| Abstract|| |
Background: Sealers play an important role in the success of root canal treatment. The efficacy of root canal sealer is enhanced by its tubular penetration and adaptation properties.
Aim: The aim of this study is to evaluate the interfacial adaptation and penetration depth of Bioroot RCS and MTA Plus sealers to root dentin.
Materials and Methods: A total of 60 single-rooted mandibular premolar teeth were prepared using Pro Taper rotary Ni-Ti files and were randomly divided into three groups (n = 20 each) according to the type of sealer used for obturation. After obturation with lateral condensation, half of the samples in each group (n = 10 each) were sectioned transversely for measuring tubular depth penetration under confocal laser scanning microscopy. Longitudinal sections were obtained for remaining half samples to evaluate the adaptation of sealer using scanning electron microscope. Data were analyzed using two-way ANOVA and Tukey post hoc tests.
Statistical Analysis Used: Data were analyzed using two-way ANOVA and Tukey post hoc tests.
Results: AH Plus sealer has shown significantly higher depth of penetration and minimum gaps than bioceramic sealers (P < 0.05) MTA Plus sealer exhibited significantly more interfacial gaps and less penetration depth than Bioroot RCS (P < 0.05).
Conclusions: At all root regions, AH plus sealer exhibited minimum gaps and more tubular penetration whereas MTA Plus sealer exhibited more gaps and less penetration.
Keywords: Bioceramic sealers; confocal laser scanning microscopy; interfacial adaptation; penetration depth
|How to cite this article:|
Arikatla SK, Chalasani U, Mandava J, Yelisela RK. Interfacial adaptation and penetration depth of bioceramic endodontic sealers. J Conserv Dent 2018;21:373-7
|How to cite this URL:|
Arikatla SK, Chalasani U, Mandava J, Yelisela RK. Interfacial adaptation and penetration depth of bioceramic endodontic sealers. J Conserv Dent [serial online] 2018 [cited 2019 Jul 16];21:373-7. Available from: http://www.jcd.org.in/text.asp?2018/21/4/373/237746
| Introduction|| |
The objective of root canal treatment is to treat periapical lesions or to prevent their development. Poorly filled areas of root canal system can be a source of bacterial growth, as it was reported that 58% of treatment failures were due to incomplete obturation. Hence, a tridimensional filling of the canal space with an inert, biocompatible material is the ultimate goal to prevent bacterial leakage. Although gutta-percha, the most commonly used core filling material can be adapted reasonably to the canal walls, it is essential to place a root canal sealer, because of the canal irregularities and size of the dentinal tubules. Endodontic sealers aid in sealing the canal system by filling the anatomical irregularities, ramifications and dentinal tubules, thus improving the adaptation of root filling at the dentin material interface. Ideally, root canal sealer must be biocompatible, should have low surface tension and better wettability thus providing fluid-tight seal. Epoxy resin-based root canal sealers (AH Plus, Dentsply, Germany) have an established record in endodontics and has been used as the gold standard for comparison with other sealers. The bioceramic sealer, Bioroot RCS (Septodont, Louisville, USA) is a water-based sealer composed of tricalcium silicate, zirconium oxide, and calcium chloride. When comes in contact with the physiologic solution, these sealers release calcium and forms an interfacial calcium phosphate (apatite) layer, thus developing a chemical bond with the dentinal walls., The other recently introduced MTA-based bioceramic sealer is MTA plus (Avion Biomed Inc., Bradenton, USA). It is also a water-based sealer consisting of tricalcium and dicalcium silicate, bismuth oxide, tricalcium aluminate, calcium sulfate, and gypsum. These sealers have good sealing ability, bactericidal effect, high biocompatibility, and low solubility.
The efficacy of a root canal sealer is enhanced by minimizing the amount of sealer used, ensuring good adaptation, and penetration of the sealer into root dentin. Adaptation of sealers to canal walls and marginal gaps can be assessed with scanning electron microscopy (SEM), as the defects at submicron level can be observed at the required magnification. Confocal laser scanning microscopy (CLSM) provides information about the sealer penetration and distribution inside the dentinal tubules of root canal walls with the use of fluorescent rhodamine dye marker mixed with the sealers.
The ability of sealer penetration effectively and consistently into dentinal tubules and their adaptation to the canal walls are the influencing factors for the selection of root filling materials. Thus, the aim of this study was to assess the interfacial adaptation and dentinal tubular penetration depth of Bioroot RCS and MTA Plus sealers in comparison to AH Plus sealer.
| Materials and Methods|| |
Preparation of specimens
A total of 60 recently extracted human single-rooted mandibular premolar teeth without caries, apical, or surface resorptions and cracks were selected. Teeth with curved roots, abnormal canal morphology and having pulpal calcifications were excluded from the study. To preserve the humidity of dentinal tubules, teeth were stored in saline, after disinfection with 0.5% chloramine-T solution. The crowns were decoronated at 1 mm coronal to the cementoenamel junction, using a flexible diamond disk (Novo dental products, Mumbai) under copious water irrigation to yield root sections of 12 mm length.
Access cavities were prepared, and the canal patency was verified using #10 k file (Mani Inc., Tochigi, Japan). Working length was determined and the root canals were shaped using ProTaper rotary files (DenTsply Maillefer, Switzerland) up to F3 (30/0.09). During instrumentation, canals were irrigated with 3% sodium hypochlorite, and then, the root samples were randomly divided into three groups (n = 20 each), according to the type of sealer used to obturate the canals;
- Group 1: Obturation using AH plus sealer
- Group 2: Obturation with MTA plus sealer
- Group 3: Obturation with Bioroot RCS sealer.
Obturation of the root canals
Before the obturation, the canals were irrigated with 2 ml of 17% EDTA (Dent Wash, Xenon Biomed, India) for 1 min to remove the smear layer followed by final rinse with 5 ml of distilled water. Then, the canals were dried with absorbent points. To facilitate fluorescence under confocal laser microscopy for measuring the penetration depth, the sealer was mixed with isothiocyanate fluorescent 0.1% Rhodamine dye (Macsen Labs Pvt Ltd., Rajasthan) for half of the root samples (n = 10) in each group. For standardization, 10 parts of sealer were mixed with 1 part of dye powder and mixed manually.
In AH Plus group, the sealer was mixed in 1:1 ratio of epoxide and amine pastes on a mixing pad to a homogenous consistency. In MTA Plus group, the sealer was mixed at a water/cement ratio of 0.35 with a plastic spatula, until the desired putty-like consistency was obtained. In Bioroot RCS group, the sealer was mixed according to manufacturers' instructions to a smooth, homogenous paste. A standardized #30 master cone (DenTsplyMaillefer, Switzerland) was selected, and its fit was confirmed by taking a radiograph. The canal walls were coated with the sealer and were obturated using lateral compaction technique.
The teeth were stored in 100% humidity at 37°C for 1 week to allow the complete setting of the sealer. For examining the sealer penetration depth, root samples obturated using rhodamine dye along with sealer in each group (a total of n = 30 samples) were sectioned horizontally at 3 mm and 6 mm from the apical foramen using hard-tissue microtome (Leica SP1600, Germany) under copious amount of water coolant. The remaining 30 samples (n = 10 each/group) were sectioned vertically for measuring the sealer adaptation to the root dentin perimeter.
Penetration depth measurement
All the sections were examined under confocal laser scanning microscope (CLSM 880, Carl Zeiss, Germany). Sealer penetration distance into the dentinal tubules was measured by Adobe Photoshop CS3. Using a ruler tool on the LSM image browser software, the depth of sealer penetration was measured and recorded at four standardized points (mesial, distal, buccal, and lingual) on each section. The measured readings were averaged to obtain a single mean value for each section [Figure 1].
|Figure 1: Confocal laser scanning microscopic images; Group I (AH Plus) at 6 mm (a), 3 mm (b); Group II (Bioroot RCS) at 6 mm (c), 3 mm (d); Group III (MTA Plus) at 6 mm (e), 3 mm (f)|
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Assessment of adaptation
The samples were mounted on an aluminum stub, placed in a vaccum chamber, and targeted sputter coated with gold and viewed under SEM (S-3700N, Hitachi, Japan.). Gaps at sealer and root dentin interfaces were evaluated under ×2000 magnification at coronol, middle, and apical halves of the root canal by taking photomicrographs. For each section, the maximum gap in millimicrons (μm) was recorded [Figure 2].
|Figure 2: Scanning electron microscopic images; Group I (AH Plus) at coronal (a), middle (b) and apical (c); Group II (Bioroot RCS) at coronal (d), middle (e) and apical (f); Group III (MTA Plus) at coronal (g), middle (h), and apical (i) thirds of the root canal|
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Findings were statistically analyzed using SPSS/PC software version 22 (IBM; Chicago; IL, USA). A two-way analysis of variance was used to compare the depth of penetration and interfacial gap formation in different areas. The Tukey's multiple post hoc test was used for pairwise comparison of the groups at 95% confidence level.
| Results|| |
A statistical significance was found for sealer penetration depths between AH Plus and bioceramic sealers (P< 0.05) [Table 1]. There was no statistical significance in the depth of sealer penetration between MTA Plus and Bioroot RCS sealers at both levels evaluated (P > 0.05).
|Table 1: Comparison of mean sealer penetration depth (μm) between groups by Tukeys multiple post hoc procedures|
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A significant difference was observed between the sealers regarding dentin sealer interfacial gaps [Figure 3], where AH plus exhibited minimum gaps and MTA Plus sealer showed maximum gap formation. Higher gap widths were observed in middle and apical root regions.
|Figure 3: Bar diagrammatic representation of sealers interfacial gaps (μm) at different root regions|
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| Discussion|| |
The ideal outcome in root canal obturation is to have a high volume of gutta-parcha and a minimal volume of sealer with enhanced penetration into the canal irregularities and dentinal tubules. Degree of adhesion and penetration of sealers into dentinal tubules is influenced by several factors such as physical and chemical properties of sealer cements, dentin permeability, filling technique, and smear layer removal. Smear layer removal of root canal walls is considered to be fundamental to allow sealer penetration, irrespective of the type of sealer used. Calcium silicate-based bioceramic sealers interact with dentin through the chemical uptake of calcium and silicon in the presence of a phosphate buffer solution. This mineral infiltration zone formation is triggered by the alkaline caustic effects of the sealer by products and involves the penetration of sealer minerals (carbonate, calcium, and silica) into intertubular dentin after the denaturation of collagen fibers.,
The depth of penetration of AH Plus sealer is significantly high compared to MTA Plus and Bioroot RCS sealers. The flow of a sealer which is determined by its consistency and particle size is one of the important factors to influence the tubular penetration. The flow of AH Plus sealer is superior due to the presence of higher concentration of epoxy resin. The deepest tubular penetration was observed at 6 mm from the apex than at 3 mm level of the root canal for all the tested sealers. This could be because of the fact that number of tubules and tubule patency is usually less in apical region due to sclerotic dentin. This finding is according to the previous studies where regional variation in depth of penetration has been demonstrated., The sealer penetration was found to be greater in buccolingual direction compared with the mesiodistal direction. A butterfly-like phenomenon was observed on the root cross-sections of single-rooted teeth, as a result of increased sclerosis along the tubules located on the mesial and distal sides of the canal lumen.
The degree of adhesion depends on several interacting factors including the adherent's (dentin) intermolecular surface energy and cleanliness and the adhesive (sealer) surface tension and wetting ability. AH Plus sealer exhibited the least number of gap-containing areas, a finding which is consistent with the previous studies. The superior adaptation of AH Plus could be due to its chemical bonding to root dentin by forming covalent bonds between the epoxy resin and collagen. Although the alkaline nature of bioceramic by-products have been reported to denature dentinal collagen fibers facilitating sealer penetration, both hydrophilic sealers MTA Plus and Bioroot RCS exhibited more interfacial gaps. The reason for inferior adaptation of MTA Plus could be due to poor microtags formed on setting.
In this study, in accordance with the results of previous studies,, more gaps were observed at apical level for all the sealers than at coronal level. This discrepancy can be accounted for the lower density and diameter of dentinal tubules found at the apical region. Higher mean gaps at the mid-root region could be attributed to the difficulty posed by the oval shape of premolar root canals. The use of lateral compaction has been reported to produce nonhomogenous thick sealer layers along the root canal wall, thus influencing the sealer penetration into the root dentin. This could be another possible explanation for the presence of high interfacial gaps.
The presence of voids is one of the indicators for assessing the quality of root filling and has a significant relation with the outcome of root canal treatment. However, the amount of voids within root canal fillings to cause failure is unclear. Thus, it is difficult to directly correlate the present results with the clinical outcomes of endodontic treatments.
| Conclusions|| |
Within the limitations of this in vitro study, AH Plus sealer has shown more depth of penetration and better marginal adaptation than the bioceramic sealers. Further studies using different obturation techniques are necessary to obtain a three-dimensional seal in multirooted curved canals.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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Dr. Jyothi Mandava
GITAM Dental College and Hospital, Rushikonda, Visakhapatnam - 530 045, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3]