Detection of Proximal Caries in vitro Using Standard and Task-Specific Enhanced Images from a Storage Phosphor Plate System

Computed vs. film-based radiographs' contour artifacts influence diagnosis of secondary caries

To test local grey-scale changes on dental bitewing radiographs near filling margins for image acquisition. Forty approximal preparations in caries-free amalgam filled teeth and bitewing radiographs were acquired under standardized conditions applying four techniques. Film-based analog radiographs were digitized using flat-bed scanner (FDR). Phosphor-plate computed radiographs (PCR) were directly acquired by scanning VistaScan imaging plates. Image quality was tested using Preset Filter (PF) or manually applied IntraOral Fine Filter (IF) to enhance digital images. Local changes from digital imaging processing were assessed by comparing the margin-near (MN) and margin-far (MF) zone by a multivariate repeated measurements analysis. All images were acquired with 8-bit depth (256 shades). Dentine was displayed in 79 shades for FDR and 54 shades for PCR. PF or IF locally modify bitewing radiographs by darkening marginal dentine by 8 or 29 shades, respectively. The sharpest display of the margin (shades per pixel) from dentine to filling was found for IF (26.2), followed by FDR (23.2), PF (15.3) and PCR (8.3). Computed radiography with phosphor plates generate more homogeneous images compared to flatbed-digitized film-based radiographs. The filling margin was sharpest represented with the IF filter at the detriment of an artificial darkening of the dentine near the margin of the filling. Contour artifacts by filters have the potential to confound diagnosis of secondary caries. Algorithms and filters for sensor data processing, causing local changes above 2% of the dynamic range by non-continuous mathematical functions, should only be applied with caution, manually when diagnosing and reversibly.

Radiographic modalities for diagnosis of caries in a historical perspective: from film to machine-intelligence supported systems

Radiographic imaging for the diagnosis of caries lesions has been a supplement to clinical examination for approximately a century. Various methods, and particularly X-ray receptors, have been developed over the years, and computer systems have focused on aiding the dentist in the detection of lesions and in estimating lesion depth. The present historical review has sampled accuracy ex vivo studies and clinical studies on radiographic caries diagnosis that have compared two or more receptors for capturing the image. The epochs of film radiography, xeroradiography, digital intraoral radiography, panoramic radiography and other extraoral methods, TACT analysis, cone-beam CT and artificial intelligence systems aiding in decision-making are reviewed. The author of this review (43 years in academia) has been involved in caries research and contributed to the literature in all the mentioned epochs.

Diagnostic accuracy of Digora Optime storage phosphor plates for proximal subsurface demineralization: effect of different exposure times

OBJECTIVE

The aim of this study was to compare the diagnostic accuracy of F-speed film and storage phosphor plate (SPP) exposed with different exposure times for the detection of artificial enamel subsurface demineralization.

STUDY DESIGN

Standard enamel windows of extracted premolars were exposed to a demineralizing solution. All teeth were radiographed before and after acid application with F-speed films and SPPs. Films were exposed for 0.25 seconds and SPPs were exposed using 4 exposure times. Receiver operating characteristic analysis was used for diagnostic accuracy (A(z)).

RESULTS

Significant differences were obtained among A(z)s of 0.08- versus 0.12-seconds and 0.10- versus 0.12-second exposed SPPs (P < .05). A(z)s of films were higher than the SPPs exposed with 0.08, 0.10, and 0.12 seconds (P < .05). No difference was found between the A(z)s of the 2 systems when SPPs were exposed for 0.16 seconds (P > .05).

CONCLUSIONS

Diagnostic accuracy of films and SPPs was not impaired when exposure time was 36% reduced for the latter; however, diagnosis was impaired when reduced 52%.

Diagnostic accuracy of proximal enamel subsurface demineralization and its relationship with calcium loss and lesion depth

OBJECTIVE

The aim of this study was to determine the relationship between the amount of calcium loss, lesion depth, and the accuracy of storage phosphor plate (SPP) and film radiographs for the detection of artificial proximal demineralization.

METHODS

Standard enamel windows of extracted premolars were exposed to a demineralizing solution for 60 h, 80 h, 100 h and 120 h. Solutions were analysed for calcium concentration by atomic absorption spectrometer and the lesion depths were calculated by a specific formula. All teeth were radiographed with SPPs and F-speed films before and after acid application. Images were evaluated by five observers. Stereomicroscopic and scanning electron microscopic (SEM) observations were carried out to visualize enamel surfaces after acid exposure. Receiver operating characteristic analysis was used for diagnostic accuracy (A(z)). A(z)s were compared with factorial analysis of variance and t-tests. The relationship between A(z)s and lesion depths was determined with Pearson's correlation test.

RESULTS

Strong positive correlation was found between A(z)s of both radiographic methods and lesion depths. No difference was found between the A(z)s of two radiographic systems for any of the demineralization durations (p > 0.05). Pair-wise comparisons revealed no significant difference in A(z)s of SPPs (p > 0.05), while significant differences were obtained for the A(z)s of films for different demineralization periods (p < 0.05). Stereomicroscopic and SEM observations confirmed demineralizations from superficial to deeper layers of enamel.

CONCLUSION

Subsurface enamel demineralization was not accurately detectable with either storage phosphor plates or F-speed films. The amount of calcium loss and the depth of demineralization have a strong relationship with diagnostic accuracy with a significant effect particularly on F-speed films.

The effects of digital image enhancement on the detection of vertical root fracture

AIM

To determine the effects of digital image enhancement on observer ability to detect experimentally induced vertical root fractures (VRF).

MATERIAL AND METHODS

A total of 64 extracted human mandibular premolar teeth were used in this study. In 32 teeth, VRFs were created in the bucco-lingual planes by gently tapping with screw-type root-canal pins. The remaining 32 intact teeth served as a control group. Digital images were obtained using a charge coupled device sensor. Three observers separately examined the original and four types of digitally enhanced images (enhanced using sharpness, zoom-in, reverse-contrast, and pseudo-3D functions) at 1-week intervals. All teeth were evaluated using a 5-point scale for the presence/absence of VRF. Evaluations of each image set were repeated 1 month after the initial viewings. Kappa coefficients were calculated to investigate the degree of intra- and inter-observer agreement. The areas under the receiver operating characteristic (ROC) curves (Az values) were calculated using the MedCalc statistical software. ROC values for each image type, observer and viewing were compared using t-tests. A level of alpha = 0.05 was considered significant.

RESULTS

Kappa coefficients for intra-observer agreement ranged from 0.304 to 0.679. Inter-observer agreement kappa values ranged from 0.109 to 0.399 for the first reading and from 0.106 to 0.380 for the second reading. Statistical comparisons between Az values for each observer showed no significant differences (P > 0.05) among image types.

CONCLUSION

There were no differences in diagnostic outcomes among differently enhanced images in the in vitro detection of VRF.

Task-specific enhancement filters in storage phosphor images from the Vistascan system for detection of proximal caries lesions of known size

OBJECTIVE

The aim was to compare original 8-bit images from the Vistascan storage phosphor plate system with images enhanced with specific filters for detection of proximal caries lesions and, further, to analyze the mutual sensitivity of the filtered images for different lesion sizes.

STUDY DESIGN

One hundred sixty approximal noncavitated surfaces were radiographed using the Vistascan storage phosphor plate system. Original and enhanced (Fine, Caries1, and Caries2 filters) images were assessed by 6 observers who recorded the presence/absence of proximal carious lesions. Microscopy served to detect and measure true lesion size.

RESULTS

One hundred one surfaces were sound, and 59 had lesions. The sensitivity of the Fine filter images was significantly higher than the Caries1 and Caries2 filter modalities (P < .005). The original images did not differ significantly from the Caries1 and Caries2 modalities. Both the Fine filter and the original images had a significantly higher specificity than the Caries2 modality (P < .005). The overall accuracies for the Fine filter and the original images were significantly higher than for the Caries2 modality (P < .005). The Fine filter images also had higher accuracy than the Caries1 modality (P < .05). The mutual sensitivity of the filters varied little with lesion size.

CONCLUSION

Fine filter may be a promising enhancement tool for images used for detection of shallow carious lesion, because it showed less observer variability. The task-specific enhancement filters, Caries1 and Caries2, were less accurate than the original and Fine filter images and cannot be recommended for detection of the lesion sizes included in this study.

Digital enhancement of radiographs for assessment of interproximal dental caries

OBJECTIVES

Evaluation of a particular digital caries image-enhancing mode (filter) for its effect on the validity of measurements of caries lesion depth.

METHODS

Standardized radiographs of 44 extracted teeth exhibiting interproximal caries lesions were obtained. Six radiographs were obtained of each tooth and digitized. Four radiographs were made using D-speed film with and without soft tissue scattering equivalent (STSE) at normal exposure time (0.32 s) and underexposed (0.16 s). Two were made using E-speed film with STSE normally (0.16 s) and underexposed (0.08 s). On each of the 264 radiographs, 4 independent examiners measured the central depth (CD) of 1 carious lesion per tooth both on the unchanged radiographic image and after use of the filter. Histometric CD assessments provided a gold standard for comparison with the radiographic measurements (validity). Repeated measures ANOVA was calculated for validity in relation to examiner, lesion type, filter, film type, exposure time and STSE.

RESULTS

The lesion type was identified to statistically significantly influence the validity of CD measurements. Examiner in combination with defect type (P<0.001), filter (P = 0.017), exposure (P = 0.027) and film type (P = 0.044) had an additional albeit small effect.

CONCLUSIONS

The lesion type significantly influenced the validity of CD measurements: enamel lesions were less underestimated than dentin lesions.