Perceptibility curve test for digital radiographs before and after application of various image processing algorithms.

OBJECTIVES: The aim of the present study was to compare digital radiographs before and after the application of various digital image enhancement methods by means of a perceptibility curve (PC) test. METHODS: Radiographs of an aluminium test object containing holes with sizes ranging from 0.5 mm to 1.5 mm were exposed at nine time settings, ranging from 0.05 s to 3.2 s using Digora (Soredex, Helsinki, Finland) storage phosphor system. Original digital images were then enhanced and displayed in colour-coded, contrast- and brightness-enhanced, histogram-equalized and negative modes. Thus, five series of images were created. Eight observers independently evaluated all of the images in the same random order and under the same viewing conditions. The object detail with the lowest perceptible contrast was recorded for each observer and each image type. Modified PCs were plotted according to the mean observer data. Repeated-measures ANOVA was used to compare the PCs and the perceptible number of details in original and enhanced images for each exposure (P=0.05). The Bonferroni/Dunn test was used to identify statistical differences among the groups. RESULTS: Histogram equalization showed the maximum number of perceptible details in both the lowest optimal exposure time and the widest exposure range (P<0.05). Significant differences were present in low and middle exposure ranges of images enhanced with various modalities (P<0.05), while no difference was obtained among the number of details for different enhancements in the high exposure range (P>0.05). CONCLUSION: Histogram-equalization enhancement of Digora images demonstrated subjectively superior image quality, followed by contrast and brightness enhancement.

Degradation of storage phosphor images due to scanning delay.

OBJECTIVE: To evaluate the degradation of storage phosphor images relative to scanning delay. METHODS: A series of exposures of an aluminium step-wedge with five 2 mm incremental steps were made using blue Digora storage phosphor plates (SPPs). After the first exposure the plates were immediately scanned. After the second the plates were scanned after a half hour delay, after the third after a 1 h delay and so on until a final delay of 8 h. Mean grey values (MGVs) of each step of the wedge and its background were compared using repeated measures analysis of variance (ANOVA). Difference between group means was assessed using Bonferroni/Dunn multiple comparison test (P<0.05). RESULTS: MGVs increased with the increase in scan delay. Repeated measures ANOVA revealed that MGVs of the background and each step of the wedge were significantly different from each other for all scan delays (P<0.0001). Bonferroni/Dunn test showed that MGVs from plates scanned half an hour after exposure were not significantly different from those scanned immediately (P>0.05). Longer delays gave rise to significant differences in MGVs (P<0.05). CONCLUSION: Digora SPPs show statistically significant degradation of grey level values and contrast in plates scanned half an hour or longer after exposure.

An ex vivo comparison of conventional and digital radiography for perceived image quality of root fillings.

AIM: To compare the subjective image clarity of two different speed films and the Digora phosphor plate images with respect to the length and homogeneity of root canal fillings. METHODOLOGY: Root canal treatment was performed on 20 extracted permanent mandibular first molar teeth. Standardized images of each tooth positioned in a dried mandible were obtained with E- and F-speed films and Digora storage phosphor plates (SPP) at 0 degrees and 30 degrees horizontal angulations using the optimal exposure time recommended for each system. Five endodontists and five radiologists rated the image clarity of E- and F-speed radiographs as well as the original and enhanced Digora images. The data were compared using the Wilcoxon signed rank test (P < 0.01). Inter-observer agreement was determined by Cohen's kappa. RESULTS: Enhanced digital images were rated as superior followed by E- and F-speed films and then the original digital images for the evaluation of both homogeneity and length (P < 0.01) of root canal fillings. Agreement among endodontists and radiologists measurements was high in all of the imaging methods (kappa = 0.87). CONCLUSION: Perceived image quality of the enhanced Digora images was superior to the original Digora and conventional film images for the evaluation of root fillings. However, E-speed film provided a significantly better image clarity in comparison with F-speed and original Digora images.

Fraudulent management of digital endodontic images.

AIM: To present examples of radiographic image reconstructions in endodontic treatment, to discuss the potential problems arising from the use of image processing software and to mention some current methods to prevent such counterfeit utilization of digital endodontic radiographs. SUMMARY: Conventional Ultra-Speed periapical films of root canal treatment were digitized with flatbed scanner (Umax Powerlook II, Umax Technologies, Inc., Taiwan). Digital images were altered with PHOTOSHOP 6.0 software (Adobe Corporation, San Jose, CA, USA). Carious lesions, periapical pathoses, fake root canals and artificial fillings were created, and inadequate treatment was corrected by application of various image manipulation functions of the software. KEY LEARNING POINTS: Digital endodontic images can be altered with image processing software. The use of digital radiographic data inevitably raises concerns about security, reliability and the potential for fraud.

Periodontal and alveolar bone abnormalities associated with pachydermoperiostosis.

Pachydermoperiostosis (PDP) is an unusual syndrome manifested clinically by finger clubbing, extremity enlargement, hypertrophic skin changes, and periosteal bone formation. A rare case of pachydermoperiostosis (primary hypertrophic osteoarthropathy) with oral manifestations in a 47-year-old man is presented. The possible correlation between physiological mechanisms of this disease and their influence on oral periodontal tissues and alveolar bone is discussed.

The effects of different image file formats and image-analysis software programs on dental radiometric digital evaluations.

OBJECTIVES: To determine if variations in radiodensity data are introduced by lossy Joint Photographic Experts Group (JPEG) compression and/or the use of three software programs. METHODS: An occlusal film with an aluminium step wedge was exposed, processed and digitized under standard conditions. Before the image was saved, the coordinates and the gray-scale value for each pixel in a 20 x 20 pixel area near the middle of the thickest step were recorded. These pixel coordinates and gray-scale values served as Truth 1. In addition, a digital simulated-radiographic image with assigned gray-scale values for each pixel was created and served as Truth 2. The digital data for the scanned radiograph and the simulated radiograph were saved as Tagged Image File Format (TIFF) and lossy JPEG files. Each file was opened with three software programs and the gray-scale values of homologous pixels were recorded. For these pixels in each image type, the mean gray-scale values and standard deviations were calculated. The pixel gray-scale values for each homologous pixel were also individually compared. RESULTS: When the TIFF images were opened with the three software programs, one program resulted in gray-scale values that were not concordant with truth. All JPEG images resulted in gray-scale values that were not concordant with truth. CONCLUSIONS: One software program added a column of 0s to data files. Lossy JPEG compression introduced potentially deleterious variations to radiodensity data, and at least two of the software programs performed JPEG image decompression differently.

Quantification of the lamina dura and dentin density in children.

This study used 150 periapical radiographs of primary mandibular molars along with an aluminum stepwedge consisting of 5 steps from 2 to 10mm which were exposed and developed under standard conditions. A Mustek (Taiwan, R.O.C.) flatbed scanner with transparency adapter was used to digitize the radiographs. A 600 dpi, 10 bit gray level scanning transparency scanning mode were used. The thickness of the lamina dura was measured with the electronic ruler whereas density of dentin was calculated using the density function of a software program (Image Tool 2.0). Dentin density of the bifuraction area was calculated as 7.42 +/- 37 mm=A1 in primary second molars and 11.02 +/- 1.37mm = A1 for permanent first molar teeth. Differences in the thickness of the lamina dura in primary posterior teeth ranged from 0.23 +/- 0.01mm to 0.42 +/- 0.01mm.

The effect of ethylenediamine-tetraacetic acid on Candida albicans.

OBJECTIVES: The aim of this study was to evaluate the antifungal effect of ethylenediamine-tetraacetic acid (EDTA) on Candida albicans, comparing it with that of various disinfectants and common antifungal agents. STUDY DESIGN: Two clinical oral isolates and 1 standard strain of C albicans were included in this study. Main contents of the test solutions were sodium hypochlorite, EDTA, chlorhexidine, hexetidine, benzalkonium chloride, povidone-iodine, nystatin, and ketoconazole. The agar diffusion method was used to determine the antifungal effects of the solutions. Zones of inhibition were recorded and the results were analyzed statistically by using a 2-way analysis of variance. RESULTS: EDTA demonstrated the highest antifungal activity in comparison with routine antifungal drugs and all other solutions (P <.0001). Oral cavity isolate was more resistant to the test solutions (P <.0001). CONCLUSION: The selection of irrigating and disinfecting solution in root canals of patients with a particularly high incidence of oral candidiasis gains extreme importance. EDTA may be strongly recommended during endodontic therapy of these patients.

Evaluation of bone height and bone density by computed tomography and panoramic radiography for implant recipient sites.

The objective was to compare the bone height and bone density measurements of implant recipient sites by panoramic radiography and computed tomography. Thirty-seven sites of 21 patients were evaluated using both panoramic radiography and computed tomography. The bone height was measured as the vertical distance from the alveolar crest to the closest anatomical landmark. Density was compared by means of densitometric measurements. Data was evaluated using paired t-test and Pearson's correlation coefficient analysis. Although bone heights measured with the two imaging modalities differed significantly (p < 0.05), there was a significant correlation between bone density measurements (r = 0.93, p = 0.0). Measurements of bone height as well as bone density was found to be comparable using either radiographic method.

Comparison of two methods for radiometric evaluation of resin-based restorative materials.

OBJECTIVES: To compare radiographic densitometry with indirect digital image analysis for evaluating the radiopacity of nine different resin-based restorative materials. METHODS: Discs of amalgam and nine different resin-based restorative material, 10 mm in diameter and 2 mm thick, were radiographed together with 2 mm thick discs of intact and carious human teeth and an aluminium stepwedge. Density was evaluated by digital transmission densitometry and with the histogram function of an image analysis programme (Image Tool 1.27, University of Texas Health Sciences Center, Texas, USA) following the digitization of the radiographs with a drum scanner. RESULTS: The two methods produced essentially similar results. With both methods, Dyract (Dentsply De Trey, Konstanz, Germany) had the highest radiodensity and Estilux Hybrid (Kulzer, Werheim, Germany) the lowest. CONCLUSION: Digital image analysis is a suitable alternative to transmission densitometry for evaluation of the radiopacity of restorative materials.

Densitometric evaluation of four radiographic processing solutions.

OBJECTIVE: To determine the performance of different processing solutions using an automatic processor for dental radiography. STUDY DESIGN: One brand of dental X-ray film (Minimax, Chicago, IL, USA) was developed in an automatic processor using four different brands of processing solution: Megasan (MGS, Megasan, Ankara, Turkey), (HAC, Ankara, Turkey), Fuji (Fuji Medical, Hacettepe Cedex, France) and RP X-Omat (Eastman Kodak, Rochester, NY, USA) at a range of temperatures. Performance was evaluated with respect to base plug fog density, relative speed and contrast. RESULTS: All solutions produced acceptable base plus fog values. MGS produced significantly greater densities (P < 0.05) than the other three solutions. Contrast obtained with Kodak and Fuji solutions was less than with MGS and HAC. Developing temperature recommended by the manufacturer of the processor were found to be higher than that needed to achieve a clinically acceptable film. CONCLUSIONS: Depending on the processor and processing solutions used, exposure time and processing temperature can be modified while maintaining image quality. The cheapest processing solution (MGS) gave the same results as the more expensive.