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

Abstract

SUMMARY 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>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<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.

Radiopacity measurements of direct and indirect resin composites at different thicknesses using digital image analysis

“…According to Cruz et al, an ideal radiopacity for dental composites is one that is closer to the dentin image and which ultimately produces a similar attenuation to that of sound dentin tissue 29) . Excessively radiopaque restorations may hinder a clinician's ability to spot marginal defects due to the Mach effect 30) .…”

“…In clinical situations, diagnostic challenges arise when radiographic images present barely discernible radiopacity differences between dental tissues and restorative materials 8,29) . According to Cruz et al, an ideal radiopacity for dental composites is one that is closer to the dentin image and which ultimately produces a similar attenuation to that of sound dentin tissue 29) .…”

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

“…5,24 However, an adjustment in characteristic curves of the images can occur, because photostimulable phosphor digital systems use a histogram equalization algorithm (automatic range control) during image acquisition, which corrects the contrast from the images. 24 Histogram equalization algorithm is very important, because these systems own high latitude, which makes it possible to deviate from the optimal exposure and continue generating images that are subjectively very similar.…”

“…5 The human eye has a wide dynamic range to luminous intensity, and it can distinguish between the different shades only if subsequent intensities of shades differ by .1%, 6 with the underlying visual response varying in dependence of stimulus context at the luminance-to-lightness mapping. 23 A previous study 5 reported that, when radiographic images of composites were evaluated for recurrent caries diagnosis, even if only insignificant differences in radio-opacity existed, they were able to somewhat influence a radiographic diagnosis. In the present study, a variation very close to the radio-opacity described by pixel-intensity values was observed among the different resin composites, showing no statistically significant differences.…”

“…Thus, to improve the diagnosis, it has been recommended that the restorative material needs to be more radio-opaque than dentin and, preferably, should have a radio-opacity closer to dentin, because an increase in the restorative material's radio-opacity can reduce the detection of secondary caries. 5 The healthy human eye has a wide dynamic range to luminous intensity as a result of light adaptation controlled by the pupil's ability to adjust to the luminescence that reaches the retina, 6 and the human eye can discern approximately 60 shades of grey at one time without using any aids. Compare this with a standard computer monitor, which shows images with 256 shades of grey.…”