Detection ofin vitroproximal caries in storage phosphor plate radiographs scanned with different resolutions

The effect of different spatial resolutions and enhancement filters on radiographic detection of simulated furcation defects with intraoral digital radiography

OBJECTIVE

The objective of this study was to evaluate the effects of spatial resolution and the application of enhancement filters in the diagnosis of simulated furcation defects and image quality with intraoral radiographs.

STUDY DESIGN

Periapical images were acquired with photostimulable phosphor plates of molars in dry skulls (n = 8) and mandibles (n = 10) with 4 stages of furcation defect simulation. The plates were scanned in fast scan and high resolution modes to produce different spatial resolutions. Four image filters were applied. Six observers scored the detection of furcation defects. Mean values of area under the curve in receiver operating characteristic evaluation, accuracy, sensitivity, and specificity were calculated. Mean gray value (brightness), noise, and contrast-to-noise ratio (CNR) were calculated for enamel, dentin, and alveolar bone to evaluate image quality. Analysis of variance compared the values between the different spatial resolutions and filters. The significance of difference was established at P < .05.

RESULTS

There were no significant differences in overall diagnostic values comparing image spatial resolutions and filters. Diagnostic outcomes were significantly better for the largest defects than the smallest lesions but were generally poor in detecting lesions. All structures showed greater brightness in high resolution. . Noise was greater in all structures with all enhancement filters except inversion. Dentin and alveolar bone exhibited more noise and lower CNR in high resolution.

CONCLUSIONS

Varying spatial resolution and applying enhancement filters did not significantly affect the diagnosis of furcation defects.

The influence of different scan resolutions on the detection of proximal caries lesions

Purpose

This study was conducted to evaluate the effect of different spatial resolutions of a photostimulable phosphor plate (PSP) radiography system on the detection of proximal caries lesions.

Materials and Methods

Forty-five extracted human permanent teeth were radiographed using a PSP system (VistaScan Perio Plus) and scanned at the 4 resolutions (10 lp/mm, 20 lp/mm, 25 lp/mm, and 40 lp/mm) available in the system. Three independent examiners scored the images for the presence and absence of proximal caries lesions using a 5-point scale. The presence or absence of caries was confirmed by histological sections of the examined teeth (defined as the gold standard). Intra- and inter-observer reproducibility was calculated by the weighted kappa test. One-way analysis of variance with the post hoc Tukey test was used to compare the area under the receiver operating characteristic curve for the classifications made with each resolution.

Results

For the detection of enamel lesions, the spatial resolution of 10 lp/mm was significantly superior to the other resolutions. However, the spatial resolution did not affect the detection of caries lesions in dentin (P>0.05).

Conclusion

Spatial resolution may influence the accuracy of the detection of incipient caries lesions in radiographs with PSP plates. Images with low spatial resolution seem to be more appropriate for this purpose.

Effect of Image Resolution and Compression on Fractal Analysis of the Periapical Bone

Introduction:

Fractal dimension (FD) on periapical radiographs is used as a simple descriptor of the complex architecture of the trabecular bone surrounding the dentition. It is used on periapical and panoramic radiographs as a descriptor of the complex architecture of trabecular bone surrounding teeth.

Aim:

The aim of this study was to evaluate the effect of image resolution and different compression levels on fractal dimension of alveolar bone with images obtained using storage phosphor plate (SPP) system.

Methods:

Periapical images of premolar and molar teeth on both sides of three dry human mandibles were obtained with Digora Optime (Soredex Corp., Helsinki, Finland) SPP system. The SPPs were exposed equally and scanned immediately after exposure with standard, high and very high resolutions. All the images then were compressed and saved by degrees of 0%, 25%, 50%, 75% and 90%. FD was calculated using public domain software (ImageJ with FracLac plug-in) on two non-overlapping regions of interest (ROIs) on premolar and molar periapical bone areas of each radiograph using differential box-counting method. The ROIs on corresponding images were of the same size and position. FDs were compared using two-way ANOVA and Tukey–Kramer multiple comparison tests (p=0.05).

Results:

There was no significant difference in FD calculations in different levels of compression for all the resolutions. Images obtained with high resolution scans showed significantly lower variation in FD values compared to very high and standard resolutions for all compressions (p<0.0001).

Conclusion:

The high resolution demonstrated the lowest variation in FD values in all levels of compression which makes it the most reliable and consistent resolution for measuring the FD values. The level of compression does not make a significant difference in FD values for all the scan resolutions. Scanning resolution of SPPs should be carefully chosen when evaluating the change in FD of alveolar bone for various bone disorders.

In-vitro Thermal Maps to Characterize Human Dental Enamel and Dentin

The crown of a human tooth has an outer layer of highly-mineralized tissue called enamel, beneath which is dentin, a less-mineralized tissue which forms the bulk of the tooth-crown and root. The composition and structure of enamel and dentin are different, resulting in different thermal properties. This gives an opportunity to characterize enamel and dentin from their thermal properties and to visually present the findings as a thermal map. The thermal properties of demineralized enamel and dentin may also be sufficiently different from sound tissue to be seen on a thermal map, underpinning future thermal assessment of caries. The primary aim of this novel study was to produce a thermal map of a sound, human tooth-slice to visually characterize enamel and dentin. The secondary aim was to map a human tooth-slice with demineralized enamel and dentin to consider future diagnostic potential of thermal maps for caries-detection. Two human slices of teeth, one sound and one demineralized from a natural carious lesion, were cooled on ice, then transferred to a hotplate at 30°C where the rewarming-sequence was captured by an infra-red thermal camera. Calculation of thermal diffusivity and thermal conductivity was undertaken, and two methods of data-processing used customized software to produce thermal maps from the thermal characteristic-time-to-relaxation and heat-exchange. The two types of thermal maps characterized enamel and dentin. In addition, sound and demineralized enamel and dentin were distinguishable within both maps. This supports thermal assessment of caries and requires further investigation on a whole tooth.

Detection of root perforations using conventional and digital intraoral radiography, multidetector computed tomography and cone beam computed tomography

OBJECTIVES

This study aimed to compare the accuracy of conventional intraoral (CI) radiography, photostimulable phosphor (PSP) radiography, cone beam computed tomography (CBCT) and multidetector computed tomography (MDCT) for detection of strip and root perforations in endodontically treated teeth.

MATERIALS AND METHODS

Mesial and distal roots of 72 recently extracted molar were endodontically prepared. Perforations were created in 0.2, 0.3, or 0.4 mm diameter around the furcation of 48 roots (strip perforation) and at the external surface of 48 roots (root perforation); 48 roots were not perforated (control group). After root obturation, intraoral radiography, CBCT and MDCT were taken. Discontinuity in the root structure was interpreted as perforation. Two observers examined the images. Data were analyzed using Stata software and Chi-square test.

RESULTS

The sensitivity and specificity of CI, PSP, CBCT and MDCT in detection of strip perforations were 81.25% and 93.75%, 85.42% and 91.67%, 97.92% and 85.42%, and 72.92% and 87.50%, respectively. For diagnosis of root perforation, the sensitivity and specificity were 87.50% and 93.75%, 89.58% and 91.67%, 97.92% and 85.42%, and 81.25% and 87.50%, respectively. For detection of strip perforation, the difference between CBCT and all other methods including CI, PSP and MDCT was significant (p < 0.05). For detection of root perforation, only the difference between CBCT and MDCT was significant, and for all the other methods no statistically significant difference was observed.

CONCLUSIONS

If it is not possible to diagnose the root perforations by periapical radiographs, CBCT is the best radiographic technique while MDCT is not recommended.

Evaluation of image quality parameters of representative intraoral digital radiographic systems

OBJECTIVE

The aim of this study was to compare imaging properties of 20 intraoral digital systems objectively.

STUDY DESIGN

Using a direct current x-ray source and a radiographic phantom, a series of radiographs was made from the lowest exposure time until the sensor saturated. Images were captured and stored. Incident exposures were measured using a radiation meter. Gray scale, spatial resolution, and contrast/detail detectability were evaluated. Presence of 7 distinct steps spanning the gray levels from 0 to 255 was used to define the exposure latitude. An "optimal" exposure, the lowest exposure where maximum spatial resolution and contrast/detail detectability were achieved, was determined.

RESULTS

The systems varied greatly in latitude, "optimal" exposure, and image quality. This may not be readily apparent to the naked eye or when clinical images are compared.

CONCLUSIONS

Objective assessment of image quality with a quality assurance tool makes it possible to evaluate and compare the various intraoral digital systems.

Diagnostic accuracy of Digora Optime storage phosphor plates for proximal subsurface demineralization: effect of different exposure times

OBJECTIVE

The aim of this study was to compare the diagnostic accuracy of F-speed film and storage phosphor plate (SPP) exposed with different exposure times for the detection of artificial enamel subsurface demineralization.

STUDY DESIGN

Standard enamel windows of extracted premolars were exposed to a demineralizing solution. All teeth were radiographed before and after acid application with F-speed films and SPPs. Films were exposed for 0.25 seconds and SPPs were exposed using 4 exposure times. Receiver operating characteristic analysis was used for diagnostic accuracy (A(z)).

RESULTS

Significant differences were obtained among A(z)s of 0.08- versus 0.12-seconds and 0.10- versus 0.12-second exposed SPPs (P < .05). A(z)s of films were higher than the SPPs exposed with 0.08, 0.10, and 0.12 seconds (P < .05). No difference was found between the A(z)s of the 2 systems when SPPs were exposed for 0.16 seconds (P > .05).

CONCLUSIONS

Diagnostic accuracy of films and SPPs was not impaired when exposure time was 36% reduced for the latter; however, diagnosis was impaired when reduced 52%.

Effect of combined digital imaging parameters on endodontic file measurements

INTRODUCTION

This study assessed the effect of the combination of a dedicated endodontic filter, spatial resolution, and contrast resolution on the determination of endodontic file lengths.

METHODS

Forty extracted single-rooted teeth were x-rayed with K-files (ISO size 10 and 15) in the root canals. Images were acquired using the VistaScan system (Dürr Dental, Beitigheim-Bissingen, Germany) under different combining parameters of spatial resolution (10 and 25 line pairs per millimeter [lp/mm]) and contrast resolution (8- and 16-bit depths). Subsequently, a dedicated endodontic filter was applied on the 16-bit images, creating 2 additional parameters. Six observers measured the length of the endodontic files in the root canals using the software that accompanies the system. The mean values of the actual file lengths and the measurements of the radiographic images were submitted to 1-way analysis of variance and the Tukey test at a level of significance of 5%. The intraobserver reproducibility was assessed by the intraclass correlation coefficient.

RESULTS

All combined image parameters showed excellent intraobserver agreement with intraclass correlation coefficient means higher than 0.98. The imaging parameter of 25 lp/mm and 16 bit associated with the use of the endodontic filter did not differ significantly from the actual file lengths when both file sizes were analyzed together or separately (P > .05). When the size 15 file was evaluated separately, only 8-bit images differed significantly from the actual file lengths (P ≤ .05).

CONCLUSIONS

The combination of an endodontic filter with high spatial resolution and high contrast resolution is recommended for the determination of file lengths when using storage phosphor plates.

Image resolution and exposure time of digital radiographs affects fractal dimension of periapical bone

OBJECTIVES

The aim of this study was to evaluate the effect of exposure time and image resolution on fractal dimension (FD) of periapical bone on images obtained using a storage phosphor plate (SPP) system.

MATERIALS AND METHODS

Periapical images of premolar and molar teeth on both sides of ten dry human mandibles were obtained with Digora Optime (Soredex Corp., Helsinki, Finland) SPP system. The SPPs were exposed with three exposure times (0.05, 0.12, and 0.30 s) and scanned immediately after exposure with high and super resolutions. FD was calculated using public domain software (ImageJ with FracLac plug-in) on two non-overlapping region of interest (ROIs) on premolar and molar periapical bone areas of each radiograph using differential box-counting method. The ROIs on corresponding images were of the same size and position. FDs were compared using two-way ANOVA and Tukey-Kramer multiple comparison tests (p = 0.05).

RESULTS

Images obtained with super resolution scans gave significantly higher FD values compared to high-resolution scanning for all exposures (p < 0.0001). FD values were decreasing with increase in exposure time for both resolutions (p < 0.0001). The highest FD was found for images with super resolution and shortest exposure time, which exhibited the highest noise.

CONCLUSIONS

FD analysis seems not so robust method as it was believed previously. It shows significant changes with image resolution and exposure time.

CLINICAL RELEVANCE

Exposure time and scanning resolution of SPPs should be carefully chosen when evaluating the change in FD of alveolar bone for various bone disorders.

Near-infrared transillumination of teeth: measurement of a system performance

Transillumination (TI) of dental enamel with near-infrared light is a promising nonionizing imaging method for detection of early caries lesion. Increased mineral loss (caries lesion) leads to increased scattering and absorption. Caries thus appear as dark regions because less light reaches the detector. The aim of this work was to characterize the performance of a TI system from the resolution of acquired images using the modulation transfer function at two wavelengths, 1.28 and 1.4 mum. Test charts with various values of spatial periods, mimicking a perfect caries lesion, were attached to tooth sections, followed by capture of the transmitted image, using both wavelengths. The sections were then consecutively reduced in thickness, and a sequence of all sizes of the test charts were used for repeatedly imaging procedures. The results show that the TI system can detect feature size of 250 mum with 30% modulation. From the information about how the image degrades as it propagates through enamel, we also examined the possibility of estimating the position of a simulated approximal caries lesion by comparing images obtained from the two sides of a tooth section.

Work flow with digital intraoral radiography: a systematic review

OBJECTIVE

This systematic review evaluates the six most frequently emphasized advantages of working with digital radiography: less working time, lower radiation dose to the patient, fewer retakes and errors, wider dynamic range, easier access to patient information and easier image storage and communication. Moreover, some clinical aspects and possible disadvantages of digital imaging that were not foreseen at the beginning of the digital era, such as patient discomfort, damage to the receptor, degradation of the image, cross-contamination and viewing conditions, were assessed.

MATERIAL AND METHODS

The literature search used the PubMed database with no limits and was performed during June to August 2009. Search strategies are described in the text for each of the mentioned tasks. A hand search of task-specific journals supplemented the search strategies.

RESULTS

Time seems to be saved when switching from film to digital imaging in dental practice, a dose reduction may not be obtained, retakes and errors may be increased, the dynamic range may be wider with photostimulable storage phosphor (PSP) plates but not with sensors, the effect on patient information has not been well studied and storage and communication create new challenges with regard to handling large files and image compression. In addition, patient discomfort seems to be pronounced with sensors compared with PSP plates and film, the PSP plate may be scratched in clinical use and a two-layer barrier seems to be needed to prevent contamination of the receptor. The type of monitor may not be of major concern if the image is viewed in a room with subdued light.

CONCLUSIONS

Not all of the predicted advantages with digital compared to film-based radiography hold true in daily clinical work. Of particular interest is the relationship between number of images, retakes and the dose given to the patient.

A comparison of the diagnostic accuracy of in vivo and in vitro photostimulable phosphor digital images in the detection of occlusal caries lesions

OBJECTIVES

The purpose of this study was to compare the accuracy of diagnoses of occlusal caries lesions from digital images captured using a photostimulable phosphor (PSP) sensor under in vivo and in vitro conditions and to present useful clinical data regarding the clinical application of the system.

METHODS

The study sample comprised 60 mandibular third molars (30 sound and 30 with occlusal caries) requiring extraction. A pre-extraction and post-extraction image of each tooth were acquired using a PSP sensor. A stopwatch was used to record the time required for the clinical procedures. Patient comfort or discomfort during image acquisition was also recorded. Images were evaluated twice by three observers using a five-point scale. Kappa coefficients were calculated to assess intra- and interobserver agreement. Receiver operating characteristic (ROC) curves were used to assess the diagnostic performance of each observer for both in vivo and in vitro images. The t-test was used to compare A(z) values, with a significance level set at 0.05 (alpha _ 0.05). The time required for clinical imaging procedures in patients who claimed discomfort and in those who did not was compared using the Mann-Whitney U-test.

RESULTS

Intraobserver agreement was almost perfect, whereas interobserver agreement was fair to moderate. No statistically significant differences were found in the accuracy of diagnoses of occlusal caries lesions using in vivo and in vitro digital images. The median time needed for image exposure was 1.04 min and the median time needed to complete the image acquisition procedure was 1.45 min.

CONCLUSIONS

The diagnosis of accuracy of occlusal caries lesions using in vivo and in vitro digital images yielded similar results.