|Year : 2021 | Volume
| Issue : 1 | Page : 41-45
|Effect of nonthermal atmospheric plasma on the push-out bond strength of epoxy resin-based and bioceramic root canal sealers: An in vitro study
Roopadevi Garlapati1, Kolluri Mohana Chandra1, Praveen Kumar Gali1, Bolla Nagesh1, Sayesh Vemuri1, N Gomathi2
1 Department of Conservative Dentistry and Endodontics, Sibar Institute of Dental Sciences, Guntur, Andhra Pradesh, India
2 Department of Chemistry, Indian Institute of Space Science and Technology, Thiruvananthapuram, Kerala, India
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|Date of Submission||25-Sep-2020|
|Date of Decision||25-Nov-2020|
|Date of Acceptance||12-Jan-2021|
|Date of Web Publication||05-Jul-2021|
| Abstract|| |
Aim: The aim of this study was to evaluate the effect of nonthermal atmospheric plasma (NTAP) on the bond strength of epoxy resin-based and bioceramic root canal sealers.
Materials and Methods: Freshly extracted forty (n = 40) single-rooted mandibular premolar teeth were divided into four groups (n = 10) based on the sealer used and NTAP application – Group 1: Epoxy resin-based sealer (AH Plus) without NTAP application, Group 2: Epoxy resin-based sealer (AH Plus) with NTAP application for 30 s, Group 3: Bioceramic sealer (BioRoot RCS) without NTAP application, and Group 4: Bioceramic sealer (BioRoot RCS) with NTAP application for 30 s. After NTAP application in Groups 2 and 4, all the samples were obturated using sealers according to their grouping protocols. Two-millimeter slices were obtained from each sample using hard tissue microtome, which were subjected to push-out bond strength (PBS) under the universal testing machine. Data were subjected to statistical analysis using one-way analysis of variance followed by the Post hoc tukey test. The level of statistical significance was set at P < 0.05.
Results: The PBS values were observed to be significantly higher in bioceramic sealer with NTAP application (Group 4) followed by epoxy resin-based sealer with NTAP application (Group 2).
Conclusion: NTAP application enhanced the PBS of bioceramic (BioRoot RCS) and epoxy resin-based (AH Plus) sealers compared to their control groups.
Keywords: AH Plus sealer; bioceramic sealer; nonthermal atmospheric plasma; push-out bond strength
|How to cite this article:|
Garlapati R, Chandra KM, Gali PK, Nagesh B, Vemuri S, Gomathi N. Effect of nonthermal atmospheric plasma on the push-out bond strength of epoxy resin-based and bioceramic root canal sealers: An in vitro study. J Conserv Dent 2021;24:41-5
|How to cite this URL:|
Garlapati R, Chandra KM, Gali PK, Nagesh B, Vemuri S, Gomathi N. Effect of nonthermal atmospheric plasma on the push-out bond strength of epoxy resin-based and bioceramic root canal sealers: An in vitro study. J Conserv Dent [serial online] 2021 [cited 2021 Aug 4];24:41-5. Available from: https://www.jcd.org.in/text.asp?2021/24/1/41/320673
| Introduction|| |
Successful endodontic treatment is dependent on the meticulous cleaning of the root canal system, the eradication of pathogenic microorganisms, and a three-dimensional filling of root canal space with an inert root canal filling material and attaining a fluid tight seal to prevent the ingress of microorganisms from the oral cavity and its spread to the periapical tissue.
Root canal sealers are used as a thin tacky paste which functions as a lubricant and luting agent during obturation allowing the core obturation material such as gutta-percha or other rigid materials to slide in and forms a fluid tight seal within the root canal. Sealers can fill voids, lateral canals, and accessory canals where core obturation materials cannot infiltrate. If the sealer does not perform its function, microleakage may cause endodontic treatment failure through the clinically undetectable passage of bacteria, fluids, molecules, or ions between the tooth and the restorative material. A great variety of endodontic sealers are available commercially, and they are divided into different groups according to their chemical composition.
Traditionally used root canal sealers are zinc oxide eugenol, calcium hydroxide, and glass ionomer-based sealers. Newer root canal sealers such as epoxy resin and bioceramic based are being developed to provide the improved properties. AH Plus sealer (Dentsply Maillefer, Ballaigues, Switzerland) is an epoxy resin-based sealer which contains diepoxide, calcium tungstate, N, N-dibenzyl-5-Oxanonane-diamine-1,9 TCD-diamine1-adamantane amine, and zirconium oxide. AH Plus is a widely used sealer for root canal filling due to its acceptable physical properties, low solubility, disintegration, apical sealing ability, good adhesion, antimicrobial action, and good biological properties. Baechtold et al. evaluated the adhesion capability of two sealing cement, namely MTA Fillapex and AH Plus, and reported that AH Plus sealer has greater adhesion than the MTA Fillapex.
Bioactive endodontic sealers have been developed to improve the quality of root canal obturation. BioRoot RCS (BC) (Septodont, St. Maur-des-Fosses, France) is the newest development of a bioceramic sealer. The powder mainly consists of tricalcium silicate, povidone, and zirconium dioxide. The liquid is an aqueous solution of calcium chloride with polycarboxylate. Contemporary studies on BC sealer have documented its several adequate characteristics, including its adhesive property, low dimensional change, proper radiopacity, and low solubility.
Adhesion and penetration are two important aspects to be considered in sealer selection. Studies have shown that bond strength and sealer penetration may be affected by pretreatment of root canal walls and by the type of sealer used. These procedures change the physical conditions of dentin by removing the smear layer, thereby opening the dentinal tubules and increasing the wettability of root canal dentin.
Recently, the possibility to generate nonthermal atmospheric plasma (NTAP) has enabled extending plasma applications to the treatment of root canal surfaces. The interest in plasma applications in dentistry is due to its several unique advantages over conventional approaches, such as the ability to penetrate into small and irregular root canal recesses and achieve bacterial decontamination without using potentially dangerous chemicals. NTAP has improved the bond strength between dentin and adhesive materials.
Previous studies have demonstrated that NTAP was effective and efficient in sterilization of endodontic instruments, other surgical instruments, elimination of persistent, nonaccessible biofilms, sterilization, and thorough disinfection of root canals. Raymond E. J. et al. used a plasma needle to observe the interactions between NTAP and dental tissues and concluded that plasma treatment allows cleaning of irregular and narrow channels and it is a novel tissue-saving technique. NTAP was an effective source of free radicals and have the property of eradicating microbial disinfection without causing destruction of the tissue. Whittaker et al. suggested that sterilization of surgical instruments with NTAP decreases the cross contamination during endodontic treatment.
Lu et al. used a reliable and user-friendly plasma jet device, which could generate NTAP, and it is directed into the root canal for disinfection without causing any painful sensation. Pan et al. investigated the feasibility of using NTAP in root canals infected with Enterococcus faecalis biofilms and concluded that NTAP was highly efficient in disinfecting the E. faecalis biofilms during root canal treatment.
To the best of our knowledge, there are no studies in the literature reporting the effect of NTAP on the bond strength of epoxy resin-based (AH Plus) and bioceramic (BioRoot RCS) root canal sealers. Hence, the main purpose of the present in vitro study was to evaluate and compare the effect of NTAP application on the push-out bond strength (PBS) of epoxy resin-based and bioceramic root canal sealers.
| Materials and Methods|| |
Freshly extracted forty (n = 40) single-rooted mandibular premolar teeth were selected. Crowns were decoronated below the cementoenamel junction using a low-speed hand piece, so that the lengths of all roots were adjusted to 15 mm. Patency of each root canal was checked using a size 10 K-file (Dentsply Maillefer, Ballaigues, Switzerland) and working length was established 1 mm short of the apex.
Cleaning and shaping procedures were performed using ProTaper Gold (Dentsply Sirona, USA) rotary nickel–titanium instruments. Canals were irrigated with 2 mL of 5.25% sodium hypochlorite (NaOCl) (Prime Dental Products, Maharashtra, India) between each file change followed by irrigating with 2 mL of 17% ethylenediaminetetraacetic acid (MD-Cleanser, META Biomed, Korea) to remove the smear layer formed after instrumentation. Root canals were finally flushed with 5 mL of distilled water and dried with paper points. All the samples (n = 40) were divided into four groups (n = 10):
- Group 1 (n = 10): Epoxy resin-based sealer (AH Plus) without NTAP application
- Group 2 (n = 10): Epoxy resin-based sealer (AH Plus) with NTAP application
- Group 3 (n = 10): Bioceramic sealer (BioRoot RCS) without NTAP application
- Group 4 (n = 10): Bioceramic sealer (BioRoot RCS) with NTAP application.
Nonthermal atmospheric plasma application
After cleaning and shaping of samples in Group 2 and Group 4, they were subjected to NTAP application. This was conducted at the Department of Chemistry, Indian Institute of Space Science and Technology, Thiruvananthapuram, Kerala. A glass reactor was used for NTAP application. This glass reactor consists of a 5-cm diameter and 30-cm long tube, evacuated by a mechanical pump, down to pressures lower than 2 Pa. Gas was allowed to fill the glass reactor up to a pressure of 10 Pa. NTAP was generated within the glass cylinder under vacuum by the action of an induced magnetic field from the current passing through an electrical coil surrounding the cylinder. Surfaces of the samples were treated using helium–argon gas at 60 W for 30 s. At the end of the process, radiofrequency was turned off before the samples were exposed to air.
In the control and experimental groups (after NTAP application), all the samples were obturated using the single-cone technique with size 25/.08 gutta-percha points (Dentsply Maillefer, Ballaigues, Switzerland) using AH Plus in Group 1 and Group 2 and BC sealer in Group 3 and Group 4, respectively. The roots were mounted on the self-cure acrylic resin cylinders and were subjected to hard tissue microtome (SRM Institute of Science and Technology, Kattankulathur, Chennai) to obtain 2-mm slices from the middle third of the root from each sample.
Push-out bond strength test
The obtained 2-mm slices were subjected to PBS test, and loading was performed using a universal testing machine (Instron Servohydraulic Testing System, Mechanical Department, GITAM, Visakhapatnam). The samples were placed on a base of a metal slab of universal testing machine to allow the free movement of the plunger. The compressive load was applied by exerting a download pressure on the surface of the test material in each sample, with the Instron probe moving at a constant speed of 1 mm/min. The plunger size of 1 mm had a clearance of approximately 0.2 mm from the margin of the dentinal wall to ensure contact only with the test materials. The maximum force which was applied to materials at the time of dislodgement was recorded in newtons. The PBS in megapascal (MPa) was calculated by dividing this force (N) by the surface area of the test material where N/2p × r × h, p is the constant 3.14, r is the root canal radius, and h is the thickness of the dentin slice in millimeters.
Data were entered in MS-Excel and analyzed in Version 21.0 (IBM Corp. Chicago, USA). Shapiro–Wilk test was applied to find the normality. Descriptive statistics were represented with mean and standard deviation (SD). 95% confidence intervals were calculated. One-way analysis of variance, followed by Post hoc tukey test , was applied to find significance. P < 0.05 was considered as statistically significant.
| Results|| |
[Table 1] shows the mean values and SD of the PBS (MPa) of all the groups. Results shown that NTAP-applied samples, i.e., Group 2 and Group 4, had a statistically significant increase in bond strength, more than twice that of their respective control groups, i.e., Group 1 and Group 3 (P < 0.05). Bioceramic sealer (BioRoot RCS) showed significant bond strength values compared to AH plus sealer without NTAP application (P < 0.05).
|Table 1: Mean push-out bond strength value of four different experimental groups|
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| Discussion|| |
The aim of endodontic therapy is not only elimination of microorganisms by cleaning and shaping of the root canal but also to ensure that the root canal system to be fluid free and that a single-block configuration is created that seals hermetically the root canal space. The major function of a root canal sealer is to fill imperfections and increase adaptation of the root canal filling material to the canal walls, failing which the chances of leakage and failure increase.
The ability of the PBS test is to evaluate the bonding strength surpasses that of other tests because it generates parallel fractures in the interfacial area of dentin bonding. However, a limitation of the PBS test is that it creates nonuniform stress distribution. In the present study, this limitation was prevented using 2-mm thick slices.
Root canal disinfection using NTAP can be considered as a special type of decontamination because of its importance in the endodontic procedures for a successful outcome. It has been reported that bacteria can enter dentinal tubules as deep as 500–1000 μm. NTAP has a capability of reaching deep into the complex root canal, i.e., up to 800 μm. NTAP creates reactive oxygen species, causing serious damage to microorganisms through irreversible oxidation of cell components. There is an unique advantage of direct contact with the bacteria using NTAP, which is not possible with conventional methods.
With respect to NTAP application, bioceramic sealer (Group 4) showed higher bond strength than epoxy resin-based sealer (Group 2). Lehman et al. reported that without NTAP application, the intertubular areas appear slightly roughened on etched dentin, smear plugs were removed from the tubules, and the collagen network is visible within the tubules and in the intertubular areas. With NTAP application, no collagen fibers are visible on this surface and the orifices of dentinal tubules appear irregularly enlarged, which results in the better penetration of root canal sealer into the dentinal tubules and could ensure higher mechanical retention of the root canal filling materials. This might be the possible reason for the increased PBS values of Groups 2 and 4 twice that of control groups, i.e., Group 1 and Group 3, in the present study.
The application of NTAP into the root canal walls provides a better bond strength while using bioceramic-based root canal sealers for obturation procedure. Hence, NTAP can be used as an adjuvant during endodontic treatment to increase the adhesion property of root canal sealers which might result in a successful outcome.
In the present study, compared to epoxy resin-based sealer (Group 1), bioceramic sealer (Group 3) showed higher bond strength. This may be attributed to the true self-adhesive nature of bioceramic sealer, which forms a chemical bond (through the production of hydroxyapatite during setting) with dentin. Moreover, it is hydrophilic and possesses low contact angle allowing it to spread easily over the root canal walls providing adaptation and good fluid tight seal. The results are in accordance with a previous study done by Ana Carrillo-Varguez AG et al. (2017) who reported that BC sealer with single-cone technique performed better adhesion than AH Plus to root canal dentin.
Srivastava et al. from their study observed that BioRoot RCS showed better bond strength to root dentin compared to AH Plus after using different irrigating solutions. BioRoot RCS showed better bond strength to root dentin compared to AH Plus probably due to setting reaction of the bioceramic-based sealer. It absorbs water from the dentinal tubules and forms calcium silicate hydrogel and hydroxyapatite compound. The hydroxyapatite which is present in the sealer undergoes a continuous process of crystal growth and binds chemically with the dentin. Being resin free, it is capable of flowing into the dentinal tubules with no shrinkage and provides excellent adhesion to dentin and gutta-percha and its ability to seal auxiliary canals. A study done by Dayanand Chole et al. reported that BioRoot RCS showed the highest bond strength than AH Plus and MTA Fillapex due to its true self-adhesive nature. According to Han and Okiji, the formation of a tag-like structure was suggested to be responsible for the BC sealer sealing ability and their bond strength to dentin.
Sagsen et al. (2011) evaluated the bond strength of two new calcium silicate-based and AH Plus endodontic sealers and found that AH Plus sealer had higher PBS values than MTA Fillapex because of the better flow and sealing ability of AH Plus sealer. In a study by Kumar et al., results revealed that the dislocation resistance of AH Plus to root canal dentin was significantly decreased by the use of NaOCl as a final irrigant. Reversal of the compromised PBS and also improved adhesion of epoxy resin-based sealer (AH Plus) to NaOCl-treated dentin was significantly increased when proanthocyanidin and bamboo salt were used as final irrigating solutions. Epoxy resin-based sealers (AH Plus) produces a better seal in the root canal, as they do not shrink, rather they expand and seal the root canal.
In a study done by Huang et al., bioceramic root canal sealers have shown excellent flow and appropriate film thickness, as well as favorable properties, including high calcium ion release, proper radiopacity, low dimensional change, and low solubility. From their observations, they concluded that BC sealers showed superior wetting and adhesion properties to the root canal dentin. BC sealers having excellent flow would obturate irregular spaces and penetrate into dentinal tubules, thus enhancing the seal between the root canal surface and sealers, this might contribute to the increased bond strength value of BC sealer in the present study.
As per the literature, the current in vitro study is the first one to evaluate and compare the effect of NTAP on the PBS of epoxy resin-based (AH plus) and bioceramic (BioRoot RCS) root canal sealers. However, this being an in vitro study, it cannot mimic the in vivo situation. The application of the NTAP in an in vivo condition is yet to be evaluated. For NTAP to reach the clinical use, future research activities should involve increasing numbers of dentists and move towards animal testing; on this path, assessing the safety of NTAP treatments and employing plasma sources that are realistically applicable in a clinical environment will be inevitable steps.
| Conclusion|| |
Within the limitations of this in vitro study, NTAP application significantly increased the PBS values of epoxy resin-based (AH Plus) and bioceramic (BioRoot RCS) root canal sealers. Bioceramic sealer with and without NTAP application has shown higher PBS values than that of epoxy resin-based sealer.
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Conflicts of interest
There are no conflicts of interest.
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Dr. Roopadevi Garlapati
Department of Conservative Dentistry and Endodontics, Sibar Institute of Dental Sciences, Takkellapadu, Guntur, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
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