Detection of artificially induced vertical radicular fractures using tuned aperture computed tomography

A perspective on the diagnosis of cracked tooth: imaging modalities evolve to AI-based analysis

Despite numerous clinical trials and pre-clinical developments, the diagnosis of cracked tooth, especially in the early stages, remains a challenge. Cracked tooth syndrome is often accompanied by dramatic painful responses from occlusion and temperature stimulation, which has become one of the leading causes for tooth loss in adults. Current clinical diagnostical approaches for cracked tooth have been widely investigated based on X-rays, optical light, ultrasound wave, etc. Advances in artificial intelligence (AI) development have unlocked the possibility of detecting the crack in a more intellectual and automotive way. This may lead to the possibility of further enhancement of the diagnostic accuracy for cracked tooth disease. In this review, various medical imaging technologies for diagnosing cracked tooth are overviewed. In particular, the imaging modality, effect and the advantages of each diagnostic technique are discussed. What's more, AI-based crack detection and classification methods, especially the convolutional neural network (CNN)-based algorithms, including image classification (AlexNet), object detection (YOLO, Faster-RCNN), semantic segmentation (U-Net, Segnet) are comprehensively reviewed. Finally, the future perspectives and challenges in the diagnosis of the cracked tooth are lighted.

Characterization and preliminary imaging evaluation of a clinical prototype stationary intraoral tomosynthesis system

PURPOSE

Technological advancements in dental radiography have improved oral care on many fronts, yet diagnostic efficacy for some of the most common oral conditions, such as caries, dental cracks and fractures, and periodontal disease, remains relatively low. Driven by the clinical need for a better diagnostic yield for these and other dental conditions, we initiated the development of a stationary intraoral tomosynthesis (s-IOT) imaging system using carbon nanotube (CNT) x-ray source array technology. Here, we report the system characterization and preliminary imaging evaluation of a clinical prototype s-IOT system approved for human use.

METHODS

The clinical prototype s-IOT system is comprised of a multibeam CNT x-ray source array, high voltage generator, control electronics, collimator cone, and dynamic digital intraoral detector. During a tomosynthesis scan, each x-ray source is operated sequentially at fixed, nominal tube current of 7 mA and user-specified pulse width. Images are acquired by a digital intraoral detector and the reconstruction algorithm generates slice information in real time for operator review. In this study, the s-IOT system was characterized for tube output, dosimetry, and spatial resolution. Manufacturer specifications were validated, such as tube current, kVp, and pulse width. Tube current was measured with an oscilloscope on the analog output of the anode power supply. Pulse width, kVp, and peak skin dose were measured with a dosimeter with ion chamber and high voltage accessory. In-plane spatial resolution was evaluated via measurement of MTF and imaging of a line pair phantom. Spatial resolution in the depth direction was evaluated via artifact spread measurement. The size of the collimated radiation field was evaluated for compliance with FDA regulations. A dental phantom and human specimens of varying pathologies were imaged on a clinical 2D intraoral imaging system as well as s-IOT for comparison and to explore potential clinical applications.

RESULTS

The measured tube current, kVp, and pulse width values were within 3% of the set values. A cumulative peak skin dose of 1.12 mGy was measured for one complete tomosynthesis scan using a 50-ms pulse per projection view. Projection images and reconstruction slices revealed MTF values ranging from 8.1 to 9.3 cycles/mm. Line pair imaging verified this result. The radiation field was found to meet the FDA requirements for intraoral imaging devices. Tomosynthesis reconstruction slice images of the dental phantom and human specimens provided depth resolution, allowing visibility of anatomical features that cannot be seen in the 2D intraoral images.

CONCLUSIONS

The clinical prototype s-IOT device was evaluated and found to meet all manufacturer specifications. Though the system capability is higher, initial investigations are targeting a low-dose range comparable to a single 2D radiograph. Preliminary studies indicated that s-IOT provides increased image quality and feature conspicuity at a dose comparable to a single 2D intraoral radiograph.

Detection of vertical root fractures in intact and endodontically treated premolar teeth by designing a probabilistic neural network: an ex vivo study

OBJECTIVES

Detection of vertical root fractures (VRFs) in their initial stages is a crucial issue, which prevents the propagation of injury to the adjacent supporting structures. Designing a suitable neural network-based model could be a useful method to diagnose the VRFs. The aim of this study was to design a probabilistic neural network (PNN) to diagnose the VRFs in intact and endodontically treated teeth of periapical and CBCT radiographs. Also, we have compared the efficacy of these two imaging techniques in the detection of VRFs.

METHODS

A total of 240 radiographs of teeth (120 radiographs of teeth with no VRFs and 120 teeth with vertical fractures, with half of the teeth in each category treated endodontically and the remaining half intact, i.e. not endodontically treated) were used in 3 groups for training and testing of the neural network as follows: Group 1, 180/60; Group 2, 120/120; and Group 3, 60/180. First, Daubechies 3 wavelet was applied to acquire the image analysis coefficients on two planes; then Gabor filters were used to extract the image characteristics, which were used to educate the PNN. The designed neural network was able to diagnose and classify teeth with and without VRFs. In addition, in order to determine the best training and test sets in the network, the variance of the function of network changes was manipulated at a range of 0-1 and the results were assessed in terms of the parameters evaluated, including sensitivity, specificity and accuracy.

RESULTS

In the periapical radiographs, the maximum accuracy, sensitivity and specificity values in the three groups were 70.00, 97.78 and 67.7%, respectively. These values in the CBCT images were 96.6, 93.3 and 100%, respectively, at the variance change range of 0.1-0.65.

CONCLUSIONS

The designed neural network can be used as a proper model for the diagnosis of VRFs on CBCT images of endodontically treated and intact teeth; in this context, CBCT images are more effective than similar periapical radiographs. Limitations of this study are the use of sound one-rooted premolar teeth without carious lesions and dental fillings and not simulating the adjacent anatomic structures. Further in vitro work using a full-skull simulation for CBCT and skin/bone simulation is needed.

Effect of Time Lapse on the Diagnostic Accuracy of Cone Beam Computed Tomography for Detection of Vertical Root Fractures

Accurate and early diagnosis of vertical root fractures (VRFs) is imperative to prevent extensive bone loss and unnecessary endodontic and prosthodontic treatments. The aim of this study was to assess the effect of time lapse on the diagnostic accuracy of cone beam computed tomography (CBCT) for VRFs in endodontically treated dog's teeth. Forty-eight incisors and premolars of three adult male dogs underwent root canal therapy. The teeth were assigned to two groups: VRFs were artificially induced in the first group (n=24) while the teeth in the second group remained intact (n=24). The CBCT scans were obtained by NewTom 3G unit immediately after inducing VRFs and after one, two, three, four, eight, 12 and 16 weeks. Three oral and maxillofacial radiologists blinded to the date of radiographs assessed the presence/absence of VRFs on CBCT scans. The sensitivity, specificity and accuracy values were calculated and data were analyzed using SPSS v.16 software and ANOVA. The total accuracy of detection of VRFs immediately after surgery, one, two, three, four, eight, 12 and 16 weeks was 67.3%, 68.7%, 66.6%, 64.6%, 64.5%, 69.4%, 68.7%, 68% respectively. The effect of time lapse on detection of VRFs was not significant (p>0.05). Overall sensitivity, specificity and accuracy of CBCT for detection of VRFs were 74.3%, 62.2%, 67.2% respectively. Cone beam computed tomography is a valuable tool for detection of VRFs. Time lapse (four months) had no effect on detection of VRFs on CBCT scans.

Detection of artificially induced vertical root fractures of different widths by cone beam computed tomography in vitro and in vivo

AIMS

To compare the diagnostic accuracy of cone beam computed tomography (CBCT) for the detection of artificially induced vertical root fractures (VRFs) of different widths in vitro and in vivo.

METHODOLOGY

Vertical root fractures were induced in 25 extracted nonendodontically treated single-rooted human teeth (maxillary first premolars, maxillary canines and mandibular incisors). Twenty teeth without VRFs served as a control group. CBCT scanning (3D Accuitomo 170) was performed in vitro and in vivo. For the in vivo scanning, teeth were autoclaved, embedded into bite plates, placed in sterile plastic bags and then inserted into the mouths of volunteers. Teeth with VRFs were sectioned into axial slices and examined using a stereomicroscope to measure the widths of the VRFs. Five observers assessed the presence of VRFs using axial CBCT. Values for sensitivity, specificity, accuracy and interexaminer agreement were calculated.

RESULTS

The accuracy, specificity and sensitivity of CBCT were significantly higher in vitro than in vivo for VRFs with widths 50-150 μm (P < 0.05). The sensitivity and accuracy of CBCT were significantly higher for the detection of VRFs with widths greater than 150 μm in vivo and in vitro (P < 0.05). The accuracy of CBCT in vivo was 0.29 and 0.8 for fracture widths ranging from 50 to 150 μm and wider than 150 μm, respectively. No significant differences in CBCT specificity were found between VRF widths both in vitro and in vivo. The interexaminer reliability of the raters revealed a kappa value of 0.72, demonstrating substantial agreement.

CONCLUSION

The detectability of VRFs by CBCT in vitro and in vivo was dependent upon fracture width. The accuracy of CBCT in detecting VRFs of 50-300 μm width in vivo was significantly lower compared to the in vitro accuracy.

Stationary intraoral digital tomosynthesis using a carbon nanotube X-ray source array

OBJECTIVES

Intraoral dental tomosynthesis and closely related tuned-aperture CT (TACT) are low-dose three-dimensional (3D) imaging modalities that have shown improved detection of multiple dental diseases. Clinical interest in implementing these technologies waned owing to their time-consuming nature. Recently developed carbon nanotube (CNT) X-ray sources allow rapid multi-image acquisition without mechanical motion, making tomosynthesis a clinically viable technique. The objective of this investigation was to evaluate the feasibility of and produce high-quality images from a digital tomosynthesis system employing CNT X-ray technology.

METHODS

A test-bed stationary intraoral tomosynthesis unit was constructed using a CNT X-ray source array and a digital intraoral sensor. The source-to-image distance was modified to make the system comparable in image resolution to current two-dimensional intraoral radiography imaging systems. Anthropomorphic phantoms containing teeth with simulated and real caries lesions were imaged using a dose comparable to D-speed film dose with a rectangular collimation. Images were reconstructed and analysed.

RESULTS

Tomosynthesis images of the phantom and teeth specimen demonstrated perceived image quality equivalent or superior to standard digital images with the added benefit of 3D information. The ability to "scroll" through slices in a buccal-lingual direction significantly improved visualization of anatomical details. In addition, the subjective visibility of dental caries was increased.

CONCLUSIONS

Feasibility of the stationary intraoral tomosynthesis is demonstrated. The results show clinical promise and suitability for more robust observer and clinical studies.

A new classification of endodontic-periodontal lesions

The interrelationship between periodontal and endodontic disease has always aroused confusion, queries, and controversy. Differentiating between a periodontal and an endodontic problem can be difficult. A symptomatic tooth may have pain of periodontal and/or pulpal origin. The nature of that pain is often the first clue in determining the etiology of such a problem. Radiographic and clinical evaluation can help clarify the nature of the problem. In some cases, the influence of pulpal pathology may cause the periodontal involvement and vice versa. The simultaneous existence of pulpal problems and inflammatory periodontal disease can complicate diagnosis and treatment planning. An endo-perio lesion can have a varied pathogenesis which ranges from simple to relatively complex one. The differential diagnosis of endodontic and periodontal diseases can sometimes be difficult, but it is of vital importance to make a correct diagnosis for providing the appropriate treatment. This paper aims to discuss a modified clinical classification to be considered for accurately diagnosing and treating endo-perio lesion.

Influence of cone beam CT enhancement filters on diagnosis ability of longitudinal root fractures

OBJECTIVES

To determine whether cone beam CT (CBCT) enhancement filters influence the diagnosis of longitudinal root fractures.

METHODS

40 extracted human posterior teeth were endodontically prepared, and fractures with no separation of fragments were made in 20 teeth of this sample. The teeth were placed in a dry mandible and scanned using a Classic i-CAT® CBCT device (Imaging Sciences International, Inc., Hatfield, PA). Evaluations were performed with and without CBCT filters (Sharpen Mild, Sharpen Super Mild, S9, Sharpen, Sharpen 3 × 3, Angio Sharpen Medium 5 × 5, Angio Sharpen High 5 × 5 and Shadow 3 × 3) by three oral radiologists. Inter- and intraobserver agreement was calculated by the kappa test. Accuracy, sensitivity, specificity and positive and negative predictive values were determined. McNemar test was applied for agreement between all images vs the gold standard and original images vs images with filters (p < 0.05).

RESULTS

Means of intraobserver agreement ranged from good to excellent. Angio Sharpen Medium 5 × 5 filter obtained the highest positive predictive value (80.0%) and specificity value (76.5%). Angio Sharpen High 5 × 5 filter obtained the highest sensitivity (78.9%) and accuracy (77.5%) value. Negative predictive value was the highest (82.9%) for S9 filter. The McNemar test showed no statistically significant differences between images with and without CBCT filters (p > 0.05).

CONCLUSIONS

Although no statistical differences was observed in the diagnosis of root fractures when using filters, these filters seem to improve diagnostic capacity for longitudinal root fractures. Further in vitro studies with endodontic-treated teeth and research in vivo should be considered.

Cracked tooth: a report of two cases and role of cone beam computed tomography in diagnosis

Cracked tooth is a distinct type of longitudinal tooth fracture which occurs very commonly and its diagnosis can be challenging. This type of fracture tends to grow and change over time. Clinical diagnosis is difficult because the signs and symptoms are variable or nonspecific and may even resemble post-treatment disease following root canal treatment or periodontal disease. This variety and unpredictability make the cracked tooth a challenging diagnostic entity. The use of cone beam computed tomography (CBCT) in diagnosis of complex endodontic cases has been well documented in the literature. In this paper we present two cases of cracked tooth and emphasise on the timely use of cone beam computed tomography as an aid in diagnosis and as a prognostic determinant.

Assessment of vertical root fractures using three imaging modalities: cone beam CT, intraoral digital radiography and film

OBJECTIVES

The aim of this study was to assess the accuracy of cone beam CT (CBCT) in detecting vertical root fractures and to compare the accuracy with images from an intraoral sensor and from conventional intraoral film.

METHODS

60 extracted, single-rooted human teeth were divided equally into two groups: a control group of 30 teeth and an induced fracture group of 30 teeth. All teeth were randomly placed into sockets in six dry mandibles. Each tooth was imaged by three modalities: CBCT, intraoral digital radiography and intraoral F-speed film. Three beam angulations (an orthogonal projection and additional projections with ± 20° horizontal shifts of the central ray) were used when radiographs were made using film and a digital sensor. Three oral and maxillofacial radiologists evaluated the presence of root fractures twice in each image modality using a five-point confidence rating scale. Areas under receiver operating characteristic curves (A(z)) were computed for each observer and modality and were tested for statistical differences using the Kruskal-Wallis test.

RESULTS

There was no statistical difference in the performance of the three modalities (mean of A(z) values: CBCT = 0.811, film = 0.797 and sensor = 0.775; p = 0.771).

CONCLUSIONS

There was no significant difference between intraoral film, a high-resolution complementary metal oxide semiconductor digital imaging system and CBCT in detecting vertical root fractures in mandibular single-rooted teeth.

Value of cone beam CT in detection of dental root fractures

OBJECTIVE

The primary objective of this investigation was to evaluate the detection of root fracture using cone beam CT (CBCT) images and compare these findings with real samples of extracted teeth. A second aim was to determine the importance of reconstructed images in the diagnosis of root fracture.

METHODS

Conventional periapical radiographs and CBCT images of 10 cases, each with a suspected diagnosis of root fracture, were evaluated in accordance with a pre-established scoring system by a maxillofacial radiologist who was unaware of the clinical symptoms of the patients. Then, the radiologist and an endodontist, aware of patient symptomatology, performed a second evaluation by cross-comparison of these images with clinical findings. Final patient results were based on direct visualization of each extracted tooth and its colourization.

RESULTS

CBCT shows good potential for use in the detection of root fracture as it ensures a high level of diagnostic score accuracy. Reconstructed axial views were more effective in confirming specific diagnoses than other reconstructed views. Combining the clinical and radiographic findings further improved the results.

CONCLUSIONS

CBCT can be an ideal alternative in the diagnosis of root fracture in the field of endodontics. This option may also increase assurance of dentists and oral surgeons obtaining an accurate diagnosis of their patients' problems and help decrease the potential failure of treatment and/or the prescription of unwarranted dental procedures.

Detection of experimentally induced root fractures on digital and conventional radiographs: an in vitro study

This study compared the diagnostic accuracy of digital radiographic images with conventional radiographs for the detection of experimentally induced root fractures. Horizontal fractures were induced by a mechanical force to the root of 15 single rooted teeth. Vertical fractures were induced in 15 single rooted teeth and 15 molars, respectively, by disk cutting. The teeth were mounted in dried mandibles and were radiographed with the parallel technique using a CCD-based Planmeca imaging system and F-speed films. Seven observers recorded their findings and then 2 pairs of them examined the same images together. Az values expressed the diagnostic accuracy of the imaging systems and the degree of agreement was estimated using the Cohen's kappa statistic. The areas under the ROC curves (Az) in single rooted teeth were 0.61 for conventional radiography and 0.64 for digital radiography. Digital imaging system did not perform significantly better than conventional one (p > 0.01). Digital radiographs (Az: 0.72) provided higher detection accuracy in molars than conventional images (Az: 0.51) (p = 0.0102). The digital images scored higher kappa values with narrower range than conventional. Observers in pairs did not perform significantly better than individually. The results were not affected by the observers but were affected by the cases (p < 0.001). Digital images were equivalent to F-speed films for the detection of root fractures in single rooted teeth. The digital system performed significantly better than the conventional in detecting root fractures in molars.

Detection of vertical root fractures by using cone-beam computed tomography: a clinical study

INTRODUCTION

Vertical root fractures of teeth (VRFs) often pose a diagnostic dilemma because of the difficulty in detection of these in intraoral radiographs except in certain cases with very distinct clinical findings. This often leads to unwarranted extraction of the tooth. Cone-beam computed tomography (CBCT) produces three-dimensional images and allows precise visualization and evaluation of VRFs or cracks in extracted teeth, as reported previously. This clinical pilot study was designed to determine the diagnostic accuracy of noninvasive CBCT for detection of suspected VRFs in endodontically treated teeth by using exploratory surgery to confirm the presence or absence of a fracture.

METHODS

Thirty-two teeth in 29 patients with clinical signs and symptoms suggestive of VRF were included in the study after informed consent was obtained. They underwent a limited area CBCT evaluation. All CBCT studies were blinded, and 2 board-certified oral and maxillofacial radiologists assessed the presence or absence of VRF through sequential evaluation of the three-dimensional volume. Subjects underwent surgical exploration as part of treatment, which helped establish the presence or absence of VRF.

RESULTS

Pearson correlation coefficient by using surgical finding to confirm presence/absence of fracture was 0.602, positive predictive value was 91%, and negative predictive value was 67%. The sensitivity was 88%, and specificity was 75%.

CONCLUSIONS

This study revealed the superior diagnostic accuracy of CBCT for detection of VRF.

Effectiveness of limited cone-beam computed tomography in the detection of horizontal root fracture

To compare the diagnostic accuracy of conventional film radiography, charge coupled device (CCD) and photostimulable phosphor plate (PSP) digital images and limited cone-beam computed tomography in detecting simulated horizontal root fracture. Root fractures were created in the horizontal plane in 18 teeth by a mechanical force and fragments were relocated. Another 18 intact teeth with no horizontal root fracture served as a control group. Thirty-six teeth were placed in the respective empty maxillary anterior sockets of a human dry skull in groups three by three. Intraoral radiographs were obtained in three different vertical views by utilizing Eastman Kodak E-speed film, CCD sensor, RVG 5.0 Trophy and a PSP sensor Digora, Optime. Cone beam CT images were taken with a unit (3D Accuitomo; J Morita MFG. Corp, Kyoto, Japan). Three dental radiologists separately examined the intraoral film, PSP, CCD and cone beam CT images for the presence of horizontal root fracture. Specificity and sensitivity for each radiographic technique were calculated. Kappa statistics was used for assessing the agreement between observers. Chi-square statistics was used to determine whether there were differences between the systems. Results were considered significant at P < 0.05. Cone beam CT images revealed significantly higher sensitivities (P < 0.05) than the intraoral systems between which no significant differences were found. Specificities did not show any statistically significant differences between any of the four systems. The kappa values for inter-observer agreement between observers (four pairs) ranged between 0.82-0.90 for the 3DX evaluations and between 0.63-0.71 for the different types of intraoral images. Limited cone beam CT, outperformed the two-dimensional intraoral, conventional as well as digital, radiographic methods in detecting simulated horizontal root fracture.

Use of cone-beam volumetric tomography in the diagnosis of root fractures

OBJECTIVES

The diagnosis of root fractures by conventional radiographs is still difficult because of limitations of 2D images. Cone-beam volumetric tomography improves the diagnosis capacity in dentistry, such as increased radiation dose to the patient and presence of artifacts on the image.

STUDY DESIGN

This study compared the images obtained on conventional periapical radiographs and 3D scans (Accuitomo 3DX) for the diagnosis of root fractures. Twenty patients with suspected root fractures were submitted to examination by periapical radiography and CBCT. Two professionals, unaware of the symptomatology, examined these radiographs and CBCT images according to pre-established scores, which were later checked against the signs and symptoms.

RESULTS

The results revealed statistical difference for cone-beam volumetric tomography compared with conventional radiographs in the diagnosis of root fractures.

CONCLUSION

It could be concluded that cone-beam volumetric tomography was better than conventional radiography in the diagnosis of root fractures, thereby constituting an excellent alternative for diagnosis in general practice.

Comparison of digital with conventional radiography in detection of vertical root fractures in endodontically treated maxillary premolars: an ex vivo study

OBJECTIVE

The purpose of the present study was to compare the diagnostic ability of conventional intraoral film radiography and a charged-coupled device (CCD) sensor in detecting vertical root fractures (VRF) in endodontically treated single-rooted extracted human maxillary premolars.

STUDY DESIGN

The study consisted of 60 extracted single-rooted endodontically treated maxillary premolars: 30 with clinically confirmed VRF (experimental group) and 30 with no VRF (control group). An intraoral CCD sensor and conventional Kodak Insight Film were used. Two observers evaluated the digital and conventional radiographs twice with an interval of 4 weeks. Specificity and sensitivity for each radiographic technique were calculated and subjected to statistical analysis. Kappa values were calculated for intra- and interobserver agreement. Fisher's exact test was used to evaluate detection of VRF. The overall differences in sensitivity and specificity between radiographic techniques were evaluated by McNemar test.

RESULTS

The specificity of the digital system was significantly better (P = .016) for the second observer at the first reading. There were no significant differences in sensitivity and specificity for both observers between the 2 systems for other readings (P > .05).

CONCLUSIONS

No difference was found between the intraoral CCD sensor and conventional radiography in detecting vertical root fractures for single rooted maxillary premolars ex vivo.

Effect of the number of basis images on the detection of longitudinal tooth fractures using local computed tomography

OBJECTIVES

To determine the effect of the number of basis images on the accuracy of local CT (LCT) in detecting longitudinal fractures and test the accuracy of terminal point assessment.

METHODS

Longitudinal fractures were induced in 30 of 60 posterior teeth. LCT volumes were generated from 180, 60, 36 and 20 basis images. Ten observers determined the presence of a fracture and its terminal point. Receiver operating characteristic (ROC) analysis was used to quantify detection accuracy, and kappa statistics were used to quantify the concordance between actual and observed terminal point locations.

RESULTS

A(z)-values were 0.91, 0.84, 0.74, 0.57 and 0.70 for LCT180, LCT60, LCT36, LCT20 and conventional radiography, respectively (ANOVA: P<0.0001). LCT180 and LCT60 outperformed the other modalities. The respective kappa values for terminal point assessment were 0.52, 0.40, 0.37, 0.16 and 0.32 (ANOVA: P=0.00). LCT180 and LCT60 provided better agreement.

CONCLUSIONS

LCT maintained its efficacy for detecting longitudinal fractures with 60 instead of 180 basis images. Agreement between actual and observed terminal point locations was moderate for LCT60 and LCT180.

Optimization of TACT imaging protocols for in situ visualization of cochlear electrode arrays in cat temporal bones

OBJECTIVE

To explore the effect of the number of two-dimensional (2D) images and x-ray projection angles on the resolution of reconstructed three-dimensional (3D) volumes of intracochlear electrode arrays in cadaveric cat temporal bones using Tuned Aperture Computed Tomography (TACT).

DESIGN

Multiple 2D radiographs (basis images (BI)) of implanted cadaveric cat temporal bones were acquired using a range of projection angles, and imported into the TACT workbench. 3D volumes were reconstructed using varying numbers of BIs. Contrast resolution in the image was determined by comparing the contrast ratio (using maximum and minimum grayscale values) in specified anatomic areas of interest.

RESULTS

Systematically increasing the number of BIs used in the reconstruction process resulted in a systematic increase in contrast resolution. Likewise, increasing the range of effective projection angles, as also the number of such angles used in the TACT computation also increased the contrast resolution of the resulting images.

CONCLUSIONS

Precise determination of the location of cochlear implant electrodes in situ is critical to understanding the factors influencing efficacy of electrical stimulation of the deaf ear. Renderings generated with the TACT algorithm produce 3D images permitting visualization of implant electrode features and anatomic details with resolution sufficient to accurately localize electrode contacts within scala tympani. The quality of resulting images, evaluated as a function of image contrast, improved with a larger number of BIs in the reconstruction. Wider projection angles also improved image detail in addition to generating thinner slices. Any loss in contrast was compensated for by the number of BIs. TACT can thus be optimized to provide useful data to help characterize the location of intracochlear electrode arrays.

In vitro assessment of local computed tomography for the detection of longitudinal tooth fractures

OBJECTIVE

To test the accuracy of local computed tomography (LCT) in detecting longitudinal fractures in comparison with conventional periapical radiographs.

STUDY DESIGN

Longitudinal fractures were induced in 30 of 60 teeth. The teeth were placed in a dry dentate mandible with soft tissue simulation. A laboratory LCT unit was used to acquire 180 basis projections with 1 degree separation along a 180 degree arc. Conventional radiographs served as the control modality. Correlated axial, coronal, and sagittal views were presented to 10 observers. The observers determined the presence of a root fracture by using a 5-point receiver operating characteristic confidence scale.

RESULTS

The mean A(z) for LCT was 0.91 (SD = 0.07). The mean A(z) for conventional radiography was 0.70 (SD = 0.07). The difference between the modalities was statistically significant (analysis of variance: P < .0002), whereas the differences between the observers was not (analysis of variance: P = .319).

CONCLUSION

Local CT significantly improves the detection of longitudinal fractures in vitro compared with conventional periapical radiography.

Clinical indications for digital imaging in dento-alveolar trauma. Part 1: traumatic injuries

Traumatized teeth present a clinical challenge with regard to their diagnosis, treatment plan, and prognosis. Recent developments in imaging systems have enabled clinicians to visualize structural changes effectively. Computed tomography, magnetic resonance imaging and cone beam computed tomography are among the most commonly used systems for dental and maxillofacial surgery. The purpose of this review is to describe the advantages and disadvantages of each technique and the clinical application for dento-alveolar trauma. Three clinical cases are described to illustrate the potential use of the NewTom 3G for diagnosis and treatment plan of dento-alveolar traumatic injuries.

Clinical indications for digital imaging in dento-alveolar trauma. Part 2: root resorption

Common complications of dento-alveolar trauma are pulp necrosis, pulp canal obliteration, periapical pathosis and root resorption. Different types of root resorption have been identified with traumatic injuries. Repair-related (surface), infection-related (inflammatory), ankylosis-related (osseous replacement) or extraradicular invasive cervical resorption are among the most common. Recent developments in imaging systems have enabled clinicians to visualize structural changes effectively. The diagnosis and three-dimensional imaging assessment of the resorption is important in order to determine the treatment complexity and expected outcome based on the location and extension of the root defect. This article discusses and illustrates the clinical application of cone beam computed tomography for diagnosis and treatment plan of root resorption. Four clinical cases are presented to illustrate the potential use of the NewTom 3G for root resorption.

Limited cone-beam CT and intraoral radiography for the diagnosis of periapical pathology

OBJECTIVE

To compare intraoral periapical radiography with 3D images for the diagnosis of periapical pathology.

STUDY DESIGN

Maxillary molars and premolars and mandibular molars with endodontic problems and examined with periapical radiographs and a 3D technique (3D Accuitomo) were retrospectively selected and evaluated by 3 oral radiologists. Numbers of roots and root canals, presence and location of periapical lesions, and their relation to neighboring structures were studied.

RESULTS

Among 46 teeth, both techniques demonstrated lesions in 32 teeth, and an additional 10 teeth were found in the Accuitomo images. As regards individual roots, 53 lesions were found in both techniques, and 33 more roots were found to have lesions in Accuitomo images. Artefacts were sometimes a problem in Accuitomo images. In 32 of the 46 cases, all observers agreed that additional clinically relevant information was obtained with Accuitomo images.

CONCLUSIONS

A high-resolution 3D technique can be of value for diagnosis of periapical problems.

Digital and Advanced Imaging in Endodontics: A Review

This review provides an overview of digital radiography as it exists, including advanced imaging such as computed tomography (CT), cone beam volumetric imaging, and micro-CT as relevant to the practice of endodontics. An evidence-based approach to adoption of different imaging technologies is included to assist the practitioner with the selection process of imaging modalities. Commonly used imaging terminology is introduced, as well as the advantages and disadvantages of image processing. New image reconstruction techniques have been introduced that provide information three-dimensionally to the clinician for routine endodontic and surgical treatment planning. The age of three-dimensional imaging and image processing is here. Limitations and advantages of newly introduced imaging modalities are discussed briefly.

Tuned-aperture computed tomography for detection of induced mid-buccal/lingual alveolar bone defects

BACKGROUND

The detection of bone loss in mid-buccal and lingual crests is impossible using conventional radiographs because of the superimposition of overlying anatomy and lack of three-dimensional information. The purpose of this study was to compare the diagnostic efficacy of tuned-aperture computed tomography (TACT) and conventional two-dimensional direct digital radiography (DDR) in an in vitro environment.

METHODS

A total of 45 mandibular molars had 0.8-mm lesions on mid-buccal/lingual crestal areas. Half of the sites received defects, whereas the other half served as controls. Nine DDR images were used to generate TACT slices that were further subjected to iterative restoration (TACT-IR). Eight observers used a confidence rating scale to record diagnoses. Receiver operating characteristic (ROC) analysis was done, and areas under the curves were computed (A(z)) as indicators of diagnostic accuracy. Analysis of variance (ANOVA) was used to test for effects of observer, imaging modality, and location on the detection of lesions.

RESULTS

TACT-IR performed significantly better than DDR. There was a significant difference in the accuracy of diagnosis based on observers (P <0.001).

CONCLUSION

TACT-IR appears to be the imaging modality of choice for the detection of small osseous changes on crestal bone in mid-buccal/lingual sites.

Treatment concepts for restoration of endodontically treated teeth: A nationwide survey of dentists in Germany

STATEMENT OF PROBLEM

Opinions concerning proper restoration of endodontically treated teeth (ETT) vary. A variety of techniques and materials for post-and-core restorations are available. The rationale for post placement performed by German dentists was unknown.

PURPOSE

The purpose of this study was to determine current opinions, applied techniques, and materials for the restoration of ETT in Germany.

MATERIAL AND METHODS

A nationwide questionnaire-based survey containing 18 multiple choice questions regarding treatment philosophies, favored post type, and materials for core foundations was mailed to 36,500 German general dentists. A total of 6029 questionnaires (16.5%) were returned. Data were evaluated in terms of the dentists' occupational experience and the frequency of post placement. Descriptive statistics were used to analyze the data.

RESULTS

Irrespective of their occupational experience, 52% of the surveyed dentists consider post placement for almost every postendodontic restoration of ETT. The majority of dentists (54%) believe that a post reinforces ETT. Cast posts and cores are used by 55% of all dentists, whereas 34% use prefabricated posts exclusively. Screw posts are the most popular prefabricated post type (47%). Composite resin (51%) is preferred for core foundation, followed by glass ionomer cements (GICs) (26%). Amalgam is seldom used (0.5%). Posts are placed primarily with zinc phosphate cement (51%), followed by GIC (38%).

CONCLUSION

The treatment philosophy of German dentists is not in complete agreement with recommendations found in the literature. The belief that a post would reinforce an ETT might explain the high frequency of post placements. Due to the partially inconsistent responses, it is difficult to derive a generalized treatment concept.

Volumetry of human molars with flat panel-based volume CT in vitro

The flat panel-based volume computed tomography (fpVCT) is a new CT device applicable for experimental, three-dimensional evaluation of teeth at a resolution of about 150 microm in the high contrast region. The aim of this study was to investigate whether fpVCT was suitable for quantification of the volumes of dental hard tissues and the root canal system to establish a new method for morphological studies. Fifty-two extracted third molars (maxillary: 31, mandibular: 21) were examined with a prototype of an fpVCT using a volumetry algorithm at different levels according to the radiographic density of enamel and dentine. Volumetry of the root canal system was performed after "region growing segmentation": starting from a voxel in the centre of the root canal, this algorithm searches voxels of same density in the surrounding. The volumetry of the root canal system was stopped by the investigator at the apical constriction. Results showed that dentine, enamel and root canal system could be well distinguished in three-dimensional images. Volumetry yielded the following data (cm(3), mean+/-SD): dentine 0.438+/-0.111, enamel 0.227+/-0.051, root canal system 0.052+/-0.017 and total volume 0.753+/-0.159. In conclusion, the fpVCT is appropriate for non-destructive volumetry of large numbers of teeth in experimental laboratory studies.

Three-dimensional, non-destructive visualization of vertical root fractures using flat panel volume detector computer tomography: an ex vivoin vitro case report

AIM

To detect and to visualize radiographically vertical root fractures in extracted teeth with a prototype of a novel, high resolution, three-dimensional flat panel volume detector computer tomograph (FD-VCT) system.

SUMMARY

Five teeth with root fillings and clinical symptoms such as fistulas and isolated periodontal pockets of 8 mm or more were extracted after dental radiography indicating lateral or periapical lesions. Vertical root fractures or cracks were suspected because of the symptoms and clinical findings were evident after extraction in all cases but fracture lines were not visible on routine dental radiographs acquired before extraction. The extracted teeth were explored with a prototype of a FD-VCT. Using the FD-VCT, in all cases vertical root fractures or crack lines could be detected clearly in different views, depiction-modes and cross-sections at a spatial resolution of 140 microm. The evaluation of the fracture lines and teeth could be performed in three-dimensional views. The FD-VCT findings were confirmed by detailed inspection of the extracted teeth.

KEY LEARNING POINTS

The FD-VCT is an innovative diagnostic tool for non-destructive, three-dimensional evaluation of extracted teeth in pre-clinical and experimental studies. The FD-VCT allows precise visualization and evaluation of vertical root fractures or cracks in extracted teeth. Clinical application of the system may be possible if technical modifications reduce the exposure dose: the high resolution detector systems of the FD-VCT should be combined with radiation systems that focus the radiation to the area of interest.

High resolution charge-coupled device sensor vs. medium resolution photostimulable phosphor plate digital receptors for detection of root fractures in vitro

The aim of this study was to compare the diagnostic accuracy of a high resolution charge-coupled device (CCD) sensor and a medium resolution photostimulable phosphor (PSP) plate for detecting experimentally induced root fractures and further, to evaluate differences between images taken with various horizontal and vertical angles. Forty-seven extracted single-rooted human teeth mounted in a dry human skull were used in the experiment. The teeth were radiographed, before and after root fractures were induced, with two digital receptors: the Digora PSP system (approx. 8 lp mm(-1)) and the RVG-ui(TM), a CCD sensor with a high-resolution mode (15-20 lp mm(-1)). Four images were taken with each of the receptors of each tooth: one orthogonal exposure (O-images), one exposure with a vertical angle of 15 degrees by which the root was imaged elongated (L-images), and two eccentric exposures with a horizontal angle of 15 degrees mesially and distally. Three observers marked a fracture line if detected, in each image. Three sessions were held, one assessing the O-images, one the L-images, and one in which all four images of the same tooth were displayed simultaneously (X-images). The RVG-ui images obtained higher sensitivities than the Digora PSP images (P <0.05). Sensitivity was statistically significantly higher for the X-images than for both the O-images and the L-images (P <0.05). Based on the observed means, specificities were significantly different neither between the angles, nor between the images from the two digital systems taken with the same angle (P >0.05). It may be speculated that the difference in spatial resolution between the two digital systems accounts for the differences in their sensitivity.

Tuned-aperture computed tomography versus parallax analog and digital radiographic images in detecting second mesiobuccal canals in maxillary first molars

OBJECTIVE

We sought to evaluate the detectability of second mesiobuccal (MB2) canals in the MB root of maxillary first molar teeth by comparing (1) parallax with pairs of conventional direct-exposure film intraoral radiographs (both D-speed and F-speed), (2) parallax with pairs of charge-coupled device-based digital images acquired through the use of Trophy RVG-ui, and (3) charge-coupled device-based images acquired through the use of a Trophy RVG-ui sensor and tomosynthetically reconstructed by TACT (tuned-aperture computed tomography) Workbench Software.

STUDY DESIGN

Maxillary first molars were mounted in simulated bone. Pairs of images were generated by conventional D-speed and F-speed radiography and digital radiography with a charge-coupled device-based sensor, the RVG-ui. Sequences of images were also acquired for TACT reconstruction by using the digital sensor. Observers viewed sets of images to determine the number of canals present within the MB root of each tooth. Roots were horizontally cross-sectioned and viewed under an operating microscope to determine the actual number of canals present.

RESULTS

The frequency of detection of MB2 canals was remarkably similar across techniques: 39.2% to 39.6% with parallax for both types of film and for RVG-ui images, and 37.9% with TACT. No statistically significant difference was found in the detectability of MB2 canals between the modalities tested. TACT had higher correlation coefficients than the other 3 modalities with respect to intrarater and interrater reliabilities.

CONCLUSIONS

(1) There was a less than 40% chance of locating MB2 canals in the MB root of maxillary first molar teeth by using parallax with pairs of digital or analog radiographs. (2) TACT did not significantly affect the rate of detection of MB2 canals.

Effect of iterative restoration on the detection of artificially induced vertical radicular fractures by Tuned Aperture Computed Tomography

OBJECTIVE

The purpose of this study was to evaluate the effect of the number of iterative restorations (IR) on the diagnostic accuracy of Tuned Aperture Computed Tomography images (TACT) for detection of induced vertical/oblique root fractures in mandibular teeth.

STUDY DESIGN

Fractures were induced in 28 single-rooted, endodontically treated cadaver mandibular teeth while another 26 such teeth served as controls. TACT slices reconstructed by using 9 arbitrary projections (angular disparity of 9 degrees -20 degrees) were iteratively restored 1, 2, and 3 times. Eight observers scored their diagnoses by using a confidence rating scale. Ground truth was available from direct examination with transillumination, following extraction.

RESULTS

Mean areas under the representative ROC curves for the 3 operations were 0.96 (3 IRs), 0.87 (2 IRs), and 0.86 (1 IRs). Analysis of variance demonstrated significant differences between 3 and 1 to 2 IRs (P <.01), as well as between observers (P <.01).

CONCLUSION

Diagnostic accuracy of TACT for vertical/oblique root fracture detection improved after 3 IRs.

Digital tomosynthesis-experiences with a new imaging device for the dental field

Based on the principles of classic film tomography, a new digital X-ray device for dental sites was developed and clinically evaluated. The tomosynthesis process produces several slices from a finite number of radiographs taken from different projection angles, obtaining a three-dimensional image of the jaws and teeth. During evaluation of an industrial prototype, a total of 52 tomosynthesis data sets were made covering different anatomic areas. Of those, 32 sets were assessed by ten radiologically experienced dentists. Anatomic regions not shown on conventional intraoral dental films were displayed due to the extraoral sensor. Diagnostic images of high value were mainly achieved within the scope of lateral views and transverse views in the frontal region. Even small structures such as the periodontal ligament could be shown in several planes, resulting in superposition-free representation. The elimination of metal artefacts caused by dental restorations was facilitated. However, improvements can be made in definition and resolution. Views in the sagittal plane and incomplete blurring of the contralateral jaw are difficulties that remain. The tomosynthesis process combined with a planned 3D representation is likely to be well suited for dental radiology. The use of such a device could be much less expensive than computed tomography (CT). Furthermore, it offers higher spatial resolution, exposes patients to less radiation, and could be easily used in daily practice, even chairside.

CLINICAL VALIDITY OF THE INTERACTIVE AND LOW-DOSE THREE-DIMENSIONAL DENTO-ALVEOLAR IMAGING SYSTEM, TUNED-APERTURE COMPUTED TOMOGRAPHY

Based on technical studies and clinical examinations, the clinical value of a new three-dimensional dento-alveolar imaging system, Tuned-Aperture Computed Tomography (TACT), were examined for dental applications. TACT is a conventional and low-cost tomosynthesis method in which the benefit of digitization is fully utilized. The clinical information yield of TACT has been examined for the detection of dental caries, periodontal defects and radicular fractures, and also for the pre-surgical assessment of implant placement and impacted teeth. In this article, we introduce basic TACT technology, review the literature pertaining to in vitro and in vivo studies, and describe the outline of our study of TACT to determine its clinical value in the assessment of impacted maxillary teeth.