Radiopacity of 12 visible-light-cured dental composite resins

The radiopacity of 12 VL-cured composite resins was determined with reference to an aluminum step-wedge. Two anterior composites were radiolucent while two anterior and one anterior/posterior composites exhibited the radiopacity equal to, or slightly greater than, that of human enamel. Three posterior and one inlay composites possessed the radiopacity equivalent to, or in tiny excess of, that of human enamel. Three posterior composites had the radiopacity, fairly exceeding that of human enamel. Chemical analyses of the filler particles were carried out with SEM/EDX. It became evident that radiopaque fillers contained at least one radiopaque oxide component such as BaO, ZrO2 and Yb2O3 with varying concentrations. In general, the radiopacity of the composite resin was linearly proportional to the amount of the radiopaque oxide in the filler. It was suggested that ZrO2 was radiopacifier equivalent to, or even stronger than, BaO.     

Radiopacity of composite dental materials using a digital X-ray system

The aim of this study was to evaluate the radiopacity of 32 current dental composite materials with digital technique. Digital radiographs with CCD sensor along with an aluminum step wedge, 1-mm-thick tooth slice and 1mm thick composite specimen were taken in five different combinations of exposition/voltage. The radiopacity in pixels was determined using Digora 2.6. software. The equivalent in thickness of aluminum for each material was then calculated from the calibration curve. 74.9% of all tested materials in all exposure combinations had radiopacity between 2 mm and 4 mm aluminum equivalent. The radiopacity of composites ranged from 0.61 mm Al (Gradia Direct Anterior) to 4.78 mm Al (Te-Econom). The average radiopacity for enamel and dentine was 2.05 and 1.11 mm Al. The use of digital technique for radiopacity is an easy, reliable, fast and precise way to analyze different dental materials. Most of the tested composite materials fulfill the requested criteria for radiopacity with a few exceptions.     

Is the radiopacity of CAD/CAM aesthetic materials sufficient?

ObjectivesThis study was designed to investigate CAD/CAM restorative blocks and other resin-based materials by (i) determining their chemical composition, (ii) comparing their radiopacity and (iii) correlating their radiopacity with specimen thickness.MethodsDisk specimens, of 1and 2 mm thickness (n = 3), were prepared from five CAD/CAM and six resin-based composites (RBCs). The CAD/CAM resin-composites included aesthetic types: CeraSmart (CS), Grandio Blocs (GB), Lava Ultimate (LU), plus a polymer infiltrated ceramic Vita Enamic (VE), and a feldspathic ceramic Vita Mark II (VM II). The six RBCs were for different clinical applications: direct filling, flowable, bulk fill, base and two luting cements. The specimens were radiographed alongside an aluminium step wedge and a tooth section. Digital images were analysed, and the radiopacity of each specimen was determined according to ISO 1311/2014. Statistical analyses of radiopacity, expressed as mm Al (n = 15), were carried out using the Kruskal-Wallis test followed by pairwise comparisons (α = 0.05).ResultsRadiopacities of CAD/CAM materials were, in ascending order, VE, VM II, CS, LU, and GB. At 1 mm thickness, the radiopacities of all CAD/CAM specimens were matching or slightly lower than enamel. At 2-mm thickness, the resin composite blocks were significantly more radiopaque than the ceramics VE and VM II (p < 0.0001). No statistically significant differences in radiopacity were detected between the 1-mm thick infiltrated ceramic, enamel, dentin and various resin composites except for filling and bulk fill types. The radiopacity of polymer-infiltrated ceramics was low despite the presence of radiopacifying elements and high filler content.SignificanceIdentifying thin restorations in standard radiographs is necessary with the development and expanded application of ‘digital’ dental materials in restorative treatment. This study confirmed the joint influence of composition and thickness on radiopacity. CAD/CAM restorative materials showed thickness-dependant radiopacity. But polymer-infiltrated ceramics were fairly radiolucent. There is a need to revisit radiopacity requirements for CAD/CAM restorative materials.     

Radiopacity of different resin-based and conventional luting cements compared to human and bovine teeth

This study evaluated the radiopacity of different resin-based luting materials and compared the results to human and bovine dental hard tissues. Disc specimens (N=130, n=10 per group) (diameter: 6 mm, thickness: 1 mm) were prepared from 10 resin-based and 3 conventional luting cements. Human canine dentin (n=10), bovine enamel (n=10), bovine dentin (n=10) and Aluminium (Al) step wedge were used as references. The optical density values of each material were measured from radiographic images using a transmission densitometer. Al step wedge thickness and optical density values were plotted and equivalent Al thickness values were determined for radiopacity measurements of each material. The radiopacity values of conventional cements and two resin luting materials (Rely X Unicem and Variolink II), were significantly higher than that of bovine enamel that could be preferred for restorations cemented on enamel. Since all examined resin-based luting materials showed radiopacity values equivalent to or greater than that of human and bovine dentin, they could be considered suitable for the restorations cemented on dentin.     

An evaluation of the radiopacity of composite restorative materials used in Class I and Class II cavities

The radiopacity of 28 shades of 18 composite brands, recommended for use in Class I and Class II cavities, and one amalgam were tested in accordance with the instructions in the latest draft standards of ISO for resin-based filling materials. The composition of the inorganic fillers in the materials was analyzed by optical emission spectroscopy. Twelve composites showed radiopacity greater than enamel, for five the radiopacity was lower than that of dentin, and for two materials the radiopacity was between that of enamel and dentin. The optical emission spectroscopy analyses showed a large variety in the composition of the fillers. The elements added to increase radiopacity in the composite materials are barium, strontium, zinc, zirconium, and ytterbium.     

Image quality of an intraoral storage phosphor imaging system for normal anatomical structures, proximal caries and decalcified bone changes

The delineation of normal anatomical structures and the detection of minute changes in proximal caries in extracted teeth and in bone treated with a chemical decalcification process were investigated using the intraoral digital imaging system, Digora. Cathode ray tube (CRT)-output images obtained with the Digora system, film-output images prepared through computed radiography, and conventional periapical film (conventional film) images of the various experimental materials were evaluated visually. The accuracy of detection of the enamel-dentin junction of normal teeth was greater with Digora CRT- and film-output images than with conventional film images. However, no marked differences were observed in the diagnostic power in the examination of other materials. The detection of proximal caries was similar for all three image types, regardless of the caries depth. In the decalcified bone specimens, the increases in the area under the receiver operating characteristic curve (Az value) corresponded to the degree of decalcification, and no differences were observed in the detection of bone changes among the CRT-output, film-output, and conventionals film images. These results suggest that the diagnostic value of Digora system, output primarily as CRT images, is comparable to that of film-output images and conventional film images, and that it is potentially applicable to clinical diagnosis.     

Radiopacity of compomers, flowable and conventional resin composites for posterior restorations.

The objective of this study was to densitometrically determine the relative radiopacity (aluminum [Al]-equivalent values) of dentin, enamel, and 20 resin composite materials currently used for posterior restorations. Specimens 5 mm in diameter and 2 mm thick were fabricated from 20 materials (n = 7) for a total of 140 specimens. Human molars were longitudinally sectioned 2.0 mm thick to include both enamel and dentin. The optical densities of enamel, dentin, restorative materials, lead, and aluminum step wedge were obtained from radiographic images, using a transmission photodensitometer. The Al equivalent (mm) for each material was calculated from the linear regression equation of the log of normalized optical density and Al mm thickness obtained from the step wedge. A linear regression of the logarithm of normalized optical density and Al mm thickness was plotted (r2 = 0.9953), and the relative radiopacities, expressed as equivalent thickness of Al, were ranked ordinally. All materials tested, with the exception of an unfilled resin adhesive, complied with ISO Standard 4049, being at least as radiopaque as a 2.0 mm thickness of 99.6% pure Al. Four of six flowable composites had radiopacity values that fell between that of dentin and enamel, while two materials were more radiopaque than enamel. The three compomers tested had radiopacities greater than enamel. In addition, all traditional light- and chemical-cure resin composite materials tested were more radiopaque than enamel. All materials tested, with the exception of one adhesive resin, were at least as radiopaque as dentin and complied with ISO Standard 4049. Clinicians should be able to distinguish these restorative materials radiographically from recurrent decay, voids, gaps, or other defects that lead to clinical failure. Utilization of materials ranked more radiopaque than enamel would enable clinicians to distinguish the restorative material from tooth structure.     

大块充填树脂在牙体修复中的应用与研究进展

传统复合树脂在临床应用中分层充填,步骤较多,树脂的聚合收缩可导致修复体边缘微渗漏、术后敏感等,导致修复失败.2009年,大块充填树脂(bulk-fill resin-based composite)应运而生,改良的基质单体、改性强化的纳米混合填料以及独特的光引发剂,使得大块充填树脂能够一层充填4 mm,其简化操作步骤、节约椅旁时间、并能显著降低聚合收缩和聚合应力.本文就大块充填树脂的分类、固化原理、性能等方面进行阐述和讨论,并提出大块充填树脂的应用发展方向.     

Dental acrylic resin radiopacity: literature review and survey of practitioners' attitudes.

This study was initiated to ascertain the existence and some specifics of medical problems caused by traumatic ingestion/aspiration of fragments of radiolucent dental prostheses, and to evaluate opinions of radiopacity inclusion. A survey of 50 United States departments of oral surgery and emergency medicine yielded a 60% response. Results indicated that such medical problems are seen and would be reduced by incorporation of radiopaque materials. However, current technology cannot produce clinically acceptable levels of radiopacity without degrading physical and esthetic properties of the acrylic resin.     

Differences in aluminum equivalent values of endodontic sealers: conventional versus digital radiography

The aims of this study were to compare film and digital radiography in assessing the radiopacities of root canal sealers and to establish the relation in aluminum equivalent values of different methods. Standard disks of 5 different sealers were exposed together with an aluminum step wedge by using occlusal films and storage phosphor plates. Optical density of the sealers was evaluated by transmission densitometry, and mean gray values were determined by digital analysis. The data were analyzed by using two-way analysis of variance (P = .05). Pairwise comparisons were made by using Tukey post hoc and paired t tests (P = .05). The order from the most radiopaque to the most radiolucent sealer was the same for both methods; however, aluminum equivalent values determined by transmission densitometry were significantly higher (P < .01). Aluminum equivalent values of the 2 radiographic methods were 7%-20% different. The International Standards Organization standard for the radiopacity of dental root canal sealing materials needs modifications for digital systems.     

An ex vivo comparison of conventional and digital radiography for perceived image quality of root fillings

AIM: To compare the subjective image clarity of two different speed films and the Digora phosphor plate images with respect to the length and homogeneity of root canal fillings. METHODOLOGY: Root canal treatment was performed on 20 extracted permanent mandibular first molar teeth. Standardized images of each tooth positioned in a dried mandible were obtained with E- and F-speed films and Digora storage phosphor plates (SPP) at 0 degrees and 30 degrees horizontal angulations using the optimal exposure time recommended for each system. Five endodontists and five radiologists rated the image clarity of E- and F-speed radiographs as well as the original and enhanced Digora images. The data were compared using the Wilcoxon signed rank test (P < 0.01). Inter-observer agreement was determined by Cohen's kappa. RESULTS: Enhanced digital images were rated as superior followed by E- and F-speed films and then the original digital images for the evaluation of both homogeneity and length (P < 0.01) of root canal fillings. Agreement among endodontists and radiologists measurements was high in all of the imaging methods (kappa = 0.87). CONCLUSION: Perceived image quality of the enhanced Digora images was superior to the original Digora and conventional film images for the evaluation of root fillings. However, E-speed film provided a significantly better image clarity in comparison with F-speed and original Digora images.     

Influence of inorganic filler content on the radiopacity of dental resin cements

Digital radiography was used to measure the radiopacity of 18 resin cements to determine the influence of inorganic filler content on radiopacity. Four disk specimens (n=4) of each light-curing cement were digitally radiographed alongside an aluminum step wedge using an intraoral sensor (XIOS Plus, Sirona, Germany), and their mean gray value measured. Percentage of filler by weight was determined using an analytical combustion furnace. Data were statistically analyzed using one-way ANOVA and Tukey's test (α=0.05). All materials were more radiopaque than dentin and 12 materials were more radiopaque than enamel. Filler percentage ranged between 17.36 to 53.56 vol% and radiopacity between 1.02 to 3.40 mm Al. There were no statistically significant differences in inorganic filler percentage and radiopacity among the different shades of the same material (p>0.05), but the highest radiopacity was measured for the material which contained a higher percentage of filler.     

The radiopacity of glass ionomer dental materials

Although some glass ionomer dental materials are described as radiopaque by the manufacturer, it is rare for the actual degree of radiopacity to be specified. Using a technique previously described for measurement of the radiopacity of enamel, dentine and composite resin dental materials, the radiopacity of a number of glass ionomer materials, including restorative, lining and luting cements, was determined.     

Conventional versus storage phosphor-plate digital images to visualize the root canal system contrasted with a radiopaque medium

The pulp tissue was removed from 20 mandibular first molar teeth using 2.5% NaOCl irrigation and hand files. The dried canals were infused with radiopaque contrast medium. Standardized conventional and Digora digital images were obtained of each tooth positioned in a dried mandible at 0- and 30-degree horizontal angulations. Three evaluators rated the image clarity of the 0- and 30-degree original, enhanced, three-dimensional, zoom, and reverse digital image modes as superior, equal, or inferior to corresponding 0- and 30-degree conventional radiographs. The ratings were compared using the Wilcoxon signed rank test. The original, three-dimensional, zoom, or reverse digital images were inferior to the conventional radiographs for clarity of canal anatomy. The enhanced digital images were not always inferior to the conventional radiographs and were the only images superior to the original digital images. Overall, evaluators rated the image clarity of root canal anatomy on conventional radiographs better than on Digora images. However, factors in the experimental design may have contributed to this result.     

Radiopacity of nonmetallic root canal posts

PURPOSE: This study determined the radiopacity of a group of nonmetallic posts. MATERIALS AND METHODS: Four specimens were cut from 7 posts, and tooth sections were cut from extracted teeth. Radiographic images of all specimens along with an aluminum step wedge were obtained on occlusal films. Optical density readings for each specimen image were determined with a transmission densitometer. Radiopacity values were subsequently calculated as equivalents of aluminum thickness. RESULTS: Analysis of variance revealed significant differences in radiopacity values among the posts (P < .001). One nonmetallic post that was made of zirconium had a radiopacity value significantly greater than that of enamel. Another, made of glass fibers, acrylic resin, and fillers, had a radiopacity that was greater than that of dentin but smaller than that of enamel. The remaining 3 nonmetallic posts had radiopacity values lower than dentin. CONCLUSION: The 3 posts with radiopacity that was lower than dentin cannot be considered sufficiently radiopaque.     

Radiopacity and physical properties of titanium-polymethacrylate composite.

Titanium-polymethacrylate composite was prepared as an x-ray-opaque filler for composite core materials. The base monomers of the composite were 2,2-bis [4-(3-methacryloyloxy-2-hydroxypropoxy) phenyl] propane (Bis-GMA) and triethyleneglycol dimethacrylate (TEGDMA). Pure titanium powder was used as a radiopaque element. Two functional methacrylates--isopropyl dimethacryloyl isostearoyl titanate (KR-7) and 4-methacryloyloxyethyl trimellitate anhydride (4-META)--were adopted as couplers of titanium powder. The radiopacity of composites was determined in terms of their equivalent thickness of aluminum per unit thickness of material. Compressive and transverse strengths of the composites were measured by use of coupled and untreated titanium fillers. The composites that contained 70% and 80% titanium by weight showed more radiopacity than enamel and less than amalgam. Radiopacity was controlled by the content of titanium filler in the composite. The decrease in compressive and transverse strengths of the composites was 0.7 to 15.9% and 43.7 to 52.9%, respectively, after one year's immersion in water. The decrease in transverse strength was remarkable; however, this deterioration was diminished by use of both KR-7 and 4-META as couplers for titanium. Thus, prepared titanium-polymethacrylate composite may be used as a radiopaque composite filler for self-curing composite core materials.     

A laboratory comparison of three imaging systems for image quality and radiation exposure characteristics

AIM: To measure and compare the relationships between image quality and X-ray exposure for three types of intraoral imaging system (conventional film, phosphor plate system and CCD-based system). METHODOLOGY: Kodak 'Insight' F-speed film, Digora FMX (phosphor plate system) and Visualix USB (CCD system) were used to produce series of radiographic images of two tooth-bearing jaw specimens (maxillary molar and mandibular molar regions) at a range of X-ray exposures from 10 ms to 2000 ms (all at 6 mA and 60 kV). Digital images were viewed from a computer monitor and films viewed on a conventional light box. Five observers scored each image using a five-point subjective image quality scale (0-4). RESULTS: Optimum image quality (4) was seen for conventional film. Neither digital system achieved this score at any exposure, achieving in both cases a maximum mean score of 3.1 (adequate visualization). The two digital systems, however, provided adequate visualization at substantially lower exposure times. Dose reduction over conventional film for maximum quality images with Visualix USB was 20%, but for Digora FMX it was 70%. All three systems gave acceptable (quality score of two or higher) images over a broad range of exposures. CONCLUSIONS: In terms of subjective image quality, F-speed film performed better than the two digital systems, but this must be weighed against the ability of the two digital systems to give adequate image quality at lower radiation doses.     

Radiodensity of base, liner and luting dental materials

The aim of this study was to determine the radiodensity of base, liner and luting dental materials and to compare them with human enamel and dentin. Four classes of materials were examined: conventional glass ionomers (CG)—Vitro Cem, Ketac Bond, Vidrion F, Vidrion C; resin-modified glass ionomers (RMGI)—Fuji II LC, Vitrebond; resinous cement (RC)—Rely-X ARC; and zinc phosphate cement (ZP)—Cimento LS. Five 2-mm-thick standard samples of each material and five 2-mm-thick enamel and dentin samples were produced. An aluminum step wedge served as control. Samples were positioned over a phosphor plate of Digora digital system, exposed to X-ray, and the radiodensity obtained in the software Digora for Windows 2.0. Data were submitted to Kruskal–Wallis and Dunnett multiple comparisons test (α=0.05). According to statistical analysis, the following sequence in degree of radiodensity could be seen among the groups: Cimento LS (ZP) > Vitro Cem (CG) = Fuji II LC (RMGI) = Rely-X ARC (RC) = Vitrebond (RMGI) > Ketac Bond (CG) > enamel = Vidrion F (CG) > Vidrion C (CG) = dentin. The presence of radiopaque fillers such as zinc, strontium, zirconium, barium, and lanthanium rather than material type seems to be the most important factor when analyzing material radiodensity. Almost all investigated materials presented an accepted radiodensity.     

Effects of different exposure values on diagnostic accuracy of digital images.

OBJECTIVE: The aim of this in vitro study was to compare the effects of different exposure values on the image clarity of 3 digital radiographic systems and 1 conventional direct-exposure emulsion x-ray film. METHOD AND MATERIALS: Three digital radiographic systems, Digora, RVG, and Sidexis, were compared with the conventional dental x-ray film, Ektaspeed Plus. A medullary bone fragment and human teeth were radiographed with varying voltage, exposure time, and focus-receptor distance. Clinical criteria to evaluate image clarity were detail resolution, sharpness, contrast resolution, and artifacts of the different tooth and jaw structures. RESULTS: The optimal exposure times for digital imaging varied between 0.02 and 0.13 seconds and depended on the objects and the imaging systems. Optimal resolution was obtained when a voltage of 60 kV was used. The focus-receptor distance of 33 to 40 cm resulted in the best contrast and sharpness. Digital images did not always provide the detail resolution or sharpness achieved by conventional radiographs. CONCLUSION: The recommended exposure time for digital images amounted to approximately half the time needed for conventional film. Digital images had to be modified by adjusting the contrast and brightness to optimize the visibility of the areas to be diagnosed.     

Characterization of the inorganic fraction of resin composites

The purposes of this study were to determine the weight fraction of filler in thirty-nine resin-based materials including flowable and packable composites, and to examine the morphology of the filler particles. The percentages of inorganic fillers by weight were determined by Thermogravimetric Analysis and by ashing in air technique at 900 degrees C. The size and shape of the filler particles were examined using scanning electron microscopy (SEM) after dissolution of the organic matrix. The weight fraction of inorganic fillers ranged between 41.6 and 84.6%. Wide variations were found among materials of the same category. Values found in the present study were sometimes different from those given by the manufacturers. The SEM photomicrographs showed various shapes, and sizes of inorganic fillers. Compared with universal hybrid restorative materials, flowable composites have lower filler loading and packable resin composites did not show higher values as claimed by some manufacturers. Various factors may explain the observed discrepancies between the manufacturer's data and our results. The silane treatment as well as the incorporation of organic material as part of the fillers of the composite could be responsible for those differences.