Scanning resolution and the detection of approximal caries.

OBJECTIVE: To determine a proper scanning resolution for digitizing bitewing radiographs in the detection of approximal caries. METHODS: Fifty-two premolars and 48 molars were mounted in blocks and imaged on conventional film (Ektaspeed Plus, Eastman-Kodak, Rochester, NY USA) simulating a bitewing projection. The 15 bitewing radiographs were then scanned with a flatbed scanner at three resolutions 150, 300 and 600 d.p.i. The digitized images were displayed in random order on a high-resolution cathode ray tube monitor. Ten observers assessed the caries status of 200 approximal surfaces. They scored lesion presence on a 5-point confidence scale and depth on a 3-point scale. The observer's scores were compared with the results from a histological examination. Data were analysed using analysis of variance, by calculating signed observer error, absolute observer error and observer confidence. RESULTS: Lesion depth had a significant effect on confidence of lesion recognition. The main effect of resolution and the interaction between resolution and lesion depth were significant. Pair-wise comparison showed a significant difference between resolutions in case of sound surfaces and surfaces with dentinal lesions for absolute error. The confidence increased as the resolution increased but no significant difference was found between 300 and 600 d.p.i. The best score for depth estimation was obtained at the 300 d.p.i. scanning resolution. CONCLUSIONS: When bitewing radiographs are scanned with a flatbed scanner, a resolution of 300 d.p.i. seems the best choice. At this resolution the digital file size is manageable without significant loss of the information necessary for caries diagnosis.     

Detection of proximal caries with high-resolution and standard resolution digital radiographic systems

AIMS: The aim of this study was to: (1) compare the diagnostic accuracy of the high-resolution and standard resolution settings of four digital imaging systems for caries diagnosis and (2) compare the effect on the diagnostic accuracy of reducing the high-resolution image sizes to the standard resolution dimensions, and vice versa. MATERIALS AND METHODS: 90 extracted human premolars were mounted in groups of 5 in plaster blocks, containing 4 test teeth and 1 non-test tooth. Two blocks at a time were placed in a jig to simulate a bitewing radiograph. Radiographs were taken using four digital systems (Planmeca Dixi 2; Gendex Visualix HDI; Dürr Vistascan; Digora Optime), each at two resolution settings. Next, the teeth were sectioned and a total of 65 surfaces were incorporated in the study. Additionally, the bicubic interpolation method was applied to reduce the high-resolution original images and to enlarge the standard resolution images. The original, reduced and enlarged images were randomly shown to five observers in two random sessions. The observers were asked to assess caries depth on a 4-point scale. The observers' scores were compared with the results from a histological examination. Data were analysed using the statistical theory for multivariate discrete data. Cohen's kappa was used to determine the agreement with the gold standard. RESULTS: None of the comparisons between the spatial resolution settings, or the comparisons between increased or reduced image size and the original image sizes, showed significant differences in the probability of caries detection (chi2=26.59, df=26, P approximately 0.50). The four digital systems used in this study differ significantly in the probability of caries detection (chi2=41.55, df=24, P<0.02). Compared with the gold standard, the Gendex Visualix HDI CCD sensor has the highest measure of agreement (kappa=0.31). CONCLUSION: Caries diagnosis does not improve when using high-resolution settings compared with the standard settings. The use of bicubic convolution interpolation for zooming has no detectable effect on caries diagnosis and therefore is recommended to use when enlarging or reducing radiographs. The probability of caries detection, however, was different for the sensor systems of the different manufacturers.     

Diagnostic accuracy of different imaging modalities in detection of proximal caries

Objective

The purpose of this study was to assess the in vitro diagnostic ability of visual inspection, film, charge-coupled device (CCD) sensor, photostimulable phosphor (PSP) sensor and cone beam CT in the detection of proximal caries in posterior teeth compared with the histological gold standard.

Methods

Visual inspection, film, CCD, PSP and cone beam CT images were used to detect proximal caries in the mesial and distal surfaces of 138 teeth (276 surfaces). Visual inspection and evaluation of all intraoral digital and conventional radiographs and cone beam CT images were performed twice by three oral radiologists. Weighted kappa coefficients were calculated to assess intra- and interobserver agreement for each image set, and scores were compared with the histological gold standard using receiver operating characteristic (ROC) analysis to evaluate diagnostic ability.

Results

Intraobserver kappa coefficients calculated for each observer for each method of detecting caries ranged from 0.739 to 0.928. Strong interobserver agreement ranging from 0.631 to 0.811 was found for all detection methods. The highest Az values for all three observers were obtained with the cone beam CT images; however, differences between detection methods were not statistically significant (P > 0.05).

Conclusion

Visual inspection, film, CCD, PSP plates and cone beam CT performed similarly in the detection of proximal caries.     

Digital subtraction radiography in artificial recurrent caries detection.

The diagnostic accuracy of digital subtraction radiography in detection of artificial recurrent caries lesions was assessed in this project. The use of digital subtraction radiography has been shown to markedly increase the accuracy of the detection of destruction in the periodontal bone, but the method has not been evaluated in secondary caries detection. Defects of three different sizes, simulating recurrent caries, were sequentially prepared in the interproximal cavity preparation margins of 28 teeth. Two composite restorative materials with different radiographic densities were used as posterior restorations, and a radiograph was obtained of each defect size and restorative material. The radiographs were digitized and subtracted from the reference images, and the conventional radiographs and the subtraction images were evaluated by seven observers. The data were analysed with ROC statistics. Subtraction radiography was found to be superior to conventional radiography in recurrent caries detection, mainly by reducing the false-positive diagnoses. The radiopacity of the restorative material had a significant effect on accuracy with conventional but not with subtraction radiography.     

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 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.     

Digital skeletal radiography: spatial resolution requirements for detection of subperiosteal resorption

Forty direct-magnification (2:1 enlargement) radiographs showing various severities of subperiosteal resorption and 40 normal studies were selected and digitized. Images were processed to produce varying resolution, from 1.42 to 11.4 Ip/mm, corresponding to pixel sizes ranging from 0.04 to 0.32 mm. The conventional and digitized images were evaluated by six radiologists giving their decision confidence on a graded scale. Receiver operating characteristic analyses were performed from these data to compare the digital images with the conventional films. The results show significant improvement in diagnostic accuracy as pixel size decreases to the level of 0.08 mm. Digital images with pixel sizes of 0.04 mm (11.4 Ip/mm) were not significantly different from the magnification radiographs in terms of observer performance. In conclusion, for high-resolution skeletal imaging as needed for detection of subperiosteal resorption, spatial resolution of 5.7 Ip/mm or less resulted in a significant loss of diagnostic accuracy, as compared with conventional films.     

Near-infrared reflection at 780 nm for detection of early proximal caries in posterior permanent teeth in vitro

Objectives:The aim of this in vitro study was to evaluate the diagnostic potential of near-infrared reflection at 780 nm (NIRR_780nm) for early proximal caries detection on the occlusal, buccal and oral surfaces of molars and premolars under simulated, clinically relevant conditions. The findings were validated by micro-computed tomography (µCT).Methods:Bitewing radiography (BWR) was used as a comparative diagnostic method. 250 sound or decayed permanent teeth were examined using NIRR_780nm and BWR. The NIRR_780nm findings were evaluated using yes/no decisions depending on the presence of caries lesions, as the enamel-dentin junction was not detectable in the majority of samples. All NIRR_780nm, BWR and µCT findings were obtained twice by two trained examiners. NIRR_780nm images were evaluated both occlusally alone and combined occlusally, lingually and buccally. All findings were presented in a cross-table. Sensitivity, specificity and area under the curve (AUC) values were calculated. Reliability assessment was performed using κ statistics.Results:Underestimation of caries was observed for NIRR_780nm in 26.0% of all surfaces and for BWR in 32.8% of all surfaces. Overestimation was 10.0% for NIRR_780nm and 0.4% for BWR. Trilateral NIRR_780nm assessment exhibited an overall accuracy of 67.2 %, an underestimation of 13.6% and an overestimation of 19.2%. Trilateral NIRR_780nm exhibited 63.0% sensitivity and 69.6% specificity, while BWR exhibited 26.7% sensitivity but 100% specificity for proximal caries detection.Conclusion:NIRR_780nm is not suitable for reliable detection of early proximal caries, even with the application of an ideal setup and optimized in vitro conditions.     

A comparison of conventional intra-oral radiography and computer imaging techniques for the detection of proximal surface dental caries.

The detection of proximal surface caries by the visual interpretation of bitewing radiographs is known to be relatively inaccurate. The present study was designed to examine whether computer image processing could improve the diagnostic accuracy. A computer-aided, software-driven, TV-based system was used to digitize conventional radiographs and digitally process the images using histogram equalization and grey-scale inversion to enhance the images. The computer-enhanced images were compared with conventional intra-oral radiographs for the detection of proximal surface caries using receiver operating characteristic analysis. The results indicate that the digital image processing techniques used did not improve the diagnostic accuracy of dental radiographs. No significant difference in diagnostic accuracy could be detected between the non-enhanced digital images and conventional film-based images for the detection of proximal surface caries.     

In vitro comparison of two types of digital X-ray sensors for proximal caries detection validated by micro-computed tomography

Objectives:We aimed to compare the diagnostic accuracy of two intraoral digital X-ray sensors—the charged-coupled device (CCD) and complementary metal-oxide-semiconductor (CMOS)—for proximal caries detection in permanent molar and premolar teeth. Micro-CT served as the reference standard.Methods:250 samples were mounted in three-dimensional (3D)-printed phantoms, and their proximal surfaces were evaluated by ICDAS criteria directly to create a balanced sample. Bitewing radiography was conducted using 3D-constructed X-ray phantoms with a CCD sensor at a 0.08 s and a CMOS sensor at 0.12 and 0.16 s exposure time. Two examiners determined the diagnostic decisions twice at appropriate intervals. Three diagnostic thresholds for sound surfaces and enamel and dentin caries were defined and presented in a cross-table. Sensitivity and specificity values and overall accuracy were calculated, and receiver operating curves were generated and compared. Reliability assessment was performed using linear weighted κ statistics.Results:The overall accuracies between the reference standard and different sensors and exposure times were 63.1% (CCD), 67.1% (CMOS sensor at 0.12 s) and 70.7% (CMOS sensor at 0.08 s). High specificity but low sensitivity values were found for all examination conditions at all thresholds. The area under the curve comparison values revealed no significant difference between sensor types and exposure times. Linear-weighted κ analysis revealed almost perfect agreement for all assessments.Conclusion:No significant difference was found for diagnostic performance of proximal caries detection between the different sensors and exposure times. The increased exposure time did not lead to a significant diagnostic benefit.     

Sensitivity, resolution and image quality with a multi-head SPECT camera.

This investigation sought to determine which collimation factors were most important in providing superior image quality with a three-headed SPECT device. The relationship between sensitivity, resolution and SPECT image quality was studied. Two different sets of parallel-hole collimators were used. The ultrahigh-resolution collimators have higher spatial resolution (8.9 versus 11.0 mm), but only 55% of the sensitivity of the high-resolution collimators. A phantom with hot rods was imaged with both collimator sets. Observers compared images with the ultrahigh-resolution collimators to images of varying counts with the high-resolution collimators and determined which high-resolution images matched the ultrahigh-resolution images in image quality. Eleven patient studies were acquired with both collimator sets for equal time, and observers chose which image set they preferred. Transverse images of brain and liver studies were simulated with varying resolution and counts and subjectively compared. The phantom study indicated that the improvement in resolution led to image quality comparable to increasing the number of counts by a factor of 2.5 to 3.4. The clinical studies showed that the ultrahigh-resolution collimators were preferred in a large majority of the cases. These trends were also seen in the simulation study. These results confirm that higher resolution collimators should be used with multihead SPECT devices. The improvement in resolution more than compensates for the loss in sensitivity, leading to an overall improvement in 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.     

A new screening method to detect proximal dental caries using fluorescence imaging

ObjectivesThis study aimed to assess the screening performance of the quantitative light-induced fluorescence (QLF) technology to detect proximal caries using both fluorescence loss and red fluorescence in a clinical situation. Moreover, a new simplified QLF score for the proximal caries (QS-Proximal) is proposed and its validity for detecting proximal caries was evaluated as well.MethodsThis clinical study included 280 proximal surfaces, which were assessed by visual-tactile and radiographic examinations and scored by each scoring system according to lesion severity. The occlusal QLF images were analysed in two different ways: (1) a quantitative analysis producing fluorescence loss (ΔF) and red fluorescence (ΔR) parameters; and (2) a new QLF scoring index. For both quantitative parameters and QS-Proximal, the sensitivity, specificity, and area under the receiver operating characteristic curve (AUROC) were calculated as a function of the radiographic scoring index at the enamel and dentine caries levels.ResultsBoth ΔF and ΔR showed excellent AUROC values at the dentine caries level (ΔF = 0.860, ΔR = 0.902) whereas a relatively lower value was observed at the enamel caries level (ΔF = 0.655, ΔR = 0.686). The QS-Proximal also showed excellent AUROC ranged from 0.826 to 0.864 for detecting proximal caries at the dentine level.ConclusionThe QS-Proximal, which represents fluorescence changes, showed excellent performance in detecting proximal caries using the radiographic score as the gold standard.