performers, and there was a statistically significant difference in the POBS achieved in the groups with canal brush.
However, the intergroup comparison between the IA and CA groups where the canal brush was not used was not statistically significant.
The intergroup comparison showed a significant difference in both the mean values (N) and POBS (MPa).
Thus, it follows that the combined usage of CA with canal brush gave the highest (statistically significant) POBS value. The worst performers were the two subgroups in which no intermediate irrigant was used. The usage of IA and CA did not lead to statistically significant results when no canal brush was used.
Thus, it may be safe to conclude that, when the canal brush was used in tandem with CA, the POBS was the best. Thus, clinically, we might see a benefit of an improved long-term prognosis if an intermediate irrigant was used where both NaOCl and CHX were to be used.
| Discussion|| |
The cleaning of root canal system is done using a set protocol of irrigating solutions. The most commonly used irrigant – NaOCl has been used in various concentrations and time periods along with a variation of increasing the temperature of the solution. In the presence of water, it ionizes into Na+ and the hypochlorite ion, OCl− and establishes equilibrium with hypochlorous acid (HOCl). At a pH of 9 and above, chlorine in the form of OCl− predominates, whereas at acidic and neutral pH, HOCl is predominant. HOCl imparts antibacterial activity, whereas hypochloric acid disrupts various important and vital functions of the bacterial cell which results in cell death.,
The two desirable properties that NaOCl should have, but doesn't, are the properties of substantivity and Smear Layer removal. It is to incorporate these two properties in an irrigation protocol for disinfection of the root canal system that chlorhexidine and acidic solutions such as CA and ethylenediaminetetraacetic acid (EDTA) were introduced into the irrigation protocols.
A suggested irrigating protocol proposed by Zehnder to treat the radicular dentin before obturation consists of irrigation with NaOCl to dissolve the organic tissue components, irrigation with EDTA to get rid of the smear layer, followed by irrigation with CHX to increase the antimicrobial spectrum and impart substantivity.
Chlorhexidine provides dentin substantivity leading to a prolonged antimicrobial effect on the root canal system, as it binds to hard tissue. It is the acids which help to clear away the debris accumulated post the use of NaOCl and they also lead to mild dentinal dissolution leading to a funneling of the dentinal tubules that exist perpendicular to the long axis of the tooth. The activity of chlorhexidine depends on its pH which is also reduced greatly in the presence of organic matter.
Chlorhexidine permeates the cell wall of the microbes or outer membrane and attacks the cytoplasm of the bacteria or inner membrane or the yeast plasma membrane. In high concentrations, chlorhexidine causes the intracellular components to coagulate.,
Chlorhexidine is free of some of the unwanted properties of NaOCl (i.e, strong irritation at the periapex and bad smell). However, CHX cannot replace NaOCl by itself as it has no tissue-dissolving capability and just like NaOCl has no effect on the smear layer and biofilm.
Residual organic tissue has a negative effect on the quality of the seal that is achieved by the permanent root canal filling and necessitates the use of NaOCl during root canal instrumentation. Chlorhexidine, unlike acidic formulations and NaOCl, does not cause dentin to erode and therefore 2% chlorhexidine is a preferred choice for maximized antibacterial effect toward the end of the chemomechanical preparation.
To overcome all the drawbacks and incorporate substantivity and cleansed dentinal walls, it was recommended to use NaOCl followed by Chlorhexidine and then a final flush of either EDTA or CA.
Basrani et al. in 2007 showed that an intermingling of the NaOCl with chlorhexidine led to the formation of PCA. The presence of this viscous dark brown precipitate was first reported by Vivacqua-Gomes et al. in 2002. The orange-brown color of the precipitate formed is a result of chlorhexidine getting hydrolyzed into smaller fragments, due to breaking of the bond between nitrogen and carbon, leading to the formation of a by-product-PCA.
These findings are clinically relevant, as it was conclusively established that PCA is toxic, and as an aromatic amine, the primary toxic effect is methemoglobin formation. In the root canal system, this precipitate, if formed, occludes the dentinal tubules,, can lead to discoloration of tooth being treated, and might interfere with the sealing ability of root canal fillings.,,,
However, the chemical composition of this precipitate is questionable because through nuclear magnetic resonance spectroscopy analysis, it was observed that a mixture of chlorhexidine acetate and NaOCl does not produce PCA.
The products formed are parachlorophenylguanidyl -1.6-diguanidyl-hexane and parachlorophenylurea. It was shown that mixing EDTA with chlorhexidine creates a white precipitate without PCA.
It has thus been recommended to use a flush of normal saline in between the usages of NaOCl and chlorhexidine to avoid interaction. Further, an intermittent intracanal flush of IA, 50% CA, or phosphoric acid has been recommended to remove residual NaOCl, before using chlorhexidine to prevent the formation of PCA.,,,
IA has been known to prevent the formation of the precipitate, while saline, distilled water, or CA is only capable of minimizing it.
The decrease in the bond strength of AH Plus™ is statistically significant in the presence of this precipitate.
Thus, if an irrigation protocol has to include both NaOCl and chlorhexidine as irrigants to benefit from their respective attributes, then a way has to be found to prevent the interaction of the two solutions, or at the least, to use an intermediary which neutralizes the action of the irrigant being used first. Another option would be to physically remove the precipitate which has formed. To this end, endodontic canal brushes could be used to physically sweep away the precipitate.
A rotary handpiece-attached microbrush was developed by Ruddle in 1998 to help remove the smear layer and debris from instrumented root canal walls.
Both the Ruddle brush™ and Canal Brush™ fit into the category of canal brushes.
Roeko CanalBrush™ (Coltene Whaledent, Langenau, Germany) is an endodontic microbrush that was made commercially available. This microbrush has high flexibility and is molded entirely from polypropylene and can also be used manually with a rotary movement. However, it is more efficacious when it is attached to a contra-angled handpiece and is used at 600 rpm. Weise et al. demonstrated that the use of this small and highly flexible CanalBrush™ along with an irrigant removed debris more effectively from simulated canal irregularities and extensions.
Many in vitro studies have been conducted by researchers to test whether or not endodontic brushes improve debris and smear layer removal from the root canals.,
Garip et al. demonstrated that, in the middle and apical part of the root canal where the canal configuration is narrow and where it was in close contact with the root canal surface, the use of canal brush led to a cleaner surface.
In this study, the canals were irrigated with 5.25% NaOCl during instrumentation and then were rinsed with an intermediate irrigant (95% IA or 10% CA).
The use of IA as an intermediate flush between NaOCl and chlorhexidine prevents the formation of the precipitate (PCA) because alcohol is a vaporescent, tensioactive agent, it is overly electronegative and can have deeper penetration into the tubules to remove the residual NaOCl present in the canals.
CA as an intermittent irrigant allowed the least amount of PCA formation in the root canal system. Use of a small and highly flexible canal brush with irrigating solutions removes debris effectively from root canal irregularities and extensions. Canal brush has high efficacy when attached to contra-angled handpieces and used at speeds of 600 rpm.
A canal that is completely filled with the sealer is equivalent to a thick layer of sealer. Sealer alone was used to fill the prepared canals only to allow a distinct measurement of the bond strength of the sealer-dentin interface.
A push-out approach was employed, in particular, to dynamically test the fatigue resistance of adhesive-dentin bonds in the root canal space.,,, In this method, load is applied through a plunger mounted in the universal testing machine. The plunger must provide near complete coverage of the testing material without touching the root canal wall. This method is useful to test adhesion of root canal sealers and retention of posts luted in root canals.
Goracci et al. expressed that push-out technique was more reliable and precise than the microtensile technique for measurement of bond strength to dentin and should be run to suit the convenience of providing specimens and statistical analysis. Providing 2 mm thick specimens eliminated the probability of nonuniform stress distribution.
CA should be further studied for its use as an intermediate irrigant between NaOCl and chlorhexidine as it will improve the cleaning of the root canal walls and will improve the lateral penetration of sealer into the tubules.
Furthermore, we have to consider a few drawbacks of this study, i.e., sealer was used to completely fill-up the canal space, which is not advocated by many studies. Moreover, in this study, the apical segment of the root canals was not subjected to POBS.
In a push-out test, punch diameter may affect the bond strength. No effect was observed when the diameter was 90% of the canal diameter, but bond strength was lower when the punch diameter was 50%–60% of the canal size. In push-out tests, it is difficult to determine whether failure occurred at dentin-sealer interface or at sealer gutta-percha interface, so evaluation should be made by scanning electron microscope analysis.
The results obtained at the end of this study showed without a doubt that the usage of a canal brush at the end of an irrigation protocol which includes both NaOCl and CHX, led to a statistically significant improvement in the POBS of the sealer. The best performing group was the one in which CA was used as an intermediate irrigant along with a canal brush at the end of the irrigation protocol. The POBS of this group was higher than that seen in any of the other subgroups. The group that did the next best was the one in which IA was used along with a canal brush. The subgroups not using the canal brush were found to be poorer performers and there was a statistically significant difference in the POBS achieved in the groups with canal brush. However, the intergroup comparison between the IA and CA groups where the canal brush was not used was not statistically significant. The intergroup comparison showed a significant difference in both the mean values (N) and POBS (MPa). Thus, it follows that the combined usage of CA with canal brush gave the highest (statistically significant) POBS value.
Thus, it may be safe to conclude that, when the canal brush was used in tandem with CA, the POBS was the best. Thus, clinically, we might see a benefit of the long-term prognosis if an intermediate irrigant was used with a canal brush where both NaOCl and chlorhexidine were to be used.
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Conflicts of interest
There are no conflicts of interest.
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