Asma’a A. Al-Ekrish

A comparative study of the accuracy and reliability of multidetector computed tomography and cone beam computed tomography in the assessment of dental implant site dimensions.

OBJECTIVES The aim of this study was to investigate the accuracy and reliability of linear measurements of edentulous ridges recorded from 16-row multidetector CT (MDCT) images and cone beam CT (CBCT) images acquired using a flat panel detector (FPD) with a large field of view (FOV), both independently and in comparison with each other. METHODS Edentulous areas of human dry skulls were marked with gutta-percha markers to standardize the plane of the transverse cross-sections and path of measurements. The skulls were imaged using a 16-row MDCT scanner and a CBCT device with a large FOV and a FPD. Ridge dimensions were recorded from reformatted sections by two observers and compared with measurements recorded directly from the bone. The measurement errors and intra and interexaminer reliability were calculated for each modality and compared with each other. RESULTS The overall mean of the absolute errors was 0.75 mm for MDCT and 0.49 mm for CBCT. The mean of the CBCT absolute errors was smaller than that of the MDCT absolute errors for the overall data, as well as for the site-specific data. The intraexaminer reliability score was 0.994 for MDCT and 0.995 for CBCT. The interexaminer reliability was 0.985 for MDCT and 0.958 for CBCT. CONCLUSIONS Both MDCT and CBCT were associated with a clinically and statistically significant measurement error. CBCT measurements were significantly more accurate than those of MDCT. The measurements recorded from both modalities had a high inter and intraexaminer reliability. Accuracy of measurements was found to be more operator dependent with CBCT than with MDCT.

Comparative study of the prevalence of temporomandibular joint osteoarthritic changes in cone beam computed tomograms of patients with or without temporomandibular disorder

OBJECTIVES To compare the prevalence of temporomandibular joint (TMJ) osteoarthritic changes in cone beam computed tomography (CBCT) images of temporomandibular disorder (TMD) and non-TMD patients. STUDY DESIGN A retrospective analysis of CBCT images of the joints of TMD and non-TMD patients was performed. The presence or absence of osteoarthritic changes (condylar erosion, osteophyte, subcortical cyst, or generalized sclerosis) in each TMJ was evaluated. The prevalence within the two study groups were compared by using Chi-square statistics. RESULTS At least one type of osteoarthritic change was present in78.6% of joints in the TMD group and 79.7% in the non-TMD group. No significant difference was found in prevalence of osteoarthritic changes between the TMD and non-TMD groups in the overall study sample or within the subsets of gender and age in the groups. CONCLUSIONS The lack of a significant difference in prevalence of TMJ osteoarthritic changes in TMD and non-TMD patients highlights the equivocal relationship between osseous TMJ morphology and degenerative bone disease.

Do Ultra-Low Multidetector Computed Tomography Doses and Iterative Reconstruction Techniques Affect Subjective Classification of Bone Type at Dental Implant Sites?

PURPOSE To investigate whether ultra-low-dose multidetector computed tomography (MDCT) combined with the reconstruction techniques filtered backprojection (FBP), adaptive statistical iterative reconstruction (ASIR), or model-based iterative reconstruction (MBIR) alters the subjective classification of revised Lekholm and Zarb (LZ) bone types at prospective dental implant sites. MATERIALS AND METHODS Three cadavers underwent a reference MDCT examination using a standard dose volume (CT dose index [CTDIvol]: 29.4 mGy) and reconstructed with FBP in addition to five test protocols (LD1-LD5) using ultra-low doses (CTDIvol: 4.19, 2.64, 0.99, 0.53, and 0.29 mGy, respectively) and reconstructed with FBP, ASIR 50, ASIR 100, and MBIR. Transverse cross-sectional images of the jawbones were obtained, and three examiners subjectively classified the bone type in each image using the revised LZ classification. The bone type classifications obtained using the reference examination were compared with those obtained from the test protocols for each examiner, and kappa statistic was used to analyze the level of agreement between the reference and test protocols. The clinical significance of the differences was analyzed with Wilcoxon signed rank test. RESULTS Examiners 1 and 2 found moderate to strong agreement between the reference and test protocols, while Examiner 3 found strong to almost perfect agreement (P < .001). The Wilcoxon signed rank test did not demonstrate a clinical significance of the differences between the reference and test protocols for any of the three examiners. CONCLUSION MDCT dose reductions of up to 99% did not significantly alter the subjective classification of bone at dental implant sites.

Localization of the inferior alveolar canal using ultralow dose CT with iterative reconstruction techniques

Objectives: To compare subjective and objective localization of the inferior alveolar canal (IAC) on multidetector CT (MDCT) images obtained by ultralow doses in combination with the reconstruction techniques of filtered backprojection (FBP), adaptive statistical iterative reconstruction (ASIR), or model-based iterative reconstruction (MBIR) as compared to standard dose MDCT and FBP. Methods: Three cadavers were imaged with a reference standard dose MDCT examination (volume CT dose index: 29.4 mGy) reconstructed with FBP and 5 low dose protocols (LD1-5) (volumeCT dose index: 4.19, 2.64, 0.99, 0.53, 0.29 mGy) reconstructed with FBP, ASIR 50, ASIR 100, and MBIR. Linear measurements from the crest of the ridge to the roof of the IAC were recorded. The results from the test protocols were compared with those from the reference using Bland–Altman plots. Results: Only three test protocols allowed the identification of the position of the IAC on all the sample sites: LD1/FBP and LD1/ASIR 100 and LD2/FBP. All three protocols allowed identification of the IAC with comparable results to the reference dose protocol; the 95% confidence interval limits for the measurement differences were ± 0.41 mm, but the differences were not statistically significant. The calculated effective dose for the LD2 protocol, for a scan length of 5 cm, was 27.7 µSv. Conclusions: Using FBP, comparable IAC measurements were achieved with 91% reduction in dose compared with a standard exposure protocol. The use of ASIR and MBIR did not improve identification of the IAC in MDCT low dose images.

Apparent discontinuity of the roof of the glenoid fossa on cone-beam computed tomography images of an asymptomatic temporomandibular joint

The thickness of the roof of the glenoid fossa (RGF) is highly variable, but there are no reported cases of absence of mineralized bone at the RGF in an asymptomatic patient. We present the rare finding of a large apparent discontinuity of the RGF discovered incidentally on cone-beam computed tomography (CBCT) images of an asymptomatic temporomandibular joint in a 22-year-old female, which was proven to be a normal joint on magnetic resonance images. The apparent discontinuity of the RGF in this case, considered in the light of known measurements of the RGF, may actually represent very thin bone that could not be visualized because of the relatively large CBCT voxel size. A review of the published literature revealed no clinical significance of a thin RGF.

The validity of different display monitors in the assessment of dental implant site dimensions in cone beam computed tomography images

Abstract Objective. To determine if the differing contrast resolution of various LCD monitors affects the reliability or accuracy of measurements of proposed implant sites. Materials and methods. Edentulous areas of human dry skulls were marked with radiopaque markers in order to standardize the plane of the transverse cross-sections of the ridges and path of measurements. The skulls were imaged by a CBCT device and the images stored in proprietary format on the workstation. The data sets were then transferred, with the proprietary reformatting software, to two different laptops using CDs. Transverse cross-sectional images of the ridges were reformatted on all three computers and ridge dimensions were recorded using the linear measurement tool of the proprietary software. Ridge dimensions were recorded directly from the three different monitors by two observers and compared to measurements recorded directly from the bone. The measurement errors and intra- and inter-examiner reliability were calculated for each monitor and compared with each other. Results. Intra- and inter-examiner reliability scores for the measurements recorded from all three devices were very high and ranged between 0.993–0.999. The mean of the absolute errors was 0.55 mm for the workstation, 0.61 mm for laptop 1 and 0.68 mm for laptop 2. The absolute errors were statistically significant for all three monitors (p-value < 0.001), but there was no statistically significant difference between the absolute errors obtained from the three monitors. Conclusions. No differences in the reliability or accuracy of measurements of implant site dimensions were obtained using color LCD monitors with different contrast resolution capabilities.

Comparative analysis of prevalence of apical periodontitis in smokers and non-smokers using cone-beam computed tomography

Objective The aim of this study was to compare the prevalence and size of periapical lesions among smokers and non-smokers using cone-beam computed tomography (CBCT). Materials and methods Retrievable CBCT datasets for 46 male patients ≥18 years during a consecutive period from 2008 to 2016 were examined. The medical, smoking history and other clinical findings (signs of previous dental trauma; Decayed Missing Filled Teeth (DMFT) scores; the percentage of root filled teeth; and oral hygiene status) were obtained. Periapical status of all included teeth was assessed by CBCT images. Statistical analysis was conducted using t-test, Pearson correlation and multiple regression. Results The prevalence of apical periodontitis was 13.93% in smokers and 14.26% in non-smokers with no significant difference (p = 0.936). The mean of the average size of lesions between the two groups were almost comparable, 3.50 mm in smokers and 2.89 mm in non-smokers (p = 0.567). Pearson correlation and multiple regression analysis showed that the percentage of lesion present and the average lesion size were not correlated to any independent variable. Conclusions While smoking is considered a risk factor for marginal periodontitis, there was no difference between smokers and non-smokers in terms of apical periodontitis.

Ultralow Dose MSCT Imaging in Dental Implantology

Introduction: The Council Directive 2013/59 Euratom has a clear commitment for keeping medical radiation exposure as low as reasonably achievable and demands a regular review and use of diagnostic reference levels. Methods: In dental implantology, the range of effective doses for cone beam computed tomography (CBCT) shows a broad overlap with multislice computed tomography (MSCT). More recently, ultralow dose imaging with new generations of MSCT scanners may impart radiation doses equal to or lower than CBCT. Dose reductions in MSCT have been further facilitated by the introduction of iterative image reconstruction technology (IRT), which provides substantial noise reduction over the current standard of filtered backward projection (FBP). Aim: The aim of this article is to review the available literature on ultralow dose CT imaging and IRTs in dental implantology imaging and to summarize their influence on spatial and contrast resolution, image noise, tissue density measurements, and validity of linear measurements of the jaws. Conclusion: Application of ultralow dose MSCT with IRT technology in dental implantology offers the potential for very large dose reductions compared with standard dose imaging. Yet, evaluation of various diagnostic tasks related to dental implantology is still needed to confirm the results obtained with various IRTs and ultra-low doses so far.

Radiology of Implant Dentistry

The article presents an overview of the goal of imaging at each stage of implant therapy and the usefulness and limitations of multidetector computed tomography (MDCT) in achieving those goals. Various MDCT protocols of use in implant imaging also are presented, with an emphasis on dose reduction and the use of iterative reconstruction techniques. Also discussed are options for viewing and analysis of CT images, issues related to appropriate image reformatting and interpretation, interactive treatment planning, and transfer of information from the images to the surgical field during implant surgery using surgical guides and CT-guided navigation systems.

Revised, Computed Tomography–Based Lekholm and Zarb Jawbone Quality Classification

PURPOSE To propose a revised Lekholm and Zarb classification that takes into account all possible combinations of compact and trabecular bone and to provide guidelines for increased reproducibility of the classification. MATERIALS AND METHODS Three new classes were added to the previous classification. The new classes have been designated as subclasses of bone types 2 and 3, as follows: Type 2b: Thick layer of compact bone surrounding a core of medium-density trabecular bone; Type 2c: Thick layer of compact bone surrounding a core of low-density trabecular bone; and Type 3b: Thin layer of compact bone surrounding a core of medium-density trabecular bone. Three interpretation guidelines were recommended to increase the reproducibility of the revised classification. Three experienced examiners were trained using the revised classification and provided with computed tomography (CT) sectional images of edentulous jawbones for classification. Each examiner classified the images twice with at least a 1-week interval. The intra-observer agreement was measured. RESULTS The kappa statistic for the intra-observer agreement of the examiners ranged from 0.835 to 0.919 (P < .001). CONCLUSION The high reproducibility of the proposed revised CT-based Lekholm and Zarb classification obtained in the current study suggests its efficacy in distinguishing between the various combinations of compact and trabecular bone.