Accuracy of Linear Measurements in Cone Beam Computed Tomography With Different Voxel Sizes

Accuracy of linear measurements for implant planning based on low-dose cone beam CT protocols: a systematic review and meta-analysis

OBJECTIVES

The aim of this systematic review was to verify the accuracy of linear measurements performed on low-dose CBCT protocols for implant planning, in comparison with those performed on standard and high-resolution CBCT protocols.

METHODS

The literature search included four databases (Pubmed, Web of Science, Embase, and Scopus). Two reviewers independently screened titles/abstracts and full texts according to eligibility criteria, extracted the data, and examined the methodological quality. Risk of bias assessment was performed using the Quality Assessment Tool For In Vitro Studies. Random-effects meta-analysis was used for pooling measurement error data.

RESULTS

The initial search yielded 4684 titles. In total, 13 studies were included in the systematic review, representing a total of 81 samples, while 9 studies were included in the meta-analysis. The risk of bias ranged from medium to low. The main results across the studies indicate a strong consistency in linear measurements performed on low-dose images in relation to the reference methods. The overall pooled planning measurement error from low-dose CBCT protocols was -0.24 mm (95% CI, -0.52 to 0.04) with a high level of heterogeneity, showing a tendency for underestimation of real values. Various studies found no significant differences in measurements across different protocols (eg, voxel sizes, mA settings, or dose levels), regions (incisor, premolar, molar) and types (height vs. width). Some studies, however, noted exceptions in measurements performed on the posterior mandible.

CONCLUSION

Low-dose CBCT protocols offer adequate precision and accuracy of linear measurements for implant planning. Nevertheless, diagnostic image quality needs must be taken into consideration when choosing a low-dose CBCT protocol.

The role of implants and implant prostheses on the accuracy and artifacts of cone-beam computed tomography: an in-vitro study

To assess the accuracy of CBCT in implant-supported prostheses and to evaluate metal artifacts with and without implants or implant prostheses. Accuracy and artifacts were assessed in the dried mandible at three points on the buccal and lingual cortical plates on the mandible's body near the crest and the base. On the buccal cortical plate, these points were labelled as A, B and C near the crest and D, E and F near the base of the body of the mandible. Similarly, points a to f were marked on the lingual cortical plate corresponding to points A to F. The study had two control groups, C0 for physical linear measurement (PLM) and C1 for radiographic linear measurement (RLM) and artifact assessment. There were seven test groups, TG 1 to 7, progressing from a single implant to implant full-arch prosthesis. For accuracy assessment, PLM was compared to RLM. CBCT artifacts were investigated in images integrated at 0.25 mm, 10 mm, and 20 mm at regions of interest on concentric circles at different intersecting angles by comparing grayscale values at C1 and TG1 to 7. The data were collected and statistically analyzed. A significant difference was observed between C0 and C1, and RLM in test groups at the superior axial plane. Similarly, PLM and test RLM in the sagittal plane at A-B, B-C, and D-E were statistically significant. A significant difference between PLM and RLM was also observed in the vertical plane at A-D, B-E, and C-F. Quantification of CBCT artifacts in the presence of implants or prostheses revealed that full-arch prostheses had the highest mean grayscale value, whereas single implants with a prosthesis had the lowest. The mean grayscale change was greatest around the implant and implant prosthesis. The mean grayscale value was maximum at 20 mm voxel integration scales (VIS) and lowest at 0.25 mm. CBCT is a clinically reliable device. Metal in implants or implant-supported prostheses prevents true assessment of the peri-implant area; therefore, lower VIS is suggested in the presence of implants or implant prostheses.

Reproducibility of human landmark identification in morphological mandible prototypes: major parameters for a 3D CBCT approach

The establishment of anthropometric measurements is of fundamental importance for the correct identification of human bodies. The objective of this study was to evaluate the accuracy and reliability of two-dimensional craniometric landmarks obtained from three-dimensional cone beam computed tomography reconstructions for forensic identification of humans. Computed tomography images with voxel sizes of 0.25, 0.3, and 0.4 mm were obtained using i-CAT® three-dimensional equipment. Ten landmarks were randomly selected, and 10 measurements were demarcated in the three-dimensional reconstruction to evaluate the mandibular condyle, ramus, and body. This study demonstrated that protocols with voxels of 0.3 mm should be preferentially indicated for the evaluation of linear and angular measurements. Implementing our methodology using prototypes for clinical and forensic simulations allows comparisons with human databases in identification issues.

Quantitative and qualitative comparisons of pulp cavity volumes produced by cone beam computed tomography and micro-computed tomography through semiautomatic segmentation: An ex vivo investigation

OBJECTIVE

The aim of this study was to measure the volume and visually assess 3-dimensional (3D) virtual models of pulp cavities obtained through semiautomatic segmentation on images from 6 cone beam computed tomography (CBCT) units compared with the reference standard of micro-CT.

STUDY DESIGN

Fifteen mandibular premolar teeth were scanned with 6 CBCT units: Prexion 3D Elite, i-CAT Next Generation, NewTom 5G, Cranex 3D, 3Shape X1, and Orthophos SL 3D, using the smallest available field of view and highest resolution settings. Pulp cavity volumes were quantitatively assessed by 2 calibrated examiners. The volumes from each CBCT unit were compared with micro-CT. Qualitative assessment of the 3D reconstructions was also performed. Repeated-measures analysis of variance and the Friedman test compared the CBCT reconstructions to micro-CT. Intra- and interexaminer agreements were calculated with the intraclass correlation coefficient and kappa statistic.

RESULTS

The CBCT-based volumes were all significantly larger than micro-CT (P ≤ .0061). Prexion, X1, and Orthophos provided the segmentations that most closely resembled the reference standard. Intra- and interexaminer agreements ranged from good to excellent for quantitative measurements. Interexaminer agreement for qualitative evaluation was substantial.

CONCLUSIONS

Semiautomatic segmentation of CBCT images is a feasible method to produce virtual 3D models of the pulp cavity. Prexion, X1, and Orthophos were the CBCT units that resulted in 3D reconstructions most similar to the reference standard.

Association of Mandibular Posterior Anatomic Limit with Skeletal Patterns and Root Morphology Using Three-Dimensional Cone Beam Computed Tomography Comprehensive Analysis

This study aimed to clarify the relationship between the mandibular posterior anatomic limit (MPAL) and skeletal anteroposterior and vertical skeletal patterns, with consideration of factors that may be related. In total, 230 people were included: 49 Japanese, 122 Egyptian, and 59 Korean people. The MPAL was measured at 0, 2, 4, and 6 mm from the root furcation along the sagittal and cuspal lines at the distance from the distal root of the mandibular right second molar to the mandibular cortex of the lingual bone. Eight different MPALs were evaluated using multiple regression analysis with explanatory variables for anteroposterior and vertical skeletal patterns and qualitative variables for age, sex, population, the presence of third molars, number of roots, presence of C-shaped roots, and Angle malocclusion classification. The MPAL was significantly larger as the mandibular plane angle decreased. The MPAL near the root apex was significantly larger as the A-nasion-point B angle increased, and the MPAL near the root apex measured at the cuspal line was significantly larger for C-type roots. The present study showed that a C-shaped root affected the MPAL in addition to the anteroposterior and vertical skeletal patterns.

Evaluation of the effect of autologous conditioned serum on the radiographic characteristics of hard tissue after horizontal bone augmentation in implant dentistry

Background. Bone deficiency in different areas is problematic in implant placement. Changes in histological, histomorphometric, and radiographic properties of hard tissues in the implant placement area affect many parameters of implant success. Autologous conditioned serum (ACS) is a blood product with high levels of IL1- receptor antagonists. Augmentation surgeries are required in many cases because implant placement in the edentulous areas requires a sufficient amount of bone. Therefore, this study radiographically evaluated the effect of autologous conditioned serum after horizontal bone augmentation. Methods. In this prospective RCT, 21 patients eligible patients were evaluated. The patient underwent horizontal ridge augmentation surgery in the area. The ACS-impregnated graft was in direct con-tact with the bone. The control side underwent the same surgical protocol without using ACS. Four months after surgery, a CBCT radiograph was taken, and radiographic changes in the two areas were calculated using the differences in the amount of bone formed in the horizontal dimension as well as the Hounsfield unit (HU). The data were reported using descriptive statistical methods, including means (standard deviations) and frequencies (percentages). According to the results of the Kolmog-orov-Smirnov test, the data had a normal distribution (P>0.05); therefore, paired t-test was used to compare the means of the parameters between the two groups. Results. IRadiographic examinations showed that the horizontal dimension of bone before surgery was similar between the two groups. However, after surgery in the ACS group (33.13±6.1), it was significantly higher than in the control group (62.1±86.4) (P>0.05). Also, the rate of horizontal dimension increase (the difference before and after surgery) in the ACS group was significantly higher than in the control group. Bone density before surgery was similar between the two groups. However, after surgery, there was a significant increase in the ACS group (75.56±330.42 HUs) compared to the control group (38.35±292.38 HUs) (P>0.05). Also, the rate of density increase (the difference before and after surgery) in the ACS group was significantly higher than in the control group. Conclusion. Radiographic evaluations of hard tissues showed a significant increase in the horizontal dimension of bone and density of newly formed bone using ACS compared to the control group.

Intraoral Scanning as an Alternative to Evaluate the Accuracy of Dental Implant Placements in Partially Edentate Situations: A Prospective Clinical Case Series

(1) Background: For years, Cone-Beam Computed Tomography’s (CBCT) have been the golden standard to evaluate implant placement accuracy. By validating Intraoral Scans (IOS) as an alternative to determine implant placement accuracy, a second CBCT could be avoided. (2) Methods: Using dynamic guided implant surgery, 23 implants were placed in 16 partially edentate patients. Preoperatively, both CBCT and IOS (Trios® 3) were obtained and subsequently imported into DTX Studio™ planning software to determine the ideal implant location. A CBCT scan and an IOS including scan abutments were acquired immediately after placement. Both postoperative CBCT and postoperative IOS were used to compare the achieved implant position with the planned implant position and were projected and analyzed using the Implant Position Orthogonal Projection (IPOP) method. (3) Results: Mean differences between the CBCT and IOS methods on the mesio−distal plane were 0.09 mm (p = 0.419) at the tip, 0.01 mm (p = 0.910) at the shoulder, −0.55° (p = 0.273) in angulation, and 0.2 mm (p = 0.280) in implant depth. Mean differences between both methods on the bucco-lingual/bucco-palatal plane were 0.25 mm (p = 0.000) at the tip, 0.12 mm (p = 0.011) at the shoulder, −0.81° (p = 0.002) in angulation, and 0.17 mm (p = 0.372) in implant depth. A statistical analysis was performed using a paired t-test. All mesiodistal deviations between the two methods showed no significant differences (p > 0.05). Buccolingual/buccopalatal deviations showed no significant difference in implant depth deviation. However, significant differences were found at the tip, shoulder, and angulation (p < 0.05). These values are of minimal clinical significance. (4) Conclusions: This study supports the hypothesis that a postoperative IOS is a valid alternative for determining implant placement accuracy.

Skeletal, Dentoalveolar and Dental Changes after "Mini-Screw Assisted Rapid Palatal Expansion" Evaluated with Cone Beam Computed Tomography

The purpose of this study was to evaluate skeletal, dentoalveolar and dental changes after Mini-screw Assisted Rapid Palatal Expansion (MARPE) using tooth bone-borne expanders in adolescent patients after analyzing different craniofacial references by Cone beam computed tomography (CBCT) and digital model analysis. This prospective, non-controlled intervention study was conducted on fifteen subjects (mean age 17 ± 4 years) with transversal maxillary deficiency. Pre (T1) and post-expansion (T2) CBCTs and casts were taken to evaluate changes at the premolars and first molar areas. To compare means between two times, paired samples t- or Wilcoxon test were used following criteria. Significant skeletal changes were found after treatment for Nasal width and Maxillary width with means of 2.1 (1.1) mm and 2.5 (1.6) mm (p < 0.00005). Midpalatal suture showed a tendency of parallel suture opening in the axial and coronal view. For dentoalveolar changes, a significant but small buccal bone thickness (BBT) reduction was observed in all teeth with a mean reduction of 0.3 mm for the right and left sides, especially for the distobuccal root of the first molar on the left side (DBBTL1M) [IC95%: (−0.6; −0.2); p = 0.001] with 0.4 (0.4) mm. However, a significant augmentation was observed for the palatal bone thickness (PBT) on the left side. The buccal alveolar crest (BACL) and dental inclination (DI) showed no significant changes after treatment in all the evaluated teeth. MARPE using tooth bone-borne appliances can achieve successful skeletal transverse maxillary expansion in adolescent patients, observing small dentoalveolar changes as buccal bone thickness (BBT) reduction, which was not clinically detectable. Most maxillary expansions derived from skeletal expansion, keeping the alveolar bone almost intact with minor buccal dental tipping.

Three-dimensional quantification of the relationship between the upper first molar and maxillary sinus

Objectives

The present study aims to describe the relationship between upper first molar roots and maxillary sinus, for the first time with a truly three‐dimensional approach.

Methods

From a retrospective cone‐beam computed tomography (CBCT) sample of the upper jaw, a total of 105 upper first molars in contact with maxillary sinus from 74 patients (male 24, female 50, mean age 42) were included in the present study. Segmentation of the upper first molar and maxillary sinus in CBCT was performed utilizing a semiautomatic livewire segmentation tool in MeVisLab v.3.1. The segmentations were analyzed in 3‐matic Medical 20.0 for root volume and the contact area between upper first molar roots and maxillary sinus. Analysis of variance test was applied to detect statistically significant differences between the roots.

Results

The palatal root had the largest contact area with maxillary sinus 27.8 ± 21.4 mm² (20% of the root area) followed by the mesiobuccal 20.5 ± 17.9 mm² (17% of the root area) and distobuccal root 13.7 ± 12 mm² (14% of the root area). A significant difference in the contact area of the different roots of the upper first molar was seen.

Conclusions

This study showed that 70% of the upper first molars were in contact with the maxillary sinus. The palatal root had on average a fifth of its root surface in contact with the sinus, while for mesiobuccal this was a sixth of its root surface and distobuccal roots this was somewhat less. The true 3D relationship could help to better understand maxillary anatomy in relation to occurring pathologies and treatment planning in this area.

Prevalence and extension of the anterior loop of the mental nerve in different populations and CBCT imaging settings: A systematic review and meta-analysis

Purpose

Materials and Methods

Results

Conclusion

Development of a deep learning model for automatic localization of radiographic markers of proposed dental implant site locations

Objectives

To develop a Deep Learning Artificial Intelligence (AI) model that automatically localizes the position of radiographic stent gutta percha (GP) markers in cone beam computed tomography (CBCT) images to identify proposed implant sites within the images, and to test the performance of the newly developed AI model.

Materials and Methods

Thirty-four CBCT datasets were used for initial model training, validation and testing. The CBCT datasets were those of patients who had a CBCT examination performed wearing a radiographic stent for implant treatment planning. The datasets were exported in Digital Imaging and Communications in Medicine (DICOM), then imported into the software Horos ®. Each GP marker was manually labelled for object detection and recognition by the deep learning model by drawing rectangles around the GP markers in all axial images, then the labelled images were split into training, validation, and test sets. The axial sections of 30 CBCT datasets were randomly divided into training and validation sets. four CBCT datasets were used for testing the performance of the deep learning model. Descriptive statistics were calculated for the number of GP markers present, number of correct and incorrect identifications of GP markers.

Result

The AI model had an 83% true positive rate for identification of the GP markers. Of the areas labelled by the AI model as GP markers, 28 % were not truly GP markers, but the overall false positive rate was 2.8 %.

Conclusion

An AI model for localization of GP markers in CBCT images was able to identify most of the GP markers, but 2.8% of the results were false positive and 17% were missed GP markers. Using only axial images for training an AI program is not enough to give an accurate AI model performance.

Presurgical Assessment of Anatomical Landmark Position Using Two Views of Cone Beam Computed Tomography: A Comparative Radiological Study

BACKGROUND

Cone beam computerized computed tomography (CBCT) has been widely indicated in dental implant procedure. The first step that the doctors should perform in local hospitals is to use orthopantomography for surgical planning to avoid and limit the risk of complications. As a result, determining the magnification amount of orthopantomography to achieve a precise diagnosis is clinically important. This study investigated the difference in measurement of the mental foramen (MF) position before dental surgery using 2 views of CBCT.

MATERIALS AND METHODS

Cone beam computed tomography scan was performed for 100 patients who required implant placement. In the panoramic and three-dimensional views of CBCT, the vertical distance between the margin of the mandible and the lower border of MF, and the horizontal distance between the mandibular symphysis and the mesial anterior border of MF were calculated. The differences between the 2 views were compared using Wilcoxon-rank U test with P value ≤ 0.05 considered statistically significant.

RESULTS

The findings of this study showed a substantial statistical difference in the horizontal distance for the dentate patients in panoramic and three-dimensional views (22.7 ± 3.04 versus 21.1 ± 1.6), (22.5 ± 2.4 versus 20.9 ± 1.5) and left side (22.4 ± 2.8 versus 21.2 ± 1.6), (22.4 ± 2.8 versus 20.6 ± 1.4) of both genders. Concerning the vertical distance, a significant difference was also observed in the dentate (12.1 ± 2.1 versus 11.1 ± 1.4), (10.6 ± 1.4 versus 9.6 ± 1.3) and left side of the jaw (11.6 ± 1.95 versus 10.9 ± 1.2), (10.5 ± 1.2 versus 9.96 ± 1.4) for both genders in both views. In the edentulous and right side of the jaw, however no statistical difference was observed between male and female patients in terms of horizontal and vertical measurements.

Comparative study of the accuracy of CBCT implant site measurements using different software programs

Purpose

To measure and compare the accuracy of the linear dimensions of implant sites recorded from cone beam computed tomography (CBCT) images using Blue Sky Plan, coDiagnostiX, and RadiAnt.

Materials and Methods

Five human dry skulls were imaged with a CBCT device then sectioned to obtain sample transverse cross-sections of the edentulous ridges, and the height and width of the ridge were measured with a digital caliper to provide the gold standard measurements. The CBCT datasets were exported in DICOM format and imported into the three test software programs which were used to obtain reformatted sectional images corresponding to the sample transverse cross-sections, and the height and width of the edentulous ridge was recorded using the linear measurement tool. Reliability of the measurements were measured using the intraclass correlation coefficient. One-sample t-test (test value: zero) was used to test the statistical significance of the mean of the absolute errors for each software program. Analysis of Variance with Repeated Measures was used to test the statistical significance of the difference between the means of the absolute errors obtained by the different software programs. Statistical significance was set at a p-value of 0.05.

Results

The reliability of the gold standard and image measurements were excellent. All three software programs demonstrated a statistically significant mean absolute measurement error of between 0.43 and 0.56 mm (p-value < 0.01), but no significant difference in error values was found between any of the tested programs (p- value = 0.18).

Conclusions

There was no statistically significant difference in accuracy of linear CBCT measurements of implant sites recorded using Blue Sky Plan, coDiagnostiX, and RadiAnt.

Mandibular skeletal posterior anatomic limit for molar distalization in patients with Class III malocclusion with different vertical facial patterns

Objective

The aim of this study was to compare the differences in mandibular posterior anatomic limit (MPAL) distances stratified by vertical patterns in patients with skeletal Class III malocclusion by using cone-beam computed tomography (CBCT).

Methods

CBCT images of 48 patients with skeletal Class III malocclusion (mean age, 22.8 ± 3.1 years) categorized according to the vertical patterns (hypodivergent, normodivergent, and hyperdivergent; n = 16 per group) were analyzed. While parallel to the posterior occlusal line, the shortest linear distances from the distal root of the mandibular second molar to the inner cortex of the mandibular body were measured at depths of 4, 6, and 8 mm from the cementoenamel junction. MPAL distances were compared between the three groups, and their correlations were analyzed.

Results

The mean ages, sex distribution, asymmetry, and crowding in the three groups showed no significant differences. MPAL distance was significantly longer in male (3.8 ± 2.6 mm) than in female (1.8 ± 1.2 mm) at the 8-mm root level. At all root levels, MPAL distances were significantly different in the hypodivergent and hyperdivergent groups (p < 0.001) and between the normodivergent and hyperdivergent groups (p < 0.01). MPAL distances were the shortest in the hyperdivergent group. The mandibular plane angle highly correlated with MPAL distances at all root levels (p < 0.01).

Conclusions

MPAL distances were the shortest in patients with hyperdivergent patterns and showed a decreasing tendency as the mandibular plane angle increased. MPAL distances were significantly shorter (~3.16 mm) at the 8-mm root level.

Evaluation of alveolar process resorption after tooth extraction using the socket shield technique without immediate installation of implants: a randomised controlled clinical trial

Our aim was to evaluate resorption of the alveolar ridge using the socket shield technique (SST) without immediate placement of dental implants. This randomised controlled clinical trial included 27 patients: 14 maxillary non-molar teeth were partially extracted using the SST (test group) and 13 were extracted using a minimally traumatic extraction approach (control group). Alterations in height and thickness of the alveolar ridge were evaluated by cone beam computed tomograms taken immediately after, and 100 days after, surgery. Minor resorption was observed in the height of the buccal and palatal plates, without intergroup difference (p ≥ 0.10). The test group showed significantly better preservation of the buccal-to-palatal crest dimension (p ≤ 0.05). In the control group, preservation of buccal plate thickness was significantly greater (p ≤ 0.05), but intragroup vertical resorption of the buccal plate and reduction in the buccal-to-palatal crest distance were greater (p ≤ 0.05). The SST without the immediate placement of implants showed greater preservation of the buccal-to-palatal crest dimension and lower preservation of buccal wall thickness compared with minimally traumatic extraction. In addition, it provided superior maintenance of the baseline buccal wall height. The modified SST is a promising approach, but factors that interfere with the results should be investigated.

Identification of mandibular canal in cone beam computed tomography plane with different voxel sizes

Introduction

Identification of the mandibular canal (MC) is essential before any lower jaw surgical procedures. Understanding the anatomical variations of the MC is essential for preventing postoperative complications.

Objectives

We assessed the observer agreement for identifying the MC in cone-beam computed tomography (CBCT) images and to study the effect of changing the voxel size on such agreements.

Material and methods

We obtained images of mandibles from ten dry skulls using a water phantom with two voxels: 0.18 and 0.3 mm. The identification of the MC was made in five sites bilaterally in each mandible by two examiners.

Results

A total of 82 sites were included. Differences in measurements between images obtained with each scanning protocol and the reference images were calculated using descriptive statistics. There was an agreement between the two examiners in identifying the MC in CBCT images. No significant differences were found for identifying the MC when the voxel sizes were changed. There was a strong correlation coefficient between the two examiners for both voxel sizes (p < 0.001).

Conclusion

This study showed that voxel size, in the range from 0.18 to 0.3 mm, has no direct effect on the identification of the MC.

The dimensions of the facial alveolar bone at tooth sites with local pathologies: a retrospective cone-beam CT analysis

OBJECTIVE

To assess the impact of various local pathologies on facial alveolar bone dimensions at tooth sites.

MATERIALS AND METHODS

Cone-beam computed tomography images of 60 patients were analyzed. Healthy teeth and teeth with local pathologies (i.e., endodontically treated, periodontally diseased teeth, and teeth with periapical lesions) were included. The thickness of the facial alveolar bone was measured at five locations: (1) the bone crest (W0), (2) 25% (W25), (3) 50% (W50), (4) 75% (W75) of the distance from the bone crest to the root apex (A), and (5) in the A region (W100). The results were considered statistically significant at p < 0.0008 (adjustment according to the statistical correction for multiple testing).

RESULTS

A total of 1174 teeth (707 healthy and 467 with the local pathologies) were assessed. Periodontally diseased maxillary premolars and anterior teeth in the mandible in the W0 position, as well as maxillary molars in the W25 position, tended to have a lower facial bone thickness when compared to the healthy teeth (0.68 mm vs. 0.84 mm, p = 0.008; 0.47 mm vs. 0.55 mm, p = 0.004; and 1.27 mm vs. 1.72 mm; p = 0.009, respectively). In contrast, the observed tendency pointed towards thicker facial bone wall for the periodontally diseased mandibular anterior teeth in the W50 position (0.74 vs. 0.52, p = 0.001). Healthy maxillary molars tended to display a thicker facial alveolar bone compared to the teeth with local pathologies in the W25, W50, and W75 positions (p = 0.001, p = 0.005, and p = 0.004, respectively).

CONCLUSIONS

The present analysis has indicated that local pathologies are commonly associated with a compromised socket morphology.

CLINICAL RELEVANCE

The facial bone thickness was particularly reduced at periodontally diseased teeth, which may challenge implant therapy.

Detection of alveolar bone defects with three different voxel sizes of cone-beam computed tomography: an in vitro study

This study was conducted to assess the accuracy of cone-beam computed tomography (CBCT) of different voxel sizes in the detection of alveolar bone defects, and to select the optimal voxel size for clinical use. 46 in-vitro teeth were placed in bovine ribs in which alveolar bone defects were randomly simulated. In total, 32 alveolar bone defects and 14 teeth without periodontal defects were used. CBCT images were acquired with the use of three different voxel sizes: 0.125-mm, 0.2-mm and 0.4-mm. The scan data were 3D-reconstructed in Mimics software and evaluated by two observers with more than 5 years of experience in CBCT. Receiver operating characteristic (ROC) curves and diagnostic values were obtained. Pairwise comparison of ROC curves was made for evaluation of the diagnostic values of different voxel sizes. Kappa statistics assessed the observer reliability. Results were considered significant at P < 0.05. It showed no statistically significant difference between 0.125-mm group and 0.2-mm group, but 0.4-mm group had lower Az values that differed significantly from 0.125-mm and 0.2-mm groups (P < 0.05). Based on diagnostic value and radiation protection, 0.2-mm voxel size may be a good choice for the detection of bone defects with CBCT.

A NEWLY DEVELOPED PHANTOM FOR PHYSICAL QUALITY ASSURANCE OF DENTAL CONE-BEAM COMPUTED TOMOGRAPHY

Two phantoms for a performance evaluation of cone-beam computed tomography (CBCT) were developed and their efficiency was tested. The first phantom, for low-contrast resolution, consisted of an acrylic circular plate with three 0.5-1.0 mm diameter rods. These rods enable the user to visually evaluate the limit of observation. The second phantom, for geometric distortion, especially focused on the z-axis and consisted of two tabular acryl plates crossed perpendicularly with 1.0 mm-wide grooves in a grating form every 10.0 mm. The distances between the grooves on the axial and coronal images were evaluated. Five CBCT modalities were assessed using these phantoms. The contrast resolutions differed for each apparatus and set of exposure parameters. In terms of geometric distortion, some distortion was observed at the periphery of the field of view for both the axial and z-axis planes. These results suggest that our new phantoms can be used to evaluate CBCT.

Three-dimensional evaluation of maxillary sinus volume in different age and sex groups using CBCT

AIM

Sinus maxillaris is an important anatomical formation in many branches of dentistry due to its proximity to the field of work. Various methods have been used in literature to measure the maxillary sinus volume (MSV) such as cadavers, stereology, two-dimensional conventional radiographs, computed tomography (CT), magnetic resonance imaging (MRI). The aim of this study is to evaluate the change of maxillary sinus volume according to age and gender with MIMICS 19.0 (Materialise HQ Technologielaan, Leuven, Belgium) which is one of three-dimensional modeling software.

MATERIALS AND METHODS

This study was performed in 200 patients selected by a retrospective review of the archives of the Dicle University, Faculty of Dentistry, Department of Oral and Maxillofacial Radiology. Patients were divided into five age groups (18-24 years, 25-34 years, 35-44 years, 45-54 years, and ≥ 55 years) and by sex. Cone-beam computed tomography (CBCT) images of the patients were transferred to the MIMICS software and the MSV was measured. All statistical analyses were performed using the SPSS (Statistical Package for Social Sciences, version 21) software.

RESULTS

There was no statistically significant difference between the right and left maxillary sinus volume according to the findings obtained from our study, and maxillary sinus volume in males was found to be significantly higher than that of females. Another finding of our study is that the maxillary sinus volume decreases with age increase. Especially it was also found that the sinus volume in males in the 18-24 age group was statistically significantly higher than females.

CONCLUSION

Consequently, maxillary sinus volume measurements can be made on CT, CBCT, MRI scans using reconstruction software.

Accuracy of linear measurements on CBCT images related to presurgical implant treatment planning: A systematic review

OBJECTIVE

The aim of this systematic review was to identify, review, analyze, and summarize available evidence on the accuracy of linear measurements when using maxillofacial cone beam computed tomography (CBCT) specifically in the field of implant dentistry.

MATERIAL AND METHODS

The search was undertaken in April 2017 in the National Library of Medicine database (Medline) through its online site (PubMed), followed by searches in the Cochrane, EMBASE, ScienceDirect, and ProQuest Dissertation and Thesis databases. The main inclusion criterion for studies was that linear CBCT measurements were performed for quantitative assessment (e.g., height, width) of the alveolar bone at edentulous sites or measuring distances from anatomical structures related to implant dentistry. The studies should compare these values to clinical data (humans) or ex vivo and/or experimental (animal) findings from a "gold standard."

RESULTS

The initial search yielded 2,516 titles. In total, 22 studies were included in the final analysis. Of those, two were clinical and 20 ex vivo investigations. The major findings of the review indicate that CBCT provides cross-sectional images that demonstrate high accuracy and reliability for bony linear measurements on cross-sectional images related to implant treatment. A wide range of error has been reported when performing linear measurements on CBCT images, with both over- and underestimation of dimensions in comparison with a gold standard. A voxel size of 0.3 to 0.4 mm is adequate to provide CBCT images of acceptable diagnostic quality for implant treatment planning.

CONCLUSIONS

CBCT can be considered as an appropriate diagnostic tool for 3D preoperative planning. Nevertheless, a 2 mm safety margin to adjacent anatomic structures should be considered when using CBCT. In clinical practice, the measurement accuracy and reliability of linear measurements on CBCT images are most likely reduced through factors such as patient motion, metallic artefacts, device-specific exposure parameters, the software used, and manual vs. automated procedures.

Influence of voxel size on the accuracy of linear measurements of the condyle in images of cone beam computed tomography: A pilot study

Background

To analyze the influence of voxel size and exposure time on the accuracy of linear measurements of the condyle.

Material and Methods

Four macerated hemi-mandibles of pigs were scanned in nine different voxel size protocols. Three-dimensional models of the condyle were generated in order to establish a comparison between linear measurements obtained with each voxel protocol and those obtained with a caliper (gold standard). The comparison between the protocols was performed considering the average of the two measurements of the condyle in the latero-medial (LM) and antero-posterior (AP) axes and also through repeated measurement ANOVA with rank transformation. The level of significance was 5%.

Results

A significant difference was found between the protocols regarding the LM and AP variables (p-values = 0.0027 and 0.0263, respectively). In the LM axis, the protocol P6 (voxel size of 0.3 mm with scan time of 4.8 seconds) did not show statistical difference compared to the gold standard. The protocols P4 and P5 (voxel size of 0.25 mm with scan times of 14.7 and 26.9 seconds, respectively) were both statistically similar compared to caliper, although they have presented a longer scan time. In the AP axis, the protocol P8 (voxel size of 0.4 mm with time scan of 4.8 seconds) was statistically similar to the gold standard.

Conclusions

A smaller voxel size does not necessarily mean more accuracy regarding the linear measurements of the condyle. It is possible to obtain an acceptable level of accuracy with a larger voxel size and a shorter exposure time to radiation.

Key words:CBCT, voxel size, linear measurement, diagnostic imaging.

Reliability and accuracy of cone-beam computed tomography voxel density and linear distance measurement at different voxel sizes: A study on sheep head cadaver

Background/purpose

The reliability and accuracy of linear distance and voxel density (VD) measurements are very important in dentistry. The purpose of this study was to assess the accuracy and reliability of linear distances and VD measurements of cone-beam computed tomography (CBCT) at different voxel sizes.

Materials and methods

Eighteen-millimeter linears of size 40 gutta-percha were prepared in fresh sheep head. The head was scanned using CBCT with 0.25, 0.3, and 0.40 voxel sizes. Standard linear distances of gutta-percha were measured in panoramic CBCT images at 0.25, 0.3, and 0.4 voxel sizes. VD measurements were made separately on spongeous bone of palatal surfaces of the roots of teeth 4, 5, and 6 of maxilla and on cortical bone of teeth 4, 5, and 6 regions of the left and right hemimandibles through cross-sectional imaging.

Results

We found that linear distance measurements on panoramic image of CBCT were slightly lower than physical measurements. A significant difference was not found for the gutta-percha linear distances and cortical VD measurements at different voxel sizes (P ≥ 0.05). The correlation between measurements of VD at different voxels in cortical bone was greater than 0.85 (P = 0.000).

Conclusion

Linear distance measurements on the sheep head cadaver of 0.25, 0.3, and 0.4 voxel sizes were similar and reliable when compared with physical measurements. In minimizing radiation exposure, VD measurement of cortical bone at 0.4 voxel-based CBCT could be used to estimate cortical bone density. However, studies should be performed on the human head cadaver.

Comparison of hand and semiautomatic tracing methods for creating maxillofacial artificial organs using sequences of computed tomography (CT) and cone beam computed tomography (CBCT) images

INTRODUCTION

The aim of this study was to compare the paranasal sinus volumes obtained by manual and semiautomatic imaging software programs using both CT and CBCT imaging.

METHODS

121 computed tomography (CT) and 119 cone beam computed tomography (CBCT) examinations were selected from the databases of the authors' institutes. The Digital Imaging and Communications in Medicine (DICOM) images were imported into 3-dimensonal imaging software, in which hand mode and semiautomatic tracing methods were used to measure the volumes of both maxillary sinuses and the sphenoid sinus. The determined volumetric means were compared to previously published averages.

RESULTS

Isometric CBCT-based volume determination results were closer to the real volume conditions, whereas the non-isometric CT-based volume measurements defined coherently lower volumes. By comparing the 2 volume measurement modes, the values gained from hand mode were closer to the literature data. Furthermore, CBCT-based image measurement results corresponded to the known averages.

CONCLUSIONS

Our results suggest that CBCT images provide reliable volumetric information that can be depended on for artificial organ construction, and which may aid the guidance of the operator prior to or during the intervention.

Intraobserver and interobserver reproducibility in linear measurements on axial images obtained by cone-beam computed tomography

PURPOSE

This study was performed to investigate the intra- and inter-observer variability in linear measurements with axial images obtained by PreXion (PreXion Inc., San Mateo, USA) and i-CAT (Imaging Sciences International, Xoran Technologies Inc., Hatfield, USA) CBCT scanners, with different voxel sizes.

MATERIALS AND METHODS

A cylindrical object made from nylon with radiopaque markers (phantom) was scanned by i-CAT and PreXion 3D devices. For each axial image, measurements were taken twice in the horizontal (distance A-B) and vertical (distance C-D) directions, randomly, with a one-week interval between measurements, by four oral radiologists with five years or more experience in the use of these measuring tools.

RESULTS

All of the obtained linear measurements had lower values than those of the phantom. The statistical analysis showed high intra- and inter-observer reliability (p=0.297). Compared to the real measurements, the measurements obtained using the i-CAT device and PreXion tomography, on average, revealed absolute errors ranging from 0.22 to 0.59 mm and from 0.23 to 0.63 mm, respectively.

CONCLUSION

It can be concluded that both scanners are accurate, although the linear measurements are underestimations, with no significant differences between the evaluators.

Accuracy of linear measurements around dental implants by means of cone beam computed tomography with different exposure parameters

OBJECTIVES

The aim of this study was to determine the accuracy of linear measurements around dental implants when using CBCT unit devices presenting different exposure parameters.

METHODS

Dental implants (n = 18) were installed in the maxilla of human dry skulls, and images were obtained using two CBCT devices: G1-Care Stream 9300 (70 kVp, 6.3 mA, voxel size 0.18 mm, field of view 8 × 8 cm; Carestream Health, Rochester, NY) and G2-R100 Veraview^® (75 kVp, 7.0 mA, voxel size 0.125 mm, field of view 8 × 8 cm; J Morita, Irvine, CA). Measurements of bone thickness were performed at three points located (A) in the most apical portion of the implant, (B) 5 mm above the apical point and (C) in the implant platform. Afterwards, values were compared with real measurements obtained by an optical microscopy [control group (CG)]. Data were statistically analyzed with the significance level of p ≤ 0.05.

RESULTS

There was no statistical difference for the mean values of bone thickness on Point A (CG: 4.85 ± 2.25 mm, G1: 4.19 ± 1.68 mm, G2: 4.15 ± 1.75 mm), Point B (CG: 1.50 ± 0.84 mm, G1: 1.61 ± 1.27 mm; G2: 1.68 ± 0.82 mm) and Point C (CG: 1.78 ± 1.33 mm, G1: 1.80 ± 1.09 mm; G2: 1.64 ± 1.11 mm). G1 and G2 differed in bone thickness by approximately 0.76 mm for Point A, 0.36 mm for Point B and 0.08 mm for Point C. A lower intraclass variability was identified for CG (Point A = 0.20 ± 0.25; Point B = 0.15 ± 0.20; Point C = 0.06 ± 0.05 mm) in comparison with G1 (Point A = 0.56 ± 0.52; Point B = 0.48 ± 0.50; Point C = 0.47 ± 0.56 mm) and G2 (Point A = 0.57 ± 0.51; Point B = 0.46 ± 0.46; Point C = 0.36 ± 0.31 mm).

CONCLUSIONS

CBCT devices showed acceptable accuracy for linear measurements around dental implants, despite the exposure parameters used.

Accuracy of radiographic measurements for implant planning using cone-beam and helical computer tomography

AIM

The aim of the present study was to compare the accuracy of radiographic measurements for dental implants planning using cone-beam computed tomography (CBCT) and helical computed tomography (HCT).

METHODS

Six pig ribs were wrapped by putty impression material, with radiographic markers placed. Two CBCT and an HCT were taken following the standard protocols. Twenty-five locations were selected, with vertical and horizontal dimensions measured using the default software, as well as on the processed HCT films by a digital caliper. The actual dimensions of the ribs measured by the digital caliper served as the control. Differences between radiographic dimensions and the actual dimensions were tested by two-way analysis of variance.

RESULTS

No differences were found between measurements made by CBCT and HCT images using the default software (P > 0.05). However, both measurements were statistically-significantly lower than the control (P < 0.001), and the mean difference was 0.3 mm. Measurements made on HCT films were statistically-significantly greater than the control (P < 0.001), and the mean difference was 0.5 mm.

CONCLUSION

The accuracy of CBCT and HCT are similar, and both are reliable tools for implant planning. It is preferable to perform the planning using default software, rather than making direct measurements on films.

Effect of Voxel Size on Detection of External Root Resorption Defects Using Cone Beam Computed Tomography

BACKGROUND

Selecting a voxel size that yields minimal radiation dose with no significant compromise of the diagnostic accuracy of cone beam computed tomography (CBCT) is particularly important.

OBJECTIVES

This study aimed to assess the effect of voxel size on detection accuracy of simulated external root resorption defects using NewTom CBCT system.

MATERIALS AND METHODS

In this diagnostic study, the roots of 90 extracted human central incisors were hypothetically divided into cervical, middle, and apical thirds. Variable-size defects were prepared in the buccal and lingual surfaces of the roots and CBCT scans were obtained with four different voxel sizes (150, 200, 250, and 300). Presence or absence of defects on CBCT scans was determined by three radiologists and the results were compared with the gold standard (actual size and depth of defects). Sensitivity and specificity values were calculated and reported for different groups.

RESULTS

In the lingual surfaces, the highest specificity and sensitivity belonged to 300µm voxel size (92.9%), and 200 and 250µm voxel sizes (both 97.4%) in the cervical third, respectively. In the middle third, the highest specificity and sensitivity belonged to 250 and 200µm voxel sizes (84.6% and 100%, respectively). In the apical third, the highest specificity and sensitivity belonged to 300 µm voxel size (100% and 97.9%, respectively). In the buccal surfaces, the highest specificity and sensitivity belonged to 150 (75.0%), 300 and 250 µm voxel sizes (100%) and the minimum values belonged to 200 µm voxel size (60% and 97.3%) in the cervical third. In the apical third, the highest specificity and sensitivity were noted in 300 µm voxel size (100% and 97.6%, respectively) and the minimum values were seen in 200 and 150 µm voxel sizes (93.8%, 90.5%, respectively). In the middle third, 300, 250 and 200 µm voxel sizes yielded the highest specificity (88.9%), while 150 µm voxel size yielded the highest sensitivity (98.8%).

CONCLUSION

Considering the similar diagnostic efficacy of all voxel sizes, 300 µm voxel size can be used with adequate efficacy for detection of external root resorption defects with minimal patient radiation dose and the shortest scanning time.

The accuracy of linear measurements of maxillary and mandibular edentulous sites in cone-beam computed tomography images with different fields of view and voxel sizes under simulated clinical conditions

PURPOSE

The objective of this study was to investigate the effect of varying resolutions of cone-beam computed tomography images on the accuracy of linear measurements of edentulous areas in human cadaver heads. Intact cadaver heads were used to simulate a clinical situation.

MATERIALS AND METHODS

Fiduciary markers were placed in the edentulous areas of 4 intact embalmed cadaver heads. The heads were scanned with two different CBCT units using a large field of view (13 cm×16 cm) and small field of view (5 cm×8 cm) at varying voxel sizes (0.3 mm, 0.2 mm, and 0.16 mm). The ground truth was established with digital caliper measurements. The imaging measurements were then compared with caliper measurements to determine accuracy.

RESULTS

The Wilcoxon signed rank test revealed no statistically significant difference between the medians of the physical measurements obtained with calipers and the medians of the CBCT measurements. A comparison of accuracy among the different imaging protocols revealed no significant differences as determined by the Friedman test. The intraclass correlation coefficient was 0.961, indicating excellent reproducibility. Inter-observer variability was determined graphically with a Bland-Altman plot and by calculating the intraclass correlation coefficient. The Bland-Altman plot indicated very good reproducibility for smaller measurements but larger discrepancies with larger measurements.

CONCLUSION

The CBCT-based linear measurements in the edentulous sites using different voxel sizes and FOVs are accurate compared with the direct caliper measurements of these sites. Higher resolution CBCT images with smaller voxel size did not result in greater accuracy of the linear measurements.

Soft tissue coverage on the segmentation accuracy of the 3D surface-rendered model from cone-beam CT

OBJECTIVES

The aim of this study is to investigate the effect of soft tissue presence on the segmentation accuracy of the 3D hard tissue models from cone-beam computed tomography (CBCT).

MATERIALS AND METHODS

Seven pairs of CBCT Digital Imaging and Communication in Medicine (DICOM) datasets, containing data of human cadaver heads and their respective dry skulls, were used. The effect of the soft tissue presence on the accuracy of the segmented models was evaluated by performing linear and angular measurements and by superimposition and color mapping of the surface discrepancies after splitting the mandible and maxillo-facial complex in the midsagittal plane.

RESULTS

The linear and angular measurements showed significant differences for the more posterior transversal measurements on the mandible (p < 0.01). By splitting and superimposing the maxillo-facial complex, the mean root-mean-square error (RMSE) as a measurement of inaccuracy decreased insignificantly from 0.936 to 0.922 mm (p > 0.05). The RMSE value for the mandible, however, significantly decreased from 1.240 to 0.981 mm after splitting (p < 0.01).

CONCLUSIONS

The soft tissue presence seems to affect the accuracy of the 3D hard tissue model obtained from a cone-beam CT, below a generally accepted level of clinical significance of 1 mm. However, this level of accuracy may not meet the requirement for applications where high precision is paramount.

CLINICAL RELEVANCE

Accuracy of CBCT-based 3D surface-rendered models, especially of the hard tissues, are crucial in several dental and medical applications, such as implant planning and virtual surgical planning on patients undergoing orthognathic and navigational surgeries. When used in applications where high precision is paramount, the effect of soft tissue presence should be taken into consideration during the segmentation process.

Efficacy of a cone beam computed tomography metal artifact reduction algorithm for the detection of peri-implant fenestrations and dehiscences

OBJECTIVE

To determine whether the use of a metal artifact reduction (MAR) algorithm improves the detection of peri-implant fenestrations and dehiscences on cone beam computed tomography scans.

STUDY DESIGN

One hundred titanium fixtures were implanted into bovine ribs after the creation of defects simulating fenestrations and dehiscences. Images were acquired using four different protocols, namely, A2 (MAR on, voxel 0.2 mm), A3 (MAR on, voxel 0.3 mm), B2 (MAR off, voxel 0.2 mm), and B3 (MAR off, voxel 0.3 mm). For all protocols, receiver operating characteristic (ROC) curves were determined. Values for the areas under the ROC curves (Az) were subjected to analysis of variance.

RESULTS

Az values were not statistically different among protocols regardless of the defect type (P > .05).

CONCLUSIONS

The MAR algorithm tested by us did not improve the diagnosis of peri-implant fenestrations and dehiscences with use of either the 0.2 mm or the 0.3 mm voxel sizes.

Comparison of different methods to assess alveolar cleft defects in cone beam CT images

OBJECTIVES

This study aimed to evaluate the accuracy of three different methods for assessing the volume of cleft defects in CBCT images. The influence of field of view (FOV) and voxel sizes was also assessed.

METHODS

Using three radio-opaque plastic skulls, unilateral defects were created to mimic alveolar clefts and were filled with wax following the contralateral side contours. They were scanned in a CBCT unit using four different acquisition protocols, varying FOV and voxel sizes. Using three different methods, the defect/wax volume was evaluated on the images by defining: (1) the width, height and facial-palatal length of the defect in maximum intensity projection; (2) the areas of the defect on axial slices; and (3) the threshold and segmentation of the region of interest. The values obtained from each method using different acquisition protocols were compared with the real volume of the wax (gold standard) using ANOVA and Tukey's test.

RESULTS

Methods 2 and 3 did not differ from the gold standard (p > 0.05). Conversely, Method 1 presented statistically significant overestimated values (p < 0.01). No differences were found among the different FOV and voxel sizes (p > 0.05).

CONCLUSIONS

CBCT volumes proved reliable for the volumetric assessment of alveolar cleft defects, when using Methods 2 and 3 regardless of FOV and voxel sizes. It may be possible to improve surgical planning and outcomes by knowing the exact volume of grafting material needed prior to the surgical intervention.

Cone beam computed tomography-based models versus multislice spiral computed tomography-based models for assessing condylar morphology

OBJECTIVE

To quantitatively compare condylar morphology using cone beam computed tomography (CBCT) and multislice spiral computed tomography (MSCT) virtual three-dimensional surface models.

STUDY DESIGN

The sample consisted of secondary data analyses of CBCT and MSCT scans obtained for clinical purposes from 74 patients treated with condylar resection and prosthetic joint replacement. Three-dimensional surface models of 146 condyles were constructed from each scan modality. Across-subject models were approximated and voxel-based registration was performed between homologous CBCT and MSCT images, making it possible to create average CBCT- and MSCT-based condylar models. SPHARM-PDM software provided matching points on each corresponding model. ShapeAnalysisMANCOVA software assessed statistically significant differences between observers and imaging modalities. One-sample t-tests evaluated the null hypothesis that the mean differences between each CBCT- and MSCT-based model were not clinically significant (<.5 mm). Tests were conducted at a significance level of P < .05.

RESULTS

ShapeAnalysisMANCOVA showed no statistically significant difference between the average CBCT- and MSCT-based models (P > .68). During pairwise comparison, the mean difference observed was .406 mm (SD, .173). One sample t-test showed that mean differences between each set of paired CBCT- and MSCT-based models were not clinically significant (P = .411).

CONCLUSION

Three-dimensional surface models constructed from CBCT images are comparable to those derived from MSCT scans and may be considered reliable tools for assessing condylar morphology.

Intraosseous vascularization of anterior mandible: a radiographic analysis

The anterior mandible was initially considered a safe zone from a surgical point of view. Over time, serious complications resulting from dental implantology procedures have been reported. This has led to a greater focus on vascularization of the interforaminal region. The purpose of this article was to evaluate the anterior mandibular region in relation to the presence of canals perforating the buccal and lingual cortical plates. DICOM (Digital Imaging and Communications in Medicine) files of 100 cone beam computed tomography scans were analyzed by imaging software. All radiographic cross-sections between the mental foramina were examined to detect the presence and location of perforating buccal or lingual canals. Lingual perforating canals are present in 98% of the cohort. The most common site is the symphysis region. The presence of 2 lingual canals cranially and caudally to the genial apophysis has been found in 39%. Vestibular perforating canals are absent in 61%. The anterior mandible has several lingual perforating canals, which are variable in number and location. Imaging software is a valuable aid in presurgical planning. Because of the higher prevalence of perforating canals in the symphysis region, this site should be preserved.

An anatomical radiographic evaluation of the posterior portion of the mandible in relation to autologous bone harvest procedures

The purpose of the study was to evaluate the course of the mandibular canal and the thickness of the vestibular cortical plate in the posterior region of the mandible in relation to autologous bone harvest procedures. The study was performed on a cohort of 30 cone-beam computed tomography hemimandible images. For each hemimandible, the course of the mandibular canal and the thickness of the vestibular cortical plate have been evaluated in 4 regions: the retromolar region, the second molar region, the first molar region, and the second premolar region. The analyzed variables show a characteristic trend: the thickness of the cortical vestibular plate and the horizontal distance of the canal from the cortical vestibular plate are higher in the second molar region specifically in the area bordering on the retromolar region. In fact, the maximum thickness reaches the average value of 3.46 mm on 30 hemimandibles for slice (SD, 0.56 mm; range, 2.36-4.83 mm), and the horizontal distance reaches the average value of 6.06 mm on 30 hemimandibles for slice (SD, 1.34 mm; range, 3.65-9.27 mm); both variables decrease in more distal slices of the retromolar region. The vertical distance of the canal from the cortical crest shows the average value of 14.25 mm on 22 slices of the second molar and retromolar regions (SD of average values, 1.03 mm; range of average values, 12.92-16.25 mm; range of absolute values, 7.11-22.92 mm) exactly in regions potentially suitable for procedures of bone harvest (second molar and retromolar regions).

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.

Vertical bone measurements from cone beam computed tomography images using different software packages

This article aimed at comparing the accuracy of linear measurement tools of different commercial software packages. Eight fully edentulous dry mandibles were selected for this study. Incisor, canine, premolar, first molar and second molar regions were selected. Cone beam computed tomography (CBCT) images were obtained with i-CAT Next Generation. Linear bone measurements were performed by one observer on the cross-sectional images using three different software packages: XoranCat®, OnDemand3D® and KDIS3D®, all able to assess DICOM images. In addition, 25% of the sample was reevaluated for the purpose of reproducibility. The mandibles were sectioned to obtain the gold standard for each region. Intraclass coefficients (ICC) were calculated to examine the agreement between the two periods of evaluation; the one-way analysis of variance performed with the post-hoc Dunnett test was used to compare each of the software-derived measurements with the gold standard. The ICC values were excellent for all software packages. The least difference between the software-derived measurements and the gold standard was obtained with the OnDemand3D and KDIS3D (-0.11 and -0.14 mm, respectively), and the greatest, with the XoranCAT (+0.25 mm). However, there was no statistical significant difference between the measurements obtained with the different software packages and the gold standard (p> 0.05). In conclusion, linear bone measurements were not influenced by the software package used to reconstruct the image from CBCT DICOM data.

Accuracy of linear measurement using cone-beam computed tomography at different reconstruction angles

Purpose

This study was performed to evaluate the effect of changing the orientation of a reconstructed image on the accuracy of linear measurements using cone-beam computed tomography (CBCT).

Materials and Methods

Forty-two titanium pins were inserted in seven dry sheep mandibles. The length of these pins was measured using a digital caliper with readability of 0.01 mm. Mandibles were radiographed using a CBCT device. When the CBCT images were reconstructed, the orientation of slices was adjusted to parallel (i.e., 0°), +10°, +12°, -12°, and -10° with respect to the occlusal plane. The length of the pins was measured by three radiologists, and the accuracy of these measurements was reported using descriptive statistics and one-way analysis of variance (ANOVA); p<0.05 was considered statistically significant.

Results

The differences in radiographic measurements ranged from -0.64 to +0.06 at the orientation of -12°, -0.66 to -0.11 at -10°, -0.51 to +0.19 at 0°, -0.64 to +0.08 at +10°, and -0.64 to +0.1 at +12°. The mean absolute values of the errors were greater at negative orientations than at the parallel position or at positive orientations. The observers underestimated most of the variables by 0.5-0.1 mm (83.6%). In the second set of observations, the reproducibility at all orientations was greater than 0.9.

Conclusion

Changing the slice orientation in the range of -12° to +12° reduced the accuracy of linear measurements obtained using CBCT. However, the error value was smaller than 0.5 mm and was, therefore, clinically acceptable.

Avaliação subjetiva da aceitabilidade das imagens de tomografia computadorizada de feixe cônico para o planejamento de implantes osteointegrados

Introdução: Para realização de mensurações precisas para implantes osteointegrados, é necessário que as imagens tomográficas apresentem uma qualidade mínima, que permita a visualização clara das estruturas anatômicas. Objetivo: Diante disso, avaliou-se, subjetivamente, a aceitabilidade das imagens de diferentes protocolos de tomografia computadorizada de feixe cônico (TCFC), para o planejamento de implantes osteointegrados. Material e método: Foram obtidas imagens de TCFC de dez hemimandíbulas maceradas no equipamento K9000 3D, sendo modificada apenas a miliamperagem (Grupo I: 2 mA; Grupo II: 8 mA e Grupo III: 15 mA). As aquisições foram feitas com 80 kV, FOV de 5 × 3,7 cm, matriz de 512 × 512 e voxel de 0,076 mm de espessura. Após as aquisições, três avaliadores analisaram as reconstruções ortogonais em três tamanhos de voxel, constituindo-se, assim, nove grupos experimentais. Após a realização das mensurações de altura e espessura óssea, os avaliadores atribuíram escores (sim ou não) para a aceitabilidade das imagens para mensurações. Resultado: Os grupos apresentaram qualidade de imagem aceitável para o planejamento de implantes, com exceção das imagens adquiridas com 2 mA e analisadas com voxel de 0,076 mm e 0,535 mm. Conclusão: O protocolo de 8 mA e voxel de 2,1 mm deve ser, preferencialmente, indicado na identificação do canal mandibular, já que a dose de radiação é menor do que nos protocolos de 15 mA e a qualidade de imagem é superior aos protocolos de 2 mA; além disso, voxel de 2,1 mm apresentou maior aceitabilidade das imagens.

Impact of voxel size variation on CBCT-based diagnostic outcome in dentistry: a systematic review

The objective of this study was to make a systematic review on the impact of voxel size in cone beam computed tomography (CBCT)-based image acquisition, retrieving evidence regarding the diagnostic outcome of those images. The MEDLINE bibliographic database was searched from 1950 to June 2012 for reports comparing diverse CBCT voxel sizes. The search strategy was limited to English-language publications using the following combined terms in the search strategy: (voxel or FOV or field of view or resolution) and (CBCT or cone beam CT). The results from the review identified 20 publications that qualitatively or quantitatively assessed the influence of voxel size on CBCT-based diagnostic outcome, and in which the methodology/results comprised at least one of the expected parameters (image acquisition, reconstruction protocols, type of diagnostic task, and presence of a gold standard). The diagnostic task assessed in the studies was diverse, including the detection of root fractures, the detection of caries lesions, and accuracy of 3D surface reconstruction and of bony measurements, among others. From the studies assessed, it is clear that no general protocol can be yet defined for CBCT examination of specific diagnostic tasks in dentistry. Rationale in this direction is an important step to define the utility of CBCT imaging.

Radiographic evaluation of the symphysis menti as a donor site for an autologous bone graft in pre-implant surgery

Purpose

This study was performed to obtain a quantitative evaluation of the cortical and cancellous bone graft harvestable from the mental and canine regions, and to evaluate the cortical vestibular thickness.

Materials and Methods

This study collected cone-beam computed tomographic (CBCT) images of 100 Italian patients. The limits of the mental region were established: 5 mm in front of the medial margin of each mental foramen, 5 mm under the apex of each tooth present, and above the inferior mandibular cortex. Cortical and cancellous bone volumes were evaluated using SimPlant software (SimPlant 3-D Pro, Materialize, Leuven, Belgium) tools. In addition, the cortical vestibular thickness (minimal and maximal values) was evaluated in 3 cross-sections corresponding to the right canine tooth (3_R), the median section (M), and the left canine tooth (3_L).

Results

The cortical volume was 0.71±0.23 mL (0.27-1.96 mL) and the cancellous volume was 2.16±0.76 mL (0.86-6.28 mL). The minimal cortical vestibular thickness was 1.54±0.41 mm (0.61-3.25 mm), and the maximal cortical vestibular thickness was 3.14±0.75mm(1.01-5.83 mm).

Conclusion

The use of the imaging software allowed a patient-specific assessment of mental and canine region bone availability. The proposed evaluation method might help the surgeon in the selection of the donor site by the comparison between bone availability in the donor site and the reconstructive exigency of the recipient site.

Detection of periimplant fenestration and dehiscence with the use of two scan modes and the smallest voxel sizes of a cone-beam computed tomography device

OBJECTIVE

To assess the accuracy of cone-beam computed tomography (CBCT) in periimplant fenestration and dehiscence detection, and to determine the effects of 2 voxel sizes and scan modes.

STUDY DESIGN

One hundred titanium implants were placed in bovine ribs in which periimplant fenestration and dehiscence were simulated. CBCT images were acquired with the use of 3 protocols of the i-CAT NG unit: A) 0.2 mm voxel size half-scan (180°); B) 0.2 mm voxel size full-scan (360°); and C) 0.12 mm voxel size full scan (360°). Receiver operating characteristic curves and diagnostic values were obtained. The Az values were compared with the use of analysis of variance.

RESULTS

The Az value for dehiscence in protocol A was significantly lower than those of B or C (P < .01). They did not statistically differ for fenestration (P > .05).

CONCLUSIONS

Protocol B yielded the highest values. The voxel sizes did not affect fenestration and dehiscence detection, and for dehiscence full-scan performed better than half-scan.