| Abstract|| |
Background: Sealer penetration into dentinal tubules eliminates the pathways for bacterial leakage and entombs intratubular bacteria.
Aim: The aim of this study was to evaluate and compare the depth of radicular dentinal tubule penetration of five root canal sealers using confocal laser scanning microscopy.
Methods: Fifty freshly extracted single-rooted maxillary anterior teeth were used. After decoronation at the cementoenamel junction, they were prepared to ProTaper size F3. After irrigation with 5 mL smear clear, 5 mL 5% sodium hypochlorite and 5 mL distilled water alternatively, the samples were randomly divided into five groups (n = 10) and obturated by lateral compaction technique using the test sealers labeled by fluorescent rhodamine B dye (Mayor Diagnostics, Mumbai, India). Zinc oxide eugenol (ZOE) (Prime Dental Products), EndoREZ (Ultradent), Sealapex (SybronEndo), AH Plus (Dentsply Maillefer), and MTA-Fillapex (Angelus) formed the test groups. Teeth were then positioned in blocks of orthodontic resin. Three horizontal sections of 1-mm representing coronal middle and apical thirds were made and examined with Zeiss (laser scanning microscope [LSM] 780) confocal LSM. Images were analyzed using ZEN 2.1 software.
Statistical Analysis: Data were recorded and subjected to statistical analysis using one-way ANOVA test.
Results: Maximum penetration depth was demonstrated by AH Plus in the coronal and apical thirds, MTA-Fillapex in the middle thirds, while minimum penetration depth was seen in ZOE in the coronal and middle thirds and Sealapex in the apical thirds. None of the root canal sealers were able to penetrate the complete depth of radicular dentinal tubules.
Conclusion: While AH Plus and MTA-Fillapex showed the highest penetration into radicular dentinal tubules, ZOE and Sealapex demonstrated the least penetration.
Keywords: Confocal laser scanning microscopy; dentinal tubule; depth penetration; rhodamine B; root canal sealers
|How to cite this article:|
Mokashi P, Shah J, Chandrasekhar P, Kulkarni GP, Podar R, Singh S. Comparison of the penetration depth of five root canal sealers: A confocal laser scanning microscopic study. J Conserv Dent 2021;24:199-203
|How to cite this URL:|
Mokashi P, Shah J, Chandrasekhar P, Kulkarni GP, Podar R, Singh S. Comparison of the penetration depth of five root canal sealers: A confocal laser scanning microscopic study. J Conserv Dent [serial online] 2021 [cited 2021 Nov 30];24:199-203. Available from: https://www.jcd.org.in/text.asp?2021/24/2/199/327848
| Introduction|| |
Microorganisms with their by-products are mainly responsible for the initiation and maintenance of periapical inflammation. Canal preparation and shaping with the help of instruments and irrigants as well as intracanal medications helps disinfect and reduce the microbial load. The aim of obturation being to eliminate pathways of leakage from the apical and coronal directions and also to entomb the remaining bacteria usually present in the dentinal tubules. A favorable endodontic outcome can be predicted if the debris and contaminants are adequately removed, and the various filling materials and techniques used achieve a high degree of adaptability to the cleaned dentinal wall.
Achieving a complete three-dimensional seal of the root canal system is a great challenge. Cold lateral compaction with gutta-percha is the gold standard in obturation. The sealer creates a union between the core material and the canal wall by filling any residual spaces. It can penetrate into the accessory canals, lateral canals, and dentinal tubules thereby predictably sealing the sealer dentin interface. An inverse relationship exists between microleakage and tubular penetration of sealers. Variations in the physical and chemical properties of sealers such as working and setting time, flow, viscosity, film thickness, particle size, and composition influence their depth of penetration. A lower surface tension aids in deeper penetration,, whereas the pseudoplastic behavior exhibited by most endodontic sealers result in reduced viscosity and increased flow when shear rate increases during compaction. The presence of smear layer, number and diameter of dentinal tubules, and the presence of water have an overt effect on the sealer penetration.,
Fewer studies have extended their investigative scope beyond three sealer groups leaving the performance of other sealers open to speculation. The resulting data by investigations are thus fragmented and provides a discontinuous comparison of the more commonly used sealers. The aim of this study was to evaluate and compare the penetrability of five different root canal sealers into radicular dentinal tubules using confocal laser scanning microscopy as the evaluative tool.
Fifty recently extracted single-rooted maxillary anterior teeth were used for this investigation. The samples were rinsed under running tap water and cleaned using an ultrasonic scaler followed by ultrasonic bath. They were immersed in 5% sodium hypochlorite solution (PDP, Mumbai, Maharashtra, India) for 15 min to remove organic material. Radiographs were taken to ensure the presence of a single root canal and stored in 0.2% sodium azide solution until further use. Teeth were decoronated at the cementoenamel junction using a safe-sided diamond disc to a uniform root length of 16 mm. An ISO 10 K-file (Mani Inc., Tochigi, Japan) was inserted in the canal until its tip was just visible at the apical foramen. One millimeter was subtracted from this length and recorded as the working length.
Instrumentation was performed with ProTaper Universal (Dentsply Maillefer, Switzerland) rotary nickel-titanium instruments, according to the manufacturer's instructions. The canals were prepared to an apical size F3 to working length. Canals were irrigated between files by 1 ml of 5% sodium hypochlorite (PDP, Mumbai, Maharashtra, India) and apical patency was maintained by passing an ISO 10 K-file (Dentsply Maillefer, Switzerland) through the apical foramen between files. As a part of the final irrigation protocol, canals were irrigated with 5 ml of SmearClear (SybronEndo, CA, USA) followed by 5 ml of 5% sodium hypochlorite for 1 min each with a side vented 30 G needle. A final rinse was performed with 5 ml of distilled water to remove any remaining irrigating solution and absorbent paper points were used to dry the canals.
The samples were randomly divided into five groups (n = 10) and obturated using the respective sealers, namely, Zinc oxide eugenol (ZOE) (Prime Dental Products), EndoREZ (Ultradent), Sealapex (SybronEndo), AH Plus (Dentsply Maillefer), and MTA-Fillapex (Angelus). All obturations were performed by a single experienced endodontist to maintain standardization in technique. To facilitate fluorescence under confocal microscopy, the sealers were stained with 3 drops of rhodamine B isothiocyanate dye powder (Chemaux Private Ltd., Mumbai, Maharashtra, India) made in solution form (0.1 mg/ml) and mixed until a uniform consistency was obtained. Size 30 0.06 master cone was coated with the dye-sealer mixture and placed to the entire working length with uniform light pumping stokes. The remainder of canal was obturated using cold lateral compaction technique. Care was taken before obturating teeth belonging to the EndoREZ group, to keep the canal damp before commencing obturation. At the conclusion of lateral compaction excess EndoREZ, gutta-percha was seared off and 40 s light-curing was done. Cavit G (3M ESPE, Germany) was used for sealing the coronal end of canals. The teeth were then stored in an incubator at 37°C and 100% relative humidity, for 7 days.
Each tooth was positioned in a block of orthodontic resin and left undisturbed until the resin set. Three horizontal sections of 1 mm thickness were made at 3, 6, and 9 mm from the root apex, using a low-speed precision IsoMet cutter (Buehler Ltd, IL, USA) at a speed of 200 rpm with continuous water cooling. Sections were then polished by LaboPol-5 (Struers, Ohio, USA) diamond disks under continuous water cooling. All samples were examined with Zeiss (laser scanning microscope [LSM] 780) confocal LSM (CLSM) (Germany). Images were analyzed by the ZEN 2.1 software (Carl Zeiss Misroscopy GmbH, Jena, Germany) at ×20 magnification. The penetration depth of sealers into the dentinal tubules was depicted by fluorescence. Using the ruler tool of the software, penetration depths were measured and recorded at 4 standardized points in each section [Figure 1]. The canal wall served as the starting point, and sealer penetration was measured to a maximum depth of 1000 μm. A mean of all four depths (Point 1–4) was representative of the mean penetration depth for that section. The mean of 10 such sections (taken from 10 different teeth) was the mean penetration depth for that group at the respective level (apical, middle, and cervical). Data were tabulated and subjected to statistical analysis using the SPSS software (SPSS Inc. Released 2008, SPSS statistics for Windows, Version 17.0, Chicago, IL, USA). ANOVA test with post hoc test was used for intergroup comparison with P value set at 0.05.
|Figure 1: Four standardized points (Point 1–4) where 2 perpendicular lines intersect the canal circumference were used to record the depth of sealer penetration|
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| Results|| |
[Figure 2] shows representative confocal microscopy images depicting the depth of sealer penetration. [Table 1] shows the mean depth (μm) of sealer penetration for five sealers in the coronal, middle, and apical zones, respectively. Intergroup comparisons yielded the following observations. Penetration depths of AH Plus were greater than ZOE in the apical and coronal levels (P < 0.05) and EndoREZ at the apical level (P < 0.05). Penetration depths of ZOE were lower than all other sealers in the middle and coronal third (P < 0.05). MTA-Fillapex penetrated significantly deeper than all other sealers in the middle third (P < 0.05). In the apical third, Sealapex showed lower penetrability than MTA-Fillapex and EndoREZ (P < 0.05).
|Table 1: Mean (standard deviation) tubular penetration depth (μm) of all sealers|
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|Figure 2: Confocal laser scanning microscope images of coronal, middle and apical third (left to right) showing the depth of penetration in Zinc Oxide Eugenol (a), EndoRez (b), Sealapex (c), AH Plus (d) and MTA Fillapex (e) sealers that were scanned from the canal periphery in the outward direction|
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| Discussion|| |
Light microscopy and scanning electron microscopy (SEM) have traditionally been used to evaluate the penetrability of sealers. However, both techniques have their associated drawbacks. Light microscopy makes it difficult to distinguish the sealer from dentin, while SEM lacks the overall view of small magnification and has the potential to create artifacts during sample preparation. CLSM on the other hand, offers a greater depth of field, reduces of background information away from the focal plane and has the ability to collect serial optical sections from thick specimens.
The penetration depth of all sealers in the coronal thirds was significantly greater than the apical third. This finding was along expected lines and could be ascribed to one or more of the following reasons. A greater diameter and number of the dentinal tubules coronally, lesser tubule density apically, propensity of sclerotic dentin to form toward the apical region, the reduced effectiveness of irrigants at the apex of the root canal and greater lateral compacting forces coronally during obturation.,,
In this study, AH Plus demonstrated the greatest penetrability at apical and coronal thirds whereas ZOE exhibited the lowest penetrability in the coronal and middle thirds. Deeper penetration of resin sealers than conventional root canal sealers is not new and has been noted in previous studies.,, Flow of a root canal sealer is defined as its ability to penetrate into dentinal tubules, lateral canals, accessory canals, and root canal wall irregularities. It is considered the main factor to influence the penetrability of a sealer. Consistency, particles size, and shear rate of a sealer determine its flow. Studies have shown resin sealers to exhibit excellent flow.,, Poor flow of ZOE-based sealer had been attributed due to the lack of resin in its composition., Kaplan et al. and Faria-Júnior et al. assessed the flow rate of five endodontic sealers and concluded ZOE-based sealers to have significantly lower flow than calcium hydroxide- and resin-based sealers.
Study conducted by De Deus et al. demonstrated greater tubular penetration of ZOE-based sealers results when it is used in association with thermoplasticized technique than cold lateral compaction technique. The cold lateral compaction technique used could also have resulted in the relatively poor performance of ZOE sealer in the current study.
While obturation techniques have a significant influence on the penetration of ZOE-based sealers the same is not true with epoxy-based sealers. Epoxy resin-based sealers like AH Plus rely more on the phenomenon of capillary action than hydraulics to be drawn into dentinal tubules and a longer setting time leverages this effect. This could also be the reason for greater penetration of AH Plus which possesses a longer setting time compared to EndoREZ. In addition, EndoREZ is based on a hydrophilic monomer having affinity for moisture in the dentinal tubules. It is imperative for the canal to be damp before the sealer is applied. This potentially makes the sealer technique sensitive as the right amount of moisture has to be left behind. This could probably be the reason why penetration depths of EndoREZ were significantly lower than AH Plus and MTA-Fillapex. In the middle third, the penetration depth of MTA-Fillapex was significantly greater (P < 0.05) than all other groups. This result is in accordance with the findings of Kuçi et al. and Nikhil et al. and consistent with the studies by Silva et al. and Zhou et al. which showed MTA-Fillapex to possess greater flow and smaller particle size than AH Plus.
All steps including obturation were performed in teeth without embedding their roots and probably could have resulted in overestimation of penetration depths. Doing otherwise would have simulated the in vivo hydraulics of sealer-tubule more closely, thereby impeding the sealer penetration freely into tubules. This was an inherent limitation for the current investigation.
| Conclusion|| |
None of the sealers were able to penetrate the whole extension of the dentinal tubules. Under the limitation of the present study, AH Plus (at 3 and 9 mm from apex) and MTA-Fillapex (at 6 mm from the apex) exhibited the greatest penetration depths, whereas ZOE (at 6 and 9 mm from apex) and sealapex (at 3 mm from apex) presented the lowest penetration depths into radicular dentinal tubules.
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Conflicts of interest
There are no conflicts of interest.
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Dr. Shishir Singh
Department of Conservative Dentistry and Endodontics, Terna Dental College and Hospital, Sector 22, Nerul, Navi Mumbai - 400 706, Maharashtra
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2]