Alternative X-ray filters for an intra-oral digital radiographic system

Expounding structures of roller compacted concrete dam specimens by means of hard conventional X-ray inspection

A simple solution to improve the contrast between the different concrete composites in X-ray imaging (radiography and tomography) of a highly compressed composite sample of real size roller compacted concrete (RCC) specimens is presented. This is made by applying a 9.5 mm thick Copper (Cu) filter at the output window of the X ray tube in a conventional X-ray inspection equipment. Our results show that with the employed filtration, at 140 kV and 200 kV, we were able to distinguish the gravel from the other concrete composites even in a highly compacted specimen. Cement and sand grains as well as porosity were not detected mainly due to the low spatial resolution of our detector system. This suggests a further improvement by using the now available high voltage microfocus X-ray tube (>= 200 kV), a bow-tie (or through) Cu filters and a high resolution flat panel detector for phase contrast imaging on real size compacted concrete specimens.

Radiopacity for Contemporary Luting Cements Using Digital Radiography under Various Exposure Conditions

PURPOSE

This study examined the radiopacity of contemporary luting cements using direct digital radiography under a range of exposure conditions.

MATERIALS AND METHODS

Disc specimens (N = 80, n = 10 per group, ø5 mm × 1 mm) were prepared from 8 resin-based luting cements (BisCem Clearfil SA Luting, Duolink, Maxcem Elite Multilink Speed, Panavia F 2.0, RelyX Unicem Clicker, V-link). The specimens were radiographed using a charge-coupled device sensor along with an 11-step aluminum step wedge (1.5-mm incremental steps) and 1-mm-thick tooth cut using five tube voltage/exposure time setups (60 kVp, 0.10/0.08 seconds; 70 kVp, 0.10/0.08/0.06 seconds) at 4 mA and 30 cm. The radiopacity of the specimens was compared with that of the aluminum step wedge and human enamel and dentin using NIH ImageJ software (available at http://rsb.info.nih.gov/ij/). A linear regression model for the aluminum step wedge was constructed, and the data were analyzed by ANOVA and Duncan post hoc test.

RESULTS

Maxcem Elite (5.142 to 5.441) showed the highest radiopacity of all materials, followed in order by Multilink Speed (3.731 to 3.396) and V-link (2.763 to 3.103). The radiopacity of Panavia F 2.0 (2.025 to 2.429), BisCem (1.825 to 2.218), Clearfil SA Luting (1.692 to 2.145), Duolink (1.707 to 1.993), and RelyX Unicem Clicker (1.586 to 1.979) were between enamel (2.117 to 2.330) and dentin (1.302 to 1.685). The radiopacity of 70 kVp conditions was higher than that of the 60 kVp conditions.

CONCLUSIONS

The radiopacities of the tested luting materials were greater than those of dentin or aluminum, satisfying the criteria of the International Organization for Standardization, and they differed significantly from each other in the exposure setups.

Evaluation of low-contrast perceptibility in dental restorative materials under the influence of ambient light conditions

OBJECTIVES

This study aimed to assess how details on dental restorative composites with different radio-opacities are perceived under the influence of ambient light.

METHODS

Resin composite step wedges (six steps, each 1-mm thick) were custom manufactured from three materials, respectively: (M1) Filtek™ Z350 (3M/ESPE, Saint Paul, MN); (M2) Prisma AP.H™ (Dentsply International Inc., Brazil) and (M3) Glacier(®) (SDI Limited, Victoria, Australia). Each step of the manufactured wedge received three standardized drillings of different diameters and depths. An aluminium (Al) step wedge with 12 steps (1-mm thick) was used as an internal standard to calculate the radio-opacity as pixel intensity values. Standardized digital images of the set were obtained, and 11 observers independently recorded the images, noting the number of noticeable details (drillings) under 2 dissimilar conditions: in a light environment (light was turned on in the room) and in low-light conditions (light in the room was turned off). The differences between images in terms of the number of details that were observed were statistically compared using ANOVA, Cronbach's alpha coefficient and Wilcoxon and Kruskal-Wallis tests, with a significance level setting of 5% (α = 0.05).

RESULTS

The M2 showed higher radio-opacity, the M1 displayed intermediate radio-opacity and the M3 showed lower radio-opacity, respectively; however, all three were without significance (p > 0.05) compared with each other. The differences in radio-opacity resulted in a significant variation (p < 0.05) in the number of noticeable details in the image, which were influenced by characteristics of details, in addition to the ambient-light level.

CONCLUSIONS

The radio-opacity of materials and ambient light can affect the perception of details in digital radiographic images.

Influence of Radiopacity of Dental Composites on the Diagnosis of Secondary Caries: The Correlation Between Objective and Subjective Analyses

This study aimed to objectively evaluate the radiopacity of different dental composites and their subjective influence on diagnosing secondary caries–like lesions and how these results correlate. For objective analysis, three resin specimens (1 mm thick, with a 4-mm internal diameter) were made with four composites: 1) Charisma; 2) Filtek Z250; 3) Prisma AP.H; and 4) Glacier. Three human teeth were selected and then mesio-distally sectioned (1 mm thick) to make the dental specimens. An aluminum (Al) wedge (12 steps, 1 mm thick, 99.8% purity) was used as an internal standard to calculate the radiopacity. For subjective analysis, 20 human teeth were selected and then prepared with a mesio-occluso-distal (MOD) inlay cavity, with half the teeth receiving a round cavity to simulate the carious lesion. The MOD was restored using the composites at four different times. Standardized radiographs were acquired and then digitized (300 dpi and eight-bit TIFF) for both analyses. A histogram objectively measured the pixel intensity values of the images, which were converted into millimeters of Al using linear regressions. Eight observers subjectively evaluated the images using a five-point rating scale to diagnose the caries. The data were statistically analyzed using the Student t-test, the Kappa test, diagnostic testing, and the Pearson correlation coefficient (α=0.05). All materials showed radiopacity values compatible with dental tissues (p&gt;0.05); Glacier was similar to dentin and Prisma AP.H was similar to enamel, while the remaining materials showed a middle radiopacity. Prisma AP.H and Glacier differed (p&lt;0.05) in relation to their accuracy to caries diagnosis, with Glacier having greater accuracy. There was a correlation between objective and subjective analyses with negative linear dependence. An increase in the material's radiopacity could have a subjectively negative influence on the diagnosis of secondary caries; thus, an ideal radiopacity for a dental composite is closer to the dentin image and produces similar attenuation to X-rays than does dentin.