The effect of delayed scanning of storage phosphor plates on occlusal caries detection.

OBJECTIVE: The aim of this study was to determine (1) the effect of various scan delays on pixel intensity measurements and (2) the diagnostic accuracy of occlusal caries detection. METHODS: 72 non-cavitated extracted human permanent molar teeth with sound and carious occlusal surfaces were radiographed using the DIGORA® storage phosphor plates (SPPs) (Soredex Corporation, Helsinki, Finland). Plates were scanned immediately and 10 min, 30 min, 60 min and 120 min after exposure. Three different plates were used for each scan delay. An aluminium (Al) wedge was used to evaluate the change in mean grey values (MGVs) for scan delays. Diagnostic accuracy for occlusal caries detection was performed by scoring all the digital images. The true presence of caries was determined by stereomicroscopy. Comparison of MGVs of the Al wedge for immediate and delayed scans was made using repeated measures analysis of variance (ANOVA) and Tukey-Kramer tests. The accuracy was expressed as the area under the receiver operating characteristics curves (A(z)). A(z)s were compared using two-way ANOVA and t-tests. Kappa was used to measure inter and intraobserver agreement. RESULTS: The mean A(z)s of immediately scanned plates were higher than the A(z)s of plates scanned with four different delays (p < 0.05). The A(z) of immediately scanned images was significantly higher than the A(z)s of images with 60 min and 120 min scan delays (p < 0.05) but not for 10 min and 30 min delays (p > 0.05). MGVs of immediately scanned plates were significantly higher than the plates scanned with four different delays (p < 0.05). Agreement decreased with increasing scan delays. CONCLUSION: Scanning of DIGORA SPPs should not be delayed beyond 30 min for accurate occlusal caries diagnosis.

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

OBJECTIVE: The aim of this study was to determine the relationship between the amount of calcium loss, lesion depth, and the accuracy of storage phosphor plate (SPP) and film radiographs for the detection of artificial proximal demineralization. METHODS: Standard enamel windows of extracted premolars were exposed to a demineralizing solution for 60 h, 80 h, 100 h and 120 h. Solutions were analysed for calcium concentration by atomic absorption spectrometer and the lesion depths were calculated by a specific formula. All teeth were radiographed with SPPs and F-speed films before and after acid application. Images were evaluated by five observers. Stereomicroscopic and scanning electron microscopic (SEM) observations were carried out to visualize enamel surfaces after acid exposure. Receiver operating characteristic analysis was used for diagnostic accuracy (A(z)). A(z)s were compared with factorial analysis of variance and t-tests. The relationship between A(z)s and lesion depths was determined with Pearson's correlation test. RESULTS: Strong positive correlation was found between A(z)s of both radiographic methods and lesion depths. No difference was found between the A(z)s of two radiographic systems for any of the demineralization durations (p > 0.05). Pair-wise comparisons revealed no significant difference in A(z)s of SPPs (p > 0.05), while significant differences were obtained for the A(z)s of films for different demineralization periods (p < 0.05). Stereomicroscopic and SEM observations confirmed demineralizations from superficial to deeper layers of enamel. CONCLUSION: Subsurface enamel demineralization was not accurately detectable with either storage phosphor plates or F-speed films. The amount of calcium loss and the depth of demineralization have a strong relationship with diagnostic accuracy with a significant effect particularly on F-speed films.

Perception of anatomical structures in digitally filtered and conventional panoramic radiographs: a clinical evaluation.

OBJECTIVES: The aims of the study were to compare subjective image quality of clinical images obtained with a storage phosphor plate (SPP)-based digital and conventional film-based panoramic system for the visualization of various anatomical structures and to evaluate the effect of various processing algorithms on image interpretation. METHODS: Panoramic radiographs were taken in 42 patients both with film and with a SPP system. SPP images were treated with shadow, sharpen, negative, greyscale sigma and greyscale exponential filters. Four observers subjectively evaluated films and unfiltered and filtered SPP images for the visibility of anatomical structures with various radiodensities as well as for overall image quality on a three-point rating scale. The statistical methods used were Kruskal-Wallis, odds ratio analysis and Cohen's kappa. RESULTS: No statistically significant difference was found between film and unfiltered digital images except for low-contrast structures (P > 0.05). Film images were preferred for the visibility of low-contrast structures (P < 0.05). Best overall image quality was obtained with sharpened images (P < 0.05) followed by films and unfiltered digital images. Among all filtered images, sharpened ones received the highest ratings for the visibility of all anatomical structures (P < 0.05). The intra- and interobserver agreement ranged between moderate and substantial and between fair and moderate, respectively. CONCLUSIONS: Film and unfiltered SPP-based panoramic images performed equally well in terms of overall quality; however, films were best for the perception of low-contrast structures. The sharpening filter may be recommended for enhancing SPP panoramic images to improve the visual perception of most of the anatomical structures as well as overall quality.

Detectability of chemically induced periapical lesions by limited cone beam computed tomography, intra-oral digital and conventional film radiography.

OBJECTIVE: Our aim was to compare the Accu-I-Tomo (3DX), the Digora Optime image plate system and F-speed film in detecting chemically created apical lesions. METHODS: Lesions were created by applying perchloric acid apical to extracted teeth in jaw specimens for 1, 1.5 or 2 h. After being repositioned, teeth were radiographed with Accu-I-Tomo limited cone beam CT (LCBCT), Digora Optime storage phosphor plates (SPP) and F-speed films. Six observers scored the presence of lesions using a five-grade scale. The accuracy of each observer and modality was assessed through receiver operating characteristic (ROC) analysis and A(z) values were compared using two-way ANOVA. Pairwise comparisons of imaging systems were carried out using the Mann-Whitney U-test. Differences in A(z) values were compared using Friedman and Dunn's tests. Kappa (kappa) was used to measure interobserver agreement. RESULTS: The A(z) values were larger for LCBCT than for SPP and film for all acid durations. For 1 h of acid duration a significant difference was found between LCBCT and film (P = 0.02) and between LCBCT and SPP (P = 0.0043), For 1.5 h a significant difference (P = 0.006) was found between LCBCT and SPP only. For 2 h acid duration, there was no significant difference between LCBCT and film or SPP (P>0.05). Between SPP and film no significant difference was found for any acid duration (P>0.05). kappa ranged between fair and moderate for LCBCT and between slight and fair for SPP and film. CONCLUSION: LCBCT images provided better than or similar detectability as film and SPP images of chemically created periapical lesions.

Imaging of root canal fillings: a comparison of subjective image quality between limited cone-beam CT, storage phosphor and film radiography.

AIM: To compare the subjective quality of limited cone-beam computed tomography (LCBCT), storage phosphor plate (SPP) and F-speed film images for the evaluation of length and homogeneity of root fillings. METHODOLOGY: Root canals of 17 extracted permanent mandibular incisor teeth were filled. With the teeth placed in their jaws, images were obtained with Accu-I-Tomo LCBCT, Digora Optime image plate system and F-speed film using exposure parameters yielding 'clinically' acceptable density and contrast. Three radiologists and three endodontists independently rated the quality of all images in respect to homogeneity and the length of root fillings using a 3-graded scale. Evaluations were undertaken in two sessions. In the first, the coronal LCBCT images were not included. In the second, both coronal and sagittal LCBCT images were rated along with F-speed film and SPP images. RESULTS: were compared using the Friedman test (P < 0.05). Pair-wise comparisons of systems were completed using the Wilxocon signed-ranks test (P < 0.05). Kappa was used to measure interobserver agreement. Results Digora images were rated superior, consecutively followed by F-speed films and LCBCT images, for the evaluation of both homogeneity and length of root fillings in both the evaluation sessions (P < 0.05). Kappa ranged from slight to moderate for the length evaluation of root fillings and from poor to fair for the evaluation of homogeneity of root fillings. CONCLUSION: Image quality of storage phosphor images was subjectively as good as conventional film images and superior to LCBCT images for the evaluation of both homogeneity and length of root fillings in single-rooted teeth.