Radiopaque Resin Research Articles

Assessment and selection of filler compounds for radiopaque PolyJet multi-material 3D printing for use in clinical settings.

The aim of this research was to assess a selection of radiopaque filler compounds for increasing radiopacity in a resin suitable for Polyjet multi-material 3D printing. A radiopaque resin has potential applications in medicine to produce patient-specific anatomical models with realistic radiological properties, training aids, and skin contacting components such as surgical or procedural guides that require visibility under fluoroscopy. The desirable filler would have a high level of radiopacity under ionising imaging modalities, such as X-ray, CT, fluoroscopy or angiography. Nine potential filler compounds were selected based on atomic number and handling risk: barium sulphate, bismuth oxide, zirconium oxide, strontium oxide, strontium fluoride, strontium carbonate, iodine, niobium oxide and tantalum oxide. The fillers were evaluated using selected criteria. A weighted material selection matrix was developed to prioritise and select a filler for future 3D printing on a multi-material 3D printer. Zirconium oxide was the highest scoring filler compound in the material selection matrix, scoring 4.4 out of a maximum of 5. MED610TM resin doped with zirconium oxide was shown to be UV curable, and when cured is non-toxic, environmentally friendly, and has the ability to display antimicrobial properties. In terms of radiopacity, a sample with thickness 1.5 mm of MED610™ resin doped with 20 wt.% zirconium oxide produced X-ray radiopacity equivalent to 3 mm of aluminium. Zirconium oxide was selected using the material selection matrix. This radiopaque resin can be used to produce anatomical models with accurate radiological properties, training aids or skin contacting devices that require visibility under ionising imaging modalities. The 3D printing validation run successfully demonstrated that the material selection matrix prioritised a filler suitable for radiopaque multi-material 3D printing.

Resistance against Fracture in Teeth Managed by Root Canal Treatment on Restoring with Onlays, Inlays, and Endocrowns: A Comparative Analysis

To compare the fracture resistance in teeth managed by root canal treatment after restoring with different types of onlays, inlays, and endocrowns prepared with hybrid ceramics and pulp chambers restored with fiber-reinforced composite and resin composite that were radiopaque, light-cured, and flowable. The present study was carried out on 252 extracted mandibular molars. All the specimens were divided into six groups randomly. Each group consisted of 42 specimens. Group 1 consisted of intact teeth without any access cavity. It was the control group. Group 2 consisted of teeth with endocrown and empty pulp chamber. Group 3 consisted of teeth with mesio-occlusal-distal (MOD) onlay prepared with hybrid ceramics and pulp chamber filled with flowable, light-cured, radiopaque resin composite. Group 4 consisted of teeth with MOD onlay and pulp chamber filled with fiber-reinforced composite. Group 5 consisted of teeth with MOD inlay and pulp chamber filled with flowable, light-cured, radiopaque resin composite. Group 6 consisted of teeth with MOD inlay and pulp chamber filled with fiber-reinforced composite. Inlay, onlay, and endocrowns were prepared with computer-aided design (CAD) and computer-aided machine (CAM) using hybrid ceramics. Universal testing machine was used for the measurement of the fracture resistance of each specimen. Inferential statistics were performed by applying Fisher's exact test and chi-square test. Fracture strength was found to be maximum in the intact teeth group followed by the endocrown. The fracture strength was minimum in the inlay group. The fracture strength was intermediate in the onlay groups. Endocrown showed maximum fracture resistance as compared to the inlay and onlay restorations. Proper management of root canal-treated teeth is one of the greatest challenges for endodontists. It has been observed that tooth preparation design and the material used for the restoration of root canal-treated teeth play a vital role in the resistance against fracture in the teeth.

Real-Time Guided Endodontics with a Miniaturized Dynamic Navigation System Versus Conventional Freehand Endodontic Access Cavity Preparation: Substance Loss and Procedure Time

IntroductionThis study aimed to evaluate substance loss and the time required for access cavity preparation (ACP) using the conventional freehand method (CONV) versus a miniaturized dynamic navigation system of real-time guided endodontics (RTGE) in an in vitro model using 3-dimensional–printed teeth. MethodsNine human anterior maxillary teeth were selected and micro–computed tomographic scanned. Root canals were virtually reduced to 2 mm below the cementoenamel junction. The teeth were digitally duplicated and mirrored to yield 6 different models with 6 single-rooted teeth each. The models were 3-dimensionally printed using radiopaque resin and consecutively mounted on a dental mannequin for ACP. Two operators with 12 and 2 years of clinical experience, respectively, received 6 models (36 teeth) each and performed ACP on half of the models using RTGE (after digital planning) and CONV on the other half 2 weeks later. The time was recorded. Postoperative substance loss was measured by cone-beam computed tomographic imaging. The differences in time and substance loss between the methods and operators were evaluated by the t test. ResultsOverall, substance loss was significantly lower with RTGE than CONV (mean = 10.5 mm3 vs 29.7 mm3), but both procedures took a similar time per tooth (mean = 195 vs 193 seconds). Operator 1 (more experienced) achieved significantly less substance loss than operator 2 with CONV (mean = 19.9 vs 39.4 mm3) but not with RTGE (mean = 10.3 vs 10.6 mm3). ConclusionsRTGE is a practicable, substance-sparing method performed in comparable time as CONV. Moreover, RTGE seems to be independent of operator experience.

Core-shell structured SiO2@ZrO2@SiO2 filler for radiopacity and ultra-low shrinkage dental composite resins

To overcome the interfacial problem between X-ray radiopaque ZrO2 fillers and polymer resin in dental composites, monodispersed SiO2@ZrO2@SiO2 (SZS) microspheres with narrow size distribution were prepared by a controlled sol-gel method. In the presence of SiO2 coating layer over SiO2@ZrO2 (SZ) microspheres, they were easily silanized same as SiO2 microspheres. Ethoxylated bisphenol A dimethacrylate (EBPADMA) with a higher molecular weight and a lower viscosity was used as base resin monomer mixed with a low amount of diluent triethylene glycol dimethacrylate (TEGDMA). Additionally, the addition of a small amount of pore agent acetone dicarboxylic acid (ADCA) produced some voids, thereby effectively reducing the polymerization shrinkage of the resin. The prepared dental composites combining 52 wt% monodispersed silica microsphere, 20 wt% SZS microspheres, exhibited significantly enhanced capacity in radiopacity (higher than tooth enamel) and very low shrinkage (<0.1%). It also has better mechanical properties than resin composites filled with SiO2 microspheres, and its strength can meet practical applications. The properties of the radiopaque dental composite were to be further tuned by varying the amount of SZS microspheres contents, and the radiopaque resin has an advantage over the commercial one in that it is clinically nondestructive.

Accuracy of a milled digital implant surgical guide: An in vitro study

Statement of problemAn accurate surgical template for guided implant surgery is essential for the success of an implant restoration. However, reports on the accuracy of digitally designed and computer numeric controlled (CNC) machine-milled surgical templates are sparse. PurposeThe purpose of this in vitro study was to investigate the accuracy of an implant surgical guide digitally designed by using data from cone beam computed tomography (CBCT) scans and milled with a 5-axis CNC machine. Material and methodsSix representative radiographic templates were prepared from radiopaque resin plates. For each guide, a CBCT scan was made, and the extracted Digital Imaging and Communications in Medicine (DICOM) data were imported into a planning software program (ORGANICAL Dental Implant). Nine implants were virtually designed for each guide. The design data were imported into a 5-axis CNC machine, and the radiographic guides were fixed onto the CNC machine (Organical Multi S). Bore holes for surgical guide sleeves were milled directly in the radiographic template, which was converted into a surgical template. After the milling process, the surgical guides were scanned by using a laboratory cast scanner. The deviation between the position of the sleeve bore hole in the milled template and that in the virtual implant planning was digitally calculated. ResultsThe mean global deviation of the surgical guide was 0.16 ±0.06 mm in the circle center of the sleeve top, and the mean angular deviation was 0.61 ±0.40 degrees. The sleeve-implant distance and the sleeve axis angle showed no significant influence on the in vitro accuracy of the implant surgical guide. ConclusionsThe mean deviation of the surgical guide prepared by using the virtual planning software program and 5-axis CNC milling procedure in this study was 0.16 ±0.06 mm in the center of the sleeve top. Thus, the guide had acceptable precision.

Anatomic and Radiologic Study of Renal Avascular Plane (Brödel's Line) and Its Potential Relevance on Percutaneous and Surgical Approaches to the Kidney.

The aim of the present anatomic and radiologic study was to evaluate the location, extension, and characteristics of the Brödel's plane and eventually define its different patterns. We evaluated 15 human normal kidneys sampled from unembalmed cadavers without clinical history or anatomical evidence of renal diseases. Kidneys with the surrounding perirenal fat tissue were removed en bloc with the abdominal segment of the aorta. The renal artery was injected with acrylic and radiopaque resins. A CT examination of the injected kidneys was performed. After the imaging acquisition, the specimens were treated with sodium hydroxide for removal of the parenchyma to obtain the vascular casts. All the CT images were elaborated using dedicated three-dimensional (3D) software with the aim to improve the possibility to identify the Brödel's plane. The avascular plane was identified directly on the vascular casts and confirmed on the corresponding 3D images. The avascular plane was located in all cases medially to the lateral convex border of the kidneys. The recorded mean distance was 2.04 cm (range 1.8-2.4 cm). Three patterns of distribution of the Brödel's line were identified. In five (33.3%) cases the avascular plane was extended from the apical to the inferior segment of the kidneys (type 1); in six (40%) from the superior to the inferior segment (type 2); and in four (26.7%) from the apical to the middle segment (type 3). Fourth and fifth order vessels crossing the Brödel's line were detected in all the analyzed cases. The renal avascular plane showed a different extension allowing us to cluster three different patterns. Preoperative identification of the Brödel's line patterns could help surgeons to minimize hemorrhagic complications during percutaneous and surgical procedures requiring an incision of the renal parenchyma such as traditional or robot-assisted nephrolithotomy or partial nephrectomy for endophytic renal tumors. Radiologic studies validated that the described patterns in the clinical practice are strongly needed.

Anatomical study of renal arterial vasculature and its potential impact on partial nephrectomy.

To validate Graves' classification of the intrarenal arteries and to verify the absence of collateral arterial blood supply between different renal segments, in order to maximize peri-operative and functional outcomes of partial nephrectomy. The study was performed on 15 normal kidneys sampled from eight unembalmed cadavers. Kidneys with the surrounding perirenal fat tissue were removed en bloc with the abdominal segment of the aorta. The renal artery was injected with acrylic and radiopaque resins, with the specimen suspended in water. CT examination of the injected kidneys was performed to analyse the branches located deeply. After imaging acquisition, the specimens were treated with sodium hydroxide for removal of the parenchyma to obtain vascular casts. Ten casts (66.6%) showed the classic subdivision of the main artery into single posterior and anterior branches. With regard to the distribution of the segmental or second-order arteries, only two casts (13%) showed a pattern similar to that described by Graves, characterized by four segmental (second-order) branches coming from the anterior renal artery (apical, superior, middle and inferior). In the remaining 13 kidneys (87%) a different arterial vascular network was detected. In 10 casts (80%) a single renal segment was vascularized by two or more different branches coming from an artery leading to another segment (multiple vascularization). Multiple vascularization was observed in three (20%) apical segments, five (33%) superior segments, six (40%) middle segments, seven (47%) inferior segments and two (13%) posterior segments. This study shows that in the human kidneys the arterial vasculature is frequently different from that described by Graves. Moreover, in a significant percentage of cases, a single renal segment receives two or more branches that originate from an artery leading to another segment.

SU-E-I-112: Pre-Clinical Imaging with an Ultra-High Resolution X-Ray Detector.

To explore the possible applications for a newly developed ultra-high resolution, small field-of-view (FOV) micro-solid state x-ray image intensifier (micro-SSXII) detector. The micro-SSXII is based on an 8 micron, 1004 by 1002 electron-multiplying CCD (EMCCD) optically coupled to a 100-micron thick CsI(Tl) phosphor through a fiber optic window resulting in a FOV of 8 mm with a resolution limit of more than 20 lp/mm. The system has the capability of providing real-time images at low exposures because of the high variable gain of the EMCCD. Several phantoms were prepared by filling catheter tubes of 470 micron internal diameter with separate mixtures of a casting resin with different ratios of three different contrast agents (Omnipaque 350, barium sulphate, tantalum powder). These were imaged with the micro-SSXII at 50 kVp to help select the best mixture for use in making a cast of a rat kidney whose vasculature would then be made radiopaque and visualized. The images of all phantoms showed clumping of these contrast agents within the resin resulting in a non-uniform mix. The image of the phantom filled with Omnipaque and resin in a 1:4 ratio showed the best mixture although large bubble formation of the iodine was observed. This combination was used to make a cast of a rat kidney vasculature and imaged with the micro-SSXII. Small iodine bubbles with diameters as small as 25 microns were clearly delineated in the rat kidney vessels confirming the sharp detail capability of the micro-SSXII. The micro-SSXII in combination with a soft x-ray spectrum can provide excellent images of small animal casts prepared with an appropriate radiopaque resin to study finer details of the vasculature. This new imager has the potential to be used for region-of-interest x-ray image guidance for interventional studies in small animals. Supported in part by: NIH Grants R01-EB008425, R01-EB002873 and an equipment grant from Toshiba Medical Systems Corp.

In vitro analysis of the radiodensity of indirect composites and ceramic inlay systems and its influence on the detection of cement overhangs

The purpose of this study was to evaluate the radiodensity of indirect restorative systems and to determine its influence on detection of resin cement overhangs. Sixty sound molars with similar dimensions were selected, and MOD inlay preparations were made in a standardized fashion with 6 degrees taper of the walls. Restorations were made with a porcelain, Duceram LFC, and with three indirect composites, Solidex, Artglass, and Targis. Digital radiographic images were taken before and after cementation of the inlays (Digora system) and were analyzed on two regions, the cervical and the isthmus floor. Digital radiodensity measurements were performed on standardized points symmetrically distributed over each restoration and tooth structure. Cement overhangs were detected through visual analysis by three evaluators. Data were statistically analyzed utilizing ANOVA following Tukey's test (p < 0.05), showing that Solidex presented lower radiodensity than Duceram LFC, and both Artglass and Targis presented similar higher levels of radiodensity than the other groups. Radiodensity of cervical regions was always greater than for isthmus floor regions. Detection of the resin cement overhangs is easier observed on Solidex and Duceram LFC. Radiodensity is highly influenced by restorative material type and tooth regions. The detection of radiopaque resin cement overhangs is influenced by radiodensity of restorative materials.

Radiographic detection of overhangs formed by resin composite luting agents

Objectives: An in vitro model was used to assess the ability of standard radiographic techniques to detect marginal overhangs of resin composite luting agents beside porcelain and resin composite inlays. Methods: The radiodensity of five commercially available luting resins was determined using ISO 4049 methodology. For four of the luting agents, artificial overhangs (0.5 × 0.5 × 2 mm) were created at the cervical margin of standard resin composite and porcelain inlays. Radiographs were recorded, using wax as a tissue equivalent, and the overhangs reduced incrementally in depth by 0.5 mm with serial images at each depth. The images were assessed in random sequence by three observers. Results: There were significant differences between the radiopacity of the luting resins. These correlated well with the ability of the observers to detect marginal overhangs adjacent to resin composite inlays. Conclusions: Even with the most radiopaque luting material, a substantial marginal ledge could not be detected in association with a radiopaque resin composite inlay. The threshold for detection of the overhang was lower when using a radiolucent porcelain inlay.

Radiopaque epoxy resins

AbstractTransparent, X‐ray contrast (radiopaque) epoxy resins were obtained by dissolving up to 25 wt % triphenylbismuth in the commercial epoxy resin prepolymers EPON‐815, DER‐330, DER‐383, and DEN‐431 which were then hardened with diethylenetriamine. The radiopacities of the mixtures were found to be proportional to the molar concentration of the radiopaque additive. The systems follow the relationship, R = Ro + (Ra − Ro) Va Ma where R, Ro, and Ra are the radiopacities of the mixture, the pure epoxy resin, and triphenylbismuth, respectively (expressed in mm aluminum/mm resin); Ma and Va denote the molar concentration and molar volume of the bismuth compound. Ra for triphenylbismuth was found to be 7.4 ± 0.2 mm Al/mm resin; the average value of Ro for the four epoxies equals 0.16 ± 0.1 mm Al/mm resin. The amount of amine required to harden the radiopaque resins was far less for the epoxy novolac resin DEN‐431 than for the three bisphenol‐A based epoxies. The concentration of triphenylbismuth required to impart a radiopacity equivalent to that of aluminum measures 14.6 wt % in EPON‐815, 14.8 wt % in DER‐330, 14.9 wt % in DER‐383, and 15.9 wt % in DEN‐431. The radiopaque resins remain transparent indefinitely, even when exposed to water. © 1995 John Wiley &amp; Sons, Inc.

Comparative tissue tolerance of a new endodontic sealer

An experimental radiopaque resin root canal sealer was tested for tissue biocompatibility in rat connective tissue. The controls were four widely used sealers: Sealapex, Kerr's sealer, AH-26, and Roth's sealer. Polyethylene tubes were filled with the sealers and allowed to set for 24 hours in 100% humidity. Each sealer was implanted in the connective tissue of Sprague-Dawley rats and removed after 3, 10, 20, 30, and 60 days, fixed, and histologically prepared for light microscope evaluation. At each time period there was practically no difference in the reaction of all the sealers. By 60 days, the total picture was one of well-tolerated biocompatibility.

Impact of compensatory enlargement of atherosclerotic coronary arteries on angiographic assessment of coronary artery disease.

To determine whether compensatory enlargement of atherosclerotic coronary arteries occurs and to what degree it affects the angiographic assessment of coronary artery disease, we performed postmortem coronary angiography of 30 human hearts with suspected coronary artery disease and studied 70 histologic cross sections of the proximal left anterior descending artery and proximal right coronary artery. Angiographic and morphometric analyses of 50 stenoses in proximal and middle sections of the left anterior descending artery, right coronary artery, and left circumflex artery were performed. The control group of 10 human hearts without suspected coronary artery disease was evaluated in the same way. For this purpose, coronary arteries were filled with a methylmethacrylic radiopaque resin at a pressure of 100 mm Hg and closely embedded in a methylmethacrylic resin by use of which shrinkage and mechanical artifacts could be avoided. The area circumscribed by the internal elastic lamina was taken as a measure of the area of the arterial lumen if no plaque had been present. The angiographic and corresponding morphometric degree of stenosis was assessed. A significant correlation (r = 0.85, p less than or equal to 0.0001) was found between the internal elastic lamina area and the area of the plaque (lesion area), suggesting that coronary arteries may enlarge as lesion area increases. With the morphometric degree of stenosis, the expected anatomic diminution of the coronary artery was abolished (r = 0.79, p less than or equal to 0.0001), indicating compensatory enlargement in atherosclerotic segments. Accordingly, the degree of stenosis assessed from in vitro angiograms was underestimated. Compensatory coronary enlargement of the stenotic segment was the main reason for angiographic underestimation. The underestimation factor of up to 3.50 for very mild stenoses decreased to 1.37 at an angiographic degree of 50% area stenosis and 30% diameter stenosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Dangers of using radiolucent dental materials

It is not uncommon for dental patients to inadvertently swallow radiolucent dental materials. Usually, they pass through the gastrointestinal tract without difficulty, but objects can become impacted. Acrylic resins should be made radiopaque by using a special radiopaque resin.