Synthesis, physical properties, and root canal sealing of experimental MTA- and salicylate-based root canal sealers

Synthesis, physical properties, and root canal sealing of experimental MTA- and salicylate-based root canal sealers | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Synthesis, physical properties, and root canal sealing of experimental MTA- and salicylate-based root canal sealers Rafael Vitti, Flávia Cardoso, Flávia Pereira, Evandro Piva, Cesar Zanchi, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5315187/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Objectives: To develop and evaluate the physical properties and sealing ability within the root canal of three experimental sealers based on MTA and a salicylate resin. Materials and Methods: The experimental sealers were composed of two pastes. The base paste was prepared using 1,3-butyleneglycol disalicylate and bismuth oxide. Three different catalytic pastes were formulated, creating three groups: [MTA] n,n,dihydroxyethyl-p-toluidine (DPT), titanium dioxide (TiO 2 ), and mineral trioxide aggregate (MTA); [MTA-HA] DPT + TiO 2 + MTA + hydroxyapatite (HA); and [MTA-DCPD] DPT + TiO 2 + MTA + dibasic calcium phosphate dihydrate (DCPD). MTA Fillapex (Angelus) was used as the commercial reference (control). The sealers were manipulated at a 1:1 ratio (base paste:catalyst). Tests for working time and setting time, flow, and film thickness were conducted following ISO 6876:2012 standards. Single-rooted human teeth root canals were utilized for evaluating root canal filling using micro-computed tomography, push-out bond strength testing, and sealer penetration into dentinal tubules using confocal microscopy. Failure patterns in the push-out test were classified as adhesive, cohesive, or mixed. Sealer micromorphology was analyzed via scanning electron microscopy. Data were analyzed statistically (α=0.05). Results: MTA Fillapex showed the longest working and setting times, highest flow, the lowest film thickness, and better penetration into dentinal tubules. There was no difference in void among evaluated sealers. Overall, MTA-DCPD sealer showed the lowest bond strength values for cervical and apical thirds. Micromorphological analysis revealed similar crystallographic properties among all sealers. Conclusions: The sealers tested showed reduced working and setting times, with flow and film thickness according to ISO 6876:2012. Their void volume and bond strength were similar to MTA Fillapex, except for MTA-DCPD. Clinical Relevance: The experimental root canal sealers demonstrated suitable physical properties and good adaptation within the root canal. mineral trioxide aggregate hydroxyapatite calcium phosphate physical properties adaptation Figures Figure 1 Figure 2 Figure 3 Introduction The success of endodontic treatment relies on various factors aimed at curing and preventing contamination of the tooth and periapical tissues [ 1 , 2 ]. Once mechanical and chemical cleaning of the root canals is completed, a properly fitted obturation to these canal walls ensures a secure seal, preventing the ingress of microorganisms or tissue fluids [ 3 – 5 ]. Gutta-percha in combination with root canal sealer plays a critical role in establishing the adequate adhesion of the obturation to dentin walls [ 5 ]. The quest for biocompatible and bioactive materials in root canal obturation holds promise due to their capacity to induce healing and bone regeneration [ 6 ]. Over time, root canal sealers with ion release have been proposed to enhance apical sealing by promoting mineral deposition on the canal walls [ 6 – 14 ]. Calcium-containing root canal sealers constitute a significant category in this context, showcasing good apical sealing capacity and chemical-mechanical interaction with root dentin [ 6 , 13 , 14 ]. These sealers consist of calcium silicate, calcium aluminate, and other calcium sources [ 15 ]. MTA (mineral trioxide aggregate) is a widely used material in dentistry known for its good marginal adaptation, anti-inflammatory properties, and its capability to induce mineralized tissue formation [ 16 ]. Despite its advantages, MTA has limitations such as dental discoloration, extended setting time, high cost, and increased cytotoxicity post-manipulation. Hence, several studies have explored the addition of other calcium sources to root canal sealers to enhance their physicochemical and biological properties [ 11 , 17 – 19 ]. Stoichiometric hydroxyapatite and dibasic calcium phosphate dihydrate (DCPD) are other calcium sources also under study for incorporation into root canal sealers. They exhibit favorable properties, including good osteoconductivity and satisfactory cellular response [ 7 – 11 ]. Root canal sealers based on salicylate resins have also been studied and utilized to enhance handling and physical properties. Additionally, these resins demonstrate satisfactory performance owing to their anti-inflammatory properties [ 20 , 21 ]. The combination of different calcium sources with salicylate resin in root canal sealers can enhance their physicochemical properties. Moreover, a higher amount of MTA in these endodontic sealers compositions increases calcium release and pH [ 11 ]. New studies assessing the interaction of these calcium sources with salicylate resin could contribute to a better understanding of clinical performance while seeking to improve the physicochemical and biological properties of these materials. Therefore, the aim of this study was to assess the physical properties and sealing ability of experimental root canal sealers based on MTA and butylene glycol disalicylate. The hypothesis tested was that the experimental root canal sealers compared to the commercial reference (control) would demonstrate superior outcomes in the evaluated properties. Material and methods Experimental design In this in vitro study, the factors investigated included (i) the type of root canal sealer at 4 levels (three experimental and one commercial sealers) for all tests, and (ii) root canal thirds at 3 levels (cervical, middle, and apical) for the push-out test. The response variables comprised quantitative analysis of working time (n=3) and setting time (n=3), flow (n=3), and film thickness (n=3); qualitative and quantitative assessment of the percentage volume of void spaces using micro-computed tomography (n=10) and push-out bond strength (n=10); as well as qualitative analysis of sealer penetration into dentinal tubules through confocal microscopy (n=10) and sealer micromorphology using scanning electron microscopy (n=3). Synthesis of salicylate resin The salicylate resin (1,3-butyleneglycol disalicylate) was synthesized via transesterification reaction of methyl salicylate (Synth Laboratory, São Paulo, SP, Brazil) with two different alcohols, at a molar ratio of 1:3. Titanium isopropoxide (Sigma-Aldrich, St. Louis, MO, USA) served as the catalyst agent. The reaction was maintained at 200°C for 2 hours. The resulting product underwent purification through vacuum distillation and was characterized via nuclear magnetic resonance (NMR) spectroscopy and Fourier-transform infrared spectroscopy (FTIR), which revealed a distinct peak of hydroxyl groups within the spectral range of 3300 cm -1 . Formulation and handling of root canal sealers The experimental root canal sealers consisted of two pastes. The base paste comprised 1,3-butyleneglycol disalicylate and bismuth oxide (Vetec, Duque de Caxias, RJ, Brazil). Three catalyst pastes were formulated using different types of calcium phosphate (white MTA, hydroxyapatite, and DCPD): [Group 1: MTA] n,n-dihydroxyethyl-p-toluidine (DPT; Sigma-Aldrich), titanium dioxide (TiO 2 ; Sigma-Aldrich), and MTA (Angelus, Londrina, PR, Brazil); [Group 2: MTA-HA] DPT + TiO 2 + MTA + hydroxyapatite (Sigma-Aldrich); [Group 3: MTA- DCPD] DPT + TiO 2 + MTA + DCPD (Vetec). MTA Fillapex (Angelus) served as the commercial reference (control) (Table 1). Table 1. Composition of root canal sealers tested. Groups Composition (% weight) MTA Base paste: 1,3-butyleneglycol disalicylate (60%) and bismuth oxide (40%). Catalyst paste: MTA (60%), DPT (39%) e TiO 2 (1%). MTA-HA Base paste: 1,3-butyleneglycol disalicylate (60%) and bismuth oxide (40%). Catalyst paste: MTA (40%), DPT (39%), hydroxyapatite (20%) e TiO 2 (1%). MTA- DCPD Base paste: 1,3-butyleneglycol disalicylate (60%) and bismuth oxide (40%). Catalyst paste: MTA (40%), DPT (39%), DCPD (20%) e TiO 2 (1%). MTA Fillapex Base paste: methyl salicylate butylene glycol colophony, bismuth trioxide, fumed silicon dioxide. Catalyst paste: fumed silicon dioxide, titanium dioxide, mineral trioxide aggregate, pentaerythritol, rosinate, p-toluenesolfonamide. DPT: n,n-dihydroxyethyl-p-toluidine; TiO 2 : titanium dioxide; DCPD: dibasic calcium phosphate dihydrate. The endodontic sealers were proportioned using equal volumes of the two pastes (base and catalyst) on a glass slab. Manipulation was performed using a metal spatula nº 24 (SS-White Duflex, Rio de Janeiro, RJ, Brazil) for 30 seconds, ensuring thorough homogenization of the two pastes. Flow and working time The flow and working time tests were conducted following the International Organization for Standardization (ISO) 6876:2012 (revised and confirmed in 2017). Following the aforementioned manual manipulation of the tested root canal sealers, 0.05 mL of each sealer was placed at the center of a second glass slab (40 x 40 mm, 5 mm thick, and 20 g). At 180 seconds after the start of manipulation, a third glass slab with the same dimensions and mass was centrally placed atop the sealer, followed by a metallic device weighing 100 g, totaling a mass of 120 g on the sealer. Ten minutes later, the weight was removed, and the maximum and minimum diameters of the compressed disc formed by the sealer were measured using a digital caliper with a precision of 0.01 mm (model 100.170, Digimess, São Paulo, SP, Brazil). The test was repeated if the two diameters showed a difference greater than 1 mm (n=3). The mean values and standard deviation were calculated and recorded (mm) to obtain the flow values. New samples were manipulated under the same conditions to evaluate working time (n=3). Working time was recorded when the sealer reached 90% of the diameter measured in the flow test. Setting Time The setting time test was realized following the ISO 6876:2012 specification (revised and confirmed in 2017). Gypsum molds (10 mm diameter, 1 mm thickness) were pre-stored in an incubator at 37°C and 95% relative humidity for 24 hours. The root canal sealers (n=3) were proportioned and manipulated as previously described. Subsequently, these materials were inserted into the gypsum molds freshly removed from the incubator. A glass slide (1 mm thick) was placed over the mold/sealer assembly for surface leveling. Following this, an indenter with a 100 g load and a flat-end 2 mm diameter was positioned perpendicular to the specimens and carefully lowered vertically onto the sealer surface. The process was repeated until no indentations were visible on the specimen surface (n=3). The indenter tip was cleaned before each reading. The time between the start of manipulation and when no visble indentations could be seen on the sealer was recorded as the setting time. Film thickness For the film thickness measurement (n=3), acrylic plates (50 mm width x 50 mm length x 5 mm thickness) were stacked on top of each other, confirming a total thickness of 10 mm using a digital caliper accurate to 0.001 mm (model 5-30mm series 345, Mitutoyo, Tokyo, Japan). After manipulating the root canal sealers, they were placed on an acrylic plate, with a second acrylic plate positioned on top of the sealer. Subsequently, a compressive load of 150N (MBio I 500, BioPDI) was applied to this plate-sealer-plate assembly. The thickness of this assembly was then measured again using the caliper with an accuracy of 0.001 mm (Mitutoyo), and the difference between the initial and final measurements was recorded as the film thickness (µm). This test was also conducted in accordance with the ISO 6876:2012 specification (revised and confirmed in 2017). Endodontic preparations A pilot study was conducted to calibrate the operators (FGRC and FMP) and to determine the minimum number of samples per group (sample calculation) for tests not included in the ISO 6876:2012 specification (void and push-out bond strength tests) with α=0.05 and 80% power. Extracted human single-rooted canines and premolars for therapeutic reasons were selected. Initially, standardization of the teeth occurred through macroscopic inspection using a stereomicroscope with 20x magnification (Leica Microsystems, Wetzlar, Germany) to verify intact roots and complete apices. Teeth with carious lesions, cracks, and/or any other lesions in the root were discarded. Teeth with a minimum of 10 mm of root length were included in this study. The teeth were also radiographed to visualize canal anatomy in mesiodistal and buccolingual directions; those showing calcifications, incomplete root apex, or prior endodontic treatment were excluded. The selected teeth were stored in distilled water at 4°C for use within 6 months after Ethics Committee approval (CAAE 82540618.9.1001.5501). Subsequently, the teeth were sectioned 1 mm above the cementoenamel junction to obtain a flat and deep dentin surface using a low-speed diamond disc under water-cooling (Isomet 1000, Buehler, Lake Bluff, IL, USA). Root canal irrigation was performed using 2.5% sodium hypochlorite solution, followed by its aspiration and re-insertion. Canal exploration was then performed with Kerr file #15 (Dentsply-Maillefer, Ballaigues, Switzerland) until reaching the apical foramen. The working length was determined for each sample by subtracting 1 mm from the total length traveled by the file during exploration. The canals were further prepared using rotary instruments Mtwo NiTi (VDW; VDW GmbH, Munich, Germany) up to size 40.04 and irrigated with 2.5% sodium hypochlorite solution after each instrument change. All apices of the samples were sealed with utility wax to allow the flow and reflux of irrigating solutions. Root canal preparation was finalized through instrumentation at the working length. The samples underwent syringe irrigation using Navi Tips (Ultradent Products, South Jordan, UT, USA) positioned 2 mm from the working length. Final irrigation consisted of 5 mL of 2.5% sodium hypochlorite, followed by 5 mL of 17% EDTA (pH 7.7; Odahcam, Dentsply, Petrópolis, RJ, Brazil), and concluded with 5 mL of 2.5% sodium hypochlorite. After the final irrigation, the canals were dried using White Mac (Ultradent) and Capillary Tips (Ultradent) and dried with absorbent paper points corresponding to instrument size 40.04. Obturation was performed using the single cone technique with 40.04 gutta-percha cones (Mtwo, VDW) previously calibrated on a millimeter ruler. Subsequently, the root canal sealers were manipulated as previously described and spread over the gutta-percha cone surface for insertion into the root canals. Excess gutta-percha was removed at the canal orifice using heated pluggers and cold vertical compression. The quality of obturation was assessed through radiographic imaging. The roots were kept in an incubator at 37°C and 100% humidity for 7 days. Micro-computed tomography Computed tomography imaging was conducted on the obturated teeth (n=10) using a microtomograph (SkyScan 1173, Bruker, Kontich, Belgium) with exposure parameters set at 70 kV and 114uA. A 1 mm thick aluminum filter was applied, exposure time set at 320 milliseconds, a rotation step of 0.5, and a full 360-degree rotation around the vertical axis. The isotropic resolution was 17 µm. Images were reconstructed using the NRecon software (v1.6.1.0; Bruker, Kontich, Belgium) with specific reconstruction parameters: 1 ring artifact correction, 35% beam hardening correction, and smoothing of 2 for all images. ImageJ software was utilized for analyzing the volume of obturation material and the presence of voids. The binarization process was employed, involving processing grayscale levels to obtain a black-and-white image exclusively. The range of grayscale required to recognize the obturation material and voids was determined from a density histogram using the global thresholding method. Subsequent arithmetic and logical operations were applied to create separate binary images of the root canal and obturation material. The voids volume was calculated using the formula: % voids = void volume x 100 / obturation material volume Push-out bond strength The samples were fixed onto acrylic plates using sticky wax (Kota, São Paulo, SP, Brazil). This assembly was sectioned using a metallographic cutter (Isomet 1000, Buehler) with a diamond disc (0.03 mm thickness) at low speed (350 rpm) and water cooling. The cuts were made from the root apex towards the cervical portion, and the samples were cut to an approximate thickness of 1 mm in each of the thirds (cervical, middle, and apical). The cervical part of each section was marked with a pen, and the thickness was verified using a digital caliper with an accuracy of 0.001 mm (Mitutoyo). Each root was sectioned into six slices: two apical, two middle, and two cervical. The first slice from each root third was used for the push-out test, while the second slice was used for dentinal penetration (confocal). Subsequently, the specimens were stored for 3 hours at 37ºC. For the push-out test (n=10), the first slice was placed into a universal testing machine (Instron 1144, Norwood, USA) at a speed of 0.5 mm/min and a load cell of 500N until displacement of the filling occurred. The tip used touched only the filling mass (sealer and gutta-percha) in the evaluated thirds. The specimen was mounted in the universal testing machine apico-coronally, meaning the smaller diameter was facing upwards and the larger one downwards (the cut part marked with the pen) to prevent any interference caused by the anatomical narrowing of the root canal during the test. The force values required for the displacement of the filling in each specimen (thickness) were obtained in Newtons (N) and converted to MegaPascals (MPa) by dividing the force value by the bonding area of the filling material (mm 2 ). To calculate the bonding area, the formula used was: RU = π (R1 + R2) [(R1 – R2) 2 ] 1/2 + h 2 The π is 3.14, where R1 is the radius of the root opening at the apical face of the root, R2 is the radius of the root opening at the cervical face of the root, and h is the slice thickness. Each third was examined using a stereomicroscope at 20x magnification (Leica Microsystems) to determine the failure pattern frequency: adhesive (no visible sealer on dentin walls), cohesive (complete dentin walls covered with sealer), or mixed (combination of adhesive and cohesive; partial dentin coverage with sealer). Sealer penetration into dentinal tubules The 0.1% by weight of rhodamine B (Sigma Chemicals, St. Louis, MO, USA) was added in the root canal sealers during their manipulation. The root canals (n=10) were comprehensively assessed, and representative images of micropermeability patterns (sealer penetration) were recorded. Images were captured using a laser scanning confocal microscope equipped with a 63x oil immersion lens (NA 1.4) and an illumination system comprising an argon/helium laser (488 nm) and a helium-neon laser (633 nm) with absorption and emission wavelengths suitable for rhodamine B and fluorescein. Fluorescence images were acquired from optical sections of 20μm, located 1 mm below the surface (z-axis). Sealer micromorphology All root canal sealers tested were manipulated and inserted into silicone molds with 8 mm internal diameter and 1.6 mm height (n=3) on a glass plate for microstructure evaluation using scanning electron microscopy (SEM; JSM 5600LV, JEOL, Tokyo, Japan). A polyester strip and a glass slide were placed over the sealer to flatten the surfaces. The samples were kept in an oven at 37ºC for 24 hours. Subsequently, the samples were removed from the silicone molds and placed in a desiccator for complete moisture removal. The specimens were then positioned on a conductive carbon adhesive tape attached to a metal stub for gold sputter coating (Bal-Tec SCD-050 Sputter Coater, Liechtenstein) prior to SEM analysis. Statistical analyses The statistical analyses included preliminary tests to assess the normality of the sample distribution. Upon confirming normality (ρ>0.05 in the Shapiro-Wilk test) and homoscedasticity (ρ>0.05 in the Levene test), parametric statistical tests were employed, except for the push-out bond strength data (ρ=0.020 in the Shapiro-Wilk test). One-way analysis of variance (ANOVA) with Tukey's post-hoc test (α=0.05) were used for parametric data. The push-out bond strength data were evaluated using the Kruskal-Wallis and Student-Newman-Keuls test (α=0.05). The Dunnett test was performed to compare the experimental groups with the control group. Statistical analysis was conducted using SPSS 22.0 (Statistical Package for the Social Sciences). Results Table 2 shows that the control group exhibited statistically the highest values in working and setting times, as well as in flow (ρ 0.05). Table 2 Means (± SD) of working and setting times (min), flow (mm), and film thickness (µm). Sealer Working time Setting time Flow Film thickness MTA 16.2 (0.8) a* 191.7 (14.4) a* 23.87 (0.88) a* 48 (1.48) a* MTA-HA 15.7 (0.3) a* 183.3 (14.4) a* 22.05 (0.60) a* 45 (1.07) a* MTA- DCPD 15.3 (0.6) a* 183.3 (38.1) a* 22.37 (0.35) a* 46 (2.01) a* MTA Fillapex 30.2 (0.8) 258.3 (28.8) 28.35 (0.83) 25 (3.52) Different letters indicate statistical differences between the sealers (column) for each test (ρ < 0.05). Asterisk (*) indicates statistical differences between the experimental sealers and the control group (column) (ρ < 0.05). Control group: MTA Fillapex. In the micro-computed tomography analysis, assessing the entire extension of the root canal, despite minor qualitative differences in root canal obturation (Fig. 1 ), the evaluated experimental groups did not exhibit differences among themselves or with the control group concerning the volume of void spaces (ρ > 0.05) (Table 3 ). Table 3 Means (± SD) of voids volume in root canals. Sealer Voids (%) MTA 7.37 (9.69) MTA-HA 8.09 (4.63) MTA-DCPD 8.47 (8.09) MTA Fillapex 5.27 (7.54) For the push-out bond strength test, the Kruskal-Wallis test revealed interaction between the factors of experimental root canal sealers and root thirds (ρ = 0.009), with significant differences observed only for the material factor (ρ 0.05), except for the MTA-DCPD group in the cervical third (ρ = 0.017). No differences in bond strength were observed among the root thirds for all groups (ρ > 0.05). Table 4 Means (± SD) of bond strength (MPa) of root canal sealers and root thirds. Sealer Cervical Middle Apical Pool mean MTA 2.12 (1.20) ab 2.61 (1.60) a 2.59 (1.49) ab 2.44 (1.54) MTA-HA 4.82 (3.39) a 2.94 (1.14) a 5.92 (4.19) a 4.56 (3.88) MTA-DCPD 1.24 (0.44) b* 1.91 (0.96) a 2.46 (1.45) b 1.87 (1.20) MTA Fillapex 2.92 (2.29) 3.07 (2.45) 3.62 (2.75) 3.20 (2.65) Different letters indicate statistical differences between the sealers (columns) (ρ < 0.05). Asterisk (*) indicates statistical differences between the experimental sealers and the control group (column) (ρ < 0.05). Control group: MTA Fillapex. Cohesive failure was predominant for all tested root canal sealers, with MTA Fillapex presenting the highest percentage of cohesive failures (Table 5 ). Table 5 Distribution of failure patterns of the root canal sealers. Sealers Adhesive Cohesive Mixed MTA 13% 70% 17% MTA-HA 6% 78% 16% MTA-DCPD 11% 73% 16% MTA Fillapex 3% 89% 8% Figure 2 comprises representative images obtained by laser confocal microscopy of the cervical section of the root thirds of all groups. The control group (MTA Fillapex) exhibited the most extensive cement penetration into root dentin qualitatively. The micromorphology analyses of all root canal sealer samples assessed in this study are depicted in Fig. 3 . The dominance of amorphous particles is evident for all groups, with the presence of cylindrical particles (yellow arrow) and point crystals (red arrow). Notably in MTA (Fig. 3 A), there are clusters of particles with varying dimensions (asterisk), whereas in MTA Fillapex (Fig. 3 D), particles appear more dispersed. The MTA-HA (Fig. 3 B) and MTA-DCPD (Fig. 3 C) samples also reveal the formation of cubic-shaped particles, which are larger, more homogeneous, and more abundant compared to MTA Fillapex (Fig. 3 D). Discussion The hypothesis was rejected since the control group exhibited statistically the highest values in working and setting times, as well as in flow (Table 2 ). However, regarding film thickness, all experimental root canal sealers showed higher values without statistical differences between them (Table 2 ). Both working and setting times are dependent on the chemical composition of root canal sealers, particle size, manipulation temperature, and relative humidity of the environment [ 11 ]. All evaluated root canal sealers contain MTA (Table 1 ) and set through two main chemical reactions: the progressive hydration of orthosilicate ions (SiO 4 4− ) and the chemical reaction between MTA and salicylate resin [ 11 , 22 ]. During manipulation, these two components come into contact, and calcium reacts with salicylate to create an ionic polymer. Hydration occurs as the tricalcium silicate particles in MTA react with water, forming a hydrated solution of amorphous calcium silicate, taking set, and forming a solid and uniform network [ 18 ]. Thus, the differences found in the working and setting times of the evaluated materials can be attributed to the chemical composition of each sealer. The manipulated MTA Fillapex contains approximately 13% MTA in its composition [ 23 ]. Thus, a possible explanation for the experimental root canal sealers showing the lowest working and setting times values lies in the MTA-salicylate resin ratio. The higher quantity of MTA present in the experimental materials (40–60% in the catalyst paste; Table 1 ), around 20–30% of the manipulated sealer mass, accelerates the MTA-salicylate chemical reaction, resulting in shorter working and setting times (Table 2 ). The same MTA-salicylate resin ratio, which grants MTA Fillapex longer setting and working times, seems to account for its higher flow in comparison to the experimental sealers (Table 1 ). A larger amount of salicylate resin makes the material more fluid and consequently increases its flowability. The particle size of MTA also influences viscosity and, consequently, flow. Smaller particles lead to a larger contact area during the reaction with salicylate resin, increasing viscosity and reducing flow [ 24 , 25 ]. MTA Fillapex presents MTA particles with an average size of 12 µm, while the MTA used in the experimental root canal sealers had an average size of 5 µm (manufacturer's data). It's important to highlight that all tested root canal sealers comply with ISO 6876:2012 [ 26 ], which recommends that endodontic sealers should have a flow greater than 20 mm. A root canal sealer should demonstrate moderate flow, as excessive flow increases the likelihood of material extrusion into the periapical region. Conversely, low flow reduces sealer penetration into irregularities of the main canal and accessory canals, compromising the material's sealing ability [ 27 ]. All tested sealers exhibit pseudoplastic behavior, where their viscosity reduces while flow increases. This occurs due to the shear forces acting on the sealer during its application [ 27 , 28 ]. The MTA-resin salicylate ratio in the experimental root canal sealers is sufficient for these materials to exhibit a film thickness within the limit required by ISO 6876:2012 (≤ 50 µm) [ 26 ]. This parameter is crucial for proper distribution of the root canal sealer within the root canals [ 29 ], particularly during the insertion of gutta-percha [ 5 , 30 ]. The increased film thickness of the experimental root canal sealers might be associated with the size of the MTA particles, as the particle size in these materials generates a larger surface area and increases viscosity, as mentioned above. Additionally, the amount of radiopacifier (bismuth oxide) used in these materials may influence material hydration, affecting their film thickness [ 31 ]. Bismuth oxide has a high molecular weight, and its presence alters the physical properties of sealers, leading to internal flaws and increased thickness [ 32 ]. MTA Fillapex contains approximately 10.5% bismuth oxide [ 33 ], while the experimental root canal sealers used in this study had 40% in the base paste (Table 1 ), totaling around 20% of the manipulated sealer. The filling of root canals and the presence of voids, measured by micro-computed tomography, showed minor qualitative differences in root canal obturation among the groups (Fig. 1 ). Furthermore, the experimental groups did not exhibit differences in void spaces compared to the control group (Table 3 ). This indicates that all experimental root canal sealers demonstrated satisfactory performance in filling the root canals. The presence of voids within the root canal post-obturation emerges as a critical factor that may compromise the clinical prognosis of endodontic treatment [ 34 ]. This condition significantly hampers the sealing of the root canal, increasing the potential for periradicular tissue fluid movement into the root canals. Moreover, the presence of voids can facilitate the entry of microorganisms into the periradicular tissues, potentially triggering or perpetuating apical periodontitis [ 30 , 35 ]. Analysis using computerized microtomography, encompassing the entire length of the root canal, did not reveal significant differences in voids volume (Table 3 ). These findings confirm that all experimental root canal sealers displayed satisfactory performance in root canal filling, with values comparable to the control group. The experimental and commercial root canal sealers evaluated are MTA-based and have a similar chemical composition [ 11 ]. An important aspect to consider is that the evaluated teeth were single-rooted, and the obturation technique employed was single-cone with vertical compaction. Previous studies have emphasized that the technique used in obturation can significantly impact the quality of the procedure [ 36 ]. The proper obturation achieved by all experimental root canal sealers, due to the low formation of voids, might have positively influenced the push-out bond strength values. However, it's important to note that the best bond strength result doesn't always reflect complete filling of the root canal space [ 37 ]. This might explain why all evaluated sealers showed similar volumes of voids (Table 3 ) and, at the same time, different push-out bond strength values (Table 4 ). Cohesive failures were predominant for all root canal sealers (Table 5 ). This could be explained by its thinner film thickness compared to the experimental sealers (Table 2 ). A greater thickness and cohesion of the sealer are linked to better adhesion to the root canal, as a thin layer of root canal sealer with low cohesive strength is more susceptible to contraction and material displacement [ 38 ]. These results, in comparison with literature data, suggest that besides the quantity of voids, the push-out bond strength results from a combination of factors, including root canal anatomy, obturation technique, and mainly the physicochemical properties, particle amount, viscosity, and flowability of the root canal sealers [ 39 , 40 ]. The penetration of root canal sealers into dentinal tubules may exhibit a bactericidal effect by establishing contact with residual bacteria residing within these tubules. Furthermore, the presence of sealers in dentinal tubules provides a mechanical interlocking, enhancing the retention of sealer within the root canal [ 28 ]. The penetration of root canal sealer into the root canal is influenced by various factors, including the efficacy of smear layer removal, the presence of moisture, the number and diameter of dentinal tubules, the anatomy of the root canal system, as well as the physicochemical properties of the sealers themselves [ 41 ]. Thus, both the volume of void spaces (Table 3 and Fig. 1 ) and the depth of sealer penetration into dentinal tubules (Fig. 2 ) may influence the success of endodontic therapy MTA Fillapex exhibited extensive cement penetration into the root dentin (Fig. 2 ). The alkaline nature of this sealer denatures collagen fibers, facilitating its penetration [ 42 ]. Additionally, good sealer penetration is related to its high flowability, inherent to the chemical composition and smaller particle size of MTA-based sealers [ 24 , 25 ]. The higher flowability (Table 1 ) and the higher molar ratio between calcium and phosphorus atoms (Ca/P ratio) in MTA Fillapex (Ca/P ~ 2.5) [ 43 ], compared to the tested experimental root canal sealers, may explain the superior results in the control group. Figure 3 illustrates that all tested root canal sealers contain a significant amount of amorphous particles in cylindrical and point crystal forms. In the MTA group, there are clusters of particles with varying dimensions (Fig. 3 A). In contrast, these particles appear more dispersed in the MTA Fillapex group (Fig. 3 D). Additionally, the MTA-HA (Fig. 3 B) and MTA-DCPD (Fig. 3 C) groups exhibit cubic-shaped particles. Larger particles tend to have a smaller surface area (contact area) of the sealer, consequently affecting the material's working and setting times (Table 1 ) [ 24 , 25 ]. These particles observed in the SEM images are presumed to be isolated or agglomerated particles of MTA, hydroxyapatite, and DCPD. Further analysis involving energy dispersive x-ray spectroscopy (EDS) coupled with SEM is warranted to confirm the composition of these particles. The SEM images provided insights into the structural morphology of the particles present in the evaluated sealers. The size and geometry of these particles significantly influence the sealer hydration kinetics [ 15 , 18 ]. The hydration process initiates following the dissolution of the powder (MTA, HA, and DCPD) and the subsequent crystallization of particles, characterized by the presence of cubic and point crystals (Fig. 3 ). The findings of the present study associated with outcomes from other researchers assessing similar root canal sealers [ 11 , 22 , 44 ], demonstrate that the evaluated experimental root canal sealers exhibit satisfactory physical properties and root canal sealing. However, future investigations are required to assess the esthetic compromise of these materials in anterior teeth, understand the clinical impacts of these experimental sealers on the longevity of endodontic treatment, especially when applied using different obturation techniques in multi-rooted teeth, and in endodontic retreatment. Conclusion Overall, based on the presented results, it can be concluded that the experimental root canal sealers exhibited adequate physical properties and adaptation within the root canal. They (i) demonstrated reduced working and setting times compared to MTA Fillapex, (ii) showed flow and film thickness within the values recommended by ISO 6876:2012, and (iii) exhibited a volume of voids and bond strength similar to MTA Fillapex, except for the MTA-DCPD group in the cervical third. Declarations Acknowledgement This work was supported by the São Paulo Research Foundation (FAPESP; grant number: 2015/19887-0). Compliance with Ethical Standards Conflict of Interest The authors declare no conflict of interest. Funding This work was supported by the São Paulo Research Foundation (FAPESP; grant number: 2015/19887-0). Ethical Approval All procedures performed were in accordance with the ethical standards of the institutional ethics committee approval (CAAE 82540618.9.1001.5501). 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J Endod. 39:1281-1286. https://doi.org/10.1016/j.joen.2013.06.012 Rostirolla FV, Leitune VCB, Bohns FR, Portella FF, Samuel SMW, Collares FM (2019). Calcium phosphates as fillers for methacrylate-based sealer. Clin Oral Investig 23:4417-4423. https://doi.org/10.1007/s00784-019-02898-w. International Organization for Standardization. ISO-6876. Dental root canal sealing materials. Geneva: ISO; 2012. Wu MK, Fan B, Wesselink PR (2000). Leakage along apical root fillings in curved root canals. Part I: effects of apical transportation on seal of root fillings. J Endod 26:210-216. https://doi.org/10.1097/00004770-200004000-00003 Nikhil V, Bansal P, Sawani S (2015). Effect of technique of sealer agitation on percentage and depth of MTA Fillapex sealer penetration: A comparative in-vitro study. J Conserv Dent 18:119-123. https://doi.org/10.4103/0972-0707.153073 Mendes AT, Silva PBD, Só BB, Hashizume LN, Vivan RR, Rosa RAD, Duarte MAH, Só MVR (2018). 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Huang Y, Celikten B, de Faria Vasconcelos K, Ferreira Pinheiro Nicolielo L, Lippiatt N, Buyuksungur A, Jacobs R, Orhan K (2017). Micro-CT and nano-CT analysis of filling quality of three different endodontic sealers. Dentomaxillofac Radiol 46:20170223. https://doi.org/10.1259/dmfr.20170223 Pane ES, Palamara JE, Messer HH (2013). Critical evaluation of the push-out test for root canal filling materials. J Endod 39:669-673. https://doi.org/10.1016/j.joen.2012.12.032 Kim S, Kim S, Park JW, Jung IY, Shin SJ (2017). Comparison of the percentage of voids in the canal filling of a calcium silicate-based sealer and gutta percha cones using two obturation techniques. Materials (Basel) 10:1170. https://doi.org/10.3390/ma10101170 Atmeh AR, Alharbi R, Aljamaan I, Alahmari A, Shetty AC, Jamleh A, Farooq I (2022). The effect of sealer application methods on voids volume after aging of three calcium silicate-based sealers: a micro-computed tomography study. Tomography 8:778-788. https://doi.org/10.3390/tomography8020064 Ch T, Shaik I, Khan MM, Parvekar P, Mirza MB, Mustafa M, Tiwari H (2021). The sealer penetration into the dentinal tubules: an appraisal of different irrigation systems. J Pharm Bioallied Sci 13(Suppl 2):S1280-S1285. https://doi.org/10.4103/jpbs.jpbs_95_21 Arikatla SK, Chalasani U, Mandava J, Yelisela RK (2018). Interfacial adaptation and penetration depth of bioceramic endodontic sealers. J Conserv Dent 21:373-377. https://doi.org/10.4103/JCD.JCD_64_18 Elsayed MA, Hassanien EE, Elgendy AAE (2021). Ageing of totalfill BC sealer and MTA fillapex in simulated body fluid. Eur Endod J 6:183-188. https://doi.org/10.14744/eej.2020.43043 Silva MGSE, Münchow EA, Vitti RP, Sinhoreti MAC, Piva E, Ogliari FA, Zanchi CH (2018). Pentaerythritol tetrasalicylate in the chemical composition of root canal sealers. Braz Dent J 29:48-53. https://doi.org/10.1590/0103-6440201801441 Additional Declarations No competing interests reported. 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Also discoverable on Platform About Our Team In Review Editorial Policies Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5315187","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":372743101,"identity":"40f42c01-1183-4b20-a4eb-9191bbe28163","order_by":0,"name":"Rafael Vitti","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA2UlEQVRIiWNgGAWjYFACxgdAQoKBgZn5AIghQ4QWZgOQSgkeZrYEEIOHWC0gpTxgBmEt5u2HGT8XtlnU2bPzfH51o8aCh4H98NEN+LTInElmlp7ZBnIY7zbrnGMg29LSbuDTIsGQf0Ca5wxEi3EOG1CLBI8Zfi38j5l/Q7TwPDPO+UeMFolkNmmeCrAW5se5bURpecxmPaNCQrLnMJsZc26fBA8bQb/wJzPfLjCo42fvP/z4c863Ojl+9sPH8GoBAWYozSYBJgkpR9bC/IEY1aNgFIyCUTDyAAAdyDe9WWC7yQAAAABJRU5ErkJggg==","orcid":"","institution":"State University of Campinas","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Rafael","middleName":"","lastName":"Vitti","suffix":""},{"id":372743103,"identity":"b00225d7-196f-4974-9eee-5e0e0b57af10","order_by":1,"name":"Flávia Cardoso","email":"","orcid":"","institution":"Universidade de Taubaté","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Flávia","middleName":"","lastName":"Cardoso","suffix":""},{"id":372743104,"identity":"a8a597d4-07f0-4184-9463-4343cfa87cea","order_by":2,"name":"Flávia Pereira","email":"","orcid":"","institution":"Universidade de Taubaté","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Flávia","middleName":"","lastName":"Pereira","suffix":""},{"id":372743105,"identity":"829b57a7-226d-41fa-a608-a7c5902fb51b","order_by":3,"name":"Evandro Piva","email":"","orcid":"","institution":"Universidade Federal de Pelotas","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Evandro","middleName":"","lastName":"Piva","suffix":""},{"id":372743106,"identity":"64690b06-c607-4eaa-88bd-9af7047bdbbe","order_by":4,"name":"Cesar Zanchi","email":"","orcid":"","institution":"Universidade Federal de Pelotas","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Cesar","middleName":"","lastName":"Zanchi","suffix":""},{"id":372743107,"identity":"815f39d7-64dd-4664-a682-e77880d82e16","order_by":5,"name":"Gabriel Abuna","email":"","orcid":"","institution":"East Carolina University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Gabriel","middleName":"","lastName":"Abuna","suffix":""},{"id":372743108,"identity":"53b620d9-9e87-4255-ade6-54dbd8b206d3","order_by":6,"name":"Carolina Lima","email":"","orcid":"","institution":"Grande Rio University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Carolina","middleName":"","lastName":"Lima","suffix":""},{"id":372743109,"identity":"071c4ec4-f696-4ec7-b4fc-6aa77d89e296","order_by":7,"name":"Emmanuel Silva","email":"","orcid":"","institution":"Grande Rio University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Emmanuel","middleName":"","lastName":"Silva","suffix":""},{"id":372743110,"identity":"44ab19b6-7b53-4a9b-8034-7ea732183b04","order_by":8,"name":"Flávio Aguiar","email":"","orcid":"","institution":"State University of Campinas","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Flávio","middleName":"","lastName":"Aguiar","suffix":""},{"id":372743111,"identity":"bc03d3fe-e48c-4dd6-9b12-73967f58c2c2","order_by":9,"name":"Mário Alexandre Sinhoreti","email":"","orcid":"","institution":"State University of Campinas","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Mário","middleName":"Alexandre","lastName":"Sinhoreti","suffix":""}],"badges":[],"createdAt":"2024-10-23 03:08:14","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5315187/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5315187/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":68438494,"identity":"039e684b-dcc9-4376-8bfc-bd628181dbef","added_by":"auto","created_at":"2024-11-07 09:13:15","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":91510,"visible":true,"origin":"","legend":"\u003cp\u003eThree-dimensional computed tomography images displaying the filling of root canals by the root canal sealers.\u003c/p\u003e\n\u003cp\u003e(A) MTA; (B) MTA-HA; (C) MTA-DCPD; (D) MTA Fillapex.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5315187/v1/641b01546b009397adef81c0.png"},{"id":68438496,"identity":"e056cbdd-ced7-41d7-a41a-8c94bfd6b74f","added_by":"auto","created_at":"2024-11-07 09:13:15","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":161472,"visible":true,"origin":"","legend":"\u003cp\u003eLaser confocal microscopy images showing the penetration of cements into dentinal tubules\u003c/p\u003e\n\u003cp\u003e(A) MTA; (B) MTA-HA; (C) MTA-DCPD; (D) MTA Fillapex.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5315187/v1/d2efb340d97b7a915930e6c7.png"},{"id":68438643,"identity":"27ddbb0f-7b0b-4a16-977f-d80807759ac7","added_by":"auto","created_at":"2024-11-07 09:21:15","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":210707,"visible":true,"origin":"","legend":"\u003cp\u003eScanning electron microscopy (SEM) images depicting the micromorphology \u003cbr\u003e\nof the sealers.\u003c/p\u003e\n\u003cp\u003e(A) MTA; (B) MTA-HA; (C) MTA-DCPD; (D) MTA Fillapex. Asterisk: particle cluster. \u003cbr\u003e\n \u0026nbsp;Yellow arrow: cylindrical particle. Red arrow: point particle.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5315187/v1/4bf41b2f81d1715bd3bc9da6.png"},{"id":70871996,"identity":"f07da1b6-70d2-4807-803d-7b6524385140","added_by":"auto","created_at":"2024-12-08 15:53:45","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":940596,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5315187/v1/9d42ddd5-b0a3-478b-b76f-4ea037a7a157.pdf"},{"id":68438497,"identity":"7d5f41e8-63ae-402c-98c4-49c06da873d7","added_by":"auto","created_at":"2024-11-07 09:13:15","extension":"png","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":1620863,"visible":true,"origin":"","legend":"","description":"","filename":"GraphicalAbstract.png","url":"https://assets-eu.researchsquare.com/files/rs-5315187/v1/6bf2157290e8319dc49a8048.png"}],"financialInterests":"No competing interests reported.","formattedTitle":"Synthesis, physical properties, and root canal sealing of experimental MTA- and salicylate-based root canal sealers","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe success of endodontic treatment relies on various factors aimed at curing and preventing contamination of the tooth and periapical tissues [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Once mechanical and chemical cleaning of the root canals is completed, a properly fitted obturation to these canal walls ensures a secure seal, preventing the ingress of microorganisms or tissue fluids [\u003cspan additionalcitationids=\"CR4\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Gutta-percha in combination with root canal sealer plays a critical role in establishing the adequate adhesion of the obturation to dentin walls [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe quest for biocompatible and bioactive materials in root canal obturation holds promise due to their capacity to induce healing and bone regeneration [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Over time, root canal sealers with ion release have been proposed to enhance apical sealing by promoting mineral deposition on the canal walls [\u003cspan additionalcitationids=\"CR7 CR8 CR9 CR10 CR11 CR12 CR13\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Calcium-containing root canal sealers constitute a significant category in this context, showcasing good apical sealing capacity and chemical-mechanical interaction with root dentin [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. These sealers consist of calcium silicate, calcium aluminate, and other calcium sources [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMTA (mineral trioxide aggregate) is a widely used material in dentistry known for its good marginal adaptation, anti-inflammatory properties, and its capability to induce mineralized tissue formation [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Despite its advantages, MTA has limitations such as dental discoloration, extended setting time, high cost, and increased cytotoxicity post-manipulation. Hence, several studies have explored the addition of other calcium sources to root canal sealers to enhance their physicochemical and biological properties [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan additionalcitationids=\"CR18\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Stoichiometric hydroxyapatite and dibasic calcium phosphate dihydrate (DCPD) are other calcium sources also under study for incorporation into root canal sealers. They exhibit favorable properties, including good osteoconductivity and satisfactory cellular response [\u003cspan additionalcitationids=\"CR8 CR9 CR10\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eRoot canal sealers based on salicylate resins have also been studied and utilized to enhance handling and physical properties. Additionally, these resins demonstrate satisfactory performance owing to their anti-inflammatory properties [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. The combination of different calcium sources with salicylate resin in root canal sealers can enhance their physicochemical properties. Moreover, a higher amount of MTA in these endodontic sealers compositions increases calcium release and pH [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. New studies assessing the interaction of these calcium sources with salicylate resin could contribute to a better understanding of clinical performance while seeking to improve the physicochemical and biological properties of these materials.\u003c/p\u003e \u003cp\u003eTherefore, the aim of this study was to assess the physical properties and sealing ability of experimental root canal sealers based on MTA and butylene glycol disalicylate. The hypothesis tested was that the experimental root canal sealers compared to the commercial reference (control) would demonstrate superior outcomes in the evaluated properties.\u003c/p\u003e"},{"header":"Material and methods","content":"\u003cp\u003e\u003cem\u003eExperimental design\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eIn this in vitro study, the factors investigated included (i) the type of root canal sealer at 4 levels (three experimental and one commercial sealers) for all tests, and (ii) root canal thirds at 3 levels (cervical, middle, and apical) for the push-out test. The response variables comprised quantitative analysis of working time (n=3) and setting time (n=3), flow (n=3), and film thickness (n=3); qualitative and quantitative assessment of the percentage volume of void spaces using micro-computed tomography (n=10) and push-out bond strength (n=10); as well as qualitative analysis of sealer penetration into dentinal tubules through confocal microscopy (n=10) and sealer micromorphology using scanning electron microscopy (n=3).\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eSynthesis of salicylate resin\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe salicylate resin (1,3-butyleneglycol disalicylate) was synthesized via transesterification reaction of methyl salicylate (Synth Laboratory, S\u0026atilde;o Paulo, SP, Brazil) with two different alcohols, at a molar ratio of 1:3. Titanium isopropoxide (Sigma-Aldrich, St. Louis, MO, USA) served as the catalyst agent. The reaction was maintained at 200\u0026deg;C for 2 hours. The resulting product underwent purification through vacuum distillation and was characterized via nuclear magnetic resonance (NMR) spectroscopy and Fourier-transform infrared spectroscopy (FTIR), which revealed a distinct peak of hydroxyl groups within the spectral range of 3300 cm\u003csup\u003e-1\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eFormulation and handling of root canal sealers\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe experimental root canal sealers consisted of two pastes. The base paste comprised 1,3-butyleneglycol disalicylate and bismuth oxide (Vetec, Duque de Caxias, RJ, Brazil). Three catalyst pastes were formulated using different types of calcium phosphate (white MTA, hydroxyapatite, and\u0026nbsp;DCPD): [Group 1: MTA] n,n-dihydroxyethyl-p-toluidine (DPT; Sigma-Aldrich), titanium dioxide (TiO\u003csub\u003e2\u003c/sub\u003e; Sigma-Aldrich), and MTA (Angelus, Londrina, PR, Brazil); [Group 2: MTA-HA] DPT + TiO\u003csub\u003e2\u003c/sub\u003e + MTA + hydroxyapatite (Sigma-Aldrich); [Group 3: MTA- DCPD] DPT + TiO\u003csub\u003e2\u003c/sub\u003e + MTA + DCPD (Vetec). MTA Fillapex (Angelus) served as the commercial reference (control) (Table 1). \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTable 1. Composition of\u0026nbsp;root canal sealers tested.\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"617\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eGroups\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eComposition (% weight)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eMTA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eBase paste:\u0026nbsp;1,3-butyleneglycol disalicylate\u0026nbsp;(60%) and\u0026nbsp;bismuth oxide\u0026nbsp;(40%).\u003c/p\u003e\n \u003cp\u003eCatalyst paste:\u0026nbsp;MTA (60%), DPT (39%) e\u0026nbsp;TiO\u003csub\u003e2\u003c/sub\u003e (1%).\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eMTA-HA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eBase paste:\u0026nbsp;1,3-butyleneglycol disalicylate\u0026nbsp;(60%) and\u0026nbsp;bismuth oxide\u0026nbsp;(40%).\u003c/p\u003e\n \u003cp\u003eCatalyst paste: MTA (40%),\u0026nbsp;DPT\u0026nbsp;(39%),\u0026nbsp;hydroxyapatite\u0026nbsp;(20%) e\u0026nbsp;TiO\u003csub\u003e2\u003c/sub\u003e (1%).\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eMTA-\u0026nbsp;DCPD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eBase paste:\u0026nbsp;1,3-butyleneglycol disalicylate\u0026nbsp;(60%) and\u0026nbsp;bismuth oxide\u0026nbsp;(40%).\u003c/p\u003e\n \u003cp\u003eCatalyst paste: MTA (40%),\u0026nbsp;DPT\u0026nbsp;(39%),\u0026nbsp;DCPD\u0026nbsp;(20%) e\u0026nbsp;TiO\u003csub\u003e2\u003c/sub\u003e (1%).\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eMTA Fillapex\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eBase paste: methyl salicylate butylene glycol colophony, bismuth trioxide, fumed silicon dioxide.\u003c/p\u003e\n \u003cp\u003eCatalyst paste: fumed silicon dioxide, titanium dioxide, mineral trioxide aggregate, pentaerythritol, rosinate, p-toluenesolfonamide.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;DPT: n,n-dihydroxyethyl-p-toluidine; TiO\u003csub\u003e2\u003c/sub\u003e: titanium dioxide; DCPD:\u0026nbsp;dibasic calcium phosphate dihydrate.\u003c/p\u003e\n\u003cp\u003eThe endodontic sealers were proportioned using equal volumes of the two pastes (base and catalyst) on a glass slab. Manipulation was performed using a metal spatula n\u0026ordm; 24 (SS-White Duflex, Rio de Janeiro, RJ, Brazil) for 30 seconds, ensuring thorough homogenization of the two pastes.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eFlow and working time\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe flow and working time tests were conducted following the International Organization for Standardization (ISO) 6876:2012 (revised and confirmed in 2017). Following the aforementioned manual manipulation of the tested root canal sealers, 0.05 mL of each sealer was placed at the center of a second glass slab (40 x 40 mm, 5 mm thick, and 20 g). At 180 seconds after the start of manipulation, a third glass slab with the same dimensions and mass was centrally placed atop the sealer, followed by a metallic device weighing 100 g, totaling a mass of 120 g on the sealer. Ten minutes later, the weight was removed, and the maximum and minimum diameters of the compressed disc formed by the sealer were measured using a digital caliper with a precision of 0.01 mm (model 100.170, Digimess, S\u0026atilde;o Paulo, SP, Brazil). The test was repeated if the two diameters showed a difference greater than 1 mm (n=3). The mean values and standard deviation were calculated and recorded (mm) to obtain the flow values.\u003c/p\u003e\n\u003cp\u003eNew samples were manipulated under the same conditions to evaluate working time (n=3). Working time was recorded when the sealer reached 90% of the diameter measured in the flow test.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eSetting Time\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe setting time test was realized following the ISO 6876:2012 specification (revised and confirmed in 2017). Gypsum molds (10 mm diameter, 1 mm thickness) were pre-stored in an incubator at 37\u0026deg;C and 95% relative humidity for 24 hours. The root canal sealers (n=3) were proportioned and manipulated as previously described. Subsequently, these materials were inserted into the gypsum molds freshly removed from the incubator. A glass slide (1 mm thick) was placed over the mold/sealer assembly for surface leveling.\u003c/p\u003e\n\u003cp\u003eFollowing this, an indenter with a 100 g load and a flat-end 2 mm diameter was positioned perpendicular to the specimens and carefully lowered vertically onto the sealer surface. The process was repeated until no indentations were visible on the specimen surface (n=3). The indenter tip was cleaned before each reading. The time between the start of manipulation and when no visble indentations could be seen on the sealer was recorded as the setting time.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eFilm thickness\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eFor the film thickness measurement (n=3), acrylic plates (50 mm width x 50 mm length x 5 mm thickness) were stacked on top of each other, confirming a total thickness of 10 mm using a digital caliper accurate to 0.001 mm (model 5-30mm series 345, Mitutoyo, Tokyo, Japan). After manipulating the root canal sealers, they were placed on an acrylic plate, with a second acrylic plate positioned on top of the sealer. Subsequently, a compressive load of 150N (MBio I 500, BioPDI) was applied to this plate-sealer-plate assembly. The thickness of this assembly was then measured again using the caliper with an accuracy of 0.001 mm (Mitutoyo), and the difference between the initial and final measurements was recorded as the film thickness (\u0026micro;m). This test was also conducted in accordance with the ISO 6876:2012 specification (revised and confirmed in 2017).\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eEndodontic preparations\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eA pilot study was conducted to calibrate the operators (FGRC and FMP) and to determine the minimum number of samples per group (sample calculation) for tests not included in the ISO 6876:2012 specification (void and push-out bond strength tests) with\u0026nbsp;\u0026alpha;=0.05 and 80% power.\u003c/p\u003e\n\u003cp\u003eExtracted human single-rooted canines and premolars for therapeutic reasons were selected. Initially, standardization of the teeth occurred through macroscopic inspection using a stereomicroscope with 20x magnification (Leica Microsystems,\u0026nbsp;Wetzlar, Germany) to verify intact roots and complete apices. Teeth with carious lesions, cracks, and/or any other lesions in the root were discarded. Teeth with a minimum of 10 mm of root length were included in this study. The teeth were also radiographed to visualize canal anatomy in mesiodistal and buccolingual directions; those showing calcifications, incomplete root apex, or prior endodontic treatment were excluded. The selected teeth were stored in distilled water at 4\u0026deg;C for use within 6 months after Ethics Committee approval (CAAE 82540618.9.1001.5501). Subsequently, the teeth were sectioned 1 mm above the cementoenamel junction to obtain a flat and deep dentin surface using a low-speed diamond disc under water-cooling (Isomet 1000, Buehler,\u0026nbsp;Lake Bluff, IL, USA).\u003c/p\u003e\n\u003cp\u003eRoot canal irrigation was performed using 2.5% sodium hypochlorite solution, followed by its aspiration and re-insertion. Canal exploration was then performed with Kerr file #15 (Dentsply-Maillefer,\u0026nbsp;Ballaigues, Switzerland) until reaching the apical foramen. The working length was determined for each sample by subtracting 1 mm from the total length traveled by the file during exploration. The canals were further prepared using rotary instruments Mtwo NiTi (VDW; VDW GmbH, Munich, Germany) up to size 40.04 and irrigated with 2.5% sodium hypochlorite solution after each instrument change.\u003c/p\u003e\n\u003cp\u003eAll apices of the samples were sealed with utility wax to allow the flow and reflux of irrigating solutions. Root canal preparation was finalized through instrumentation at the working length. The samples underwent syringe irrigation using Navi Tips (Ultradent Products, South Jordan, UT, USA) positioned 2 mm from the working length. Final irrigation consisted of 5 mL of 2.5% sodium hypochlorite, followed by 5 mL of 17% EDTA (pH 7.7; Odahcam, Dentsply, Petr\u0026oacute;polis, RJ, Brazil), and concluded with 5 mL of 2.5% sodium hypochlorite. After the final irrigation, the canals were dried using White Mac (Ultradent) and Capillary Tips (Ultradent) and dried with absorbent paper points corresponding to instrument size 40.04.\u003c/p\u003e\n\u003cp\u003eObturation was performed using the single cone technique with 40.04 gutta-percha cones (Mtwo, VDW) previously calibrated on a millimeter ruler. Subsequently, the root canal sealers were manipulated as previously described and spread over the gutta-percha cone surface for insertion into the root canals. Excess gutta-percha was removed at the canal orifice using heated pluggers and cold vertical compression. The quality of obturation was assessed through radiographic imaging. The roots were kept in an incubator at 37\u0026deg;C and 100% humidity for 7 days.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eMicro-computed tomography\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eComputed tomography imaging was conducted on the obturated teeth (n=10) using a microtomograph (SkyScan 1173, Bruker, Kontich, Belgium) with exposure parameters set at 70 kV and 114uA. A 1 mm thick aluminum filter was applied, exposure time set at 320 milliseconds, a rotation step of 0.5, and a full 360-degree rotation around the vertical axis. The isotropic resolution was 17 \u0026micro;m. Images were reconstructed using the NRecon software (v1.6.1.0; Bruker, Kontich, Belgium) with specific reconstruction parameters: 1 ring artifact correction, 35% beam hardening correction, and smoothing of 2 for all images.\u003c/p\u003e\n\u003cp\u003eImageJ software was utilized for analyzing the volume of obturation material and the presence of voids. The binarization process was employed, involving processing grayscale levels to obtain a black-and-white image exclusively. The range of grayscale required to recognize the obturation material and voids was determined from a density histogram using the global thresholding method. Subsequent arithmetic and logical operations were applied to create separate binary images of the root canal and obturation material.\u003c/p\u003e\n\u003cp\u003eThe voids volume was calculated using the formula:\u003c/p\u003e\n\u003cp\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;% voids = void volume x 100 / obturation material volume\u003c/p\u003e\n\u003cp\u003e\u003cem\u003ePush-out bond strength\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe samples were fixed onto acrylic plates using sticky wax (Kota, S\u0026atilde;o Paulo, SP, Brazil). This assembly was sectioned using a metallographic cutter (Isomet 1000, Buehler) with a diamond disc (0.03 mm thickness) at low speed (350 rpm) and water cooling. The cuts were made from the root apex towards the cervical portion, and the samples were cut to an approximate thickness of 1 mm in each of the thirds (cervical, middle, and apical). The cervical part of each section was marked with a pen, and the thickness was verified using a digital caliper with an accuracy of 0.001 mm (Mitutoyo). Each root was sectioned into six slices: two apical, two middle, and two cervical. The first slice from each root third was used for the push-out test, while the second slice was used for dentinal penetration (confocal).\u003c/p\u003e\n\u003cp\u003eSubsequently, the specimens were stored for 3 hours at 37\u0026ordm;C. For the push-out test (n=10), the first slice was placed into a universal testing machine (Instron 1144, Norwood, USA) at a speed of 0.5 mm/min and a load cell of 500N until displacement of the filling occurred. The tip used touched only the filling mass (sealer and gutta-percha) in the evaluated thirds. The specimen was mounted in the universal testing machine apico-coronally, meaning the smaller diameter was facing upwards and the larger one downwards (the cut part marked with the pen) to prevent any interference caused by the anatomical narrowing of the root canal during the test. The force values required for the displacement of the filling in each specimen (thickness) were obtained in Newtons (N) and converted to MegaPascals (MPa) by dividing the force value by the bonding area of the filling material (mm\u003csup\u003e2\u003c/sup\u003e). To calculate the bonding area, the formula used was:\u003c/p\u003e\n\u003cp\u003eRU =\u0026nbsp;\u0026pi;\u0026nbsp;(R1 + R2) [(R1 \u0026ndash; R2)\u003csup\u003e2\u003c/sup\u003e]\u003csup\u003e1/2\u003c/sup\u003e + h\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\n\u003cp\u003eThe\u0026nbsp;\u0026pi;\u0026nbsp;is 3.14, where R1 is the radius of the root opening at the apical face of the root, R2 is the radius of the root opening at the cervical face of the root, and h is the slice thickness.\u003c/p\u003e\n\u003cp\u003eEach third was examined using a stereomicroscope at 20x magnification (Leica Microsystems) to determine the failure pattern frequency: adhesive (no visible sealer on dentin walls), cohesive (complete dentin walls covered with sealer), or mixed (combination of adhesive and cohesive; partial dentin coverage with sealer).\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eSealer penetration into dentinal tubules\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe 0.1% by weight of rhodamine B (Sigma Chemicals, St. Louis, MO, USA) was added in the root canal sealers during their manipulation. The root canals (n=10) were comprehensively assessed, and representative images of micropermeability patterns (sealer penetration) were recorded. Images were captured using a laser scanning confocal microscope equipped with a 63x oil immersion lens (NA 1.4) and an illumination system comprising an argon/helium laser (488 nm) and a helium-neon laser (633 nm) with absorption and emission wavelengths suitable for rhodamine B and fluorescein. Fluorescence images were acquired from optical sections of 20\u0026mu;m, located 1 mm below the surface (z-axis).\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eSealer micromorphology\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eAll root canal sealers tested were manipulated and inserted into silicone molds with 8 mm internal diameter and 1.6 mm height (n=3) on a glass plate for microstructure evaluation using scanning electron microscopy (SEM; JSM 5600LV, JEOL, Tokyo, Japan). A polyester strip and a glass slide were placed over the sealer to flatten the surfaces. The samples were kept in an oven at 37\u0026ordm;C for 24 hours. Subsequently, the samples were removed from the silicone molds and placed in a desiccator for complete moisture removal. The specimens were then positioned on a conductive carbon adhesive tape attached to a metal stub for gold sputter coating (Bal-Tec SCD-050 Sputter Coater, Liechtenstein) prior to SEM analysis.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eStatistical analyses\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe statistical analyses included preliminary tests to assess the normality of the sample distribution. Upon confirming normality (\u0026rho;\u0026gt;0.05 in the Shapiro-Wilk test) and homoscedasticity (\u0026rho;\u0026gt;0.05 in the Levene test), parametric statistical tests were employed, except for the push-out bond strength data (\u0026rho;=0.020 in the Shapiro-Wilk test). One-way analysis of variance (ANOVA) with Tukey\u0026apos;s post-hoc test (\u0026alpha;=0.05) were used for parametric data. The push-out bond strength data were evaluated using the Kruskal-Wallis and Student-Newman-Keuls test (\u0026alpha;=0.05). The Dunnett test was performed to compare the experimental groups with the control group. Statistical analysis was conducted using SPSS 22.0 (Statistical Package for the Social Sciences).\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eTable\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e shows that the control group exhibited statistically the highest values in working and setting times, as well as in flow (\u0026rho;\u0026thinsp;\u0026lt;\u0026thinsp;0.05). However, regarding film thickness, all experimental root canal sealers showed higher values without statistical differences between them (\u0026rho;\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eMeans (\u0026plusmn;\u0026thinsp;SD) of working and setting times (min), flow (mm), and film thickness (\u0026micro;m).\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"5\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSealer\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eWorking time\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSetting time\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFlow\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFilm thickness\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMTA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16.2 (0.8) a*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e191.7 (14.4) a*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e23.87 (0.88) a*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e48 (1.48) a*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMTA-HA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15.7 (0.3) a*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e183.3 (14.4) a*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e22.05 (0.60) a*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e45 (1.07) a*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMTA- DCPD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15.3 (0.6) a*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e183.3 (38.1) a*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e22.37 (0.35) a*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e46 (2.01) a*\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMTA Fillapex\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e30.2 (0.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e258.3 (28.8)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e28.35 (0.83)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e25 (3.52)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eDifferent letters indicate statistical differences between the sealers (column) for each test (\u0026rho;\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Asterisk (*) indicates statistical differences between the experimental sealers and the control group (column) (\u0026rho;\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Control group: MTA Fillapex.\u003c/p\u003e\n\u003cp\u003eIn the micro-computed tomography analysis, assessing the entire extension of the root canal, despite minor qualitative differences in root canal obturation (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e), the evaluated experimental groups did not exhibit differences among themselves or with the control group concerning the volume of void spaces (\u0026rho;\u0026thinsp;\u0026gt;\u0026thinsp;0.05) (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eMeans (\u0026plusmn;\u0026thinsp;SD) of voids volume in root canals.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"2\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSealer\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eVoids (%)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMTA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e7.37 (9.69)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMTA-HA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e8.09 (4.63)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMTA-DCPD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e8.47 (8.09)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMTA Fillapex\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e5.27 (7.54)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eFor the push-out bond strength test, the Kruskal-Wallis test revealed interaction between the factors of experimental root canal sealers and root thirds (\u0026rho;\u0026thinsp;=\u0026thinsp;0.009), with significant differences observed only for the material factor (\u0026rho;\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e illustrates that all experimental root canal sealers exhibited satisfactory push-out bond strength values, as their means did not significantly differ from the control group (\u0026rho;\u0026thinsp;\u0026gt;\u0026thinsp;0.05), except for the MTA-DCPD group in the cervical third (\u0026rho;\u0026thinsp;=\u0026thinsp;0.017). No differences in bond strength were observed among the root thirds for all groups (\u0026rho;\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab4\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eMeans (\u0026plusmn;\u0026thinsp;SD) of bond strength (MPa) of root canal sealers and root thirds.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"5\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSealer\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCervical\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMiddle\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eApical\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ePool mean\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMTA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.12 (1.20) ab\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.61 (1.60) a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.59 (1.49) ab\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.44 (1.54)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMTA-HA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.82 (3.39) a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.94 (1.14) a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.92 (4.19) a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e4.56 (3.88)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMTA-DCPD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.24 (0.44) b*\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.91 (0.96) a\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.46 (1.45) b\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.87 (1.20)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMTA Fillapex\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.92 (2.29)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.07 (2.45)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.62 (2.75)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.20 (2.65)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eDifferent letters indicate statistical differences between the sealers (columns) (\u0026rho;\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Asterisk (*) indicates statistical differences between the experimental sealers and the control group (column) (\u0026rho;\u0026thinsp;\u0026lt;\u0026thinsp;0.05). Control group: MTA Fillapex.\u003c/p\u003e\n\u003cp\u003eCohesive failure was predominant for all tested root canal sealers, with MTA Fillapex presenting the highest percentage of cohesive failures (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e).\u003c/p\u003e\n\u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u003ctable id=\"Tab5\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eDistribution of failure patterns of the root canal sealers.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003ccolgroup cols=\"4\"\u003e\u003c/colgroup\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSealers\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAdhesive\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eCohesive\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMixed\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMTA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e70%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e17%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMTA-HA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e78%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMTA-DCPD\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e11%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e73%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eMTA Fillapex\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e89%\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e8%\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e comprises representative images obtained by laser confocal microscopy of the cervical section of the root thirds of all groups. The control group (MTA Fillapex) exhibited the most extensive cement penetration into root dentin qualitatively.\u003c/p\u003e\n\u003cp\u003eThe micromorphology analyses of all root canal sealer samples assessed in this study are depicted in Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e. The dominance of amorphous particles is evident for all groups, with the presence of cylindrical particles (yellow arrow) and point crystals (red arrow). Notably in MTA (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eA), there are clusters of particles with varying dimensions (asterisk), whereas in MTA Fillapex (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eD), particles appear more dispersed. The MTA-HA (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eB) and MTA-DCPD (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eC) samples also reveal the formation of cubic-shaped particles, which are larger, more homogeneous, and more abundant compared to MTA Fillapex (Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eD).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe hypothesis was rejected since the control group exhibited statistically the highest values in working and setting times, as well as in flow (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). However, regarding film thickness, all experimental root canal sealers showed higher values without statistical differences between them (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eBoth working and setting times are dependent on the chemical composition of root canal sealers, particle size, manipulation temperature, and relative humidity of the environment [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. All evaluated root canal sealers contain MTA (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) and set through two main chemical reactions: the progressive hydration of orthosilicate ions (SiO\u003csub\u003e4\u003c/sub\u003e\u003csup\u003e4\u0026minus;\u003c/sup\u003e) and the chemical reaction between MTA and salicylate resin [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. During manipulation, these two components come into contact, and calcium reacts with salicylate to create an ionic polymer. Hydration occurs as the tricalcium silicate particles in MTA react with water, forming a hydrated solution of amorphous calcium silicate, taking set, and forming a solid and uniform network [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Thus, the differences found in the working and setting times of the evaluated materials can be attributed to the chemical composition of each sealer. The manipulated MTA Fillapex contains approximately 13% MTA in its composition [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Thus, a possible explanation for the experimental root canal sealers showing the lowest working and setting times values lies in the MTA-salicylate resin ratio. The higher quantity of MTA present in the experimental materials (40\u0026ndash;60% in the catalyst paste; Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), around 20\u0026ndash;30% of the manipulated sealer mass, accelerates the MTA-salicylate chemical reaction, resulting in shorter working and setting times (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe same MTA-salicylate resin ratio, which grants MTA Fillapex longer setting and working times, seems to account for its higher flow in comparison to the experimental sealers (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). A larger amount of salicylate resin makes the material more fluid and consequently increases its flowability. The particle size of MTA also influences viscosity and, consequently, flow. Smaller particles lead to a larger contact area during the reaction with salicylate resin, increasing viscosity and reducing flow [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. MTA Fillapex presents MTA particles with an average size of 12 \u0026micro;m, while the MTA used in the experimental root canal sealers had an average size of 5 \u0026micro;m (manufacturer's data).\u003c/p\u003e \u003cp\u003eIt's important to highlight that all tested root canal sealers comply with ISO 6876:2012 [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e], which recommends that endodontic sealers should have a flow greater than 20 mm. A root canal sealer should demonstrate moderate flow, as excessive flow increases the likelihood of material extrusion into the periapical region. Conversely, low flow reduces sealer penetration into irregularities of the main canal and accessory canals, compromising the material's sealing ability [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. All tested sealers exhibit pseudoplastic behavior, where their viscosity reduces while flow increases. This occurs due to the shear forces acting on the sealer during its application [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe MTA-resin salicylate ratio in the experimental root canal sealers is sufficient for these materials to exhibit a film thickness within the limit required by ISO 6876:2012 (\u0026le;\u0026thinsp;50 \u0026micro;m) [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. This parameter is crucial for proper distribution of the root canal sealer within the root canals [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e], particularly during the insertion of gutta-percha [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. The increased film thickness of the experimental root canal sealers might be associated with the size of the MTA particles, as the particle size in these materials generates a larger surface area and increases viscosity, as mentioned above. Additionally, the amount of radiopacifier (bismuth oxide) used in these materials may influence material hydration, affecting their film thickness [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Bismuth oxide has a high molecular weight, and its presence alters the physical properties of sealers, leading to internal flaws and increased thickness [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. MTA Fillapex contains approximately 10.5% bismuth oxide [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e], while the experimental root canal sealers used in this study had 40% in the base paste (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e), totaling around 20% of the manipulated sealer.\u003c/p\u003e \u003cp\u003eThe filling of root canals and the presence of voids, measured by micro-computed tomography, showed minor qualitative differences in root canal obturation among the groups (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Furthermore, the experimental groups did not exhibit differences in void spaces compared to the control group (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). This indicates that all experimental root canal sealers demonstrated satisfactory performance in filling the root canals.\u003c/p\u003e \u003cp\u003eThe presence of voids within the root canal post-obturation emerges as a critical factor that may compromise the clinical prognosis of endodontic treatment [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. This condition significantly hampers the sealing of the root canal, increasing the potential for periradicular tissue fluid movement into the root canals. Moreover, the presence of voids can facilitate the entry of microorganisms into the periradicular tissues, potentially triggering or perpetuating apical periodontitis [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. Analysis using computerized microtomography, encompassing the entire length of the root canal, did not reveal significant differences in voids volume (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). These findings confirm that all experimental root canal sealers displayed satisfactory performance in root canal filling, with values comparable to the control group.\u003c/p\u003e \u003cp\u003eThe experimental and commercial root canal sealers evaluated are MTA-based and have a similar chemical composition [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. An important aspect to consider is that the evaluated teeth were single-rooted, and the obturation technique employed was single-cone with vertical compaction. Previous studies have emphasized that the technique used in obturation can significantly impact the quality of the procedure [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe proper obturation achieved by all experimental root canal sealers, due to the low formation of voids, might have positively influenced the push-out bond strength values. However, it's important to note that the best bond strength result doesn't always reflect complete filling of the root canal space [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. This might explain why all evaluated sealers showed similar volumes of voids (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) and, at the same time, different push-out bond strength values (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). Cohesive failures were predominant for all root canal sealers (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). This could be explained by its thinner film thickness compared to the experimental sealers (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). A greater thickness and cohesion of the sealer are linked to better adhesion to the root canal, as a thin layer of root canal sealer with low cohesive strength is more susceptible to contraction and material displacement [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. These results, in comparison with literature data, suggest that besides the quantity of voids, the push-out bond strength results from a combination of factors, including root canal anatomy, obturation technique, and mainly the physicochemical properties, particle amount, viscosity, and flowability of the root canal sealers [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe penetration of root canal sealers into dentinal tubules may exhibit a bactericidal effect by establishing contact with residual bacteria residing within these tubules. Furthermore, the presence of sealers in dentinal tubules provides a mechanical interlocking, enhancing the retention of sealer within the root canal [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. The penetration of root canal sealer into the root canal is influenced by various factors, including the efficacy of smear layer removal, the presence of moisture, the number and diameter of dentinal tubules, the anatomy of the root canal system, as well as the physicochemical properties of the sealers themselves [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. Thus, both the volume of void spaces (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e1\u003c/span\u003e) and the depth of sealer penetration into dentinal tubules (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e2\u003c/span\u003e) may influence the success of endodontic therapy\u003c/p\u003e \u003cp\u003eMTA Fillapex exhibited extensive cement penetration into the root dentin (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The alkaline nature of this sealer denatures collagen fibers, facilitating its penetration [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. Additionally, good sealer penetration is related to its high flowability, inherent to the chemical composition and smaller particle size of MTA-based sealers [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. The higher flowability (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) and the higher molar ratio between calcium and phosphorus atoms (Ca/P ratio) in MTA Fillapex (Ca/P\u0026thinsp;~\u0026thinsp;2.5) [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e], compared to the tested experimental root canal sealers, may explain the superior results in the control group.\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e3\u003c/span\u003e illustrates that all tested root canal sealers contain a significant amount of amorphous particles in cylindrical and point crystal forms. In the MTA group, there are clusters of particles with varying dimensions (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e3\u003c/span\u003eA). In contrast, these particles appear more dispersed in the MTA Fillapex group (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e3\u003c/span\u003eD). Additionally, the MTA-HA (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e3\u003c/span\u003eB) and MTA-DCPD (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e3\u003c/span\u003eC) groups exhibit cubic-shaped particles. Larger particles tend to have a smaller surface area (contact area) of the sealer, consequently affecting the material's working and setting times (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. These particles observed in the SEM images are presumed to be isolated or agglomerated particles of MTA, hydroxyapatite, and DCPD. Further analysis involving energy dispersive x-ray spectroscopy (EDS) coupled with SEM is warranted to confirm the composition of these particles.\u003c/p\u003e \u003cp\u003eThe SEM images provided insights into the structural morphology of the particles present in the evaluated sealers. The size and geometry of these particles significantly influence the sealer hydration kinetics [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. The hydration process initiates following the dissolution of the powder (MTA, HA, and DCPD) and the subsequent crystallization of particles, characterized by the presence of cubic and point crystals (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe findings of the present study associated with outcomes from other researchers assessing similar root canal sealers [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e], demonstrate that the evaluated experimental root canal sealers exhibit satisfactory physical properties and root canal sealing. However, future investigations are required to assess the esthetic compromise of these materials in anterior teeth, understand the clinical impacts of these experimental sealers on the longevity of endodontic treatment, especially when applied using different obturation techniques in multi-rooted teeth, and in endodontic retreatment.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eOverall, based on the presented results, it can be concluded that the experimental root canal sealers exhibited adequate physical properties and adaptation within the root canal. They (i) demonstrated reduced working and setting times compared to MTA Fillapex, (ii) showed flow and film thickness within the values recommended by ISO 6876:2012, and (iii) exhibited a volume of voids and bond strength similar to MTA Fillapex, except for the MTA-DCPD group in the cervical third.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the S\u0026atilde;o Paulo Research Foundation (FAPESP; grant number: 2015/19887-0).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompliance with Ethical Standards\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of Interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the S\u0026atilde;o Paulo Research Foundation (FAPESP; grant number: 2015/19887-0).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical Approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll procedures performed were in accordance with the ethical standards of the institutional ethics committee approval (CAAE 82540618.9.1001.5501).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInformed Consent\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot Applicable\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eBuckley M, Sp\u0026aring;ngberg LS (1995). 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J Conserv Dent 21:373-377. https://doi.org/10.4103/JCD.JCD_64_18\u003c/li\u003e\n \u003cli\u003eElsayed MA, Hassanien EE, Elgendy AAE (2021). Ageing of totalfill BC sealer and MTA fillapex in simulated body fluid. Eur Endod J 6:183-188. https://doi.org/10.14744/eej.2020.43043\u003c/li\u003e\n \u003cli\u003eSilva MGSE, M\u0026uuml;nchow EA, Vitti RP, Sinhoreti MAC, Piva E, Ogliari FA, Zanchi CH (2018). Pentaerythritol tetrasalicylate in the chemical composition of root canal sealers. Braz Dent J 29:48-53. https://doi.org/10.1590/0103-6440201801441\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"mineral trioxide aggregate, hydroxyapatite, calcium phosphate, physical properties, adaptation","lastPublishedDoi":"10.21203/rs.3.rs-5315187/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5315187/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eObjectives:\u003c/strong\u003e To develop and evaluate the physical properties and sealing ability within the root canal of three experimental sealers based on MTA and a salicylate resin.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMaterials and Methods:\u003c/strong\u003e The experimental sealers were composed of two pastes. The base paste was prepared using 1,3-butyleneglycol disalicylate and bismuth oxide. Three different catalytic pastes were formulated, creating three groups: [MTA] n,n,dihydroxyethyl-p-toluidine (DPT), titanium dioxide (TiO\u003csub\u003e2\u003c/sub\u003e), and mineral trioxide aggregate (MTA); [MTA-HA] DPT + TiO\u003csub\u003e2\u003c/sub\u003e + MTA + hydroxyapatite (HA); and [MTA-DCPD] DPT + TiO\u003csub\u003e2\u003c/sub\u003e + MTA + dibasic calcium phosphate dihydrate (DCPD). MTA Fillapex (Angelus) was used as the commercial reference (control). The sealers were manipulated at a 1:1 ratio (base paste:catalyst). Tests for working time and setting time, flow, and film thickness were conducted following ISO 6876:2012 standards. Single-rooted human teeth root canals were utilized for evaluating root canal filling using micro-computed tomography, push-out bond strength testing, and sealer penetration into dentinal tubules using confocal microscopy. Failure patterns in the push-out test were classified as adhesive, cohesive, or mixed. Sealer micromorphology was analyzed via scanning electron microscopy. Data were analyzed statistically (α=0.05).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e MTA Fillapex showed the longest working and setting times, highest flow, the lowest film thickness, and better penetration into dentinal tubules. There was no difference in void among evaluated sealers. Overall, MTA-DCPD sealer showed the lowest bond strength values for cervical and apical thirds. Micromorphological analysis revealed similar crystallographic properties among all sealers.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions:\u003c/strong\u003e The sealers tested showed reduced working and setting times, with flow and film thickness according to ISO 6876:2012. Their void volume and bond strength were similar to MTA Fillapex, except for MTA-DCPD. Clinical Relevance: The experimental root canal sealers demonstrated suitable physical properties and good adaptation within the root canal.\u003c/p\u003e","manuscriptTitle":"Synthesis, physical properties, and root canal sealing of experimental MTA- and salicylate-based root canal sealers","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-11-07 09:13:10","doi":"10.21203/rs.3.rs-5315187/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"af239a9c-fb91-41e1-8661-5625ca810c06","owner":[],"postedDate":"November 7th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-12-08T15:53:13+00:00","versionOfRecord":[],"versionCreatedAt":"2024-11-07 09:13:10","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5315187","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5315187","identity":"rs-5315187","version":["v1"]},"buildId":"GqpaHPwrfC8PjnIFayRh5","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}