|Year : 2022 | Volume
| Issue : 3 | Page : 289-296
Effect of therapeutic fractionated radiotherapy on bond strength and interfacial marginal adaptation of Adseal, MTA Fillapex, and EndoSequence BC sealer: An in vitro study
Monika Khangwal1, Ravinder Solanki2, Hena Rahman3
1 Department of Conservative Dentistry and Endodontics, Post Graduate Institute of Dental Sciences, Rohtak, Haryana, India
2 Department of Oral and Maxillofacial Surgery, Post Graduate Institute of Dental Sciences, Rohtak, Haryana, India
3 Department of Conservative Dentistry and Endodontics, GMC, Jalaun, Uttar Pradesh, India
|Date of Submission||22-Jan-2022|
|Date of Decision||02-Feb-2022|
|Date of Acceptance||27-Mar-2022|
|Date of Web Publication||1-Sep-2022|
Dr. Monika Khangwal
Department Conservative Dentistry and Endodontics, Post Graduate Institute of Dental Sciences, Rohtak, Haryana
Source of Support: None, Conflict of Interest: None
Introduction: The study aimed to assess the impact of fractionated radiation on push-out bond strength of sealer to dentin interface and on marginal adaptation of the sealer (Adseal, MTA Fillapex, and EndoSequence BC sealer) to irradiated dentin.
Materials and Methods: Ninety maxillary central incisors were randomly divided into two groups: with irradiation (n = 45) and without (n = 45). All the samples to be radiated were exposed to fractionated dosage (60 Gy) through Co-60 gamma (1.17 and 1.33 Mev) photons. Specimens were prepared and subdivided into three subgroups (n = 15 each) according to assigned sealer Adseal, MTA Fillapex, and EndoSequence BC sealer. Later, the samples were sectioned into a 1 mm thick segment at each root third for bond strength and scanning electron microscope (SEM) analysis. SEM micrographs were analyzed with an ORION version 6 image analyzer. The percentage of failure mode after debonding was evaluated with a stereomicroscope. Bond strength data were analyzed using two-way analysis of variance and the Tukey's post hoc test.
Results: Bond strength was significantly (P < 0.0001) decreased after radiotherapy (0.76 ± 0.12 Mpa) versus without radiation (0.93 ± 0.18 Mpa). Furthermore, when the pooled average of sealers was compared, significantly highest bond strength was perceived in Adseal (0.98 ± 0.18 Mpa) followed by EndoSequence BC (0.84 ± 0.13 Mpa). Coronal sections showed significantly (P < 0.0001) higher bond strength (0.99 ± 0.16 Mpa) compared to the middle (0.81 ± 0.14 MPa) and apical third (0.74 ± 0.12 Mpa). Qualitative SEM revealed a higher interfacial gap between sealer and irradiated radicular dentin. The percentage of mean change was recorded significantly high in MTA Fillapex (52%), then in EndoSequence BC (31%), and least was in Adseal (17%).
Conclusions: Irradiated teeth resulted in consequential decreased adhesiveness and bond strength of dentin to root canal filling material. In addition, the highest bond strength was noticed in Adseal.
Keywords: Bond strength, interfacial gap, irradiated dentin, radiotherapy, root canal sealer
|How to cite this article:|
Khangwal M, Solanki R, Rahman H. Effect of therapeutic fractionated radiotherapy on bond strength and interfacial marginal adaptation of Adseal, MTA Fillapex, and EndoSequence BC sealer: An in vitro study. Saudi Endod J 2022;12:289-96
|How to cite this URL:|
Khangwal M, Solanki R, Rahman H. Effect of therapeutic fractionated radiotherapy on bond strength and interfacial marginal adaptation of Adseal, MTA Fillapex, and EndoSequence BC sealer: An in vitro study. Saudi Endod J [serial online] 2022 [cited 2022 Oct 5];12:289-96. Available from: https://www.saudiendodj.com/text.asp?2022/12/3/289/354828
| Introduction|| |
Head-and-neck (H/N) cancers have been increasing progressively and are coupled with high morbidity and transience. The tongue is the most frequently pretentious part of the oral cavity (32.7%). Squamous cell carcinoma is the most common histological type of cancer (93.3%) followed by verrucous carcinoma (1.52%). Radiotherapy is the principal treatment for H/N cancers in addition to surgery and chemotherapy. Fractionated irradiation is the most commonly followed regime in these cancers, as this protocol allows the repopulation of healthy tissue between fractional doses; consequently diminishing the early side effects., However, therapeutic radiations in H/N region are still accomplished with complications in the oral cavity and oropharynx. Few studies have demonstrated that ionizing radiation has a deleterious effect on dentinal substructure due to the generation of free radicals (superoxide and nascent oxygen/hydrogen)., These deleterious effects include defragmentation and disintegration of collagen fibers and matrix, morphological changes, organic and inorganic content variation, and reduction in dentin microhardness., Radiation-induced caries is another most frequently faced complication that has a rapid onset; and the menace of its incidence and progression increases during or instantaneously after radiotherapy. Nevertheless, radiation caries is not only caused simply by the irradiation but also is consequence of xerostomia and direct modifications in the mineral content of enamel and dentin ultrastructure.,, Changes in dentinal substructure are more predisposed to increased pulpal inflammatory reactions. Perhaps, radiated patients immediately may necessitate endodontic treatment for functional rehabilitation from the despondent agonizing condition. Such nonsurgical root canal therapy may avoid extractions and risk of osteoradionecrosis.,, For endodontic successful therapy, the selection of sealer is of paramount imperative. Adseal is a new generation of epoxy resin sealers. It has satisfactory physical properties with successful biological recital and covalent bonding to radicular dentin. EndoSequence BC is a biocompatible sealer and includes calcium phosphate ions that emulate elemental composition and crystalline arrangement of tooth and bone apatite., MTA Fillapex, another calcium silicate-based sealer, has excellent promising sealing competence and a variety of properties that encourage its clinical relevance, such as apexification, repairing of radicular perforation, and treatment of internal root resorption., This study aimed to assess the impact of therapeutic fractionated radiation on the push-out bond strength of endodontic sealer to dentin interface and interfacial/mean marginal gap width between root canal sealer and irradiated dentin.
| Materials and Methods|| |
This research project with all prospective procedures was conducted in government medical college, Jalaun, Uttar Pardesh, India. Extracted 90 human maxillary central incisors with the straight canal (angle <5°) were collected. Exclusion criteria followed were teeth with moderate (angle is 5°–20°) or emphasized curvature (angle >20°) according to Schneider's classification, multiple canals, calcified pulp chamber, undeveloped tooth, internal resorption, preceding endodontic treatment, and metallic restorations that could generate secondary radiations. These prototype specimens were decoronated at the cementoenamel junction to obtain a 15-mm root length. Selected teeth specimens were decontaminated as per the Center for Disease Control and Prevention by submersion in 5.25% sodium hypochlorite solution for 30 min and were stored at room temperature in a sterile saline solution. All samples were randomly divided into two groups: without irradiation (n = 45) and with irradiation (n = 45) and further both the groups were subdivided into three subgroups (n = 15 each) according to obturation with gutta-percha and assigned sealer.
All the samples with the radiation group to be subjected to fractionated radiotherapy before root canal treatment were positioned in plastic tubes containing distilled water. For consistent distribution of radiation dose, distilled water was leveled 0.5 cm above the samples. In between fractions, samples were stored in artificial saliva (Aritech Chemazone Private Limited, Kurukshetra, Haryana) with 7.0 pH and 37°C. The radiation dose was administered through Co-60 gamma (1.17 and 1.33 Mev) photons Bhabhatron-II TAW Cobalt-60 Teletherapy machine. using a single anterior field at a 5 × 5 cm2 dimension. The distance between the source and water surface was kept at 80.5 cm as per protocol. A total dose of 60 Gy in fractions of 1.7 Gy/day for 5 days a week for 7 weeks was administered. After irradiation, all samples, i.e., both irradiated and nonirradiated were stored in artificial saliva.
Root canal treatment
After radiotherapy, all samples were prepared and embedded in resin block for root canal treatment, and canal patency was maintained with 15 K-file. ProTaper rotary system (Dentsply/Maillefer, Ballaigues, Switzerland) was used for biomechanical preparation till apical size F3 maintaining working length 1 mm short of apex. During biomechanical preparation, a 30-gauge Neoendo Sidevent Irrigation Needle (Orikam Healthcare Pvt. Ltd., Gurgaon, Haryana, India) was used to irrigate the canal in between each preparation with 5 ml of 5% sodium hypochlorite (Pyrax Polymars, Roorkee, Uttarakhand) by placing it 1 mm short of the working length. In the end, flushing was done with 17% EDTA (Pyrax Polymars, Roorkee, Uttarakhand) for 5 min, followed by 5% sodium hypochlorite, and a final rinse with saline. After irrigating, canals were dried using sterile paper points (Sure Endo Paper Points, Osmanabad, India). All the samples of the radiated and nonradiated subgroups were obturated with gutta-percha and assigned sealer, i.e., Adseal (Meta Biomed Co, Korea), MTA Fillapex (Angelus, Londrina, Brazil), and EndoSequence BC sealer (Brasseler USA) using the lateral condensation technique. The access cavities of all samples were conserved with a temporary sealing material (T-Fill MAARC, New Delhi, India) and stored in relative humidity at 37°C for episode of the following period, i.e., (thrice the setting time) 2 h and 15 min for Adseal, 16 h for EndoSequence BC sealer, and 2 h for MTA Fillapex before subjected to bond strength analysis.
Push-out bond strength investigation and computation
Each root was segmented perpendicular to accomplish a cross-section of 1-mm thickness with IsoMet 1000 precision saw (Horizon, Secunderabad, Telangana). The thickness of segments was measured and confirmed by the Vernier calliper. The segments were cleaned, and apical surfaces were marked with nail paint. This noticeable surface was positioned in such a manner that the loading forces by punch tip were employed from apical to the coronal direction. The first segment of all root samples at the level of coronal, middle, and apical third was derived for bond strength investigation under a universal testing machine (UTM Series 9045 Star Testing System, Mumbai, Maharashtra, India) at a crosshead speed of 0.5 mm/min. Punch tips with a diameter of 0.4 mm (apical), 0.6 mm (middle), and 1.0 mm (coronal) were assigned accordingly. A continuous invariable force was projected until complete dislocation or dislodgment of the root canal obturating material occurred. The push-out bond strength was calculated in megapascal (MPa) by dividing the loading forces in Newton at which bond failure occurred by the adhesive surface area of each sample. The bonded surface area was anticipated using the formula, A = 2·πrh, in which π = 3.14, r = ½ of the diameter of root canal filling material, h = thickness of the sample (1 mm).
Push out bond stress (MPa) = loading force (N)/adhesive surface area (mm2).
After finishing with bond strength analysis, the sections were inspected under a stereomicroscope (×25 magnification) to verify the failure mode. Its categorization was as below: (a) adhesive failure (complete dislodgment of sealer from dentinal surfaces), (b) cohesive failure (dentinal surfaces entirely covered with sealer), and (c) mixed presentation, i.e., partial coverage with sealer (both adhesive and cohesive failures). The second segment at a level of the coronal, middle, and apical third of each root was employed for a qualitative investigation of sealer/dentin marginal gap under a scanning electron microscope (SEM) (EVO LS 10, Zeiss, Germany). For the evaluation of marginal gaps, the segments were decontaminated from all the organic wreckage by 5 mol hydrochloric acid for 45s and finally rinsed with distilled water. The process was repeated again with 2.5% sodium hypochlorite for 10 min for deproteinization. Later, the sections were dehydrated with 50% of ethanol for the evaluation of sealer infiltration into the root dentin. All specimens were gold-palladium sputter-coated and examined under SEM at a magnification of 1000/1 kx, initiating at ×200. SEM micrographs samples were quantitatively evaluated according to the marginal gap between the sealer and the dentin using the ORION version 6 (E.L.I. S.P.R.L., Belgium) software system. Marginal gap width at various levels (i.e., coronal, middle, and apical) of all the samples was recorded in micrometer.
The collected data were interpreted for normality by the Shapiro–Wilk test and homogeneity of variance by Levene's test. Push-out bond strength valuation was analyzed using a two-way analysis of variance and mean the difference between the groups was done by post hoc Tukey's test. P < 0.05 indicates a statistically significant difference and it is denoted by different letters in all the tables.
| Results|| |
There was a statistical significant difference for the factors (radiated/nonradiated, sealers, and root third section) radiation (P < 0.0001), sealer (P < 0.0001), and for root third section (P < 0.0001). There was a statistically highly significant difference seen for the values between the groups (P < 0.01) with the combined effect of group, root third, and groups + root third interaction. Although these inter and intragroup comparisions did not affect the bond strength values (P > 0.05).
Radiated versus nonradiated groups
Significantly lesser bond strength (P < 0.0001) was observed in with irradiation group (0.76 ± 0.12 Mpa) compared to without irradiation group (0.93 ± 0.18Mpa) as shown in [Table 1]. When sealers were compared in the overall groups (radiated and nonradiated groups), the significantly highest bond strength was noticed in AdSeal (0.98 ± 0.18 Mpa), followed by EndoSequence BC (0.84 ± 0.13 Mpa), and then MTA Fillapex (0.73 ± 0.12 Mpa). On comparison of the pooled average of the root third section in overall groups (radiated and nonradiated groups) as presented in [Table 2], coronal sections showed significantly (P < 0.0001) higher bond strength (0.99 ± 0.16 Mpa) compared to the middle (0.81 ± 0.14 MPa) and apical third (0.74 ± 0.12 Mpa).
|Table 1: Push-out bond strength means (MPa) of sealers/dentin interface in without or with irradiation group|
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|Table 2: Push-out bond strength means (MPa) of sealers/dentin interface in overall, i.e., both without and with radiation groups at different root third section|
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Bond failure analysis
The presentation of bond failure analysis as shown in [Table 3] revealed that adhesive failure was most prominent in Adseal after radiotherapy in all root third section. In MTA Fillapex, high percentage of adhesive failure was noted as compared to EndoSequence BC in all root sections (coronal, middle, and apical) in both with and without irradiation groups, predominately, these failures were higher in with radiation group.
|Table 3: Percentage of failure modes after bond strength analysis for Adseal, MTA Fillapex, and EndoSequence BC sealers at the different root third in specimens without and with irradiation|
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SEM micrographs showing marginal adaptation at various root third sections are shown in [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]. According to SEM qualitative evaluation, Adseal demonstrated improved marginal adaptation to radicular dentin in without irradiation group than EndoSequence BC or MTA Fillapex in overall root third sections. The high numeral of interfacial gaps between sealer and radicular dentin was noted in the irradiation group irrespective of sealers. Mean marginal gap width as recorded and valuated quantitatively using ORION version 6 image analyzer software is elaborated in [Table 4]. The percentage of mean change was recorded significantly high in MTA Fillapex (52%), then in EndoSsequence BC (31%) and least was in Adseal (17%).
|Figure 1: Scanning electron microscope micrographs at ×1000 magnification showing five consecutive reading of marginal gap width using ORION version 6 image analyzer between Adseal and nonradiated dentin interface at the C - (Coronal), M - (Middle), and A - (Apical) third root section|
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|Figure 2: Scanning electron microscope micrographs at ×1000 magnification showing five consecutive readings of marginal gap width using ORION version 6 image analyzer between MTA Fillapex and nonradiated dentin interface at the C - (Coronal), M - (Middle), and A - (Apical) third root section|
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|Figure 3: Scanning electron microscope micrographs at ×1000 magnification showing five consecutive reading of marginal gap width using ORION version 6 image analyzer between EndoSequence BC and nonradiated dentin interface at the C - (Coronal), M - (Middle), and A - (Apical) third root section|
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|Figure 4: Scanning electron microscope micrographs at ×1000 magnification showing five consecutive reading of marginal gap width using ORION version 6 image analyzer between Adseal and radiated dentin interface at the C - (Coronal), M - (Middle), and A - (Apical) third root section|
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|Figure 5: Scanning electron microscope micrographs at ×1000 magnification showing five consecutive reading of marginal gap width using ORION version 6 image analyzer between MTA Fillapex and radiated dentin interface at the C-(coronal), M-(middle), A-(apical) third root section|
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|Figure 6: Scanning electron microscope micrographs at ×1000 magnification showing five consecutive reading of marginal gap width using ORION version 6 image analyzer between EndoSequence BC and radiated dentin interface at the C - (Coronal), M - (Middle), and A - (Apical) third root section|
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|Table 4: Mean marginal gap width (μm) (mean±standard deviation) of two groups in three sealers overall, i.e., coronal, middle, and apical third region|
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| Discussion|| |
Fractionated radiotherapy is the imperative treatment protocol in H/N cancers. Although the radiation dose is focused and controlled, still it damages surrounding healthy tissues and induces oral complications. The severity of oral complications depends on the daily and total collective dose of radiation. Therapeutic radiation causes inflammatory responses, vascular and edematous variations in parenchymal tissues of the salivary gland which further results in frequent complications, such as (a) Xerostomia, (b) reduced salivary flow, (c) alterations in the composition of saliva, (d) decline in salivary pH, and (e) reproduction of cariogenic flora in the oral cavity. Osteoradionecrosis is one of the complications that occur due to radiation-induced free radical generation, reduced vascularity, and tissue hypoxia., Worse acute inflammatory mucosal responses are associated with modified fractionation protocol where manifold irradiation fractions are projected per day as compared to conventional fractionation inducing one fraction per day. Average collective irradiation of more than 65 Gy is associated with severe oral mucositis. 50–70 Gy is the clinical dose range in squamous cell carcinomas patients. To replicate radiation procedures of cancer patients, a conventionally fractionated dose of 60 Gy in the division of 1.7 Gy/day was induced. Fractionated ionizing radiation augments the reproduction of healthy tissue between divisions of dosages thus decreasing untimely side effects and also relevantly reducing speedily proliferating malignant cells., An additional imperative feature to imitate clinical circumstances in the research was the storage of samples in synthetic saliva between the fractional radiations., But during irradiation, samples were submerged in distilled water since artificial saliva is viscous and electrolyte concentrates could influence the consistent delivery of radiations. Therapeutic radiation is also related to intimidating complications in dentition, i.e., radiation caries. In severe cases, a formerly healthy dentition can be completely affected within a short-time episode. In the current study, the push-out bond strength of irradiated radicular dentin was decreased as compared to nonradiated samples. It might be due to the consequences of ionizing radiation that are associated with alterations in dentin crystalline substructure such as eradication of dentinal tubules, modifications, and derangement of organic and inorganic content of intertubular, peritubular, or intratubular dentin, and reduction in microhardness., Radiation ionizes water to form free radicals and hydrogen peroxide. These free radicals result in the disintegration and deproteinization of collagen fibers and their peptide bonds. Dentinal tubules are laced with water that comprises 12% of its organic content. When root dentin enters the field of exposure, radiation dissociates water into free radicals that result in denature of primary, secondary, and tertiary proteins of collagen matrix that tends to dehydrate dentinal tubules; thereby reducing its adhesiveness with the sealers. Numerous studies have also certified that a total collective radiation dose of 60–70 Gy resulted in the disintegration of the odontoblastic process and dehydration of dentinal tubules due to free radicals, consequentially altering the physical and chemical substructure of extracted teeth. Push-out bond strength investigation was preferred in the current project as this technique is comprehensively conventional and applied for significant assessment of bond strength between obturation and radicular dentin at the microscopic level.
Adseal (Epoxy resin-based sealers) have exceptional physical properties due to the formation of a covalent bond with polyamines of collagen networks. These chemical reactions with the amide group result in the formation of rigid and strong cross-linked epoxide ring polymer. Adseal infiltrates intensely into the micro-irregularities of dentin because of its excellent flowability. That rationally counts for its low polymerization shrinkage and longer polymerization time, resulting in higher bond strength. Rational elucidation for decreased push-out bond strength of irradiated Adseal/gutta-percha filled samples may be due to the fact that ionizing radiation defragments and disintegrate collagen fiber arrangements of dentin organic matrix. Precisely, these collagen scaffolds are the edifice for hybridization and bonding micro mechanically for hydrophobic epoxy resins.
EndoSequence BC Sealer is an injectable calcium phosphate silicate bioceramic sealer. It is a hydrophilic, biocompatible, and antibacterial sealer due to its extreme alkaline pH. Initiation and completion of its setting reaction are always under adequate dentinal moisture to form a hydroxyapatite-like structure. Bioceramic sealer is accomplished with elemental bonding to form a gap-free interface. Numerous aspects can influence the union or bonding of a root canal Endosequence BC sealer to dentin such as water content, the integrity of collagen matrix fold and the Ca: P ratio of tooth structure. Alterations in any of these prevent mineralization progression and setting reaction, thus, decreasing the bond strength of these sealers. Therapeutic radiation has deleterious effects on the organic and mineral content of dentin that stand forth for the validation of reduced bond strength in irradiated EndoSequence BC sealer specimens.
MTA Fillapex sealer is composed of MTA and salicylate resin. Its bond strength was low compared to the epoxy resin sealer as documented earlier. It might be due to its high viscosity and incomplete polymerization. Its viscous consistency hinders movement at the molecular level, hence, decreasing the flow of sealer into irregularities of root canal intricacies. Moreover, MTA is set by the formation of a hydroxyapatite-like structure, which decreases its bonding ability with dentin. Furthermore, free radicals engendered by ionizing radiation cause eradication of the dentinal tubule and alteration in dentin infrastructure, thereby further reducing its bonding efficacy. The outcome of the present study was in agreement with the other studies documenting higher bond failure in MTA Fillapex in contrast to epoxy resins irrespective of radiation therapy., Furthermore, the proportion of bond failures increased significantly after radiotherapy in all groups. Supplementary bond strength of Adseal (epoxy resin) as compared to EndoSequence BC Sealer was higher irrespective of radiotherapy. An explanation to uphold this conclusion could be due to their low polymerization shrinkage and dimensionally stable covalent bonding configurations. SEM micrograph analytic evaluation also discovered furthermore that the mean marginal gap width between sealer and dentin was higher in MTA Fillapex followed by EndoSequence BC Sealer and least in Adseal sealer. SEM micrographs analysis was done with ORION version 6 image analyzer software. This software system allows image analysis and calibration even at the lowest scale. Images can be stored with 256 Gy levels per pixel. The minimum dimensions and veracity of margin/interface gap between root canal filling material and radicular dentin are significant and imperative for the prevention of microleakage, consequently enhancing the endodontic success rate.
Adseal (epoxy resin) being a hydrophobic sealer, has excellent flow, gradual polymerization allows its deeper penetration into dentinal tubules to form a stable covalent bond. These chemical bonding resulted in high-bond strength and minimum marginal gap/voids. Furthermore, changes in crystalline substructure and collagen matrix due to radiotherapy had no significant effect on the bond strength of resin-based materials as previously reported. It has been reported that hydrophobic resin produces stable stiff bonding and decreases absorption of water with time.
Above all, bond strength in all radiated and nonradiated specimens was significantly higher in the coronal third followed by the middle then the apical third., These findings could be explicated as the apical third being the narrow multifaceted area with a lesser number and smaller width of dentinal tubules that impedes in infiltration and bonding of the root canal filling material with dentin. Numerical escalation of H/N cancer is a reason of foremost apprehension. The irradiated patient may necessitate endodontic treatments to restore health from despondent agonizing radiation-induced caries and pulpitis.
This study scheme broadens the perception for additional investigations regarding the choice of root canal material and endodontic scheduling for better concern and care of irradiated patients. However, our study has certain limitations. Due to the in vitro nature of the study, we were unable to simulate the precise clinical conditions of the oral cavity. The radiation dose to the mounted specimen could vary from the actual patient dose due to the lack of surrounding soft and hard tissues. Thus, therapeutic dose-relative effect and reduced radiation effect due to surrounding tissue should also be considered in future studies.
| Conclusions|| |
Irradiated teeth resulted in consequential decreased adhesiveness and bond strength of dentin to root canal filling material. The highest bond strength was perceived in ascending order-Adseal > EndoSequence BC > MTA Fillapex. Above all hydrophobic epoxy resins were successful to form a stable bond in irradiated teeth as compared to hydrophilic calcium-silicate-based sealers, i.e., EndoSequence bioceramic and MTA Fillapex sealer. Hence, if endodontic intervention is required in radiotherapy patients, hydrophobic epoxy resin sealers could be preferred. These preliminary results necessitate more insightful scrutiny. Further in vitro studies and clinical trials on irradiated teeth should be undertaken to assess the sealing competence and clinical recital of different root canal filling materials.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
[Table 1], [Table 2], [Table 3], [Table 4]