| Abstract|| |
Aim: Comparative assessment of apical sealing ability of a novel Smart-Seal System, Resilon, and conventional Gutta-Percha system using a bacterial leakage model.
Materials and Methods: Seventy freshly extracted human single rooted teeth with fully formed apices were randomly divided into three groups (20 each) and two control groups (5 positive and 5 negative). Teeth were de-coronated, and roots were standardized to a working length of 16 mm. Root canal preparation was done with rotary pro-taper file system in all groups. Group A was obturated using Smart-Seal system (Hydrophilic), Group B using Resilon/Epiphany system (Hydrophilic), and Group C using Gutta-Percha (GP)/AH plus system (Hydrophobic) in a single cone technique. Using Enterococcus faecalis, a split chamber bacterial leakage model was developed to evaluate the sealing ability of three obturation systems. Samples will be monitored every 24 hours for 60 days.
Results: All three groups have shown leakage. Novel Smart-Seal System and Resilon have shown similar results and relatively lesser samples leaked in comparison to GP obturations at the end of the observation period. There was no significant difference amongst Resilon and Smart-Seal System (P > 0.05) but there was a significant difference amongst them when compared to GP obturations (P < 0.05).
Conclusion: Hydrophilic obturations of the root canal shows a better resistance to bacterial leakage as compared to hydrophobic obturations.
Keywords: Enterococcus faecalis; gutta-percha; hydrophilic; hydrophobic; resilon; smart-seal system
|How to cite this article:|
Hegde V, Arora S. Sealing ability of a novel hydrophilic vs. conventional hydrophobic obturation systems: A bacterial leakage study. J Conserv Dent 2015;18:62-5
|How to cite this URL:|
Hegde V, Arora S. Sealing ability of a novel hydrophilic vs. conventional hydrophobic obturation systems: A bacterial leakage study. J Conserv Dent [serial online] 2015 [cited 2019 Jul 16];18:62-5. Available from: http://www.jcd.org.in/text.asp?2015/18/1/62/148898
| Introduction|| |
Since its introduction in 1914 by Callahan, gutta-percha (GP) has been the standard obturation material utilized in root canal therapy. The three main functions of obturation are to negate any bacteria remaining within the root canal system; to stop the inflow of periapical tissue-derived fluid from re-entering the root canal and the availing in surviving bacteria; and to obviate coronal leakage of bacteria.  Even though GP expresses many benign properties, including chemical stability, biocompatibility, non-porosity, radiopacity and the ability to be manipulated and abstracted, it does not always meet the three main functions of obturation. GP does not bond to the internal tooth structure, resulting in incomplete seal.  This promotes a poor barrier to bacteria microleakage and is considered to be one of the most fragile phase in root canal therapy.  Till today no available material and/or technique gives rise to a consummate seal of the entire root canal system. Therefore, root canal filling materials should be introduced that possess an amended capacity to obviate bacterial ingress in the long term.  Another consequential characteristic of GP that plays a paramount role in its inability to meet the desired results is its hydrophobic nature. In advanced Endodontics, application of heat is a paramount adjunct in order to either provide a bettter flow and adaptation or searing of the GP at the orifices of the canals in the pulp chamber. GP on application of heat leads to shrinkage with time and subsequent microleakage. In the wake of this concept in order to ameliorate the bonding of the material to the canal walls and to negate the application of heat, materials having hydrophilic properties were introduced. Resilon/Epiphany (Pentron Clinical Technologies, Wallingford, CT) is the first obturation system to claim the ability to compose a "monoblock" between the canal walls and obturation material. Resilon is a polycaprolactone polymer which contains bioactive glass and radiopaque fillers. Epiphany is a dual-remedy resin sealer and primer, which bonds to both the dentinal wall and the Resilon cone. 
The most recent advancement in endodontic obturating materials utilizes a hydrophilic polymer in the root canal, The Smart-Seal System (Prosmart - DRFP Ltd. Stamford, UK). The system consists of premade obturation points (Pro-Points) containing a polyamide core with an outer bonded hydrophilic polymer coating and an accompanying sealer which is further provided with polymer powder to be incorporated during the manipulation of the sealer. The endodontic points are designed to expand laterally without expanding axially by absorbing residual dihydrogen monoxide from the instrumented root canal space and the naturally present moisture in the dentinal tubules.  The Pro-Point showed an approximately 14% expansion after 20 minutes.  The inner core of Pro-points is composed of two proprietary nylon polymers: Trogamid T and Trogamid CX. The polymer coating is a cross-linked copolymer of acryl-o-nitrile and vinyl-pyrrole done, which has been polymerized and cross-linked utilizing allyl methacrylate and a thermal initiator. The lateral expansion of Pro-points is claimed to occur non-uniformly, with the expandability depending on the extent to which the hydrophilic polymer is pre-stressed (that is contact with a canal wall will reduce the rate or extent of polymer expansion).  The advent of more prevalent taper master cones that proximately match the size and taper of nickel-titanium (NiTi) rotary files has rejuvenated interest in single-cone obturation techniques. , Pro-points are designed to match the sequence of NiTi rotary files, in turn single cone obturation is recommended for Pro-Points. Currently no literature, has compared the leakage resistance of a single-cone hydrophobic obturations with that of hydrophilic obturation. The purport of this investigation was to compare the sealing ability of a novel Smart-Seal system and Resilon, a synthetic polymer-predicated, and a GP obturation system utilizing a split chamber bacterial leakage model. Enterococcus faecalis was selected for use in this study because it is implicated in the etiology of secondary endodontic infections. 
| Materials and Methods|| |
Seventy freshly extracted human single-rooted teeth with straight canals and mature apices were randomly divided into three test groups (20 canals each) and two control groups (5 positive and 5 negative). Teeth were decoronated, leaving approximately 16 mm of root. They were subsequently immersed in 6% NaOCl for 6 hours and stored in distilled water. Working length (WL) was determined by subtracting 1 mm from the length at which a # 10 K-file was visible at the foramen. Root canal preparation was subjected to crown down technique with rotary pro-taper files till file size F2 with full sequence. After each file, 1 ml of 3% sodium hypochlorite was used as an irrigating solution delivered with 27 gauge side venting needles inserted 3mm from the apex. EDTA gel (RC Help, Prime Dental Products Pvt. Ltd., Mumbai, India) was used as a lubricant. This was followed by a rinse of 3 ml of 17% aq. EDTA (Dent Wash, Prime Dental Products Pvt. Ltd., Mumbai, India) for 1min. Upon completion of instrumentation, the canals were dried using sterile absorbent points.
The Specimens were divided into three groups (N = 20). In Group A Teeth were obturated with 0.06 taper master polyamide polymer cone using, single cone technique, with no accessory cones being used. The sealer used in this group was Smart-Paste Sealer (Prosmart DRFP Ltd. Stamford, UK), an epoxy amine resin based sealer with active polymer powder. In Group B obturation was done using the Resilon/Epiphany system. A dry paper point was soaked with Epiphany primer and used to coat the root canal walls. The Resilon core material master point was then coated in Epiphany sealer and inserted into the canal. Once the obturation was completed the coronal surface was light cured for 40 seconds. Group C was obturated using GP/AH Plus system using single cone technique.
Positive controls were not obturated. Except for the apical 2 mm and the occlusal table, all teeth in the experimental and positive control groups received three coats of clear nail polish. Negative control teeth were cleaned, shaped, and obturated with GP/AH plus single cone technique. Three coats of clear nail polish covered 100% of the root surface. Teeth were incubated in 100% humidity at 37°C for 3 weeks before the introduction of E. faecalis.
The bacterial leakage model used was adapted from Khayat et al.  The tapered ends of 2 mL Eppendorf plastic tubes (Eppendorf-Elkay, Shrewsbury, MA) were resected and the teeth inserted with the apex pointing down. The junction between the tube and the extruded root was sealed with hot glue. Three coats of clear nail polish were placed over the set glue. The tooth and plastic tube assembly was snugly fit into a hole in the cap of a scintillation vial (Fischer Scientific, Pittsburgh, PA), and the junction was sealed with hot glue and a coat of nail polish. All tooth-tube-cap assemblies were sterilized with ethylene oxide gas and the 20-mL glass scintillation vials were autoclaved. The root of each tooth was immersed approximately 2 mm into the Difco Purple Broth Base (Beckton Dickinson, Sparks, MD) contained in the scintillation vials. The indicator changes color from purple to yellow when the pH drops below 6.8. The sterile broth and mounted teeth were observed for 5 days to ensure no contamination occurred before inoculation. The inoculation consisted of 0.1 mL of a 20-hour culture of E. faecalis OG1X at 107 colony-forming units/mL (CFU/mL) grown in brain heart infusion (BHI). E. faecalis OG1X is a derivative of an oral isolate that has cariogenic potential.  A standard curve of E. faecalis cell numbers versus optical density was formed and used to determine the culture dosage necessary for inoculation. The top chambers were reinoculated every 7 days. Gram staining was performed when the broth changed color, and light microscopy was used to confirm the presence of E. faecalis. Survival analysis and log-rank testing compared the survival curve patterns of the three groups. The Fisher exact test was used to compare leakage between all groups.
| Results|| |
Statistical Analysis was performed using SPSS Version 16. The survival curves are shown in [Figure 1]. All positive controls leaked within 24 hours; none of the negative controls leaked. Within the first 24 hours, 0 Smart-Seal System, 3 Resilon/Epiphany teeth, and 5 GP/AH Plus teeth leaked. At the end of week 1, 2 Smart-Seal System, 6 Resilon/Epiphany teeth, and 12 GP System teeth leaked. After 60 days, 9 Smart-Seal System, 10 Resilon/Epiphany teeth, and 18 GP/AH Plus teeth leaked [Figure 1]. Survival analysis and log-rank test showed no statistically significant differences between the groups with respect to leakage over time (P = 0.509) [Table 1]. The Fisher exact test also showed no significant difference in the number of teeth that leaked at the end of the observational period between different groups (P = 0.169) [Table 2].
|Figure 1: Graph showing survival analysis for the groups over the time period of 60 days|
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|Table 1: Total number of samples showing leakage/no leakage after 60 days|
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|Table 2: Fisher exact and long rank test for overall multiple comparison between the groups|
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| Discussion|| |
The ultimate goal of obturation is to avert the re-infection of root canals that have been biomechanically cleaned, shaped and disinfected by instrumentation, irrigation. Successful obturation requires the utilization of materials and techniques capable of densely filling the entire root canal system and providing a fluid tight seal from the apical segment of the canal to the canal orifice in order to avert re-infection.  Therefore, the goal of three-dimensional obturation is to achieve an impermeable fluid tight seal within the entire root canal system which will further avail in averting oral and apical microleakage.  The major demerit evaluated with GP is its inability to reinforce endodontically treated tooth. , GP does not chemically bond to the dentin wall that is does not compose the monoblock system. According to Teixeira et al.,  GP does not from a monoblock even with the utilization of a resin-based sealer such as AH plus, because the sealer does not bind to GP. Moreover, due to the hydrophobic nature of the GP cones the sealer tends to pull away from the GP on setting.  Numerous in vitro studies have shown that GP obturated teeth leak at high rates. There has been an effort to develop incipient obturation materials such as Smart-Seal System and Resilon that may provide a superior seal of the root canal by providing a "monoblock" that adheres and bonds to the dentinal wall. Within the parameters of this study, it did not appear that a consummate seal occurred for any of the systems tested, but the seal achieved with the hydrophilic obturations was far more superior to the hydrophobic system.
In this study Resilon/Epiphany system has shown high leakage percentages. This could be attributable to a higher film thickness and more predominant polymerization shrinkage as a result of single cone filling technique utilized in this study: It has antecedently been demonstrated that greater the thickness of the sealer, greater will be the volumetric shrinkage, which results in an increase in shrinkage stress. Moreover, it has withal been shown that Resilon core exhibits extensive surface thinning and weight loss after incubation with bacterial and salivary enzymes. Biodegradation of Resilon may thus contribute to the leakage of bacteria at the sealer-Resilon interface. Novel Smart-Seal System has shown significantly lesser leakage to the GP/AH Plus system. This can be attributed to the self-expanding nature of the polyamide polymer. A polymeric endodontic point that takes advantage of water-induced, non-isotropic radial expansion to adapt to canal irregularities.  The points can expand up to around 17% and will still give the same X-ray appearance as with conventional root-filling materials.  Using an E. faecalis bacterial leakage model, albeit not significantly different, both Smart-Seal System and Resilon/Epiphany showed less leakage than GP/AH Plus sealer. This may be caused, in part, by the longer setting time and low viscosity of AH Plus and Epiphany sealers.  Enhanced flow may result in less cracking and disseverment from the dentinal walls upon setting as well as sanction for better flow into adjunct canals and other irregularities. According to Timpawat et al., the utilization of bacteria to assess leakage is considered to be of more dominant clinical and biological pertinence that the dye penetration. Many Different strains of bacteria have been used to assess marginal leakage and this has lead to contradictory results.  The turbidity of the broth in the apical chamber is the first indication of contamination by microorganism.  A bacterial model system was used in this study because it is more clinically relevance. However, it does not quantify the amount of the bacteria that can penetrate through the canal. Therefore, the amount of leakage that could potentially lead to clinical failure is not quantified. Therefore, it is difficult to determine whether the lack of statistical significant observed in this study indicates into any clinical significance.  Future studies should include obtaining a more sizably voluminous sample size for a more significance as well as involving longer periods of evaluation. In integration, a quantitative analysis of microleakage and investigations into other characteristics of Smart-Seal System such as its ability to habituate to canal irregularities, solubility, dimensional stability, and antimicrobial properties would ameliorate assessment of the value of Smart-Seal System as an obturation material.
| Conclusion|| |
With the introduction of hydrophilic obturation techniques, the sealing ability achieved is of greater significance as compared to the conventional GP obturations. The hydrophilic nature of the material should be considered as an important factor when selecting an obturating system. Amongst the hydrophilic systems the Smart-Seal System shows a unique property of self-expanision along with the naturally occurring expansion due to hydrophilic nature. Furthermore clinical experiences would be required to validate the success of the hydrophilic obturation systems.
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Dr. Vibha Hegde
1101B Rajkamal Apt. Parel, Mumbai - 400 012, Maharashtra
Source of Support: None, Conflict of Interest: None
[Table 1], [Table 2]