Image processing and enhancement provided by commercial dental software programs

Can Digital Enhancement Restore the Image Quality of Phosphor Plate-Based Radiographs Partially Damaged by Ambient Light?

To assess the effect of digital enhancement on the image quality of radiographs obtained with photostimulable phosphor (PSP) plates partially damaged by ambient light. Radiographs of an aluminum step wedge were obtained using the VistaScan and Express systems. Half of the PSP plates was exposed to ambient light for 0, 10, 30, 60, or 90 s before being scanned. The resulting radiographs were exported with and without digital enhancement. Metrics for brightness, contrast, and contrast-to-noise ratio (CNR) were derived, and the ratio of each metric between the exposed-to-light and non-exposed-to-light halves of the radiographs was calculated. The resulting ratios of the radiographs with digital enhancement were subtracted from those without digital enhancement and compared among each other. For the VistaScan system, digital enhancement partially restored brightness, contrast, and CNR. For the Express system, digital enhancement only restored CNR and not the impact of ambient light on brightness and contrast. Specifically, digital enhancement restored 23.48% of brightness for the VistaScan, while percentages below 1% were observed for the Express. Digital enhancement restored 53.25% of image contrast for the VistaScan and 5.79% for the Express; 40.71% of CNR was restored for the VistaScan, and 35% for the Express. Digital enhancement can partially restore the damage caused by ambient light on the brightness and contrast of PSP-based radiographs obtained with the VistaScan, as well as on CNR for the VistaScan and Express systems. The exposure of PSP plates to light can lead to unnecessary retakes and increased patient exposure to X-rays.

The influence of image display systems on observers' preference for visualizing subtle dental radiographic abnormalities

OBJECTIVE

The objectives of this study were to assess observers' preference for standard screens (SSs) or medical displays (MDs) in visualizing difficult-to-diagnose radiographic dental abnormalities and their preference for dental filter tools when utilized with MD systems.

STUDY DESIGN

A retrospective data set of 60 in vivo radiographs consisting of intraoral (n = 20), panoramic (n = 20), and cone beam computed tomography (n = 20) images was created. Three image display monitors, including an SS, an MD, and an MD with 3 dental filter configurations (bone-low density enhancement filter, tooth-high density enhancement filter, and a combined filter representing regular MD), were utilized to assess 4 observers' monitor preferences in detecting radiographically subtle dental abnormalities. The data were analyzed by using binomial distribution. A P value ≤.05 was considered statistically significant.

RESULTS

Although observers expressed preference for MD for visualizing some abnormalities when examining intraoral and panoramic radiographs, MD was not preferred for detection of any abnormalities with cone beam computed tomography. There were no significant differences in preference for SS or MD overall (P ≥ .2024). Observers expressed significant preference for the filters in visualizing all but 2 abnormalities (P ≤ .0252).

CONCLUSIONS

The use of MD monitors enabled with dental filter tools may be preferred for visualizing certain subtle abnormalities.

Dental Diagnosis and Treatment Assessments: Between X-rays Radiography and Optical Coherence Tomography

A correct diagnosis in dental medicine is typically provided only after clinical and radiological evaluations. They are also required for treatment assessments. The aim of this study is to establish the boundaries from which a modern, although established, imaging technique, Optical Coherence Tomography (OCT), is more suitable than the common X-ray radiography to assess dental issues and treatments. The most common methods for daily-basis clinical imaging are utilized in this study for extracted teeth (but also for other dental samples and materials), i.e., panoramic, intraoral radiography, and three-dimensional (3D) cone beam computed tomography (CBCT). The advantages of using OCT as an imaging method in dentistry are discussed, with a focus on its superior image resolution. Drawbacks related to its limited penetration depth and Field-of-View (FOV) are pointed out. High-quality radiological investigations are performed, measurements are done, and data collected. The same teeth and samples are also imaged (mostly) with an in-house developed Swept Source (SS)-OCT system, Master-Slave enhanced. Some of the OCT investigations employed two other in-house developed OCT systems, Spectral Domain (SD) and Time Domain (TD). Dedicated toolbars from Romexis software (Planmeca, Helsinki, Finland) are used to perform measurements using both radiography and OCT. Clinical conclusions are drawn from the investigations. Upsides and downsides of the two medical imaging techniques are concluded for each type of considered diagnosis. For treatment assessments, it is concluded that OCT is more appropriate than radiography in all applications, except bone-related investigations and periodontitis that demand data from higher-penetration depths than possible with the current level of OCT technology.

COVID-19 and beyond: implications for dental radiography

Due to the coronavirus pandemic, all routine dental care in the UK ceased on 25 March 2020. Liverpool University Dental Hospital (LUDH) responded by commencing an emergency dental service on the same date. Clinicians were redeployed within the Hospital to meet the needs of the service, including staffing of the radiology department. LUDH followed Royal College recommendations by taking extraoral radiographs in preference to intraoral radiographs due to the risk of inducing an aerosol. Issues were identified with clinical diagnosis from sectional panoramic radiographs, which led to the introduction of extraoral bitewings being taken as an alternative. A quality assurance audit found that these images provided a substantially lower radiation dose and produced excellent quality images with improved diagnostic accuracy. This article aims to summarise how our radiography practices changed in response to the coronavirus and how the lessons that we have learnt provide an opportunity to modify and improve future practice, beyond the pandemic.

Can adaptive post-processing of storage phosphor plate panoramic radiographs provide better image quality? A comparison of anatomical image quality of panoramic radiographs before and after adaptive processing

OBJECTIVE

The objective of the present study was to study the effect of adaptive image processing on the visibility of anatomical structures in storage phosphor plate (SPP) panoramic images.

MATERIALS AND METHODS

Three hundred SPP panoramic X-ray radiographs of children and adolescents were used. The radiographs were post-processed using general operator processor (GOP) technology, resulting in both a standard-processed and a GOP-processed radiograph. Four specialists in dental radiology compared the structural image quality of all standard-processed and GOP-processed panorama images for six anatomical structures, using a six-point scale for visual grading characteristics (VGC) analysis.

RESULTS

For three of the anatomic structures - the root canal space of the mandibular left first premolar, mandibular canal left side and periodontal ligament space of the mandibular right first molar - there was a statistically significant difference to the GOP's advantage. For the three remaining structures - dentino-enamel junction of the maxillary right first molar, crista alveolaris of the mandibular left molar area and floor of maxillary sinus right side - no significant difference between standard processing and GOP processing was obtained.

CONCLUSIONS

The study demonstrates that it is possible to improve the quality of SPP radiographs and the visibility of anatomical structures by using the GOP technique. Manufacturers' image-processing programs can be further developed, as there is a possibility of improving the diagnostic content of an image with external processing.

Image quality assessment of pre-processed and post-processed digital panoramic radiographs in paediatric patients with mixed dentition

Purpose

To determine the impact of an image processing technique on diagnostic accuracy of digital panoramic radiographs for the assessment of anatomical structures in paediatric patients with mixed dentition.

Materials and Methods

The study consisted of 50 digital panoramic radiographs of children aged from 6 to 12 years, which were later on processed using a dedicated image processing method. A modified clinical image quality evaluation chart was used to evaluate the diagnostic accuracy of anatomical structures in maxillary and mandibular anterior and maxillary premolar region of processed images.

Results

A statistically significant difference was observed between pre and post-processed evaluation of anatomical structures (P<0.05) in the maxillary and mandibular anterior region. The anterior region was found to be more accurate in post-processed images. No significant difference was observed in the maxillary premolar region (P>0.05). The Inter-observer and intra-observer reliability of both pre and post processed images were excellent (>0.82) for anterior region and good (>0.63) for premolar region.

Conclusion

The application of image processing technique in digital panoramic radiography can be considered a reliable method for improving the quality of anatomical structures in paediatric patients with mixed dentition.

Photoacoustic imaging for monitoring periodontal health: A first human study

The gold-standard periodontal probe is an aging tool that can detect periodontitis and monitor gingival health but is highly error-prone, does not fully characterize the periodontal pocket, and causes pain. Photoacoustic imaging is a noninvasive technique that can address these limitations. Here, a range of ultrasound frequencies between 16-40 MHz were used to image the periodontium and a contrast medium based on cuttlefish ink was used to label the pockets. A 40 MHz ultrasound frequency could spatially resolve the periodontal anatomy, including tooth, gum, gingival margin, and gingival thickness of tooth numbers 7-10 and 22-27. The photoacoustic-ultrasound measurements were more precise (0.01 mm) than those taken with physical probes by a dental hygienist. Furthermore, the full geometry of the pockets could be visualized with relative standard deviations of 10% (n = 5). This study shows the potential for non-invasive monitoring of periodontal health with photoacoustic-ultrasound imaging in the dental clinic.

Caries detection enhancement using texture feature maps of intraoral radiographs

Objectives

Dental caries are caused by tooth demineralization due to bacterial plaque formation. However, the resulting lesions are often discrete and thus barely recognizable in intraoral radiography images. Therefore, more advanced detection techniques are in great demand among dentists and radiographers. This study was performed to evaluate the performance of texture feature maps in the recognition of discrete demineralization related to caries plaque formation.

Methods

Digital intraoral radiology image analysis protocols incorporating first-order features (FOF), co-occurrence matrices, gray tone difference matrices, run-length matrices (RLM), local binary patterns (LBP), and k-means clustering (CLU) were used to transform the digital intraoral radiology images of 10 patients with confirmed caries, which were retrospectively reviewed in a dental clinic. The performance of the resulting texture feature maps was compared with that of radiographic images by radiologists and dental specialists.

Results

Significantly improved detection of caries spots was achieved by employing the CLU and FOF texture feature maps. The caries-affected area with sharp margins was well defined using the CLU approach. A pseudo-three-dimensional effect was observed in outlining the demineralization zones inside the cavity with the FOF 5 protocol. In contrast, the LBP and RLM techniques produced less satisfactory results with unsharp edges and less detailed depiction of the lesions.

Conclusions

This study illustrated the applicability of texture feature maps to the recognition of demineralized spots on the tooth surface debilitated by caries and identified the best performing techniques.

Changes in the Height of Velopharyngeal Closure Relative to the Cervical Spine From Infancy Through Adolescence in Patients With Cleft Palate

OBJECTIVE

Palpation is often used to identify C1, an intraoperative landmark, for placement of the pharyngoplasty. However, little is known about the relationship between the palatal plane (PP) and this cervical spine landmark across select variables. This study seeks to analyze variations in the height of velopharyngeal closure relative to C1 across differing cleft types and age groups.

DESIGN

Retrospective, cross-sectional analysis.

SETTING

Large, multidisciplinary center for craniofacial disorders.

METHODS

Clinical lateral cephalograms were analyzed in nonsyndromic patients who underwent primary palatoplasty. Regression analysis and analysis of covariance were completed to determine how age and cleft type impact underlying cervical and velopharyngeal measures.

RESULTS

Age ( P < .001) and cleft type ( P = .036) were significant predictors of the distance between the height of velopharyngeal closure and C1. Those with greater severity of clefting demonstrated larger distances between the height of velopharyngeal closure and C1. Compared to normative data, children with cleft palate have significantly larger distances between the PP and C1. The height of velopharyngeal closure above C1 was observed to range from 3.6 to 12.6 mm across cleft populations.

CONCLUSIONS

This study demonstrates the variability in C1 as a landmark across variables including cleft type and age. Because of differences in the height of velopharyngeal closure across cleft types relative to C1, it is necessary to preoperatively quantify the vertical distance between the PP and palpable intraoperative landmark, C1, to determine the appropriate height of pharyngoplasty insertion.

Effect of Contrast Inversion Enhancement on the Accuracy of Endodontic File Length Determination in Digital Radiography

OBJECTIVE

The aim of this ex vivo study was to evaluate the accuracy of endodontic file length measurement on digital periapical radiographs after application of contrast inversion digital enhancement.

MATERIALS AND METHODS

Forty single-rooted single-canal mature permanent human teeth with canals measuring 20-24 mm in length were used in this study. ISO #08 K-files were placed in the root canals of the teeth. The file lengths were measured with a digital caliper as the gold standard. Standard periapical digital images were obtained with the Digora storage phosphor plates and Digora Optime scanner as the original images. The contrast inversion option of Scanora software program version 5.1 was used to produce enhanced images. Three radiologists and three endodontists measured file lengths on the original and enhanced images. The measurements were compared using repeated measures ANOVA and Bonferroni tests (α=0.05).

RESULTS

There were significant differences between the measurement accuracy of the original and enhanced images (p<0.05). The enhanced images exhibited longer measurements compared to the original images. However, the two sets of digital radiographs provided significantly longer measurements compared to the gold standard (p<0.05).

CONCLUSION

The contrast inversion tool of Scanora software program decreases measurement accuracy of the length of small endodontic files on digital periapical radiographs. It is suggested that contrast inversion should not be used in determining the lengths of small endodontic files.

Effects of nonsurgical periodontal treatment on the alveolar bone density

The aim of this study was to evaluate the effects of nonsurgical periodontal treatment on alveolar bone density (ABD) and bone height (BH) using direct digital radiography. Nineteen patients (mean age: 36 ± 7.3 years) with generalized chronic periodontitis were examined at baseline, 90 (90 AT) and 180 (180 AT) days after nonsurgical periodontal therapy. Radiographs were taken from two sites with specific characteristics: 39 sites with probing pocket depth (PPD) ≤ 3 mm and clinical attachment level (CAL) ≤ 1 mm (shallow sites); and 62 sites with PPD ≥ 5 mm and CAL ≥ 3 mm (deep sites). The ABD was assessed considering the bone regions of interest at the alveolar bone crest (ROI I) and at the medullar bone (ROI II). The BH was assessed considering the distance from the alveolar bone crest to the cementoenamel junction. Mann-Whitney test was used for the overall demographic data, Wilcoxon test was used to compare the baseline, 90 AT and 180 AT data as well as to compare the groups and subgroups within the same evaluation period. The significance level was set at 5%. The deep sites showed a significant increase of ABD in ROI I at 90 AT (p<0.007) and at 180 AT (p<0.005). ABD decrease was seen in ROI II at 180 AT (p<0.04) while BH reduced only in shallow sites at 90 AT. In conclusion, an increase in ABD was observed in deep sites of patients with generalized chronic periodontitis. However, no significant change in alveolar BH was observed in these sites.

The 'Sharpen' filter improves the radiographic detection of vertical root fractures

AIM

To compare the diagnostic accuracy of digital enhancement filters in the diagnosis of vertical root fractures.

METHODOLOGY

The sample consisted of 40 single-rooted teeth randomly divided into two groups: experimental and control. Vertical root fractures were induced in the experimental group using a universal testing machine. All teeth were individually radiographed with three different horizontal angles using the Digora Optime(®) digital system. Three observers separately examined the original and filtered images (3D Emboss, Negative, Sharpen and Shadow). The area under Receiver Operating Characteristic curve values (Az) for each protocol were compared by one-way anova with post hoc Bonferroni test. The significance level was set at 5%.

RESULTS

The highest Az value was obtained using the Sharpen filter, with significant differences from the original and other filtered images (P < 0.05). The 3D Emboss filter had the lowest Az value, which was significantly different from the other filtered images (P < 0.05).

CONCLUSION

When using the Digora Optime(®) system, the 'Sharpen' filter is recommended to improve the radiographic detection of vertical root fractures.

A retrospective study of digital subtraction technique to detect sclerotic changes in alveolar bone on intraoral radiographs of bisphosphonate-treated patients

OBJECTIVES

Several reports have suggested that sclerotic changes in cancellous bone of the jaw and thickening of the lamina dura are characteristic radiographic changes of an early silent stage of bisphosphonate (BP)-related osteonecrosis of the jaw. No quantitative evaluation has been reported to support this hypothesis. Emago(®) software (Oral Diagnostic Systems, Amsterdam, Netherlands) can perform digital subtraction on intraoral radiographs even if they were obtained by non-standardized radiography, provided the dimensional error is within a certain limit. The purpose of this study was to evaluate whether sclerotic changes of alveolar bone or thickening of lamina dura in patients using BP can be detected using the subtraction function of Emago.

METHODS

The authors selected 46 pairs of intraoral radiographs of the mandibular molar area in dental patients. All radiographs were obtained at intervals of 6 months or more. Among the 46 pairs, 7 pairs were from patients who were being treated with BP (study subjects), and 39 pairs were from patients who had not been using BP (controls). All pairs of radiographs underwent digital subtraction by Emago. The number of pixels of the sclerotic areas was counted and compared between subjects and controls.

RESULTS

The sclerotic changes were significantly distinguishable in two of the seven subjects (28.6%) using BP.

CONCLUSIONS

Digital subtraction function of Emago was able to detect sclerotic changes in alveolar bone. Therefore, it is suggested that the subtraction function of Emago is a useful tool for quantitatively detecting sclerotic changes that are observed at an early, silent stage of BP-related osteonecrosis of the jaw.

A Subjective Assessment of Perceived Clarity of Indirect Digital Images and Processed Digital Images with Conventional Intra-oral Periapical Radiographs

OBJECTIVES

To compare and analyze the perceived clarity and diagnostic value of Conventional periapical Radiographs (CRs) with those of their Digitized Periapical Images (DIs) and Processed Digitized Periapical Images (PDIs) counterparts.

MATERIAL AND METHODS

Forty two intraoral periapical radiographs of patients with clinically suspected periapical pathosis were made to constitute the group of CRs. These were photographed by using a Canon Power Shot SD500 (7.1 Megapixel) digital camera and the unaltered images were transferred to a computer laptop, to form the group of DIs. Subsequently, the contrast and brightness of these images were modified to represent the group of PDIs. Two experienced oral radiologists independently evaluated 5 specific apical and periapical region parameters of all the 42 CRs, DIs and PDIs for perceived image quality and diagnostic value and graded them on a three point grading scale. Conventional radiographs served as the control. Data were analyzed by using paired t-test and Kappa analysis.

RESULTS

The clarity and diagnostic quality of the PDIs were statistically significant as compared to those of their conventional counterparts. In comparison, the DIs group fared badly, with deterioration of the image quality. The interobserver agreement was good and all the results were statistically significant.

CONCLUSION

Indirectly digitizing the radiographs by employing a digital camera and further digitally processing the images resulted in an improvement in their perceived clarity and they enhanced their diagnostic properties.

Image quality assessment in panoramic dental radiography: a comparative study between conventional and digital systems

This study is designed to compare and evaluate the diagnostic image quality of dental panoramic radiography between conventional and digital systems. Fifty-four panoramic images were collected and divided into three groups consisting of conventional, digital with and without post processing image. Each image was printed out and scored subjectively by two experienced dentists who were blinded to the exposure parameters and system protocols. The evaluation covers of anatomical coverage and structures, density and image contrast. The overall image quality score revealed that digital panoramic with post-processing scored the highest of 3.45±0.19, followed by digital panoramic system without post-processing and conventional panoramic system with corresponding scores of 3.33±0.33 and 2.06±0.40. In conclusion, images produced by digital panoramic system are better in diagnostic image quality than that from conventional panoramic system. Digital post-processing visualization can improve diagnostic quality significantly in terms of radiographic density and contrast.

Performance of a photostimulable storage phosphor digital system with or without the sharpen filter and cone beam CT for detecting approximal enamel subsurface demineralization

OBJECTIVES

The aim of this study was to assess the performance of photostimulable storage phosphor (PSP) radiographs with or without using the sharpen filter and cone beam CT (CBCT) for detecting enamel subsurface demineralization.

METHODS

Enamel subsurface demineralization was induced on one of the approximal surfaces of 120 sound human teeth. Standardized images of all teeth were acquired after the demineralization phase using the Digora(®) Optime (Orion Corp./Soredex, Helsinki, Finland) (PSP) and the i-CAT™ (Imaging Sciences International, Hatfield, PA) (CBCT) systems. Three calibrated observers interpreted the images using a five-point scale (1, demineralization definitely absent; 2, demineralization probably absent; 3, unsure; 4, demineralization probably present; and 5, demineralization definitely present). Diagnoses were validated by cross-sectional microhardness profiling in the test areas of the approximal surfaces. Interobserver agreement was analysed using kappa statistics. Accuracy was estimated by the areas under the receiver operating characteristic curves (Az), which were compared using the Kruskal-Wallis test (α = 5%).

RESULTS

Interobserver agreement was higher for CBCT (κ = 0.7-0.8), followed by sharpen-filtered (κ = 0.6-0.7) and original (κ = 0.5-0.6) images. CBCT presented the highest accuracy value (Az = 0.897) compared with the original (Az = 0.792) and sharpen-filtered (Az = 0.712) images. However, no statistical differences were observed between the imaging modalities (p = 0.0794).

CONCLUSIONS

It can be concluded that PSP radiographs with or without using the sharpen filter and the CBCT images may be useful adjuncts for detecting subtle approximal enamel demineralization.

Length of endodontic files measured in digital radiographs with and without noise-suppression filters: an ex-vivo study

OBJECTIVES

The aim of this study is to evaluate if theoretically possible edge shifts induced by noise-suppression filters potentially occur on objects found in digital radiographs. Most manufacturers carry out noise-suppression filtering of their images before they are displayed to the user. It is not usually possible for the user to disrupt the function of the filters. The use of these filters can lead to deletion of small image structures.

METHODS

K-files (ISO size 06, 08, 10 and 15) were placed in the root canals of 6 human teeth located in cadaver jaw segments. File tip positions were measured on original and filtered digital images by three observers. The file position was marked on each filtered image and compared with the unfiltered ones.

RESULTS

The 5 × 5 pixel-sized median and mean filters caused the largest underestimation of measured lengths between -7.87 pixels and -10.8 pixels (-306.93 μm and -421.2 μm). Maximum standard deviation for length differences was found for the calculated position ( = gold standard) and the original unfiltered images with 13.31 pixels. The standard deviation found for the 5 × 5 mean and median filter was 7.62 pixels and 8.68 pixels.

CONCLUSION

Different studies showed that noise-suppression filters can induce edge shifts in diagnostic radiographs. The high standard deviations found for length differences between the defined gold-standard and the original images indicate that theoretical edge shifts may not be clinically relevant for length measurements of endodontic files.

Gray Value Differences to Dentin of Root Posts Radiographed with Digital Intraoral Systems and Conventional X-ray Films

Digital radiographs often provide significantly higher gray value differences between root posts and root dentin than conventional x-ray films.

The influence of bonding agents on the decision to replace composite restorations

This in vitro study evaluated the validity of the decision to replace of a restoration based upon the radiolucent zone beneath a resin composite.

MATERIALS AND METHODS

Class II cavities were prepared on the approximal surfaces of 40 molars. The teeth were divided into four groups. Clearfil SE Bond, PQ1 or Single Bond was applied in the experimental groups. No bonding agent was used in the control group. Following the restorations, digital radiographs were obtained and independently evaluated by two oral radiologists and two specialists in restorative dentistry to determine the need for replacement. The coronal portions of the teeth were then sectioned and the interfaces between the restorations and cavity walls were examined using an optical light microscope. Possible adhesive pooling and voids were examined under a light microscope. Inter-examiner reliability was evaluated with the Cohen's kappa (kappa) test. Sensitivity, specificity and negative and positive predictive values were calculated. Kruskal-Wallis, followed by the Mann-Whitney U-test, determined differences among the pooling thicknesses of the different adhesives.

RESULTS

Various sensitivity and specificity degrees were obtained from the groups in which different adhesive systems were used. The PQ1 adhesive system was the best for identifying well-adapted restorations with the highest true non-replacement diagnosis (TND = 0.70). Clearfil SE Bond had the highest false positive scores. Adhesive pooling was significantly different in the experimental groups of the current study (p < 0.05).

CONCLUSION

Replacement decisions for a resin composite restoration based upon digital images frequently resulted in false-positive or negative decisions.

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.

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.

Noise in subtraction images made from pairs of intraoral radiographs: a comparison between four methods of geometric alignment

OBJECTIVES

To compare noise levels in subtraction images produced by four methods of geometric alignment.

METHODS

50 pairs of intraoral radiographs (Digora Optime; Soredex, Tuusula, Finland) were used in this study. Two programs were used to correct geometric differences: ToothVis 1.4 (TV) and DentalStudio 2.0 (DS). Three reference points were manually positioned in both programs (methods 1 and 2); four (method 3) and ten (method 4) reference points were positioned within TV in each of the 50 pairs of images. The standard deviation (SD) of the histogram defining the distribution of grey shades in the subtraction image was used as the statistical parameter for evaluation of homogeneity, i.e. the noise in the subtracted images.

RESULTS

The mean and median shade of grey values were lower for images after geometric correction in TV (126.6\126.8, 126.9\126.8 and 126.1\126.7, for three- four- and ten-point alignment, respectively) than those performed with the positioning module of DS (128.7\127.5) (P<0.05). For the SD, the mean values were significantly lower with TV (4.6, 4.0 and 3.3 for three-, four- and ten-point alignment, respectively) than with DS (6.8). The range of SD values was the largest for four-point alignment with TV (0.7-15.4), smaller for three-point alignment with DS (1.5-15.4) and three-point alignment with TV (0.5-13), and the smallest with ten-point alignment in TV (0.5-8.7).

CONCLUSIONS

The SD of the grey-shade histogram showed that subtraction images produced with ToothVis 1.4 software were statistically less noisy than images produced with Dental Studio 2.0 software. There is a relationship between the number of reference points chosen and the noise in the subtraction images.

Digital radiography in general dental practice: a field study

OBJECTIVES

The aim of this study was to conduct a field study to survey the performance of digital radiography and how it was used by dentists in general dental practice.

METHODS

19 general dental practitioners were visited at their clinics. Ambient light (illuminance) was measured in the rooms where the monitors were placed. Different technical display parameters were noted. Test images and two phantoms--one low-contrast phantom and one line-pair resolution phantom--were used to evaluate the digital system. How the dentists used the enhancement program was investigated by noting which functions were used.

RESULTS

Average illuminance in the operating room was 668 lux (range 190-1250 lux). On radiographs of the low-contrast phantom taken at the clinic, the ability to observe the holes decreased as illuminance increased. On average, the "light percentage" initially set on the monitor had to be decreased by 17% and contrast by 10% to optimize the display of the test images. The general dental practitioners used the enhancement programs most often to alter brightness and contrast to obtain the subjectively best image. Large differences between the clinics were noted.

CONCLUSION

Knowledge of how to handle digital equipment in general dental practice should be improved. A calibrated monitor of good quality should be a given priority, as should proper ambient light conditions. There is a need to develop standardized quality controls for digital dental radiography.

Morphometric analysis of experimentally induced periapical lesions: radiographicvshistopathological findings

OBJECTIVES

To evaluate the accuracy and reliability of conventional (Kodak Ektaspeed Plus film) and digitized radiographic images to detect the presence as well to estimate the size, as measured by an image analysis programme, of periapical radiolucencies induced in dog teeth in comparison with the histomorphometric data obtained from the same lesions by conventional and fluorescence microscopy.

METHOD

After the removal of pulp, the root canals of five premolars from the same animal were left exposed for 7 days after which they were sealed for 60 days. At day 53, three more premolars were opened and left exposed to the oral cavity for 7 days. Intact premolars were used as control. Conventional radiographs were taken at day 0, day 7, day 30, day 45 and day 60. Morphometry in digitized radiographic images and histological sections were compared at day 7 and day 60 after setting the experimental series.

RESULTS

Radiographically, periapical lesions were only detected 30 days after coronal sealing. A progressively increasing radiolucent lesion area was observed at day 45 and day 60. Histopathologically, 7 days after pulp removal dense inflammatory infiltrate and root resorption in the periapical region was observed. At day 7 and day 60, the lesion sizes were similar when evaluated by both conventional and fluorescence microscopy. Lesion size was about 20% larger in digitized radiographs in comparison with histological measurements.

CONCLUSIONS

Although image digitization could not improve the detection of the early stages of periapical lesions, it provides a valuable quantitative assessment of extensive periapical lesions. In addition, fluorescence light microscopy enhances the visualization of the apical and periapical structures and seems to be a highly useful tool for histological evaluation, valuable for both qualitative and quantitative studies of periapical disease.

Clinical efficacy of a new software developed for dental digital subtraction radiography

OBJECTIVES

The aim of this study was to test and compare the efficacy of software developed recently for digital subtraction radiography (DSR) in vivo.

METHODS

An algorithm performing both manual and automated image reconstructions and contrast correction was developed for the manipulation of radiographic images. Pre- and post-operative radiographic images of ten patients were obtained and the automated subtraction analyses were performed using four different softwares (new software, Emago, Photoshop 8.0 and Paintshop Pro 9). Ten experienced dental specialists evaluated the clinical efficacy of each program and scored the softwares by using visual analogue scales (VAS). The results were statistically analysed and alpha was set as 0.05.

RESULTS

The newly developed algorithm received higher scores than the others (new software =67.89, Emago = 64.26, Paintshop Pro 9 = 33.41 and Photoshop 8.0 = 27.24, respectively). The clinical efficacies of the new software and Emago were not significantly different (P = 0.720); likewise, Photoshop 8.0 and Paintshop Pro 9 performed comparably (P = 0.295).

CONCLUSIONS

Considering this study, the new software and Emago would be suggested for DSR in dental practice.

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.

Accuracy and precision of a densitometric tool for jaw bone

OBJECTIVES

To develop a digital densitometric tool for jaw bone to analyse intraoral radiographs. To assess precision and accuracy for this tool and determine the minimal detection threshold for density changes.

METHODS

Bone samples deriving from the premolar region of 47 human mandibles were selected for analysis. The samples were obtained from adult cadavers in the department of anatomy (Faculty of Medicine, KULeuven) with ethical approval. Digital radiography was performed on all bone samples. Direct volumetric measurements served as gold standard density values and allowed determination of accuracy. Dual-energy X-ray absorptiometry (DXA) scans were performed on all specimens. For all radiographs, density in mm Al eq was calculated using custom-made software, Osteop. Precision and intraobserver and interobserver reliability of this method were assessed. The bone specimens were progressively decalcified. At standard time intervals the percentage of decalcification was calculated. At each decalcification step, radiographs were taken and analysed.

RESULTS

CV was always lower than 3%, which points to a good precision of the method. Correlation between the density measurements in mm Al eq and the DXA results was 0.9, for the density measurements in mm Al eq and the direct density measurements r was 0.5. The custom-made software was able to detect a change in bone mineralization of 6.6%.

CONCLUSIONS

The present method for bone densitometric analysis offers potentials for clinical evaluation of bone density and minute bone density changes in the jaw bone.

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.

Sliding window adaptive histogram equalization of intraoral radiographs: effect on image quality

OBJECTIVES

To investigate whether contrast enhancement by non-interactive, sliding window adaptive histogram equalization (SWAHE) can enhance the image quality of intraoral radiographs in the dental clinic.

METHODS

Three dentists read 22 periapical and 12 bitewing storage phosphor (SP) radiographs. For the periapical readings they graded the quality of the examination with regard to visually locating the root apex. For the bitewing readings they registered all occurrences of approximal caries on a confidence scale. Each reading was first done on an unprocessed radiograph ("single-view"), and then re-done with the image processed with SWAHE displayed beside the unprocessed version ("twin-view"). The processing parameters for SWAHE were the same for all the images.

RESULTS

For the periapical examinations, twin-view was judged to raise the image quality for 52% of those cases where the single-view quality was below the maximum. For the bitewing radiographs, there was a change of caries classification (both positive and negative) with twin-view in 19% of the cases, but with only a 3% net increase in the total number of caries registrations. For both examinations interobserver variance was unaffected.

CONCLUSIONS

Non-interactive SWAHE applied to dental SP radiographs produces a supplemental contrast enhanced image which in twin-view reading improves the image quality of periapical examinations. SWAHE also affects caries diagnosis of bitewing images, and further study using a gold standard is warranted.

Noise in subtraction images made from pairs of bitewing radiographs: a comparison between two subtraction programs

OBJECTIVES

To compare noise in subtraction images produced by two subtraction programs.

METHODS

Twenty-five pairs of bitewing radiographs exposed under clinical conditions were subtracted using two digital subtraction programs: X-PoseIt (XP) software and EMAGO/Advanced 3.43 (EM) software. Four reference points were located between the mesial surface of the upper first premolar and the distal surface of the upper first molar (the region of interest) on the same anatomical structures using XP and EM. The standard deviation (SD) of the histogram defining the distribution of the shades of grey in the region of interest was used as the statistical parameter for comparing noise in the subtraction images created by the two subtraction programs.

RESULTS

The mean and median grey shade value was lower with EM software (126.9, 126) than with XP software (128.3, 128) (P < 0.05). For the SD, the mean value was significantly lower with XP (6.2) than with EM (7.8) (P < 0.05). The range of the SD values was larger for EM (3.6-12.8) than XP (3.3-9.9).

CONCLUSIONS

The standard deviation of the grey shade histogram showed that subtraction images produced with X-PoseIt software were statistically less noisy than images produced with EMAGO/Advanced 3.43 software.

Conventional radiographsvsdigitized radiographs: image quality assessment

OBJECTIVES

The aim of this study was to compare image quality characteristics of conventional radiographs and their digital counterparts.

METHODS

100 conventional radiographs (E-speed) were used for the evaluation of density and contrast. The radiographs were made using a range of exposures under standardized conditions and were compared with digital images that resulted from scanning the above radiographs with a commercially available scanner. Resolution was evaluated with an experiment using 50 film packets and a resolution target exposed with different exposure times, using both the original radiographs and their scanned equivalents.

RESULTS

The digitized radiographs appeared to be of higher density than the conventional ones. Moreover, they demonstrated a narrower density range. Resolution was similar for both types of images.

CONCLUSIONS

Although there is an agreement with the literature that the digitized radiographs are of higher density, further investigation is required to detect the various factors that may have an effect on the quality of the digitized images.

Filmless imaging

BACKGROUND

As use of digital radiography becomes more common, many dentists are wondering if and how they can replace conventional film-based imaging with a digital system. This article briefly describes the different technologies used for digital radiography in dentistry. The article provides general practitioners with a broad overview of the benefits and limitations of digital radiography to help them understand the role the technology can play in their practices.

OVERVIEW

The two technologies now available are solid-state systems and phosphor plate systems. Each has its strong points, and the choice of which to use depends on the type of dental practice. Image processing improves the diagnostic quality of the radiographic information. Advanced image-processing techniques, such as subtraction radiography, are available for specialized clinics.

CONCLUSIONS AND CLINICAL IMPLICATIONS

Digital radiography no longer is an experimental modality. It is a reliable and versatile technology that expands the diagnostic and image-sharing possibilities of radiography in dentistry. Optimization of brightness and contrast, task-specific image processing and sensor-independent archiving are important advantages that digital radiography has over conventional film-based imaging.

The effects of incremental brightness and contrast adjustments on radiographic data: a quantitative study

OBJECTIVES

To determine the border level of brightness and contrast changes in order to prevent the loss of originality of the quantitative data on digital dental radiographs.

METHODS

After measuring the baseline mean grey values (MGVs) of a fixed region of interest on the alveolar bone and an aluminium step wedge, incremental brightness and contrast adjustments were performed on a digital periapical radiograph. The distribution of the data was analysed to investigate the significance of the changes on radiodensitometric data after incremental increase of brightness and contrast.

RESULTS

The original MGVs were easily retrieved after brightness adjustments; however, the contrast increase led to more complicated density changes. The originality of the data was saved up to 50 units of contrast increase, but further than this limit, significant radiodensitometric changes occurred.

CONCLUSIONS

Contrast adjustments should be performed cautiously when making quantitative analyses on the digital radiographs.

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.

Comparative investigation of subjective image quality of digital intraoral radiographs processed with 3 image-processing algorithms

OBJECTIVE

To evaluate the subjective diagnostic image quality of clinical digital intraoral radiographs processed with 3 different image-processing algorithms.

STUDY DESIGN

One hundred digital intraoral radiographs were collected and subsequently processed in 3 sets. In the first set the radiographs were processed for correction for attenuation and visual response. In the second set the radiographs were processed with the same algorithms but with an additional shift in gray levels so that the average brightness of a region of interest was displayed with the mean brightness of the computer monitor. In the third, the radiographs were processed with the default gamma-correction in the Dimaxis program (Planmeca Oy, Helsinki, Finland). The 3 radiographs that were differently processed from the same original were displayed simultaneously on the computer monitor. Ten observers evaluated subjectively all the radiographs according to the portrayal of normal structures under the same viewing conditions. Five of them performed repeated evaluations of 20 of the 100 radiographs 2 months later.

RESULTS

The best subjective diagnostic quality was found for the radiographs processed with the new algorithms plus an additional shift in gray levels. Radiographs processed with the new algorithms were preferred when compared with those processed with the default gamma-correction. The differences between the 3 types of radiographs were significant (P <.0001). No significant intraobserver differences were found (P=.5487).

CONCLUSION

Radiographs processed for correction for attenuation and visual response might be beneficial in clinical work. Clinical radiographs processed with the new algorithms plus an additional shift in gray levels further improve the subjective impression of normal structures.