Accuracy of caries diagnosis in digital images from charge-coupled device and storage phosphor systems: an in vitro study

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.

In vitro comparison of two photostimulable phosphor plate systems for early detection of occlusal dentin caries with and without a sharpening filter

Background. Dental caries is the most important reason for tooth loss. Clinical examination is the most commonly used technique for occlusal caries diagnosis. The diagnostic power of digital systems is a matter of controversy in this field. The present study aimed to determine the diagnostic accuracy of two photostimulable phosphor plate (PSP) systems for early occlusal dentin caries in vitro.

Methods. Sixty-nine extracted molar and premolar teeth were used in this study. The teeth were mounted in triple blocks, and standard radiographs were taken by the Digora and Acteon digital radiographic systems. The original and filter 1-enhanced radiographs were evaluated by two experienced observers twice at an interval of two weeks, and dentin caries was recorded in Tables prepared for the study. The teeth were then sectioned in a buccolingual direction and evaluated under a stereomicroscope. The observers’ reports were compared with microscopic findings as the gold standard. SPSS 23 was used to calculate the kappa coefficient, sensitivity, specificity, and area under the ROC curve (AUC). Statistical significance was set at P<0.05.

Results. The internal and the external agreements in both imaging systems were good to excellent. The means of sensitivity, specificity, and AUC in the Acteon system were 34.1, 92.9, and 0.674, with 30.8, 94.8, and 0.659, respectively, in the Digora system.

Conclusion. The accuracy of early occlusal caries diagnosis was poor on both systems, and no significant difference was observed between the two systems at a 95% confidence interval. Although the AUC was slightly higher in the original images, there was no significant difference between them; however, due to their high specificity, they can prevent unnecessary treatments in the clinic.

Effect of different exposure times on caries detection and pixel value in a wireless digital system

Objectives

: The aim of this study was to assess, using the CDR Wireless®, the effect of different exposure times on caries detection and pixel intensity values.

Materials and Methods

Forty teeth were x-rayed using a Schick CDR Wireless sensor at eight different exposure times - 0.06, 0.10, 0.13, 0.16, 0.20, 0.25, 0.30, and 0.32 s. Four observers evaluated the images for presence of carious lesions scoring proximal surfaces of each tooth on a 5-point scale. Scores were compared to histological sections of the teeth. Accuracy was evaluated by means of ROC curve analysis. Radiographs of an aluminum step wedge were obtained using the same eight exposure times. Pixel intensity measurements were obtained, and mean pixel values were statistically analyzed using linear regression.

Results

The Az for each exposure time varied from 0.53 to 0.62. Two-way analysis of variance and Tukey test demonstrated that the exposure time of 0.25 s presented the best result and was significantly higher than 0.30 s and 0.35 s. In regard to mean pixel values, two different behaviors were observed, and the exposure time of 0.20 s presented mean pixel values in both phases.

Conclusion

The performance of the exposure times from 0.06 s to 0.25 s was satisfactory for proximal caries detection, and 0.25 s is the best as indicated for this finality.

Clinical Relevance

Considering that a reduction of exposure time represents a reduction of patient exposure dose, and this reduction cannot neglect image quality, the behavior of any digital system must be carefully evaluated.

In vitro visual and visible light transillumination methods for detection of natural non-cavitated approximal caries

OBJECTIVES

The objective was to evaluate a visible-light-transillumination (using Digital Imaging Fiber-Optic Transillumination machine: DIFOTI) method using occlusal view (DIFOTI-occl), axial view (buccal and lingual: DIFOTI-axial), and combination of all views (DIFOTI-all) for detecting non-cavitated approximal caries and to compare its performance to visual examination (International Caries Detection and Assessment System: ICDAS).

MATERIALS AND METHODS

Thirty extracted human premolars were selected (sound to lesions into the outer one-third of the dentine) based on micro-computed tomography (μ-CT). Teeth were mounted in a custom-made device to simulate approximal contact. DIFOTI (Electro-Optical Sciences Inc., Irvington, NY, USA) images were obtained from the occlusal, buccal, and lingual views. DIFOTI image and ICDAS examinations were performed and repeated by three trained/calibrated examiners. Sensitivity, specificity, area under receiver operating characteristics curve (A_z), inter- and intra-class correlation coefficients (ICCs), and correlation were determined.

RESULTS

Sensitivity/specificity was for DIFOTI-occl: 0.42/0.75, DIFOTI-axial: 0.86/0.93, DIFOTI-all: 0.91/0.69, and for ICDAS: 0.89/0.83. A_z for DIFOTI-occl was significantly lower than that of DIFOTI-axial (p < 0.001), DIFOTI-all (p = 0.002), and ICDAS (p = 0.005). Spearman correlation coefficients with μ-CT for DIFOTI-occl (r = 0.39) showed weak association, while DIFOTI-axial (r = 0.80), DIFOTI-all (r = 0.91), and ICDAS (r = 0.90) showed moderate association. ICCs for intra-examiner repeatability/inter-examiner agreement were for DIFOTI-occl (0.64/0.58), DIFOTI-axial (0.92/0.89), DIFOTI-all (0.85/0.83), and ICDAS (0.79/0.72).

CONCLUSIONS

The results of the current in vitro study suggest that, for detection of non-cavitated approximal caries lesions, DIFOTI performs better using axial than occlusal view.

CLINICAL RELEVANCE

Approximal non-cavitated caries detection is challenging. DIFOTI can observe images from occlusal-, buccal-, and lingual views. DIFOTI and visual (ICDAS) examinations of buccal- and lingual- and all-views are more suitable than those of occlusal view for a detection of non-cavitated approximal caries.

Digital Imaging Capability for Caries Detection

The objective of this study was to identify the diagnostic capability of photostimulable phosphor plates (PSPs) and direct digital sensors (DDSs) in the detection of interproximal caries. Studies were identified that evaluated the diagnostic capability of PSPs and DDSs in detecting interproximal caries in human teeth, in both dentin and enamel. Histologic sections were the gold standard. This systematic review searched several electronic databases. In addition, Google Scholar and reference lists of the finally included studies were screened. QUADAS-2 was applied to evaluate the risk of bias among included studies. Six studies were finally included; 4 of which were considered homogeneous enough to conduct a meta-analysis. The meta-analysis evaluated 668 interproximal human tooth surfaces. All studies used extracted human teeth ranging from no caries present to caries into dentin. Each tooth was radiographed by both PSP and DDS technologies and then submitted for histologic analysis as the gold standard. Meta-analysis showed that intraoral digital imaging is of high specificity but low sensitivity in the detection of interproximal caries. The sensitivity and specificity for different studies with PSPs varied substantially from 15% to 54% and from 84% to 100%, respectively. Direct sensor analysis sensitivity and specificity ranged from 16% to 56% and from 90% to 100%, respectively. Newer PSP and DDS technologies had statistically significant higher sensitivities, yet the differences in diagnostic capabilities between the older and newer technologies were clinically insignificant. Both digital systems were excellent in identifying surfaces without caries (specificity) but were not sensitive enough to reliably identify interproximal surfaces with caries. Clinicians must therefore remain vigilant in performing a careful clinical examination and other diagnostic tests rather than relying solely on radiographic imaging to diagnose interproximal caries.

Knowledge Transfer Statement: This study will help clinicians make an evidence-based decision when deciding which digital radiography system to use when evaluating interproximal caries. Time, patient radiation safety, cost, and image quality are factors to be considered. The performance of the different available digital imaging systems was compared with the current gold standard—a histologic analysis—via meta-analysis.

The effects of noise reduction, sharpening, enhancement, and image magnification on diagnostic accuracy of a photostimulable phosphor system in the detection of non-cavitated approximal dental caries

PURPOSE

Contrast, sharpness, enhancement, and density can be changed in digital systems. The important question is to what extent the changes in these variables affect the accuracy of caries detection.

MATERIALS AND METHODS

Forty eight extracted human posterior teeth with healthy or proximal caries surfaces were imaged using a photostimulable phosphor (PSP) sensor. All original images were processed using a six-step method: (1) applying "Sharpening 2" and "Noise Reduction" processing options to the original images; (2) applying the "Magnification 1:3" option to the image obtained in the first step; (3) enhancing the original images by using the "Diagonal/" option; (4) reviewing the changes brought about by the third step of image processing and then, applying "Magnification 1:3"; (5) applying "Sharpening UM" to the original images; and (6) analyzing the changes brought about by the fifth step of image processing, and finally, applying "Magnification 1:3." Three observers evaluated the images. The tooth sections were evaluated histologically as the gold standard. The diagnostic accuracy of the observers was compared using a chi-squared test.

RESULTS

The accuracy levels irrespective of the image processing method ranged from weak (18.8%) to intermediate (54.2%), but the highest accuracy was achieved at the sixth image processing step. The overall diagnostic accuracy level showed a statistically significant difference (p=0.0001).

CONCLUSION

This study shows that the application of "Sharpening UM" along with the "Magnification 1:3" processing option improved the diagnostic accuracy and the observer agreement more effectively than the other processing procedures.

Radiographic diagnosis of dental restoration misfit: a systematic review

The objective of this study was to perform a systematic review on the use of radiographic methods for the diagnosis of misfit in dental prostheses and restorations. The MEDLINE bibliographic database was searched from 1950 to February 2014 for reports on the radiographic diagnosis of misfits. The search strategy was limited to English-language publications using the following combined MeSH terms in the search strategy: (Dental Restoration OR Dental Prosthesis OR Crown OR Inlays OR Dental Abutments) and (Dental Leakage OR Prosthesis Fitting OR Dental Marginal Adaptation OR Surface Properties) and (Radiography, Dental OR Radiography, Dental, Digital OR Cone-Beam Computed Tomography). Twenty-eight publications were identified and read in full text, and 14 studies fulfilled criteria for inclusion. Information regarding the use of radiographic methods for the diagnosis of misfits in dental prosthesis and restorations, and in which the methodology/results comprised information regarding how the sample was collected/prepared, the method, imaging protocol, presence of a reference test and the outcomes were evaluated. QUADAS criteria was used to rate the studies in high, moderate or low quality. The evidence supporting the use of radiographic methods for the diagnosis of misfits in dental prosthesis and restorations is limited to low-/moderate-quality studies. The well-established intra-oral orthogonal projection is still under investigation and considered the most appropriate method, both when evaluating the relation between dental restoration to tooth and abutment to implant. Studies using digital radiographs have not evaluated the effect of image post-processing, and tomography has not been evaluated.

Comparison of changes in dental and bone radiographic densities in the presence of different soft-tissue simulators using pixel intensity and digital subtraction analyses

OBJECTIVES

To evaluate the influence of soft-tissue simulation materials on dental and bone tissue radiographic densities using pixel intensity (PI) and digital subtraction radiography (DSR) analyses.

METHODS

15 dry human mandibles were divided into halves. Each half was radiographed using a charge-coupled device sensor without a soft-tissue simulation material (Wm) and with 5 types of materials: acrylic (Ac), wax (Wx), water (Wt), wood (Wd) and frozen bovine tissue (Bt). Three thicknesses were tested for each material: 10 mm, 15 mm and 20 mm. The material was positioned in front of the mandible and the sensor parallel to the molar region. The radiation beam was perpendicular to the sensor at 30 cm focal spot-to-object distance. The digital images of the bone and dental tissue were captured for PI analyses. The subtracted images were marked with 14 landmark magnifications, and 2 areas of analyses were defined, forming the regions of interest. Shapiro-Wilk and Kruskal-Wallis tests followed by Dunn's post-test were used (p < 0.05).

RESULTS

DSR showed that both the material type and the thickness tested influenced the gain of density in bone tissue (p < 0.05). PI analyses of the bone region did not show these differences, except for the lower density observed in the image without soft-tissue simulation material. In the dental region, both DSR and PI showed that soft-tissue simulators did not influence the density in these regions.

CONCLUSIONS

This study showed that the materials evaluated and their thicknesses significantly influenced the density-level gain in alveolar bone. In dental tissues, there was no density-level gain with any soft-tissue material tested.

Evaluation of Cone Beam Computed Tomography (CBCT) System: Comparison with Intraoral Periapical Radiography in Proximal Caries Detection

Background and aims

With the introduction of Cone Beam Computed Tomography (CBCT) in dentistry, a question has been raised whether the technique significantly increases the diagnostic accuracy in comparison with other techniques or not. Therefore, the present study was undertaken to assess the accuracy of CBCT modality in detecting proximal carious lesions as compared to conventional periapical radiographs.

Materials and methods

This diagnostic study was carried out on 84 human extracted molars and premolars. The teeth were mounted and divided in 28 blocks of 3 teeth. Periapical and CBCT images of teeth were obtained. Five observers scored the images for the detection of proximal carious lesions using a 2-point scale (caries, present; caries, absent). The gold standard was determined by histopathologic sections. Sensitivity, specificity, PPV, NPV and receiver operating charac-teristics (ROC) curves were traced for observers in both systems. The results were analyzed by paired t-test.

Results

The area under the ROC curve, sensitivity, specificity, accuracy, positive and negative predictive values of CBCT images were 0.568, 0.835, 0.637, 0.714, 0.598 and 0.856, respectively. These parameters were 0.432, 0.837, 0.722, 0.77, 0.687 and 0.858 for the periapical conventional technique, respectively.

Conclusion

The CBCT images did not enhance detection of proximal caries in comparison with periapical images.

Effect of JPEG compression on the diagnostic accuracy of periapical images in the detection of root fracture

The ability of a periapical radiograph to exhibit the fracture depends on many factors including, but not limited to, the resolution of the image. The quality can be reduced by the image compression. The purpose of this study is to evaluate the effect of Joint Photographic Experts Group (JPEG) compressions on the diagnostic capability of periapical images in the detection of root fractures. Ten dry human mandibles containing 151 teeth were used in this study. Mandibles were radiographed with direct digital imaging sensor using the paralleling technique. Four observers detected root fracture on the images saved in one uncompressed and two compressed formats. Receiver operating characteristic (ROC) and anova analyses were performed to compare the performance of the three different systems and evaluate the effect of the compression on the accuracy of root fracture detection. Results did not show any statistically significant difference between the original, large images presented in tagged image file format (TIFF) and the two compressed images (JPEG medium file and JPEG small file images) in the detection of root fractures. The intra-rater comparison showed a significant consistency in the detection of the fracture. The compression reduced the file size considerably (from 1.77 MB to 453 and 95 Kb), but it did not affect the accuracy of root fracture detection. The file size reduction, on the other hand, is very beneficial for image electronic storage and mainly in teleradiology.

Current status of dental caries diagnosis using cone beam computed tomography

Purpose

The purpose of this article is to review the current status of dental caries diagnosis using cone beam computed tomography (CBCT).

Materials and Methods

An online PubMed search was performed to identify studies on caries research using CBCT.

Results

Despite its usefulness, there were inherent limitations in the detection of caries lesions through conventional radiograph mainly due to the two-dimensional (2D) representation of caries lesions. Several efforts were made to investigate the three-dimensional (3D) image of lesion, only to gain little popularity. Recently, CBCT was introduced and has been used for diagnosis of caries in several reports. Some of them maintained the superiority of CBCT systems, however it is still under controversies.

Conclusion

The CBCT systems are promising, however they should not be considered as a primary choice of caries diagnosis in everyday practice yet. Further studies under more standardized condition should be performed in the near future.

Comparison of digital systems and conventional dental film for the detection of approximal enamel caries

OBJECTIVES

The aims of this study were (1) to compare the accuracy of the detection of approximal enamel caries lesions using three intraoral storage phosphor plate digital systems and one conventional film-based radiographic system; and (2) to determine whether there is a correlation between the histological and radiographic measurements of enamel caries.

METHODS

160 approximal surfaces were radiographed under standardized conditions using three storage phosphor stimulable systems (DenOptix and Digora FMX with white and blue plates), and one film system (Insight film). 17 observers scored the images for the presence and depth of caries using a 4-point scale. The presence of caries was validated histologically (gold standard). Two-way analysis of variance was used to test the differences in sensitivity, specificity and overall accuracy (TP + TN). The data from the radiographic and histological measurements were statistically analysed by Spearman's rank correlation coefficient.

RESULTS

Two-way analysis of variance and the post hoc t-test demonstrated that Digora (white plate) had higher specificity and overall accuracy values than DenOptix (P = 0.021); there was no statistically significant difference among the other imaging modalities (P > 0.05). There was no significant correlation between the histological depth measurements and the radiographic measurements from Digora (blue plate) (P = 0.43), Digora (white plate) (P = 0.15), DenOptix (P = 0.17) and Insight film (P = 0.06).

CONCLUSIONS

The results suggest that (1) the performance of the three storage phosphor image plate systems was similar to that of the Insight film for detection of approximal enamel caries, and (2) the increase in histological depth of enamel caries was not significantly correlated with radiographic measurements.

Comparison of visual inspection and different radiographic methods for dentin caries detection on occlusal surfaces

OBJECTIVES

The aim of the present study was to assess the validity of the digital phosphor plate radiographic technique (Gendex Dental Systems) on occlusal surfaces in comparison with visual examination and conventional E- and F-speed films.

METHODS

The study material consisted of 54 non-cavitated third molars with a range of appearances, including apparently sound surfaces. Each surface was visually examined (VI) according to the criteria established by Ekstrand et al. Three radiographic images (E-speed, F-speed, digital phosphor plate film) were taken of each molar. The standardized radiograph technique used an alignment fixture to reproduce the focus-to-object distance as well as the object-to-film distance. Afterwards each tooth was cut into sections in the buccolingual direction with a microtome saw, and caries extension was assessed using light microscopy (LM) and microradiography (MR). The statistical analysis included the calculation of sensitivity (SE), specificity (SP) and A(z) values.

RESULTS

The following validity parameters were found for the tested diagnostic methods on the dentin caries level: VI/LM, 68.0 SE/93.1 SP/0.698 A(z); VI/MR, 68.2/87.5/0.751; E-speed/LM, 76.0/78.6/0.637; E-speed/MR, 77.3/74.2/0.681; F-speed/LM, 64.0/67.9/0.507; F-speed/MR, 68.2/67.7/0.594; Gendex/LM, 60.0/85.7/0.629; and Gendex/MR, 59.1/80.6/0.586.

CONCLUSION

The methods used showed different levels of validity: E- and F-speed films were linked to higher sensitivity values, whereas a higher specificity was recorded for the tested imaging plate system. In accordance with the diagnostic performance, the digital system can be recommended for practical use and potentially help prevent overtreatment thanks to its high SP.

Influence of image filters on the reproducibility measurements of alveolar bone loss

The reproducibility of measurements of alveolar bone loss on radiographs may be a problem on epidemiologic studies, as they are based on comparisons of the diagnosis of various examiners. The aim of the present research paper was to assess the inter- and intra-examiner reproducibility of measurements of the interproximal alveolar bone loss on non-manipulated digital radiographs and after the application of image filters. Five Oral Radiologists measured the distance between the cementoenamel junction (CEJ) to the alveolar crest or to the deepest point of the bony defect on 12 interproximal digital radiographs of molars and bicuspids of a dry human skull. The digital manipulation and the linear measurements were obtained with the Trophy Windows software (Throphy®). For each image, six different versions were created: 1) non-manipulated; 2) bright-contrast adjustment; 3) negative; 4) negative with brightness-contrast adjustment; 5) pseudo-colored; 6) pseudo-colored with brightness-contrast adjustment. In order to prevent interpretation bias because of the repetition of measurements, the examiners measured the radiographs in a random sequence. The two-way ANOVA test at 5% level of significance to compare the means of readings of the same operator with each filter indicated p<0.05 for the majority of operators, while the comparison between the mean values of operators using the same filter indicated p>0.05 for all filters. Based on the results, we concluded that linear measurements of interproximal alveolar bone loss on digital radiographs are highly reproducible among examiners. Nevertheless, the application of image filters significantly influenced the degree of intra-examiner reproducibility. Some filters even reduced the reproducibility of intra-examiner readings.

Detection of artificial occlusal caries in a phosphor imaging plate system with two types of LCD monitors versus three different films

The aim of this study was to determine diagnostic performance of a storage phosphor plate system Digora Optime (Soredex, Helsinki, Finland) with two types of LCD monitor in the detection of artificial caries when compared to Ultraspeed (D), Ektaspeed Plus (E), and Insight (F) radiographic films. Seventy extracted human molars-with artificial caries-were radiographed under identical standardized conditions using (1) a storage phosphor plate system Digora (Soredex, Helsinki, Finland), (2) Insight, (3) Ektaspeed Plus, and (4) Ultraspeed (Carestream Health Inc, Rochester, NY). All digital images and radiographs were examined by three observers for the presence or absence of artificial caries using a five-point confidence scale. Digital images were evaluated both on a LCD computer monitor (Philips 170S, Holland) and medical monitor-3 megapixel monochrome display (Me355i2, Totoku, Tokyo)-with brightness and contrast enhancement. Observer responses were evaluated using ROC analysis and other measurements for diagnostic accuracy. Storage phosphor images with medical monitor demonstrated higher mean A (z) values (0.70 +/- 0.08) than digital images with computer monitor and conventional films. Storage phosphor images with medical monitor presented the highest score, 0.97, 0.90, 0.94, for each observer, respectively. Also, true positive observations (0.82) and positive likelihood ratios (2.71) were higher in enhanced storage phosphor images with medical monitor. Caries detection of mechanically created lesions by experienced radiologists is roughly comparable when examining D-speed film images and Digora images on both the computer and medical LCD monitors, and appears to be poorer on E- and F-speed film images.

Alternative erasing times of the DenOptix system plate: performance on the detection of proximal caries

OBJECTIVE

Our aim was to investigate the DenOptix system for detection of proximal caries using alternative erasing times for the photostimulable phosphor plates.

STUDY DESIGN

Human teeth were X-rayed with phosphor plates using different erasing times. Five observers evaluated the images for the presence of caries by scoring the proximal surfaces of each tooth. Mean pixel intensity analyses were also carried out. The erasing times were evaluated using receiver operating characteristic (ROC) curve analysis. Analysis of variance for differences among erasing times and pixel intensity values was performed, followed by linear regression analysis for correlation between these variables.

RESULTS

The mean ROC curve for each erasing time varied from 0.61 to 0.66 (not significant). Analysis of variance did not show any significant effect of the erasing times on the pixel intensity values of the images (P > .05).

CONCLUSION

Erasing times for DenOptix phosphor plates from 20 to 130 s were satisfactory for diagnosis of proximal caries, and their use is therefore feasible in clinical practice.

A comparison of older and newer versions of intraoral digital radiography systems: diagnosing noncavitated proximal carious lesions

BACKGROUND

The authors conducted a study to compare the accuracy of an older and newer version of two intraoral digital systems in terms of radiographic detection of proximal carious lesions.

METHODS

Under in vitro and standardized conditions, the authors obtained radiographs of 160 noncavitated proximal surfaces using the Digora FMX (Soredex, Tuusula, Finland), the Digora Optime, the Schick CDR (Schick Technologies, Long Island City, N.Y.) and the Schick CDR Wireless (Schick Technologies) systems. Eight observers recorded proximal carious lesions on a five-point confidence scale. The presence of caries was validated histologically.

RESULTS

The new digital systems (Digora Optime and Schick CDR Wireless) had significantly higher sensitivities than their predecessors. The authors found no significant differences in specificity among the Digora FMX, Schick CDR and Schick CDR Wireless systems, all of which had a significantly higher specificity than did the Digora Optime system (P < .02). The positive predictive value for the Digora Optime system was affected by its high sensitivity and low specificity, and it was lower than that for the two CDR systems (P < .02).

CONCLUSIONS

Regarding overall accuracy, the difference between the older and newer versions of the photostimulable storage phosphor and complementary metal oxide semiconductor systems was not statistically significant. However, the authors found more false-positive diagnoses made with the Digora Optime system than with the Digora FMX system.

CLINICAL IMPLICATIONS

Though the difference in specificities was statistically significant, the authors question whether the difference between the Digora Optime and the other systems is clinically relevant. Therefore, dentists can purchase any of these systems after considering factors other than those evaluated in this study.

In vitro assessment of cone beam local computed tomography for proximal caries detection

OBJECTIVES

To compare the accuracy of local computed tomography (LCT) and conventional radiography for proximal caries detection and depth assessment.

STUDY DESIGN

An in vitro model was used consisting of 20 extracted posterior teeth with 18 caries lesions. Local computed tomography slices were reconstructed in axial and parasagittal planes from 100 basis projections. Conventional radiographs were also acquired. Eight observers determined the presence and depth of caries lesions. Receiver operating characteristic analysis and weighted kappa statistics were used.

RESULTS

Local computed tomography had a mean A(z) score of 0.82 (SD = 0.07) and conventional radiography of 0.79 (SD = 0.08; analysis of variance: P > .05). Interobserver agreement was moderate. The mean kappa for depth assessment was 0.68 (SD = 0.06) for LCT and 0.47 (SD = 0.08) for conventional radiography (analysis of variance: P < .05). Local computed tomography resulted in substantial and conventional radiography in moderate interobserver agreement.

CONCLUSIONS

There is no difference between LCT and conventional radiography for proximal caries detection. Local computed tomography was more accurate for assessing caries lesion depth.

Accuracy of Proximal Caries Depth Measurements: Comparison between Limited Cone Beam Computed Tomography, Storage Phosphor and Film Radiography

The aim of this study was to compare the accuracy of limited cone beam computed tomography (LCBCT), an image plate system and F-speed film in assessing the depth of proximal carious lesions. Radiographs of a dry mandible with sound and carious teeth were obtained with all three methods. In 41 molar and premolar proximal surfaces, 2 observers independently measured lesion depth on the images from the three modalities. The correlation of measurements was assessed with Pearson's correlation analysis. Results from imaging modalities and histological sectioning (gold standard) were compared using Bland-Altman plots. Overall comparison of the depth measurements from the imaging modalities and the gold standard was done using repeated-measures ANOVA. Pairwise comparisons of systems were done by the Bonferroni t test. The correlation between the measurements of the two observers was 0.977 for film, 0.997 for image plate system and 0.998 for LCBCT. Bland-Altman plots revealed that LCBCT agreed very closely with the gold standard while the agreement between the latter and the image plate--or film--images was moderate. The mean difference and 95% limits of agreement between LCBCT and the gold standard were smaller than those between either image plate or F-speed film and the gold standard. The LCBCT method appears as a promising tool for detection and monitoring of proximal carious lesions.

Lossy JPEG compression: easy to compress, hard to compare

OBJECTIVES

To review the literature on lossy compression in dental radiography and to discuss the importance and suitability of the methodology used for evaluation of image compression.

METHODS

A search of Medline (from 1966 to October 2004) was undertaken with the search expression "(Radiography, dental) and compression". Inclusion criterion was that the reference should be evaluating the effect of lossy image compression on diagnostic accuracy. For all included studies, information in relation to mode of image acquisition, image content, image compression, image display, and method of image evaluation was extracted.

RESULTS

12 out of 32 papers were included in the review. The design of these 12 studies was found to vary considerably. Parameters used to express the degree of information loss (DIL) were either or both compression ratio (CR) and compression level (CL). The highest acceptable CR reported in the studies ranged from 3.6% to 15.4%. Furthermore, different CR values were proposed even for the same diagnostic task, for example, for caries diagnosis CR ranged from 6.2% to 11.1%.

CONCLUSION

Lossy image compression can be used in clinical radiology if it does not conflict with national law. However, the acceptable DIL is difficult to express and standardize. CR is probably not suitable to express DIL, because it is image content dependent. CL is also probably not suitable to express DIL because of the lack of compression software standardization.

Assessment of enamel demineralization using conventional, digital, and digitized radiography

This experimental research aimed at evaluating the accuracy of enamel demineralization detection using conventional, digital, and digitized radiographs, as well as to compare radiographs and logarithmically contrast-enhanced subtraction images. Enamel subsurface demineralization was induced on one of the approximal surfaces of 49 sound third molars. Standardized radiographs of the teeth were taken prior to and after the demineralization phase with three digital systems - CygnusRay MPS®, DenOptix® and DIGORA® - and InSight® film. Three radiologists interpreted the pairs of conventional, digital, and digitized radiographs in two different occasions. Logarithmically contrast-enhanced subtraction images were examined by a fourth radiologist only once. Radiographic diagnosis was validated by cross-sectional microhardness profiling in the test areas of the approximal surfaces. Accuracy was estimated by Receiver Operating Characteristic (ROC) analysis. Chi-square test, at a significance level of 5%, was used to compare the areas under the ROC curves (Az) calculated for the different imaging modalities. Concerning the radiographs, the DenOptix® system (Az = 0.91) and conventional radiographs (Az = 0.90) presented the highest accuracy values compared with the other three radiographic modalities. However, logarithmically contrast-enhanced subtraction images (Az = 0.98) were significantly more accurate than conventional, digital, and digitized radiographs (p = 0.0000). It can be concluded that the DenOptix® system and conventional radiographs provide better performance for diagnosing enamel subsurface demineralization. Logarithmic subtraction significantly improves radiographic detection.

The effects of incremental brightness and contrast adjustments on radiographic data: a quantitative study

OBJECTIVES

To determine the border level of brightness and contrast changes in order to prevent the loss of originality of the quantitative data on digital dental radiographs.

METHODS

After measuring the baseline mean grey values (MGVs) of a fixed region of interest on the alveolar bone and an aluminium step wedge, incremental brightness and contrast adjustments were performed on a digital periapical radiograph. The distribution of the data was analysed to investigate the significance of the changes on radiodensitometric data after incremental increase of brightness and contrast.

RESULTS

The original MGVs were easily retrieved after brightness adjustments; however, the contrast increase led to more complicated density changes. The originality of the data was saved up to 50 units of contrast increase, but further than this limit, significant radiodensitometric changes occurred.

CONCLUSIONS

Contrast adjustments should be performed cautiously when making quantitative analyses on the digital radiographs.

Accuracy of diagnosing occlusal caries using enhanced digital images

OBJECTIVES

To compare the accuracy of detecting occlusal caries lesions on original images vs images digitally enhanced for sharpness, zoom and pseudocolour.

METHODS

Four hundred images of 100 extracted third molars were examined for the presence or absence of occlusal caries by four observers, using a 5-point confidence scale. The observers had no prior knowledge of the distribution of the caries. The definitive diagnosis of caries was based on a histological assessment after sectioning the teeth. The diagnostic accuracy for each imaging mode was expressed by the area of the receiver operating characteristic (ROC) curve. Differences between the areas under the ROC curves were assessed using an analysis of variance.

RESULTS

The original image had a mean ROC curve of 0.75 (95% confidence interval (CI) 0.65-0.85). The ROC curves for sharpness, zoom and pseudocolour were 0.73 (95% CI 0.63-0.83), 0.76 (95% CI 0.61-0.81) and 0.70 (95% CI 0.60-0.80), respectively. These differences were not statistically significant (P=0.96). The Cohen's kappa indicated good agreement among observers.

CONCLUSIONS

In this in vitro study, the three enhanced images used did not affect the detection of occlusal caries.

Influence of soft tissues on mandibular gray scale levels

The purpose of this study was to analyze the gray levels, expressed in pixels, of the mandibular retromolar region, with regard to the influence of muscular and fat soft tissues near this region. Fifteen dry mandibles were X-rayed with the presence of soft tissue simulators. The radiographs were digitized and evaluated by Digora software. A one cm thick layer of wax was used as a simulator of the muscular soft tissue. Animal fat samples of different thicknesses - 0.5, 1.0, 1.5 and 2.0 cm - were used as a simulator of the fat soft tissue. Results showed that the fat soft tissue simulator influenced the gray level values in pixels of the mandibular retromolar region when analyzed in different thicknesses using the Digora digitized image software.

Comparison of complementary metal oxide semiconductor and charge-coupled device intraoral X-ray detectors using subjective image quality

OBJECTIVE

To compare the subjective image quality of the newer generation Schick CDR detector employing complementary metal oxide semiconductor (CMOS) technology with images using the earlier generation charge-coupled device (CCD) Schick CDR detector.

METHODS

All radiographic images were made using the same formalin-fixed adult cadaver maxilla with surrounding natural soft tissues in place. The X-ray generator used was a Villa Sistemi Medicali Diamatic srl AP/Explor X operated at 70 kVp and 8 mA. The source-to-detector distance was set at 38 cm and an optical bench was used to ensure reproducible beam geometry. A range of exposures was applied for both detectors. A panel of nine dentists independently observed and evaluated images made at each exposure. For both detectors, the three images ranked highest were randomized for re-evaluation in panels of six images. Each image was repeated randomly a total of 10 times. Features chosen as observation points were: (1) proximal dental caries; (2) gingival soft tissues; (3) cortical bone; (4) root canal space; (5) root apices; (6) periodontal ligament space; and (7) endodontic instrument tip clarity. Comparisons were made by use of odds ratio analysis applying a 95% confidence level. Interrater and intrarater reliabilities were computed to assess consistency in observer ratings.

RESULTS

The CMOS sensor was rated as outperforming its CCD predecessor for depiction of cortical bone and root apices; the CCD detector was only rated superior for depiction of root canal space. No significant difference was found between the two detectors in perceived depiction of proximal dental caries, gingival soft tissues, periodontal ligament space or endodontic instruments. Combining rating scores from each of the tasks, CMOS and CCD detectors had a similar proportion of image ratings of excellent, acceptable and poor.

CONCLUSIONS

Regarding subjective image quality, the Schick CMOS and CCD detectors were perceived to produce radiographic images of similar overall quality.

Effect of data compression on proximal caries detection: observer performance with DenOptix photostimulable phosphor images

OBJECTIVES

To study the effect of lossy image compression on caries detection. Null hypothesis states no difference in caries detection efficacy among observers using original digital images versus images compressed at various rates of compression.

METHODS

Digital images of 41 extracted posterior teeth were obtained with a storage phosphor DenOptix (Gendex DenOptix Imaging system) system. Images were exported in Tagged Image File Format (TIFF) and compressed with Joint Photographic Experts Group File Interchange Format (JFIF), as provided by the software of the imaging system. The compressions options JFIF100%, JFIF75% and JFIF50% resulted in reducing the image size to 1:2, 1:11 and 1:16, respectively. Eight observers evaluated the presence or absence of caries on a 5-point confidence scale. The actual caries status of each proximal surface was determined by ground section histology. Responses were evaluated by receiver operating characteristic (ROC) analysis. Areas under the curves (Az) were assessed using analysis of variance (ANOVA).

RESULTS

The mean Az scores were 0.85 for original/uncompressed images, and 0.89 for JFIF100%, 0.88 for JFIF75% and 0.88 for JFIF50% images. These differences were not statistically significant (P = 0.26). Differences between observers were also not statistically significant (P = 0.12).

CONCLUSIONS

JFIF compression at the level of 1:16 can be used without significant deterioration in diagnostic accuracy for proximal caries detection.

Comparative evaluation of JPEG and JPEG2000 compression in quantitative digital subtraction radiography

OBJECTIVES

The aim of this in vitro study was to compare the impact of JPEG and the novel JPEG2000 compression standard on quantitative digital subtraction radiography (DSR) and to determine the acceptable JPEG2000 compression ratios for DSR.

METHODS

Nine dry pig mandible sections were radiographed three times ('Baseline', 'No change', and 'Gain') with standardized projection geometry. Bone gain was simulated by adding artificial bone chips (1, 4 and 15 mg). Images were registered, compressed by JPEG and JPEG2000 using compression ratios (CR) of 1 : 7, 1 : 16, 1 : 22, and 1 : 31, and then subtracted. Image distortion was assessed objectively by calculating average pixel error and peak signal to noise ratio. No change areas in compressed and subtracted 'No change-Baseline' images and bone gain volumes in compressed and subtracted 'Gain-Baseline' images were calculated for both compression standards and compared.

RESULTS

JPEG introduced less distortion at low CRs, while JPEG2000 was superior at higher CRs. At CR of 1 : 7, no significant difference between JPEG and JPEG2000 was found. JPEG2000 yielded better results for no change measurements at higher CRs. Volumes of simulated bone gain were overestimated when JPEG and underestimated when JPEG2000 compression was used.

CONCLUSIONS

At CR of 1 : 7 JPEG and JPEG2000 performed similarly, which indicates that CR of 1:7 in JPEG2000 can be used for DSR if images are registered before compression. At higher CRs, JPEG2000 is superior to JPEG but image distortions are too high for reliable quantitative DSR.

Detection of marginal defects of composite restorations with conventional and digital radiographs

The purpose of this study was to determine the validity of detecting approximal imperfections of composite fillings using three intraoral radiographic systems in vitro. Class II composite resin restorations (108) with three radiopacities (264, 306, 443% Al 99.5) of which 27 had marginal openings or overhangs, respectively, were conventionally (Ektaspeed plus) and digitally (Dexis, Digora) radiographed. Images were assessed by 10 observers for the presence of marginal gaps and overhangs, as well as for their need of restorative treatment according to a five-point confidence rating scale. The validity of the observations were expressed as areas under receiver operating characteristic (ROC) curves (Aroc). Repeated measures analysis of variance revealed significant effects of 'radiographic system' and 'diagnostic purpose'. Marginal overhangs (Aroc = 0.90) were significantly easier to diagnose than openings (Aroc = 0.63). Marginal gaps were better detected on conventional and Dexis radiographs than on Digora images. the range of sensitivities and specificities of the treatment decision was 0.53-0.56 and 0.87-0.88, respectively. It was concluded that the validity of detecting marginal defects of composite resin restorations based on radiographs was only slightly affected by the radiographic system being used. The diagnosis of marginal gaps frequently resulted in false-positive and false-negative decisions.

An introduction to digital radiography in dentistry

The aim of this article is to explain the basic principles of digital radiography, and to discuss the intra- and extra-oral imaging systems currently available. There are two main types of digital sensors available. One is based on charge coupled device technology and the other consists of phosphor storage plates. The advantages and disadvantages of each are highlighted with particular attention to orthodontics.

Accuracy of Digora system in detecting artificial peri-implant bone defects

This study was done to compare the diagnostic accuracy in detecting simulated intrabony defects around fixtures using Digora (DIG; Sordex Orion Corporation, Helsinki, Finland) compared with Ektaspeed Plus film (PLS; Eastman Kodak Co., Rochester, NY). Three titanium implant fixtures were placed in molar areas of three cadavers. Bone defects were created in the interproximal alveolar crest. Exposure time was adjusted to a PLS film and reduced to 1/5 only for DIG (1/5 DIG). The results of four observers were assessed. Sensitivity, specificity, accuracy, and under the receiver operator characteristic curve (ROC) area were evaluated. Statistical analyses were performed by using Friedman test and one-way ANOVA test. Mean sensitivity/specificity were 0.60/0.85 (DIG), 0.54/0.81 (1/5 DIG), and 0.64/0.58 (PLS). There were no statistically significant differences in the diagnostic accuracies. Digora had an equivalent performance to radiographic film in detecting intrabony defects adjacent to the implants, notwithstanding the amount of 1/5 of the exposure time.

Performance of RVGui sensor and Kodak Ektaspeed Plus film for proximal caries detection

OBJECTIVE

A high-resolution charge-coupled device was used to compare the diagnostic performances obtained with Trophy's new RVGui sensor and Kodak Ektaspeed Plus film with respect to caries detection.

STUDY DESIGN

Three acquisition modes of the Trophy RVGui sensor were compared with Kodak Ektaspeed Plus film. Images of the proximal surfaces of 40 extracted posterior teeth were evaluated by 6 observers. The presence or absence of caries was scored by means of a 5-point confidence scale. The actual caries status of each surface was determined through ground-section histology. Responses were evaluated by means of receiver operating characteristic analysis. Areas under receiver operating characteristic curves (A(Z)) were assessed through analysis of variance.

RESULTS

The mean A(Z) scores were 0.85 for film, 0.84 for the high-resolution caries mode, and 0.82 for both the low resolution caries mode and the high-resolution periodontal mode. These differences were not statistically significant (P =.70). The differences among observers also were not statistically significant (P =.23).

CONCLUSION

The performance of the RVGui sensor in high- and low-resolution modes for proximal caries detection is comparable to that of Ektaspeed Plus film.

Digital imaging modalities for dental practice

The introduction of the computed tomograph in the 1970s revolutionized medical diagnosis by initiating the transition from analogue to digital imaging. During this period, more specialized equipment for image processing was developed, such as cathode-ray tubes for image display, special sensors for image acquisition, and storage devices for image archiving. Digital imaging systems designed exclusively for use in dentistry were developed in the latter half of the 1980s. Some are now being clinically applied under conditions of close scrutiny to determine diagnostic accuracy, image quality, and radiation exposure to patients. This article reviews the enabling technologies of digital systems used in dentistry, and focuses upon intraoral digital imaging systems, concepts for digital image acquisition, and variations in radiation dose and their effects on diagnostic accuracy of caries detection.

Joint Photographic Experts Group compression of intraoral radiographs for image transmission on the World Wide Web

OBJECTIVE

The purpose of this study was to evaluate the subjective quality of Joint Photographic Experts Group (JPEG) compressed images of intraoral radiographs with file sizes of 30 kilobytes or less, which can be transmitted quickly on the World Wide Web.

STUDY DESIGN

Conventional intraoral radiographs were digitized at sampling rates of 100, 200, 300, 400, and 600 dots per inch through use of a flatbed scanner and saved in JPEG format in 11 compression degrees. Fifty-five combinations of sampling rate and compression degree were evaluated by means of a visual analog scale. Sampling rate and compression degree combinations whose quality was inferior to that of an average image were excluded. The quality of the remaining combinations was subsequently evaluated through assessment of 8 anatomical features in each image.

RESULTS

Forty of the 55 combinations provided a file size less than 30 kilobytes. Thirty combinations obtained VAS scores of 0 or higher on the standardized VAS. As a result, 16 combinations of sampling and compression conditions were selected for the second part of the study. Only one combination of sampling rate and compression degree was found to provide sufficient image quality for all 8 anatomical features.

CONCLUSIONS

Under the file size limit of the study design, the full-sized compressed image of an intraoral radiograph did not always provide sufficient quality. This problem will be reduced by improvements in telecommunications infrastructure, which will permit faster transfer of files of larger size.

The role of direct intraoral sensors in the provision of endodontic services

The recent commercial success of intraoral sensor systems largely reflects the quest to improve the quality assurances for endodontic services. The many advantages of these systems include reduced radiation exposures, real-time images, resolution improvements after initial image capture and archival benefits, although their diagnostic benefits over conventional film based radiographs remain a concern. For instance, the images from either charge-coupled device or storage phosphor sensors have yet to exceed the potential 50 microns spatial and 12-bit contrast resolutions obtained from the 1.75-6.40 microns silver grain emulsions of conventional films or the potential improvements derived from smaller (1 micron) grains. Intraoral sensor systems alone are therefore unlikely to improve the quality assurances for endodontic services.

Effect of noise on the compressibility and diagnostic accuracy for caries detection of digital bitewing radiographs

OBJECTIVES

To determine the effect of noise on the compressibility and the diagnostic accuracy for caries detection of digital bitewing radiographs.

METHODS

Bitewing radiographs of patients were obtained with a storage phosphor (Digora, Soredex, Helsinki, Finland) and compressed at different JPEG compression levels (2, 27, 53 and 128). A just noticeable difference study was performed to select a compression level to study the added noise effect. Gaussian noise was added at low, medium, and high levels to both the original and compressed images. Seven observers examined the selected approximal surfaces to identify the caries depth. ROC analysis was performed together with ANOVA at P = 0.05.

RESULTS

The compressibility of the images decreased as the noise level increased. ROC analysis revealed no significant difference between the original and compressed images within the same noise level (P > 0.06). With added noise compressed/decompressed images had a higher Az than the corresponding original images.

CONCLUSIONS

JPEG compression at level 27 can be used without a significant deterioration in diagnostic accuracy. Compression at this level seemed to reduce the effect of noise to some extent.

Film and digital radiography for detection of simulated root resorption cavities

OBJECTIVES

The purpose of this study was to evaluate observers' ability to detect simulated root resorption cavities in conventional radiographs and digital radiographs from a charge-coupled device system and a storage phosphor system and to determine whether the detectability was influenced by resorption size and exposure.

STUDY DESIGN

In teeth from dry mandibular jaw specimens, resorptive defects 1.2 mm in diameter and two different depths (0.6 and 0.9 mm) were prepared in the buccal root surface. Each tooth was radiographed at a number of different exposure settings. Observers were asked to rate their confidence that a resorption was or was not present using a five-graded confidence scale. Receiver operating characteristic analysis was used to evaluate the results.

RESULTS AND CONCLUSION

Given optimal exposures, all systems reached what might be considered clinically acceptable Az values (> 0.75). The storage phosphor system reached this value at considerably lower exposures than those required for both the film and charge-coupled device systems. There was a tendency to better detect the deeper lesions and to identify them at lower exposures.

A comparison of Kodak Ektaspeed Plus film and the Siemens Sidexis digital imaging system for caries detection using receiver operating characteristic analysis

OBJECTIVE

To evaluate the accuracy of proximal caries detection comparing enhanced and unenhanced Siemens Sidexis CCD-based digital images with Ektaspeed Plus films utilizing receiver operating characteristic analysis.

STUDY DESIGN

Sixty extracted teeth (24 posterior and 36 anterior) were imaged under identical standardized geometric and exposure conditions. Six observers, using a 5-point confidence scale, rated 120 proximal surfaces for the presence or absence of carious lesions by means of three image modalities: (1) observer enhanced and (2) unenhanced Sidexis displays, and (3) Ektaspeed Plus films. The ground truth was determined by microscopic analysis of ground sections. Receiver operating characteristic curves were generated with calculated areas (AZ) analyzed with analysis of variance for effect of reader, reading, and modality.

RESULTS

Analysis of variance demonstrated significant differences among readers, readings and modalities (mean square values of 0.012, 0.005, 0.004, F ratios of 13.604, 5.329, 5.100; p = values of 0.001, 0.043, and 0.030, respectively). Post-hoc paired comparisons of modalities using Tukey's statistic demonstrated that only film and enhanced Sidexis images were different from each other (p = 0.024). AZ scores were 0.7650, 0.7499, and 0.8008 respectively, for unenhanced Sidexis, enhanced Sidexis, and Ektaspeed Plus film.

CONCLUSION

Unenhanced digital Sidexis images were equivalent to film for the detection of proximal caries in this in vitro study. Observer enhanced Sidexis images exhibited a statistically significant lower diagnostic accuracy than the unenhanced digital and film images.

Digital radiography and caries diagnosis

Direct digital acquisition of intra-oral radiographs has been possible only in the last decade. Several studies have shown that, theoretically, there are a number of advantages of direct digital radiography compared with conventional film. Laboratory as well as controlled clinical studies are needed to determine whether new digital imaging systems alter diagnosis, treatment and prognosis compared with conventional methods. Most studies so far have evaluated their diagnostic performance only in laboratory settings. This review concentrates on what evidence we have for the diagnostic efficacy of digital systems for caries detection. Digital systems are compared with film and those studies which have evaluated the effects on diagnostic accuracy of contrast and edge enhancement, image size, variations in radiation dose and image compression are reviewed together with the use of automated image analysis for caries diagnosis. Digital intra-oral radiographic systems seem to be as accurate as the currently available dental films for the detection of caries. Sensitivities are relatively high (0.6-0.8) for detection of occlusal lesions into dentine with false positive fractions of 5-10%. A radiolucency in dentine is recognised as a good predictor for demineralisation. Radiography is of no value for the detection of initial (enamel) occlusal lesions. For detection of approximal dentinal lesions, sensitivities, specificities as well as the predictive values are fair, but are very poor for lesions known to be confined to enamel. Very little documented information exists, however, on the utilization of digital systems in the clinic. It is not known whether dose is actually reduced with the storage phosphor system, or whether collimator size is adjusted to fit sensor size in the CCD-based systems. There is no evidence that the number of retakes have been reduced. It is not known how many images are needed with the various CCD systems when compared with a conventional bitewing, nor how stable these systems are in the daily clinical use or whether proper cross-infection control can be maintained in relation to scanning the storage phosphor plates and the sensors and the cable. There is only sparse evidence that the enhancement facilities are used when interpreting images, and none that this has changed working practices or treatment decisions. The economic consequences for the patient, dentist and society require examination.

Observer agreement in the detection of proximal caries with direct digital intraoral radiography

OBJECTIVE

The aim of this study was to compare several values for consistency obtained by charged-coupled-device-based direct digital intraoral radiography with those obtained by conventional film-based radiography to evaluate observer agreement in determining the depth of proximal caries.

STUDY DESIGN

A total of 93 proximal surfaces on radiologic images that were obtained by both the conventional film-based bite-wing technique and by direct digital intraoral radiography were evaluated by six observers. One of these observers also evaluated the same images six months after the initial evaluation. The kappa value, consistency ratio, agreement ratio, and Kendall's correlation coefficient were calculated for interobserver and intraobserver agreement.

RESULTS

The overall kappa values for interobserver agreement were 0.439 and 0.424 in the direct digital system and the film-based radiography, respectively. The depth-related change of the values showed similar patterns in the two modalities for both interobserver and intraobserver agreement.

CONCLUSION

The digital intraoral system resulted in no deterioration in observer agreement, and it presents no problems for clinical use with respect to the reliability of diagnosis.