Comparison of micro-CT and cone beam CT-based assessments for relative difference of grey level distribution in a human mandible

Objectives:

The purpose of this study was to examine the ability of CT to assess the relative difference of degree of bone mineralization (grey level) parameters in a human mandible.

Methods:

Ten mandibular sections from cadavers (81.5 ± 12.1 years) were scanned using micro-CT with 27.2 μm voxel size and cone beam CT (CBCT) with 200 μm, 300 μm, and 400 μm voxel sizes. In addition, 15 clinical CBCT images from young patients (mean age 18.9 ± 3.3 years) were identified. After segmentation of bone voxels, alveolar bone and basal cortical bone regions were digitally isolated. A histogram of grey level, which is equivalent to degree of bone mineralization, was obtained from each region of the CT images. Mean, standard deviation (SD), coefficient of variation (COV), fifth percentile low (Low₅) and high (High₅) of alveolar bone and basal cortical bone regions were obtained. Percentage differences of grey level parameters between alveolar and basal cortical bones were computed.

Results:

The alveolar bone region had significantly lower Mean, Low₅ and High₅ values but significantly higher SD and COV than the basal cortical bone region for all CT images (p < 0.05). All parameters were significantly lower for the old cadaver group than for the young patient group (p < 0.05).

Conclusions:

CBCT and micro-CT provide comparable results in the assessment of relative difference in grey level distribution between alveolar and basal cortical bone regions in the human mandible. The percentage difference relative to an internal reference (basal cortical bone) can be a reliable method when assessing the degree of bone mineralization using CBCT images for both cross-sectional and longitudinal comparisons.     

Ex vivo comparison of Galileos cone beam CT and intraoral radiographs in detecting occlusal caries

Objective

The aim of this study was to compare the accuracy of cone beam CT (CBCT) with intraoral radiographs for detection of occlusal caries.

Methods

A set of 60 extracted teeth were imaged using a Sirona Galileos CBCT system (Sirona Dental Systems, Bensheim, Germany) and an intraoral Planmeca® system (Planmeca OY, Helsinki, Finland). Six observers looked at both modalities and used a five-point confidence scale to evaluate presence or absence of occlusal caries. Histology was used as the gold standard. Receiver operating characteristic analysis and weighted kappa statistics were used for statistical analysis. Differences in the area under the curve (AUC) values between observers and modalities were analysed using analysis of variance (ANOVA). Differences in sensitivity and specificity were analysed using the Wilcoxon test. Interobserver and intraobserver reliability was assessed by weighted kappa scores.

Results

The mean value and standard deviation of AUC was 0.719 ± 0.038 for CBCT and 0.649 ± 0.062 for the intraoral radiographs. The ANOVA results demonstrated that there was no significant difference between the modalities and the observers. The interobserver kappa for pairs of observers ranged from fair to substantial for bitewings (0.244–0.543) and CBCT (0.152–0.401). Four out of six observers reported higher sensitivity but lower specificity with CBCT. The Wilcoxon exact p-value showed no difference in sensitivity (0.175) or specificity (0.573) between the two modalities.

Conclusion

Based on the results we conclude that the Sirona CBCT unit cannot be used for the sole purpose of looking at occlusal caries.     

Current trends in the adoption and education of cone beam computed tomography and panoramic radiography machines across Australia

Objectives:This is a follow-up study to assess growth in the number of cone beam computed tomography (CBCT) and panoramic radiography (PR) machines in Australia. It is also the first study to evaluate the current status of both CBCT and PR education in Australia.Methods:CBCT and PR machine numbers were obtained from the radiation regulators across Australia. Australian dental schools were surveyed via email. The number of machines relative to population size and the number of dentists were calculated.Results:In 2020, there were 706 CBCT machines and 3,059 PR machines, representing a 204.3% increase in the number of CBCT machines and an 82.0% increase in the number of PR machines over six years. Majority of Australian dental schools owned PR and CBCT machines. Most taught PR acquisition and interpretation, however only one-third taught CBCT image acquisition and interpretation to predoctoral students.Conclusions:CBCT machine numbers increased by nearly three-fold while PR machines only increased by 1.6 times over a six-year period relative to population size and number of dentists. Only very few Australian dental schools provide CBCT education to predoctoral students, raising concern as to whether graduates are adequately trained upon program completion.     

The usage of digital radiography and cone beam computed tomography among Turkish dentists

Objectives

The aim of this study was to determine the prevalence of the use of digital radiography and report how it was used by Turkish dentists.

Methods

The survey was based on 383 dentists who were present at the sixteenth International Congress organized by the Turkish Dental Association. A questionnaire which consisted of 19 questions was given to the dentists who participated in the study. Data were assessed according to frequency distribution and the χ² test was used to determine the significance of differences between two independent groups.

Results

376 questionnaires were analysed. The mean age of the dentists who participated in the study was 37.14 ± 9.6 years (range: 20–63 years). The distribution of the dentists according to the 7 regions of Turkey were: Marmara 58%, Aegean 13% and Mediterranean 10%, Central Anatolia 8%, Black Sea 7%, Southeastern Anatolia 3%, Eastern Anatolia 1%. 124 dentists (33%) said they did not work with digital radiography. 95 dentists indicated that they did not use digital radiography owing to cost (60%). 252 dentists (67%) said they used digital radiography. 40% of the participants noted that the repetition of periapical radiographs was due to digital radiography. 166 dentists (55.9%) and 79.1% academicians had knowledge about cone beam CT (CBCT).

Conclusion

Digital radiography users are increasing in Turkey and levels of knowledge of CBCT and awareness of radiation safety has also increased.     

Modulation transfer function evaluation of cone beam computed tomography for dental use with the oversampling method

Objectives

The aim was to investigate the possibility of evaluating the modulation transfer function (MTF) of cone beam CT (CBCT) for dental use using the oversampling method.

Methods

The CBCT apparatus (3D Accuitomo) with an image intensifier was used with a 100 μm tungsten wire placed inside the scanner at a slight angle to the plane perpendicular to the plane of interest and scanned. 200 contiguous reconstructed images were used to obtain the oversampling line-spread function (LSF). The MTF curve was obtained by computing the Fourier transformation from the oversampled LSF. Line pair tests were also performed using Catphan®.

Results

The oversampling method provided smooth and reproducible MTF curves. The MTF curves revealed that the spatial resolution in the z-axis direction was significantly higher than that in the axial direction. This result was also confirmed by the line pair test.

Conclusions

MTF analysis was performed successfully using the oversampling method. In addition, this study clarified that the 3D Accuitomo had high spatial resolution, especially in the z-axis direction.     

Optimization of cone beam CT exposure for pre-surgical evaluation of the implant site

Objectives

The aim of this study was to investigate the possibility of reducing patient X-ray dose in the course of implant site evaluation.

Methods

Retrospective practice-based study using a Morita F170 Accuitomo cone beam CT (CBCT) scanner with variable exposure parameters and operating a small cylindrical field of view of 4 cm diameter and 4 cm height. 6 experienced dental surgeons scored the image quality of dental scans on a 5-point scale for adequacy in providing the required information in 2 categories: bone height from alveolar crest to the relevant anatomical structure and bone width.

Results

Lower-dose protocols only marginally affected the preference of the reviewers of the resulting images.

Conclusions

There is potential to reduce patient dose very significantly in CBCT examinations for implant site evaluation.     

Accuracy of peri-implant bone evaluation using cone beam CT,digital intra-oral radiographs and histology

Objectives:

The present study assesses the accuracy of three-dimensional (3D) cone beam CT (CBCT) and intra-oral radiography (CR) in visualizing peri-implant bone compared with histology.

Methods:

26 titanium dental implants were placed in dog jaws with chronic type vestibular defects. After a healing period of 2 and 8 weeks (n = 12 dogs) the animals were sacrificed. CBCT scans and CR of the specimen were recorded. Dissected blocks were prepared, and histomorphometric analysis was performed. Both modalities were measured twice by two observers and compared with histomorphometry regarding bone levels and thickness around implants as well as length and diameter of implants.

Results:

Measurements of CBCT correlated well with histomorphometry of the vestibular bone level, oral bone thickness and implant length (all p-values <0.05). Compared with histomorphometry, the mean differences between CBCT and histomorphometry were between 0.06 and 2.61 mm. Mesial bone level (MBL) and distal bone level (DBL) were underestimated by both CR and CBCT. CR and histology measurements were only significantly correlated for implant length measurements. All intraclass correlations were highly significant.

Conclusions:

3D CBCT provides usable information about bone in all dimensions around implants with varying accuracy. CR and CBCT perform similar in assessing MBL and DBL, but, within its limits, the CBCT can assess oral and buccal bone. Metallic artefacts limit the visualization quality of bone around implants and further research could elucidate the value of post-processing algorithms. When information about osseous perforation of implants is needed, CBCT may still provide clinically valuable information.     

Dental students' knowledge and attitudes towards cone beam computed tomography in Turkey

Objective

The aim of this study was to evaluate students'' knowledge and attitudes regarding cone beam CT (CBCT).

Methods

A questionnaire consisting of 11 questions was given to 472 dental students (280 pre-graduate and 192 post-graduate) at two institutions located in Ankara, Turkey (Ankara University, Faculty of Dentistry, and Gazi University, Faculty of Dentistry). Differences in responses by institution, education level and sex were statistically assessed with the χ² test.

Results

Statistical results showed that only 63.3% of students had heard of CBCT. Of these, 59.9% said they had learned about CBCT in their classes, 31.0% in seminars and 20.9% from the internet; 76.8% felt that CBCT was not given adequate coverage in their courses; 69% thought that CBCT should be taught as part of their clinical education; 91% thought it essential for CBCT to be available at dental faculties; 53.5% believed that the use of CBCT would become more widespread in the near future; and 84.9% wished to use CBCT technology in their future careers.

Conclusion

This research suggests that efforts should be made to improve students'' knowledge base regarding CBCT and that the dental school curriculum should devote more curriculum time to this promising new technology.     

Dentomaxillofacial manifestations of Gaucher's disease: preliminary clinical and radiographic findings

Objectives

A wide variety of manifestations is presented in patients with Gaucher''s disease (GD), including bone, haematology and visceral disturbances. This study was conducted to ascertain the main maxillofacial abnormalities by means of clinical survey, panoramic and cone beam CT (CBCT); to compare the patient''s group with an age–sex matched control group; and to correlate clinical and radiological data.

Methods

Ten patients previously diagnosed with GD were submitted to clinical and radiological surveys (CBCT and panoramic radiographs). The examination consisted of anamnesis, extra- and intraoral examinations and analyses of each patient''s records. Imaging data were collected from the point of view of 3 observers, and the results compared with a healthy group (20 individuals) by means of statistical analysis (Fisher''s exact test).

Results

Gaucher patients had significantly more manifestations than otherwise healthy carriers. The most prevalent findings were enlarged marrow spaces, generalized osteopenia and effacement of jaw structures (mandibular canal, lamina dura and mental foramen). Here we describe a case in which thickening of the maxillary sinus mucosa was observed on CBCT rather than opacification of the sinus as seen on panoramic radiographs. Pathological fractures, root resorption and delay on tooth eruption were not observed.

Conclusions

A poor relationship could be observed between clinical and radiological data. Patients showed important bone manifestations, which require careful diagnostic and surgical planning whenever necessary. Although panoramic radiographs have shown significant differences, CBCT is more effective in pointing out differences between patients and a control group, thus showing it as an important tool for evaluation of Gaucher patients.     

Assessment of metal artefact reduction around dental titanium implants in cone beam CT

Objectives:

The aim of this study was to investigate if the metal artefact reduction (MAR) tool used in the software of the ORTHOPANTOMOGRAPH^® OP300 (Instrumentarium Dental, Tuusula, Finland) can improve the gray value levels in post-operative implant scans.

Methods:

20 potential implant sites were selected from 5 edentulous human dry mandibles. Each mandible was scanned by a CBCT scanner, and images were produced under three different conditions: implant sites drilled but no implants inserted, implants inserted without application of MAR and implants inserted with application of MAR. Using Geomagic^® Studio 2012 (Geomagic, Morrisville, NC) and 3Diagnosys^® v. 5.3.1 (3Diemme^® SRL, Cantù, Italy) software, three scans of each mandible were superimposed. The mean gray value of identical regions of bone around the implants was derived for each condition. The differences between gray value measurements at implant sites derived from different conditions were assessed.

Results:

A significant difference was found between mean gray values from the scans with no implants inserted and with implants inserted (with and without MAR) (p = 0.012). No significant difference was revealed for gray values measured from scans with and without MAR (p = 0.975).

Conclusions:

The MAR tool in the software of the ORTHOPANTOMOGRAPH OP300 CBCT scanner does not significantly correct the voxel gray values affected by the metal artefact in the vicinity of an implant in human dry mandibles.     

Bifid mandibular canals: cone beam computed tomography evaluation

Objectives

For surgical procedures involving the posterior mandible, it is important to be familiar with the details of the bifid mandibular canal. To our knowledge, there have been no systematic studies evaluating the bifid mandibular canal using sectional imaging. The purpose of this study is to evaluate the incidence and configuration of the bifid mandibular canal using cone beam CT.

Methods

252 patients (301 mandible sides) underwent cone beam CT between October 2004 and September 2005 and were included in this study. The cone beam CT images were evaluated for the presence and configuration of the bifid mandibular canal. The patterns of bifurcation were classified into four types according to the classification of Nortjé et al (Variations in the normal anatomy of the inferior dental (mandibular) canal: a retrospective study of panoramic radiographs from 3612 routine dental patients. Br J Oral Surg 1977; 15: 55–63). The diameter of the accessory canal was classified into two categories: 50% or more and less than 50% of the diameter of the main mandibular canal.

Results

Of the 301 subjects, 47 (15.6%) demonstrated a bifid mandibular canal. They were Type I in 2, Type II in 40, Type III in 0, and Type IV in 5 cases. The diameter of the accessory canal was greater than or equal to 50% of the main canal in 23, and less than 50% in 24 cases.

Conclusions

On the basis of the cone beam CT, a bifid mandibular canal was found in 15.6% of cases, a markedly higher proportion than found in previous reports using panoramic images. Cone beam CT is considered a suitable modality for detailed evaluation of bifid mandibular canals.     

The impact of CBCT imaging when placing dental implants in the anterior edentulous mandible: a before–after study

Objectives:

To evaluate the impact of CBCT imaging when placing dental implants in the anterior edentulous mandible, using a “before–after” study design.

Methods:

Eight dental practitioners, who regularly place dental implants in independent dental practice in the North West of England, were presented with realistic simulations of four edentulous cases. The practitioners were asked to assess case difficulty, select implants and then drill osteotomies in preparation for dental implants in the lower canine regions to support a complete overdenture. In the “before” part of the study, a panoramic and a trans-symphyseal view were available. In the “after” part of the study, a CBCT image was added. Perception of case difficulty, implant selection and the incidence of perforations or “near miss perforations” of the lingual cortical plate were recorded. Two cases were regarded as “regular” and two as “challenging”.

Results:

In challenging cases, the availability of CBCT led practitioners to select narrower implants and to assess cases as more difficult. In the challenging cases only, there were fewer perforations of the lingual cortical plate after the availability of CBCT, but this difference was not statistically significant. There were no perforations in the regular cases either before or after the availability of CBCT.

Conclusions:

Perception of case difficulty and implant selection are of importance only if they change the outcome for the patient. This study provided weak evidence that CBCT is helpful in avoiding perforations in challenging cases. The availability of CBCT had no impact in regular cases.     

Artefacts in CBCT: a review

Artefacts are common in today's cone beam CT (CBCT). They are induced by discrepancies between the mathematical modelling and the actual physical imaging process. Since artefacts may interfere with the diagnostic process performed on CBCT data sets, every user should be aware of their presence. This article aims to discuss the most prominent artefacts identified in the scientific literature and review the existing knowledge on these artefacts. We also briefly review the basic three-dimensional (3D) reconstruction concept applied by today's CBCT scanners, as all artefacts are more or less directly related to it.     

Comparative study between conventional and cone beam CT-synthesized half and total skull cephalograms

Objectives

The aim of this study was to compare cephalometric measurements obtained from conventional cephalograms with total and half-skull synthesized cone beam CT (CBCT) cephalograms.

Methods

Cephalometric analyses of 30 clinically symmetric patients were conducted by a calibrated examiner on conventional and CBCT-synthesized cephalograms (total, right and left). Reproducibility was investigated using the intraclass correlation coefficient (ICC). The Bland–Altman analysis was used to assess the agreement of the measurements from each factor obtained by conventional, total, right and left CBCT-synthesized cephalograms.

Results

The ICC was above 0.9 for most of the 40 cephalometric factors analysed, revealing similar levels of reproducibility. When the measurements obtained from conventional and CBCT-synthesized cephalograms were compared, the Bland–Altman analysis showed a strong agreement between them.

Conclusions

Half-skull CBCT-synthesized cephalograms offer the same diagnostic performance and equivalent reproducibility in terms of cephalometric analysis as observed in conventional and total CBCT-synthesized cephalograms.     

Image quality and radiation exposure in 320-row temporal bone computed tomography

Objectives

The aim was to define image quality and radiation exposure in the recently introduced 320-row CT of the temporal bone (tb) in comparison to a 16-row tb CT.

Methods

A cadaveric head phantom was used for repeated tb volume CT studies (80–120 kV, 25–150 mAs), performed in a 320-row scanner (single rotation, 0.5 mm slice thickness, kernel FC 51) in comparison to 16-row helical CT using standard acquisition parameters (SAP) of 120 kV and 75 mAs (kernel FC 53). Qualitative image evaluation was performed by two radiologists using a 5-point visual analogue scale. Image noise (D_SD) was determined by region of interest (ROI) based measurements in cadaveric as well as water phantom studies. Dosimetric measurements of the effective dose (ED) and organ dose (OD) of the lens were performed.

Results

Image quality of 320-row tb CT was equivalent to 16-row CT for SAP scans, resulting in image noise levels (D_SD 16-/320-row) of 109/237 and 206/446 for air and bone respectively. D_SD differences were predominantly (>90%) attributable to the different kernels available for tb studies in 16- and 320-row CT. Radiation exposure for 16-/320-row SAP scans amounted to 0.36/0.30 mSv (ED) and 10.0/8.4 mGy (lens dose).

Conclusion

320-row volume acquisition in tb CT delivers equivalent image quality to 16-row CT while decreasing radiation exposure figures by one sixth. Image noise increase in 320-row CT is negligible with respect to image quality.     

Quantitative assessment of artefacts and identification of gaps in prosthetic crowns: a comparative in vitro study between periapical radiography and CBCT images

Objectives:To evaluate, in an in vitro study, the quantity of artefacts generated by two different restorative materials, and to determine the diagnostic accuracy of cone beam CT (CBCT) scans and periapical radiographs in identifying gaps in prosthetic crowns.Methods:A total of 30 teeth restored with metal-ceramic (n = 15) and all-ceramic (n = 15) crowns, properly adapted and with 0.30- and 0.50 mm gaps, underwent CBCT exams (with voxel sizes of 0.25 and 0.30 mm) and periapical radiographs. The artefacts generated by two different crowns were quantified and compared by the Mann–Whitney test. In addition, five examiners evaluated the presence or absence of gaps in periapical radiographs and CBCT images. The accuracy of tests was determined by the area under the receiver operatring characteristic curve and these values were compared by using the Kruskal–Wallis test.Results:There was no significant difference in artefact values between the different restorative materials and the different resolutions of CBCT images. Regarding the accuracy of the tests evaluated, periapical radiography and CBCT with voxel size 0.25 mm showed the best performance for smaller gaps (0.30 mm). For larger gaps (0.50 mm), all exams tested showed the same performance.Conclusions:Periapical radiography was still the most cost-beneficial method for the diagnosis of maladaptation in dental restorations. CBCT exams did not improve accuracy in detecting gaps in prosthetic crowns.     

Comparison of the influence of FOV sizes and different voxel resolutions for the assessment of periodontal defects

Objectives:

This study assessed the influence of different voxel resolutions of two different CBCT units on the in vitro detection of periodontal defects.

Methods:

The study used 12 dry skulls with a maxilla and a mandible. Artificial defects (dehiscence, tunnel, fenestration) were separately created on the anterior, premolar and molar teeth using burrs. A total of 14 dehiscences, 13 fenestrations, 8 tunnels and 16 non-defect controls were used in the study. Images were obtained from two different CBCT units in six voxel sizes (voxel size: 0.080, 0.100, 0.125, 0.150, 0.160 and 0.200 mm³). Kappa coefficients were calculated to assess both intra- and interobserver agreements for each image set.

Results:

Overall intraobserver kappa coefficients ranged between 0.978 and 0.973 for the 0.080-mm³ images and between 0.751 and 0.737 for the 0.160-mm³ images, suggesting notably high intraobserver agreement for detecting periodontal defects. CBCT performed significantly better at detecting fenestrations (p < 0.05) than tunnel and dehiscence defects. No statistically significant difference was found between the detection of dehiscence and tunnel defects (p > 0.05).

Conclusions:

A voxel size of 0.150 mm³ was identified as the cut-off point for overall detection of periodontal defects. CBCT should be considered the most reliable imaging modality for the diagnosis of periodontal defects.     

Metal artefact reduction with cone beam CT: an in vitro study

Background

Metal in a patient''s mouth has been shown to cause artefacts that can interfere with the diagnostic quality of cone beam CT. Recently, a manufacturer has made an algorithm and software available which reduces metal streak artefact (Picasso Master 3D® machine; Vatech, Hwaseong, Republic of Korea).

Objectives

The purpose of this investigation was to determine whether or not the metal artefact reduction algorithm was effective and enhanced the contrast-to-noise ratio.

Methods

A phantom was constructed incorporating three metallic beads and three epoxy resin-based bone substitutes to simulate bone next to metal. The phantom was placed in the centre of the field of view and at the periphery. 10 data sets were acquired at 50–90 kVp. The images obtained were analysed using a public domain software ImageJ (NIH Image, Bethesda, MD). Profile lines were used to evaluate grey level changes and area histograms were used to evaluate contrast. The contrast-to-noise ratio was calculated.

Results

The metal artefact reduction option reduced grey value variation and increased the contrast-to-noise ratio. The grey value varied least when the phantom was in the middle of the volume and the metal artefact reduction was activated. The image quality improved as the peak kilovoltage increased.

Conclusion

Better images of a phantom were obtained when the metal artefact reduction algorithm was used.     

Bone echinococcosis with hip localization: A case report with evaluation of imaging features

Hydatid disease (HD) is a zoonotic parasitic disease caused by the larvae of Echinococcus. Bone echinococcosis is rare, accounting for 0.5% to 4% of all echinococcosis. We describe a particular case of pelvic echinoccosis. A 29-year-old man initially presents with pain in his left hip for several years. After an accidental fall from a tree, he suffered a fracture of the left acetabulum. X-rays and CT scans showed an osteolytic area of the acetabulum with bony cortical interruption. MR imaging demonstrated extensive area of osteostructural alteration of the iliac wing and the left acetabulum due to multiple cysts with enhancement of the walls after administration of Gadolinium-based contrast agents. A CT-guided biopsy of an osteolytic area was performed with diagnosis of echinococcus cyst. He underwent albendazole therapy and subsequently echinococcus cyst exeresis, bone curettage, and left hip arthroplasty. Twenty-two months after surgery, CT scan showed recurrence of disease. After 4 years and 6 months of chronic therapy CT scan showed an increase in size of the cyst at the site of the disease recurrence. Five years and 4 months after the first operation, a new cyst exeresis and pelvic bone curettage with implant retention was performed. This case report demonstrates that hydatid cysts should be considered as a possible cause for non-specific pelvic pain, especially in endemic locations.