Radiopacifying Agents Research Articles

Evaluation of the Effect of Nanosilver and Bismuth oxide on the Radiopacity of a Novel Hydraulic Calcium Silicate-based Endodontic Sealer: An In vitro Study

Background and Aim: A wide range of dental materials have incorporated the concept of nanotechnology into their composition to enhance their physical and antimicrobial properties. In this pretext, silver nanoparticles (AgNPs) are among the most commonly used nanoparticles which are exceptionally noteworthy for their role in medical applications as an antibacterial agent. Another essential, desirable physical characteristic of all endodontic cements is their radiopacity, while in similar context, various radiopacifying agents such as bismuth oxide, barium sulfate, and even AgNPs have been incorporated in endodontic sealers to enhance their physical properties. The aim of the present study was to assess whether the incorporation of AgNPs and 10% bismuth oxide imparted the required radiopacity to the novel cement material (Nano CS) as per the requirement and standards laid by the International Organization for Standardization (ISO) guidelines and whether it complied with the ISO 6876:2001 specifications to achieve the necessary norms. Materials and Methods: The structural characteristics of the novel cement material (Nano CS) were observed using energy-dispersive X-ray analysis under a Zeiss Gemini 500 Field Emission Scanning Electron Microscope, while radiopacity of the test material (Nano CS) was assessed with the help of an aluminum (Al) step‐wedge using a nondestructive testing method following ISO guidelines. The optical density of the test material (Nano CS) was tested with the specimens of mineral trioxide aggregate (MTA) as the standard cement material along with the specimens of enamel and dentin that were 1 mm thick, and Al of appropriate thickness with the desired and equivalent radiopacity. Results: The findings of the present study suggested MTA to have higher radiopacity index equivalent to 4.56 ± 0.00 mm thickness of Al when compared to the test material (Nano CS) (2.78 ± 0.01 mm thickness of Al) and enamel (4.09 ± 0.01 mm thickness of Al) and dentin (2.01 ± 0.01 mm thickness of Al) specimens. Furthermore, the radiopacity index of test material (Nano CS) was found to be more when compared to dentin, though, less when compared to the enamel specimens with the results being statistically highly significant (P < 0.001). Conclusion: The addition of nanosilver and bismuth oxide to the test material (Nano CS) imparted characteristic radiopacity, though the required specifications laid down by the ISO standards were not achieved. Increasing the concentration of the additives used might be considered to bring in the required radiopacity without having a significant impact on the physical and biological properties of the test material (Nano CS) intended to be used for endodontic applications.

Graphene oxide-encapsulated baghdadite nanocomposite improved physical, mechanical, and biological properties of a vancomycin-loaded PMMA bone cement

Polymethyl methacrylate (PMMA) bone cement is commonly used in orthopedic surgeries to fill the bone defects or fix the prostheses. These cements are usually containing amounts of a nonbioactive radiopacifying agent such as barium sulfate and zirconium dioxide, which does not have a good interface compatibility with PMMA, and the clumps formed from these materials can scratch metal counterfaces. In this work, graphene oxide encapsulated baghdadite (GOBgh) nanoparticles were applied as radiopacifying and bioactive agent in a PMMA bone cement containing 2 wt.% of vancomycin (VAN). The addition of 20 wt.% of GOBgh (GOBgh20) nanoparticles to PMMA powder caused a 33.6% increase in compressive strength and a 70.9% increase in elastic modulus compared to the Simplex® P bone cement, and also enhanced the setting properties, radiopacity, antibacterial activity, and the apatite formation in simulated body fluid. In vitro cell assessments confirmed the increase in adhesion and proliferation of MG-63 cells as well as the osteogenic differentiation of human adipose-derived mesenchymal stem cells on the surface of PMMA-GOBgh20 cement. The chorioallantoic membrane assay revealed the excellent angiogenesis activity of nanocomposite cement samples. In vivo experiments on a rat model also demonstrated the mineralization and bone integration of PMMA-GOBgh20 cement within four weeks. Based on the promising results obtained, PMMA-GOBgh20 bone cement is suggested as an optimal sample for use in orthopedic surgeries.

The influence of different radiopacifying agents on hermetical sealing ability of calcium silicate and calcium aluminate dental cements

This study presents technological process for obtaining strontium enriched calcium silicate based dental ceramics and testing their microstructural and chemical properties. In brief, the influence of different radiopacifiers on microstructural properties of calcium-silicate (CaSi) and calcium-aluminate (CaAl) dental ceramics was evaluated. For synthesis of CaSi-based ceramics, calcium chloride pentahydrate (CaCl2?5H2O) and silica sol obtained by hydrothermal treatment were used. CaSi+barium-sulphate (BaSO4), CaSi+bismuth-oxide (Bi2O3), CaAl+zirconium-dioxide (ZrO2), CaAl+strontium-carbonate (SrCO3), CaAl+strontium-fluoride (SrF2),pure CaSi, pure CaAland mineral trioxide aggregate (MTA) (control material) were used. The wettability, surface free energy (SFE), microporosity, nano-porosity and micro-gap size between the material and tooth root canal were evaluated. There was no difference in total SFE among tested cements (p<0.05), while CaSi+BaSO4, CaAl+SrCO3 and CaAl+SrF2 experienced superior wetting than other cements (p<0.05). The highest microporosity was observed in CaAl, whilst adding radiopacifiers into it decrease cements microporosity (p<0.05). The lowest nanoporosity was found for CaAl+ZrO2. The gap size was not statistically different among tested ceramics (p>0.05). Altogether, strontium containing radiopacyfiers result in improved microstructural characteristics of dental ceramics.

Obtaining bioceramic cements for dental repair procedures based on hydroxyapatite and bismuth oxide

Introduction: The use of hydroxyapatite-based cements in dental and bone tissue regeneration procedures has shown favorable results. However, structural fragility and lower levels of radiopacity at clinical evaluation make it difficult to use in direct clinical procedures. Objective: This study aimed to synthesize a new cement with properties to be considered for use in dental repair procedures using hydroxyapatite and a hydrogel, with the addition of bismuth oxide as a radiopacifying agent. Methodology: The materials were obtained by a mixture of hydroxyapatite produced by the precipitation method, a hydrogel with carboxymethylcellulose and calcium silicate and bismuth oxide. The products were characterized by X-ray diffraction, Fourrier transform X-ray fluorescence, scanning electron microscopy, setting time, pH and radiographic appearance. Data were analyzed using Jamovi® software version 1.6 to calculate absolute frequencies, as well as measures of central tendency and variability. Results: The proposed cements obtained presented phase compositions without alterations in the composites, with a nanometric porous structure. Basic pH contributes to its bioactivity and antimicrobial action. The drying time of the proposed cements was prolonged. From the radiographs, the cement containing bismuth oxide was radiopaque when compared to the cement without this component. Conclusion: A new dental cement based on hydroxyapatite and bismuth oxide was obtained, homogeneous, with satisfactory radiopacity property, enabling its analysis through radiographic examinations.

The effect of adding ytterbium trifluoride on the radiopacity, compressive strength, setting time and bioactivity of biodentine: an in vitro study

Objective: This study aimed to evaluate the radiopacity, compressive strength, setting time and bioactivity ofBiodentine after modification with Ytterbium Tri-Fluoride (YbF3) in three different concentrations. Material andMethods: Radiopacity was determined using the equivalence in millimeters of aluminum (mm Al) from digitalradiographs. Compressive strength was evaluated using a universal testing machine. The initial and final settingtimes were evaluated using Gillmore needle. The bioactive potential was evaluated using the environmental scanningelectron microscope (ESEM) connected with Energy Dispersive X-ray analysis (EDX) and X-ray Diffractometer(XRD) at three different time intervals. pH was measured using a pH-meter. Data were analyzed using one-wayANOVA followed by Tukey’s post hoc tests (P< 0.05). Results: Radiopacity of Biodentine with 2.5%, 5% and 7.5%YbF3 was significantly higher than unmodified Biodentine (P < 0.05). Unmodified Biodentine showed the highestmean compressive strength values compared to all other groups (p< 0.05). The addition of YbF3 to Biodentine hasextended the final setting time except for the 2.5% YbF3 group that showed no significant difference comparedto the control. All groups showed an alkaline pH at 28 days, ESEM coupled with EDX analysis showed evidenceof dense globules of calcium phosphate on the surface indicating enhancement of bioactivity. Conclusion: 2.5%YbF3 can be a promising radiopacifying agent to Biodentine with improvement in radiopacity, bioactive potentialand maintaining the setting time and compressive strength at acceptable level as indicated by the ISO standards.KEYWORDSYtterbium trifluoride; Radiopacity; Biodentine; Bioactivity.

Influence of the addition of different radiopacifiers and bioactive nano-hydroxyapatite on physicochemical and biological properties of calcium silicate based endodontic ceramic

The purpose of this study was to investigate the influence of different radiopacifiers on the physicochemical and biological properties of novel calcium silicate based endodontic ceramic enriched with bioactive nano-particulated hydroxyapatite – ECHA. Namely, ECHA was used as a basis for mixing with the following radiopacifiers: strontium fluoride (SrF2), zirconium dioxide (ZrO2) and bismuth oxide (Bi2O3). For comparison, Portland cement (PC) and mineral trioxide aggregate (MTA) were used. The following physicochemical characteristics were examined: the radiopacity, setting time, compressive strength, porosity, wettability and pH value. The biocompatibility of the cements was assessed by crystal violet, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) and cell adhesion assays. The highest radiopacity was obtained for the ECHA + Bi2O3 mixture and MTA that were statistically significant in comparison to other materials (p < 0.05). Both initial and final setting times as well as compressive strengths were statistically lower for experimental cements than for PC and MTA (p < 0.05). The lowest total porosity was observed in the ECHA + ZrO2 group when compared with the other two experimental cements (p < 0.05), but not when compared with PC and MTA (p > 0.05). Experimental cements exhibited statistically higher contact angles of glycerol than PC and MTA (p < 0.05). For blood plasma, a statistical difference was found only between ECHA + Bi2O3 and PC (p < 0.05). All investigated materials had alkalization ability. Cell viability assays revealed that the extracts of tested cements did not exhibit cytotoxic effect on L929 cells. Scanning electron microscopy had shown a high degree of cell proliferation and adhesion of cells from apical papilla on experimental cements’ surfaces. Novel endodontic ceramics with nano-hydroxyapatite addition have satisfactory biological and physicochemical properties when compared to MTA and PC controls. Considerable lower setting time of experimental cements might present a huge advantage of these synthesized materials in clinical practice. SrF2 presents a novel promising radiopacifying agent for dental cements manufacturing.

Tooth Discoloration Using Calcium Silicate-Based Cements For Simulated Revascularization in Vitro.

The endodontic revascularization may be an alternative treatment for necrotic immature teeth, however, several treatment steps may cause tooth discoloration. This study evaluated the use of three calcium silicate-based cements with different radiopacifying agents on the color alteration (∆E) of extracted premolars after simulation of revascularization. Forty single rooted extracted premolars were shaped with #1-6 gates Glidden drills, rinsed with sodium hypochlorite, and filled with fresh human blood. Three calcium silicate-based cements with different radiopacifying agents (bismuth oxide - CSBi, calcium tungstate - CSW, and zirconium oxide - CSZr) were applied over the blood clot (n=10). The control group received the application of a temporary zinc oxide-based cement (TFZn) (n=10). ∆E was measured with a spectrophotometer, using the L*a*b* color system of the International Commission on Illumination (CIELab), in different times: prior to the preparation of the access cavity (t0); right after treatment (t1); and after one (t2), two (t3), three (t4) and four (t5) months. The tooth site for color evaluation was standardized by silicon matrix, the color reading was performed 3 times per tooth, and the teeth were stored in 37º water between evaluations. ∆E, whiteness (WID index) and yellowness (b*) were evaluated. Data were subjected to one-way ANOVA and repeated measures ANOVA, followed by Tukey's post hoc test (α=0.05). All groups were similar in ∆E1 (t0-t1). The ∆E was the lowest and constant in the control group. In all evaluation times, CSBi presented the highest ∆E (p<0.01). CSW and CSZr were similar in all evaluated times and presented intermediate ∆E values. WID index from CSBi and CSW presented more distancing from 'white' reference. CSBi presented the greatest decrease in yellowness (b* value). The cement containing bismuth oxide presented the highest color alteration values. All tested calcium silicate-based cements presented clinically perceptible discoloration. Calcium tungstate and zirconium oxide may be used as alternative radiopacifiers to decrease tooth discoloration after endodontic tooth revascularization.

Iodoform-Blended Portland Cement for Dentistry

Portland cement-based formulations blended with radiopacifying agents are popular endodontic materials for various root filling and pulp capping applications. Iodoform (CHI3) is an alternative candidate radiopacifier whose impact on the setting, bioactivity, antimicrobial properties and cytotoxicity of white Portland cement were evaluated in this study. Isothermal conduction calorimetry and 29Si magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR) showed that 20 wt% iodoform had no significant impact on the kinetics of cement hydration with respect to the formation of the major calcium silicate hydrate (C-S-H) gel product (throughout the 28-day observation). Conversely, transmission electron microscopy demonstrated that iodine was incorporated into the ettringite (Ca₆Al₂(SO₄)₃(OH)₁₂·26H₂O) product phase. Both iodoform-blended and pure Portland cements exhibited comparable biocompatibility with MG63 human osteosarcoma cells and similar bioactivity with respect to the formation of a hydroxyapatite layer upon immersion in simulated body fluid. By virtue of their high alkalinity, both cements inhibited the growth of Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. However, in all cases, iodoform enhanced the antimicrobial effect and significantly reduced the minimum bactericidal concentration of the cement. In conclusion, iodoform offers antimicrobial advantages in Portland cement-based formulations where oral biofilm formation threatens the success of root filling materials and dentine substitutes. The reactivity with the calcium aluminosulfate components of the hydrating cement matrix warrants further research to understand the long-term stability of the cement matrix in the presence of iodoform.

Inherently radiopaque polyurethane beads as potential multifunctional embolic agent in hepatocellular carcinoma therapy

The aim of the current study is to report an inherently radiopaque drug-eluted beads (DEBs) as promising embolic materials for TACE techniques. Firstly, the synthesized radiopaque iodinated polycaprolactone-polyurethanes (I-PCLUs) are synthesized by chain-extending method by using 4, 4´-isopropylidinedi-(2, 6-diiodophenol) (IBPA) as the radiopacifying agent. Then, doxorubicin (Dox) is introduced as a chemotherapeutic agent into I-PCLU beads via a double emulsification (W/O/W) method. The drug loading and controlled release behavior of two ratios of I-PCLU/Dox are found to be dependent upon the internal porous microstructure, and the radiopacity is well-retained after four weeks drug release. Besides, the I-PCLU/Dox beads exhibit positive in vitro anti-tumor effect. The in vivo intramuscular implantation and liver embolization results demonstrate that I-PCLU beads have good histocompatibility, occlusion effect and X-ray traceability. Furthermore, the drug-loaded I-PCLU beads are performed into a VX2 rabbit hepatocellular carcinoma (HCC) model using a micro-catheter, form embolization of hepatic arteries and inhibit the tumor growth after one week post-injection. Hence, this polymeric system provides a potential radiopaque chemoembolization candidate for HCC and other cancer therapies, which could bring opportunities to the next generation of multifunctional embolic agents.

Impact of Bi2O3 and ZrO2 Radiopacifiers on the Early Hydration and C-S-H Gel Structure of White Portland Cement.

Bismuth oxide (monoclinic α-Bi2O3) and zirconium oxide (monoclinic ZrO2) are the most popular radiopacifiers in commercial Portland cement-based endodontic restoratives, yet their effects on the setting and hydration reactions are not fully understood. This study compares the impact of 20 wt.% of Bi2O3 or ZrO2 on the early hydration reactions and C–S–H gel structure of white Portland cement (WPC). Cement paste samples were hydrated at 37.5 °C prior to analysis by 29Si and 27Al magic angle spinning nuclear magnetic resonance spectroscopy at 3 h and 24 h, and transmission electron microscopy at 3 h. Initial and final setting times were determined using a Vicat apparatus and reaction kinetics were monitored by isothermal conduction calorimetry. Bi2O3 was found to prolong initial and final setting times and retard the degree of hydration by 32% at 24 h. Heat evolution during the acceleration and deceleration phases of the hydration process was reduced and the exotherm arising from renewed ettringite formation was delayed and diminished in the presence of Bi2O3. Conversely, ZrO2 had no significant impact on either setting time; although, it accelerated hydration by 23% within 24 h. Increases in the mean silicate chain length and the extent of aluminum substitution in the C–S–H gel were observed in the presence of both radiopacifying agents after 24 h relative to those of the unblended WPC. The Bi2O3 and ZrO2 particles remained intact within the cement matrix and neither bismuth nor zirconium was chemically incorporated in the hydration products.

03:18 PM Abstract No. 385 Radiopaque silk-elastinlike protein polymer-based embolic

The objective of the proposed work is to develop a silk-elastinlike protein polymer (SELP) embolic suitable for the treatment of aneurysms and pseudoaneurysms. SELPs have exquisitely defined monomer sequences and molecular weights to meet functional requirements by combining the thermoresponsive properties of mammalian tropoelastin and the strength of silk. We propose to combine SELP with radiopacifying agents to generate a novel hydrogel embolic that solidifies after injection without the use of potentially toxic organic solvents or chemical crosslinkers. SELP 815K, which contains 8 silk-like, 15 elastin-like, and 1 lysine-substituted elastin-like motif per monomer repeat, was combined with an organically bound iodine or micronized tantalum in order to bestow radiopacity. Radiopacity of materials was evaluated on an Atris Q® Fluoroscope. Rheological testing was performed using an AR550-Stress Controlled Rheometer. A cone-and-plate configuration with a 20 mm 4° cone geometry was used. Viscosity was measured from 18 to 37°C using an oscillatory procedure at an angular frequency of 6.283 rad/s. This was immediately followed by a 3 hr oscillatory sweep at 37°C using 0.1% strain to monitor gelation kinetics. The SELP embolic was used to embolize a simulated internal carotid artery aneurysm (4.5 mm neck, 5.60 mm depth) in a cerebrovascular controlled flow loop. SELP was injected into the aneurysmal sac with a 2.4F 110 cm Maestro® microcatheter while a 3 mm Advocate™ balloon catheter blocked the aneurysm neck. Catheters were removed after 5 minutes and the embolic material was administered. The radiopaque SELP embolic demonstrated an injectable viscosity profile and formed a solid gel within 5 minutes of being after injection. SELP formed a dense, porous network after gelation that did not adhere to catheters. Iodine-containing radiopacification agents distributed uniformly throughout the embolic, while micronized tantalum formed micro-aggregates that were not visually apparent except under high magnification. A radiopaque SELP based embolic was developed and validated in an in vitro model of a cerebral aneurysm.

Comparative Evaluation of Tissue Response of MTA and Portland Cement with Three Radiopacifying Agents: An Animal Study

This study compared the tissue reaction of 80 wt% of White Portland cement (WPC) mixed with 20 wt% of three radiopacifying agents: Bismuth oxide/Iodoform/Zirconium oxide with MTA in rat subcutaneous connective tissue. The study was performed in 18 albino rats by implanting the WPC mixed with radiopacifying agents loaded in a polyethylene tube. Empty tubes were used as a control. At the end of 7, 30 and 60 days excisional biopsy of the implant along with surrounding tissues was done and sent for histological examination. In the 7 days experimental period there was no significant difference between groups in terms of the tissue response. In 30 and 60 days period significant difference was seen between the control (empty tube) and the other groups. But there was no significant difference between WPC mixed with radiopacifiers BiO/Iodoform/ZrO2and MTA. The tissue reaction of the tested materials, White Portland cement (WPC) + Bismuth oxide, WPC + Iodoform, and WPC + Zirconium dioxide were similar to MTA (Pro Root MTA) in all experimental periods 7 days, 30 days and 60 days.

Prevention of Tooth Discoloration Due to Calcium-Silicate Cements: A Review

Introduction: Mineral trioxide aggregate (MTA) and other calcium silicate cement similar to that are widely used in endodontic treatments. One of the widely emphasized disadvantages of these cements are the induction of tooth discoloration. The purpose of this study was to investigate the mechanisms of tooth discoloration caused by MTA and MTA-like cements and debate different methods suggested for preventing it. Methods: An electronic search was performed using databases such as Google Scholar, PubMed, PubMed Central, Science Direct, and Scopus by using keywords such as “mineral trioxide aggregate”, “calcium-silicate”, “tooth discoloration”, and “prevention”. Results: Several methods for preventing tooth discoloration caused by MTA and MTA-like cements have been proposed including the application of dentin bonding agents on dentinal walls, use of cements containing radiopacifying agents other than bismuth oxide, and addition of zinc oxide to those cements containing bismuth oxide. Conclusion: Most studies have shown that none of these methods can completely inhibit tooth discoloration but can decrease it to some length.

Analysis of pH and cytotoxic activity of locally produced radiopaque white Portland cement

Abstract Background: Portland cement (PC)-based formulations show continuous developments. Purpose: This study examined the pH and cytotoxic activity of a locally produced Malaysian white PC (MAWPC) mixed with different radiopacifying agents (barium sulfate [BS], niobium oxide [NO], and bismuth oxide [BO]) on human periodontal ligament fibroblasts (HPLFs). Materials and Methods: 0.8 g of MAWPC was mixed with 0.2 g of each radiopacifying agent and sterile distilled water. Five tablets of each group were prepared. After setting, the samples were immersed in 10-ml sterile distilled water and stored at 37°C, and the pH was measured at intervals of 0, 1, 3, 7, and 14 days using a calibrated digital pH meter. One-way ANOVA was used for data analysis (P = 0.05). For cytotoxic activity, the material extracts were prepared at three serial concentrations (25, 12.5, and 6.25 mg/ml), and 200 ml of each concentration was added into each well seeded with cultured HPLFs. The plates were then incubated for 48 h. The cell viability was evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and the data were analyzed using Kruskal–Wallis test (P = 0.05) Results: The pH values of all groups were significantly higher compared to the control group (P &lt; 0.001). With the exception of day 0, the pH values of all groups at all day intervals ranged from 9.9 to 10.9, and some significant differences were detected. Although the addition of radiopacifying agents decreased the cell viability values of MAWPC extracts (P &lt; 0.05), all groups showed favorable cytotoxicity profile. MAWPC/BO combination showed higher cell viability values compared to MAWPC/NO and MAWPC/BS. Conclusions: The addition of radiopacifying agents to MAWPC maintained its high pH and favored the viability of HPLFs.

Ytterbium Oxide as Radiopacifier of Calcium Silicate-Based Cements. Physicochemical and Biological Properties.

This study evaluated physicochemical properties, cytotoxicity and bioactivity of MTA Angelus (MTA), calcium silicate-based cement (CSC) and CSC with 30% Ytterbium oxide (CSC/Yb2O3). Setting time was evaluated using Gilmore needles. Compressive strength was evaluated in a mechanical machine. Radiopacity was evaluated using radiographs of materials and an aluminum scale. Solubility was evaluated after immersion in water. Cell viability was evaluated by means of MTT assay and neutral red staining, and the mineralization activity by using alkaline phosphatase activity and Alizarin Red staining. The data were submitted to ANOVA, Tukey and Bonferroni tests (5% significance). The bioactive potential was evaluated by scanning electron microscopy. The materials presented similar setting time. MTA showed the lowest compressive strength. MTA and CSC/Yb2O3 presented similar radiopacity. CSC/Yb2O3 showed low solubility. Saos-2 cell viability tests showed no cytotoxic effect, except to 1:1 dilution in NR assay which had lower cell viability when compared to the control. ALP at 1 and 7 days was similar to the control. MTA and CSC had greater ALP activity at 3 days when compared to control. All the materials present higher mineralized nodules when compared with the control. SEM analysis showed structures suggesting the presence of calcium phosphate on the surface of materials demonstrating bioactivity. Ytterbium oxide proved to be a properly radiopacifying agent for calcium silicate-based cement since it did not affected the physicochemical and biological properties besides preserving the bioactive potential of this material.

Preparation of radiopaque polyurethane–urea/graphene oxide nanocomposite using 4-(4-iodophenyl)-1,2,4-triazolidine-3,5-dione

New radiopaque nanocomposites were prepared based on iodinated polyurethane–urea (PUU) and graphene oxide (GO). The iodinated PUU was synthesized using 4,4′-methylenediphenyl diisocyanate (MDI), polyethylene glycol (PEG, Mn = 1000), and 4-(4-iodophenyl)-1,2,4-triazolidine-3,5-dione (IUr) as a novel chain extender and radiopacifying agent. The synthesized urazole, PUU, and the related nanocomposites are characterized by fourier transform infrared spectrum, nuclear magnetic resonance, X-ray diffraction, field-emission scanning electron microscopy, elemental analysis (CHNO), thermogravimetric analysis, and dynamic mechanical thermal analysis (DMTA). The X-ray visibility of the radiopaque PUU and nanocomposites was investigated using X-radiography. To evaluate the biocompatibility of the samples, the indirect MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay was carried out on the non-cancerous mouse fibroblast cell line NIH3T3 D4 according to the ISO10993-5 standard. The DMTA results proved introduction of the GO layers into the iodinated PUU matrix, and has improved mechanical properties of the nanocomposites compared to the pure polymer. The X-ray images showed significant radiopacity of the pure polymer and the nanocomposites.

Fast setting tricalcium silicate/magnesium phosphate premixed cement for root canal filling

MTA-based root-end filling is a promising therapeutic approach for root repair, however, difficult handling characteristics, presence of toxic elements in the material composition and long setting time are main drawbacks for clinical applications. The purpose of this study was to develop a novel fast setting silicate based premixed cement for endodontic use. The premixed cement contained tricalcium silicate (C3S) as the main constituent for hydration, magnesium phosphate cement (MPC) as setting accelerators and glycerol as water-miscible liquid. The physicochemical properties and antibacterial property of the novel cements were evaluated. Moreover, biocompatible zirconium oxide (ZrO2) was chosen as radiopacifying agent added into the premixed cement. The radiopacity, physicochemical properties, antibacterial property and cytotoxicity of the radiopaque premixed calcium silicate based cements were evaluated. The setting time of the premixed MPC/C3S cements could be modulated within the range from 70min to 205min by adjusting the content of MPC. Meanwhile, the premixed MPC/C3S cement displayed good flowability and injectability when the amount of MPC less than 20%. The addition of ZrO2 provided the premixed MPC/C3S cement with excellent radiopacity while had no significant effects on the setting time, flowability, film thickness, injectability and washout resistance. Moreover, the premixed cement with or without ZrO2 had good antibacterial property and cytotoxicity. Our results indicated that the premixed MPC/C3S/ZrO2 cement could be considered as a promising candidate for application in endodontics owing to its desirable physicochemical properties, antibacterial activity and cytocompatibility, especially relatively short setting time and good sealing ability.

Effect of filler composition of dental composite restorative materials on radiopacity in digital radiographic images

The purpose of this study was to evaluate the effect of filler composition on the radiopacity of 16 dental composite restorative materials using digital radiography. Five disc‐shaped specimens of each composite material were prepared using Teflon molds and five enamel and dentin specimens were prepared from human teeth. The composite specimens were placed on a digital sensor together with a tooth fragment and an aluminum stepwedge and a digital dental X‐ray unit was used at the same exposure conditions. The mean gray values of each composite specimen, tooth fragment, and stepwedge were measured on the digital images using a software program. Statistical analysis of the data was implemented with one‐way ANOVA and post hoc Tukey's HSD test (a = 0.05). The composites presented higher radiopacity than dental tissues (p &lt; 0.05), except Filtek Silorane which exhibited lower radiopacity than enamel (p &lt; 0.05). Linear regressions revealed a very low correlation between radiopacity and filler content of the composites. The composite restoratives presented great variations in radiopacity. Concentration and type of the radiopacifying agents included in the composites crucially affected radiopacity. The choice of the composite restorative materials is of great importance due to large variations in their radiopacity, which depends on their filler composition. POLYM. COMPOS., 39:E351–E357, 2018. © 2017 Society of Plastics Engineers

In Vitro Bioactivity and Setting Times of White Portland Cement Combined with Different Radio Pacifying Agents

Commercial formulations based on 80:20 mixtures of Portland cement and bismuth oxide (a radiopacifying agent) are used in dentistry as root-filling materials. This study compares the impact of two alternative radiopacifiers, barium sulphate and zirconium oxide, with that of bismuth oxide, on the setting times and bioactivity of white Portland cement. The findings indicate that bismuth oxide prolongs both the initial and final setting times of the cement, and that barium sulphate and zirconium oxide have no effect on this parameter. Hydroxyapatite (HA) formed on the surfaces of all test samples within 7 days of exposure to simulated body fluid, indicating that they possess the potential to stimulate new hard tissue formation. Fourier transform infrared spectroscopy, the traditional technique for the identification of HA, was not appropriate for the analysis of these cement systems owing to the overlap of signals from each of the radiopacifiers with the characteristic P-O bending modes of HA in the 570 – 610 cm-1 region. In this respect, the P-O band at 965 cm-1 of HA in the Raman spectrum was found to be a suitable means of detection since it is discrete with respect to all signals arising from the radiopacifying agents and cement phases.

Physico-chemical and Biological Properties of a New Portland Cement-based Root Repair Material

Objective:To propose bismuth carbonate, a radiopacifying agent, as a new endodontic root repair material that was added to Portland cement (PC) at 2 wt%, 5 wt%, 10 wt% and 15 wt%, and physicochemical and biological properties of each formulation were evaluated in comparison to MTA-Angelus.Methods:Mixed and powder samples were analysed by scanning electron microscopy (SEM) and X-ray power diffraction (XRD), and the semiquantitative constitution of the powder was determined by energy-dispersive spectrometer (EDS). Setting time was evaluated by Vicat needle and radiopacity analysed with digital X-ray. The pH of all tested materials was observed after immersion in water for 3, 24, 48, 72 and 168 h (or 7 days). Solubility and calcium release were measured after immersion in water for 24 h. A multiparametric assay XTT-NR-CVDE was used to evaluate the cytotoxicity of the materials in human periodontal ligament (HPDL) fibroblasts. HPDL fibroblasts were exposed to PC 15% and mineral trioxide aggregate (MTA), and the expression of proinflammatory cytokines (IL1A, IL6, IL8, TNF) and bone formation genes (ALP, COL1, RUNX2) was evaluated by real-time PCR. Mineralisation of HPDL fibroblasts cocultured with PC, PC 15% and MTA was evaluated with Von Kossa staining.Results:PC-based groups presented more irregular and larger particles than MTA. PC and MTA showed similarities as observed by XRD and EDS. Setting time of PC-based groups was increased with the addition of bismuth carbonate. All tested materials were alkaline, and pH tended to reduce over time. All cements had solubility lower than recommended, with no difference between them (P>0.05) and showed calcium release. PC 15% had similar radiopacity when compared with MTA (P>0.05). Cell viability was higher for the tested materials than the positive control (P<0.001), but there was no difference when they were compared with negative control (P>0.05). Gene expression levels were similar for all tested groups (P>0.05). Analysed cements had positive Von Kossa staining.Conclusion:Overall, the addition of 15% of bismuth carbonate did not result in significant changes to its physicochemical and biological properties when compared with MTA, except for the setting time, and may be considered a potential substitute for MTA.