Digital enhancement of radiographs: can it improve caries diagnosis?

Impact of enhancement filters of a CMOS system on halo artifact expression at the bone-to-implant interface

OBJECTIVE

To assess the impact of enhancement filters on the formation of halo artifacts in radiographs of dental implants obtained with a complementary metal oxide semiconductor (CMOS) system.

METHODS

Digital radiographs of dental implants placed in dry human mandibles were processed with the Noise Reduction smoothing filter, as well as the Sharpen 1, Sharpen 4, and Sharpen UM high-pass filters available in the CLINIVIEW™ software (Instrumentarium Dental, Tuusula, Finland). Subjective analysis involved evaluating the left, right, and apical surfaces of each implant for the presence of much, few, or no halo. The objective analysis involved measurement of the halo area using the Trainable Weka Segmentation plugin (ImageJ, National Institutes of Health, Bethesda, MD, USA). Data were analyzed using Friedman's test (subjective analysis) and ANOVA (objective analysis) (α = 5%).

RESULTS

In the subjective evaluation, the Sharpen 4 filter produced more radiographs with much halo present, and in the objective evaluation, a bigger halo area when compared to the original images and the Noise Reduction filter for all surfaces (p < 0.05).

CONCLUSIONS

When evaluating dental implants, priority should be given to original images and those enhanced with smoothing filters since they exhibit fewer halo artifacts.

CLINICAL RELEVANCE

Post-processing tools, such as enhancement filters, may improve the image quality and assist some diagnostic tasks. However, little is known regarding the impact of enhancement filters in halo formation on CMOS systems, which have been increasingly used in dental offices.

A comparison of perceived diagnostic image quality in direct digital panoramic images between standard and advanced external GOP image processing

Objective: The objective of the present study was to study the effect of adaptive image processing (GOP processing) on the visibility of anatomical structures in direct digital panoramic images. Material and methods: The study comprised panoramic images of 50 consecutive adult individuals aged 18-60 years. Nine dentists working with dental radiology compared the structural image quality of all standard-processed and GOP-processed panoramic images for six anatomical structures, using a six-point scale for visual grading characteristics analysis. Results: For all anatomic structures a statistically significant difference in favour of the GOP was found. Conclusions: The present study shows that it is possible to improve perceived diagnostic image quality of direct digital panoramic radiography using GOP technology compared to the manufacturers' standard processing. Manufacturers' image-processing programs can be further developed, as there is a possibility of improving the perceived diagnostic content of an image with external processing.

Subjective analysis of the application of enhancement filters on magnetic resonance imaging of the temporomandibular joint

OBJECTIVE

The aim of this study was to investigate the effect of enhancement filters on magnetic resonance imaging (MRI) of the temporomandibular joint (TMJ).

STUDY DESIGN

In total, 66 MRI scans of the TMJ were analyzed without filtration and with the application of 2 filters: Sharpen 1 and Sharpen 2 (OnDemand software). Two dentomaxillofacial radiologists examined the original and filtered images individually. Intra- and interobserver concordance was measured by using generalized estimating equations. The observers evaluated the subjective image quality and the visibility of 3 components of the TMJ: disk, condyle, and articular eminence. The images were ranked on a 4-point scale, from poor to excellent. The image quality of all filtered images was compared by using the χ² test and Bonferroni correction for multiple comparisons.

RESULTS

Intra- and interobserver concordance was good. The images filtered with Sharpen 1 and Sharpen 2 provided better definition of the structures compared with nonfiltered images, providing the highest scores for subjective image quality for all structures (P < .0001).

CONCLUSIONS

The use of enhancement filters led to improved subjective quality and may improve the diagnostic efficacy of MRI in TMJ evaluation.

Influence of VistaScan image enhancement filters on diagnosis of simulated periapical lesions on intraoral radiographs

OBJECTIVE:

To evaluate whether image enhancement filters of VistaScan system improve the diagnostic accuracy of simulated periapical lesions.

METHODS:

10 sockets were prepared on bovine ribs to fit a bovine tooth. Bone defects were created and successively enlarged providing four groups (n = 10): Group 0, absence of lesions; Group 1, periapical lesions with 1.6  mm in diameter; Group 2, with 1.8  mm in diameter; and Group 3, with 2.1  mm in diameter. Periapical radiographs were taken using a photostimulable storage phosphor plate and DBSWIN software. VistaScan filters were applied and the images were allocated into seven groups: Nonfiltered, Fine, Caries 1, Caries 2, Endodontic, Periodontal and Noise Reduction. All the 280 images were assessed about the presence or absence of periapical lesions. Pixel intensities standard deviation were compared between nonfiltered and filtered images. Two-Way Analysis of Variance and the post hoc Tukey's test were used to compare area under the ROC curve, sensitivity and specificity.

RESULTS:

VistaScan filters showed no significant difference for area under receiver operating characteristic curve (p = 0.124), sensitivity (p = 0.835) and specificity (p = 0.832). Area under receiver operating characteristic curve (p = 0.000) and sensitivity (p = 0.000) in 2.1  mm lesions size were significantly higher than in 1.6  mm and 1.8  mm lesions size. Pixel intensities standard deviation was significantly changed in the filtered images compared to nonfiltered ones (p < 0.01), except for Fine in the bone region (p > 0.05).

CONCLUSION:

VistaScan enhancement filters do not influence the diagnostic accuracy of simulated periapical lesions. On the other hand, larger lesions were more frequently detected. The filters change the pixel intensities reducing or intensifying the differences between similar regions.

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.

Effect of digital noise reduction on the accuracy of endodontic file length determination

PURPOSE

The aim of the present study was to evaluate the measurement accuracy of endodontic file length on periapical digital radiography after application of noise reduction digital enhancement.

MATERIALS AND METHODS

Thirty-five human single-rooted permanent teeth with canals measuring 20-24 mm in length were selected. ISO #08 endodontic files were placed in the root canals of the teeth. The file lengths were measured with a digital caliper as the standard value. Standard periapical digital images were obtained using the Digora digital radiographic system and a dental X-ray unit. In order to produce the enhanced images, the noise reduction option was applied. Two blinded radiologists measured the file lengths on the original and enhanced images. The measurements were compared by repeated measures ANOVA and the Bonferroni test (α=0.05).

RESULTS

Both the original and enhanced digital images provided significantly longer measurements compared with the standard value (P<0.05). There were no significant differences between the measurement accuracy of the original and enhanced images (P>0.05).

CONCLUSION

Noise reduction digital enhancement did not influence the measurement accuracy of the length of the thin endodontic files on the digital periapical radiographs despite the fact that noise reduction could result in the elimination of fine details of the images.

Enhancement cone beam computed tomography filters improve in vitro periimplant dehiscence detection

OBJECTIVE

To investigate whether cone beam computed tomography filters would improve periimplant dehiscence detection.

STUDY DESIGN

A hundred titanium implants were placed in bovine ribs in which defects simulating periimplant dehiscence had previously been created. After images acquisition, three oral radiologists assessed them with and without the following filters: Angio Sharpen high 5 × 5, Shadow, Sharpen 3 × 3, Sharpen Mild, and Smooth. The McNemar test verified the disagreement between all images versus the reference standard and original images versus images with filters; P < .05 was considered statistically significant.

RESULTS

Dehiscence detection using the original images and the Shadow filter disagreed from the reference standard (P < .05), as well as when using the filters instead of the original images (P < .05).

CONCLUSION

All the filters tested, with the exception of the Shadow, improved periimplant dehiscence detection. The Sharpen 3 × 3 filter was considered best for this task.

Accuracy of enhancement filters in measuring in vitro peri-implant bone level

OBJECTIVES

To identify the accuracy of enhancement filters of an intraoral phosphor-plate system for measuring the simulated peri-implant bone level.

MATERIALS AND METHODS

A total of 20 titanium implants (Titamax(®) ) were placed into six fragments of bovine ribs and defects simulating bone loss were created. Periapical radiographs were taken with a phosphor-plate system (Vista Scan(®) ) according to the paralleling standard technique, and nine enhancement filters were applied: fine, caries 1, caries 2, perio, endo, noise reduction, invert, emboss, and sculpture. The Friedman test compared the radiographic measurements of the defects to those obtained on the bovine ribs with a digital caliper. Intra- and interobserver agreement was calculated with the intra-class correlation coefficient (ICC).

RESULTS

The ICC values showed excellent intra- and interobserver agreement. The caries1, caries2, endo, and perio filters resulted on measurements statistically different from both the original images and the measurements of the digital caliper (P < 0.05). The other filters did not show statistically significant differences from the original images nor from the measurements of the digital caliper.

CONCLUSION

In addition to the original images, the fine and emboss filters resulted on the most precise measures. The caries1, caries2, endo, and perio filters were the less accurate for measuring the peri-implant bone level.

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 image enhancement improves diagnosis of nondisplaced proximal femur fractures

Today most emergency room radiographs are computerized, making digital image enhancement a natural advancement to improve fracture diagnosis. We compared the diagnosis of nondisplaced proximal femur fractures using four different image enhancement methods using standard DICOM (Digital Imaging and Communications in Medicine) after window-leveling optimization. Twenty-nine orthopaedic residents and specialists reviewed 28 pelvic images consisting of 25 occult proximal femur fractures and three images with no fracture, using four different image filters and the original DICOM image. For intertrochanteric fractures, the Retinex filter outperforms the other filters and the original image with a correct fracture type diagnosis rate of 50.6%. The Retinex filter also performs well for diagnosis of other fracture types. The Retinex filter had an interobserver agreement index of 53.5%, higher than the other filters. Sensitivity of fracture diagnosis increased to 85.2% when the Retinex filter was combined with the standard DICOM image. Correct fracture type diagnosis per minute for the Retinex filter was 1.43, outperforming the other filters. The Retinex filter may become a valuable tool in clinical settings for diagnosing fractures.

LEVEL OF EVIDENCE

Level I, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

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.

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.

Film tomography compared with film and digital bitewing radiography for proximal caries detection

OBJECTIVES

The purpose of this study was to evaluate the efficiency of conventional tomography for proximal caries detection compared with conventional bitewing and digital intraoral radiography.

METHODS

In this study, 48 extracted human posterior permanent teeth were used. Conventional bitewing radiographs, digital intraoral radiographs and conventional tomograms were obtained of the teeth. The presence or absence of caries was scored according to a five-point scale by two oral and maxillofacial radiologists. True caries depth was determined by histological examination. The diagnostic accuracy of each radiographic system was assessed by means of receiver operating characteristic (ROC) curve analysis. The mean of areas under the ROC curve (A(z)) was analysed by pairwise comparison of ROC curve. The interobserver agreement was evaluated using a t-test.

RESULTS

The statistical analysis of A(z) scores has shown no significant difference for three imaging modalities (P>0.05). There was no statistically significant difference between interobserver agreement (P>0.05).

CONCLUSIONS

This study has demonstrated that the diagnostic accuracy of conventional tomograms is comparable to that of conventional bitewing and digital intraoral radiographs for proximal caries detection.

Effect of various digital processing algorithms on the measurement accuracy of endodontic file length

OBJECTIVE

The aim of this study was to compare the accuracy of endodontic file lengths after application of various image enhancement modalities.

STUDY DESIGN

Endodontic files of three different ISO sizes were inserted in 20 single-rooted extracted permanent mandibular premolar teeth and standardized images were obtained. Original digital images were then enhanced using five processing algorithms. Six evaluators measured the length of each file on each image. The measurements from each processing algorithm and each file size were compared using repeated measures ANOVA and Bonferroni tests (P = 0.05). Paired t test was performed to compare the measurements with the true lengths of the files (P = 0.05).

RESULTS

All of the processing algorithms provided significantly shorter measurements than the true length of each file size (P < 0.05). The threshold enhancement modality produced significantly higher mean error values (P < 0.05), while there was no significant difference among the other enhancement modalities (P > 0.05). Decrease in mean error value was observed with increasing file size (P < 0.05).

CONCLUSIONS

Invert, contrast/brightness and edge enhancement algorithms may be recommended for accurate file length measurements when utilizing storage phosphor plates.

Subjective image quality of digitally filtered radiographs acquired by the Dürr Vistascan system compared with conventional radiographs

OBJECTIVES

To compare the different digital filters implemented in the Dürr Vistascan system with conventional film and to analyze the filter specificity to anatomic structures.

STUDY DESIGN

Ten panoramic image pairs and 10 periapical image pairs (1 digital and 1 conventional) were obtained from 20 patients conventionally and digitally. The display quality of different anatomic image structures was rated subjectively on a 5-point scale. The responses were evaluated using ANOVA and Tukey-Kramer post hoc tests. The intraobserver reliability was evaluated by Cohen's kappa statistics.

RESULTS

The display quality of anatomic structures was rated higher by using Caries 1 or 2 filters for periapical and Periodontal 1 or 2 filters for panoramic images, whereas nonfiltered and Noise Reduction-filtered images received the lowest scorings compared to all other digital image modalities (P < or = .0097). The superiority of conventional radiographs to the digital ones was statistically significant (P < or = .0039 and P < or = .0152 respectively).

CONCLUSIONS

Depending on the diagnostic task, digital images of the Vistascan system should be filtered before examination. Perfect conventional radiographs still remain the gold standard for image quality.

Effects of the automatic exposure compensation on the proximal caries diagnosis

OBJECTIVE

To elucidate the effect of automatic exposure compensation (AEC) on the diagnostic accuracy of proximal caries by comparing several digital intraoral imaging systems with a film.

MATERIALS AND METHODS

Twenty-seven extracted teeth served as proximal caries samples. Three digital radiographic systems; the Compuray, the Dixel, and the Sens-A-Ray without scintillator layer, and Kodak Ekta-speed Plus films were used as recording media. Radiographs of the teeth samples were obtained with each recording medium under seven to eight different exposures including the optimum level. Six oral radiologists evaluated the possibility of proximal caries with the five-grade-confidence-scale. On digital radiographs, image manipulations were allowed after the initial assessment. Receiver operating characteristic (ROC) curves were obtained at each exposure in each recording medium. The area under the ROC curve (Az) was used as the representative value of diagnostic accuracy. Diagnostic accuracy (DA) curves were obtained by plotting averaged Az values from all observers as a function of incident exposure in each system.

RESULTS

The effect of exposure variation on the DA was slight in the film while it was significantly larger in the digital systems without AEC. Among digital systems, the effect of exposure variation was smaller in the system with AEC than those without AEC. There was no significant effect on the diagnostic accuracy even if digital image manipulation was employed.

CONCLUSION

AEC minimizes the decrease of DA due to inadequate exposures. Since it compensates for the narrow exposure range in the digital intraoral sensor systems, the system with AEC may be preferable for the clinical diagnostic tasks.

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.

Extraoral imaging for proximal caries detection: Bitewings vs scanogram

OBJECTIVE

The objective of this study was to compare the diagnostic accuracy of 3 extraoral imaging modalities with an intraoral bitewing radiograph for proximal caries detection.

STUDY DESIGN

Three modalities of Cranex TOME scanograms, x-ray film and DenOptix photostimulable phosphor plates with and without digital enhancement, were compared with Insight intraoral radiographs for proximal caries detection. Nine observers evaluated images of the proximal surfaces of 45 extracted posterior teeth. The presence or absence of caries was scored using a 5-point confidence scale. The ground truth was determined from histological sections. Responses were evaluated by repeated measures analysis of variance (ANOVA) for areas under receiver operating characteristic (ROC) curves (A z ).

RESULTS

Repeated measures ANOVA (at alpha = 0.05) demonstrated significant differences among modalities ( P = .041). Paired t tests with Bonferroni correction demonstrated that Insight was superior to only unenhanced digital scanograms ( P = .003). Mean A z scores (+/-SD) were 0.73 (+/-0.08) for Insight, 0.65 (+/-0.06) for screen/film scanogram, 0.64 (+/-0.04) for unenhanced digital scanogram, and 0.66 (+/-0.07) for enhanced digital scanogram.

CONCLUSIONS

The performances of film-based and enhanced digital scanograms were not statistically different from Insight film for proximal caries detection. Unenhanced digital scanograms exhibited a statistically significant lower diagnostic accuracy than Insight film.

Simple bone cyst versus odontogenic keratocyst: differential diagnosis by digitized panoramic radiography

OBJECTIVES

To identify the contour and pixel grey levels of simple bone cyst (SBC) and odontogenic keratocyst (OKC) images that might contribute to differentiating between the two lesions.

METHODS

Panoramic radiographs of 32 SBC and 20 OKC were digitized and analysed by six examiners. The contours of the images were classified as indistinct, distinct without a sclerotic border, and distinct with a sclerotic border. The presence or absence of scalloping and the pixel grey levels of the radiolucent part of the images were also determined.

RESULTS

The sclerotic border was more frequent in the OKC, especially in the posterior segment (P = 0.0301). The presence of scalloping was more frequent in the superior segment of the SBC (P = 0.0295). The pixel values were higher in the OKC than in the SBC images (P = 0.00134).

CONCLUSIONS

Details about the contour and pixel grey levels of OKC and SBC assist in the diagnosis of these lesions.

Comparison of standard and task-specific enhancement of Digora storage phosphor images for approximal caries diagnosis

OBJECTIVES

To compare approximal caries detection on Digora storage phosphor images pre-enhanced with the automatic "caries-specific Oslo enhancement procedure" ("Oslo-enhanced" method) and storage phosphor images individually enhanced by observers particularly experienced in digital imaging using standard brightness and contrast functions of the Digora system ("Digora-enhanced" method).

METHODS

Seven staff members from four oral radiology departments rated 240 approximal surfaces for caries with regard to lesion depth in the inner and outer half of the enamel and dentine, using a 5-point confidence scale. The observations were validated histologically. A receiver operating characteristic (ROC) analysis and an analysis of variance with three dependent variables (observer confidence, observer signed error and observer absolute error) were performed.

RESULTS

The most evident difference between the methods as elucidated by the ROC analysis was the highly significant smaller interobserver and intraobserver variance with the Oslo-enhanced method for all but one observer. The methods were not different with regard to average diagnostic accuracy (A(z) values) as tested with paired t-tests, and there was no correlation between A(z) across methods. The method and lesion main effects, as well as the lesion by method interaction effect, were multivariately significant (P<0.001) in favour of the Oslo-enhanced method. On a univariate level, the method main effect was not significant for the absolute observer error (P=0.330). All other univariate effects were significant (P<0.001).

CONCLUSIONS

The accuracy of approximal caries detection with Digora storage phosphor images pre-enhanced and images individually enhanced was similar, but interobserver and intraobserver variability improved with the Oslo-enhanced method. Since image manipulation is not performed with the Oslo-enhanced method, the increased speed of the diagnostic procedure combined with the improved observer variability would probably be even more pronounced for the general dental practitioner.

Reliability of assessing interproximal bone loss by digital radiography: intrabony defects

AIM

The aim of the present study was to assess the reproducibility and validity of linear measurements of interproximal bone loss in intrabony defects on digitized radiographic images after application of different filters and magnifications.

METHODS

Immediately before surgery 50 radiographs of 50 periodontally diseased teeth exhibiting interproximal intrabony defects were obtained by a standardized technique in 50 patients. Intrasurgically the distances from the cementoenamel-junction (CEJ) to the alveolar crest (AC) and from the CEJ to the deepest extension of the bony defect (BD) were assessed. All radiographs were digitized by a flatbed scanner (resolution: 600x1200 dpi). Using the FRIACOM-soft ware, the linear distances CEJ to AC and CEJ to BD were measured at 50 intrabony defects on digitized but unchanged radiographic images and also after use of 2 different basic image processing modes (filters: enhancement of grey level differences, spreading of grey values) with 7-fold and 14-fold magnification by 2 different examiners.

RESULTS

Repeated measures MANOVA revealed reproducibility of the measurement of the distance CEJ to AC to be significantly influenced by examiner (p=0.027) and filter in combination with the height of 2 wall component of the intrabony defect (p=0.066). For the distance CEJ to BD filters had significant influence on reproducibility in correlation with vertical angulation difference (p=0.001). On the average in this study radiographic measurements tended to overestimate the amount of bone loss as assessed by intrasurgical measurements (CEJ-AC: 0.74-1.91 mm; CEJ-DB: -0.04-0.77 mm). Validity of measurement of the distance CEJ-AC was shown to be significantly influenced by the depth of the intrabony defect (p<0.003). Validity of the distance CEJ-BD was significantly influenced by intrasurgically assessed bone loss (p=0.029), horizontal angulation (p=0.066). Filters influenced the validity only in combination with examiner (p<0.001).

CONCLUSIONS

In this study, the chosen digital manipulations (filters: spreading, structure) of radiographic images failed to result in statistically significantly more reproducible or valid measurements of interproximal bone loss within intrabony defects when compared to the digitized but unchanged images. All radiographic assessments on the digitized images except for use of enhancement of grey level differences (structure) came close to the intrasurgical gold standard.

Conventional and predicted perceptibility curves for contrast-enhanced direct digital intraoral radiographs

OBJECTIVES

To construct Perceptibility Curves (PCs) for contrast-enhanced digital intraoral radiographs.

METHODS

Radiographs of a test object having holes of increasing depths were exposed using three digital systems, the CDR (Schick Technologies, Long Island, NY, USA), the Dixel (J Morita MFG, Kyoto, Japan) and the Sens-A-Ray (Regam Medical Systems, Sundsvall, Sweden). The radiographs were contrast-enhanced and PCs constructed in the conventional way using 10 observers. Predicted PCs were calculated and compared with observer data.

RESULTS

The PCs showed that contrast enhancement is effective for the perception of small contrast details, especially in the low exposure range. Predicted PCs demonstrated excellent agreement with observer data.

CONCLUSIONS

Contrast enhancement should be advantageous in digital radiography. The effects of contrast enhancement on PCs may be predicted without previous knowledge of observer performance.

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.

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.

Dental materials: 1996 literature review. Part 2

This critical review of the published literature on dental materials for the year 1996 has been compiled by the Dental Materials Panel of the UK. It continues the series of annual reviews started in 1973 and published in the Journal of Dentistry. Emphasis has been placed upon publications which report upon the materials science or clinical performance of the materials. The review has been divided by accepted materials classifications (fissure sealants, glass polyalkenoate cements, dentine bonding, dental amalgam, endodontic materials, casting alloys, resin-bonded bridges and ceramo-metallic restorations, ceramics, denture base resins and soft lining materials, impression materials, implants materials, orthodontic materials, biomechanics and image processing, resin composites and casting investment materials and waxes). Three hundred and thirteen articles have been reviewed.

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.