Accuracy of Linear Measurements and Visibility of the Mandibular Canal of Cone-Beam Computed Tomography Images With Different Voxel Sizes: An In Vitro Study

The Precision of All-on-Four Implant Position Recorded from Three Different CBCT Machines

OBJECTIVE

 To investigate the dimensional discrepancy and degree of deviation of All-on-Four implant position between different cone-beam computed tomography (CBCT) machines.

MATERIALS AND METHODS

 Four implants (4.5 × 10 mm Superline II, Dentium, South Korea) were placed in an All-on-Four style in an artificial mandible. The jaw was radiated 30 times using three different CBCT machines (Rainbow CT, Dentium; Veraview X800, Morita, Japan; Planmeca Viso G3, Planmeca OY, Finland). A total of 30 Digital Imaging and Communications in Medicine (DICOM) files were exported, n = 10. All-on-Four implants from each DICOM file were segmented and exported as an STL file (three-dimensional image) using Blue Sky Plan software (version 4.12.13/Blue Sky Bio, United States). All-on-Four implant zone dimensions (X, Y, and Z axes) and the total degree of deviation between All-on-Four implants per CBCT machine were measured using Autodesk Meshmixer software (version 3.5.474/California, United States). The data distribution's normality and variances' equality were tested with Shapiro-Wilk's and Levene's tests, respectively (p-value < 0.05). Data were analyzed using Brown-Forsythe one-way analysis of variance and Tamhane's post hoc tests to compare the differences between the groups (p-value <0.05).

RESULTS

 The respective X, Y, and Z mean dimensions of the All-on-Four implant zone were: Dentium (34.95, 14.71, and 9.97); Morita (34.88, 14.74, and 10.56); and Planmeca (34.73, 15.15, and 12.33). Significant differences between CBCT machines were found in all axes (p-value < 0.05); however, the Z-axis had the most differences. Notably, Planmeca exhibited the highest standard deviation (SD) in all axes (0.16-0.35), exhibiting the lowest consistency in the CBCT machines' readings. The Dentium exhibited the lowest deviation in the implant position, with the lowest SD (0.61). A significant difference in the total degree of deviation was spotted when only Morita was included in the comparison (p-value < 0.05).

CONCLUSION

 This study's findings are of significant importance as they reveal that the implant position recorded from the CBCT machines was most discrepant in the buccolingual dimension (Z-axis). Planmeca exhibited the least implant-dimensional accuracy of the CBCT machines, while Dentium exhibited the highest implant position accuracy. These results could significantly impact the choice of CBCT machine for implant placement, especially since an accurate CBCT image is crucial for digital implant planning.

Repeatability and effect of different voxel sizes on linear and volumetric tooth and pulp measurements using cone-beam computed tomography

OBJECTIVE

In cone-beam computed tomography (CBCT), voxel resolution and size directly affect image quality. This study aimed to analyze the effect of voxel resolution on the linear and volumetric measurements of tooth and pulp in three-dimensional images obtained with different voxel sizes and to test the repeatability of these measurements.

MATERIALS AND METHODS

CBCT images of 30 extracted single-rooted permanent teeth were obtained using 3 different voxel sizes (0.1-, 0.2-, 0.4-mm). Two observers performed volumetric and linear measurements of pulp and teeth using semi-automatic segmentation. The data were analyzed using descriptive and nonparametric tests. For interobserver reliability, the Wilcoxon signed test and Kendall's tau correlation coefficient were used. The intraobserver repeatability was analyzed using the intraclass correlation coefficient. The significance level was set at 0.05.

RESULTS

Friedman test showed no significant difference (p > 0.05) in volumetric measurements between different voxels in one of the observers, but a significant difference was found in the pulp volume measurement in the other (p < 0.001). The voxel sizes did not affect the linear measurements of both observers (p > 0.05). The interclass reliability (Wilcoxon signed test and Kendall's tau correlation coefficient) and intraobserver repeatability (intraclass correlation coefficient) decreased as the voxel size increased for linear and volumetric measurements of tooth and pulp (p > 0.05). While the values indicated "good" and "excellent" reliability for all parameters measured on the 0.1- and 0.2-mm voxels, a few "moderate" reliability values were found on the 0.4-mm voxel.

CONCLUSION

Voxel sizes of 0.1- and 0.2-mm did not significantly affect linear and volumetric tooth measurements. When the voxel size increased, the reliability and repeatability decreased. To increase measurement reliability, the voxel size should be as small as possible.

Comparing standard- and low-dose CBCT in diagnosis and treatment decisions for impacted mandibular third molars: a non-inferiority randomised clinical study

OBJECTIVE

This randomised clinical study aimed to assess the influence of low-dose cone-beam computed tomography (CBCT) on the visibility of the mandibular canal (MC) and its proximity to mandibular third molars (M3Ms) as assessed by general dental practitioners (GPs) and oral-maxillofacial surgeons (OMFSs), as well as its impact on their clinical decisions, when compared to standard-dose CBCT.

METHODS

154 impacted M3Ms from 90 patients were randomly assigned to three groups for two CBCT exposures using one standard-dose (333 mGy×cm2) and one of the three investigated low-dose (78-131 mGy×cm2) protocols. Blinded assessments of the MC visibility, M3M-MC proximity, surgical approach, crown/root sectioning, and referral decisions, were made by GPs and OMFSs on the images separately. Pairwise comparisons for MC visibility between paired scans were evaluated using Wilcoxon signed rank test, followed by a non-inferiority test with non-inferiority margin of 0.5 on a four-point scale. Differences in other variables between paired scans were evaluated using Wilcoxon signed-rank or McNemar tests.

RESULTS

The majority (78.5-99.3%) of MCs were clearly identified on standard-dose CBCT by all observers. Pairwise comparisons showed significant differences between paired scans only in MC visibility but not in the M3M-MC proximity or treatment decisions. The mean differences in MC visibility between paired scans ranged 0-0.22 with the upper bounds of the 95% confidence intervals (0.09-0.36) falling within the non-inferiority region.

CONCLUSIONS

The investigated low-dose CBCT protocols could provide acceptable image quality for the evaluation of impacted M3Ms in most cases. When compared to standard-dose CBCT, these low-dose CBCT images did not significantly affect the assessments of the M3M-MC proximity, treatment strategies, and patient management decisions made by GPs and OMFSs.

CLINICAL RELEVANCE

The low-dose protocols might be clinically acceptable for M3M management while greatly reducing radiation exposure.

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.

Automatic segmentation of mandibular canal using transformer based neural networks

Accurate 3D localization of the mandibular canal is crucial for the success of digitally-assisted dental surgeries. Damage to the mandibular canal may result in severe consequences for the patient, including acute pain, numbness, or even facial paralysis. As such, the development of a fast, stable, and highly precise method for mandibular canal segmentation is paramount for enhancing the success rate of dental surgical procedures. Nonetheless, the task of mandibular canal segmentation is fraught with challenges, including a severe imbalance between positive and negative samples and indistinct boundaries, which often compromise the completeness of existing segmentation methods. To surmount these challenges, we propose an innovative, fully automated segmentation approach for the mandibular canal. Our methodology employs a Transformer architecture in conjunction with cl-Dice loss to ensure that the model concentrates on the connectivity of the mandibular canal. Additionally, we introduce a pixel-level feature fusion technique to bolster the model's sensitivity to fine-grained details of the canal structure. To tackle the issue of sample imbalance and vague boundaries, we implement a strategy founded on mandibular foramen localization to isolate the maximally connected domain of the mandibular canal. Furthermore, a contrast enhancement technique is employed for pre-processing the raw data. We also adopt a Deep Label Fusion strategy for pre-training on synthetic datasets, which substantially elevates the model's performance. Empirical evaluations on a publicly accessible mandibular canal dataset reveal superior performance metrics: a Dice score of 0.844, click score of 0.961, IoU of 0.731, and HD95 of 2.947 mm. These results not only validate the efficacy of our approach but also establish its state-of-the-art performance on the public mandibular canal dataset.

Visibility of anatomical landmarks in the region of the mandibular third molar, a comparison between a low-dose and default protocol of CBCT

OBJECTIVE

Optimization of radiographic examinations is essential for radiation protection. The objective of the study was to investigate the clinical applicability of a low-dose CBCT protocol as compared to the default for pre-surgical evaluation of mandibular third molars.

MATERIAL & METHODS

Forty-eight patients (62 teeth) referred for pre-surgical mandibular third molar investigation were recruited after justification for CBCT. Two CBCT scans of each site were made using a default protocol and a low-dose protocol (Veraviewepocs 3D F40, J Morita Corp, Kyoto, Japan). The low-dose protocol had the same tube potential (90 kV) and exposure time (9.4 s) as the default, but with reduced tube current, from 5 mA to 2 mA. Four observers evaluated the visibility of five relevant anatomical variables. Image quality was ranked on a 3-point scale as diagnostically acceptable, doubtful, or unacceptable. The Wilcoxon signed-rank test compared differences between the two protocols. The significance level was set at p ≤ .05.

RESULTS

No significant differences were found between the two protocols for any observer regarding the visibility of the relationship and proximity between the roots and the mandibular canal; root morphology; and possible root resorption of the second molar. The periodontal ligament differed significantly in visibility between the two protocols (p ≤ .05).

CONCLUSIONS

This study indicates that a low-dose CBCT protocol with a 60% reduction of the tube current provides, in most cases, acceptable image quality for pre-surgical assessment of mandibular third molars. Optimization of CBCT protocols should be a priority according to recommended guidelines.

Accuracy of an electrical impedance device in estimation of remaining dentin thickness vs cone beam computed tomography

The objective of this study is to compare the estimated values of remaining dentin thickness (RDT) recorded by a newly introduced electrical impedance device (Prepometer) with cone beam computed tomography (CBCT) and histological in situ measurement. A total number of thirty human molars were used in this study. A deep class I cavity was prepared. The RDT for each cavity was measured with Prepometer in three different points (mesial, middle, and distal). Same specimens were imaged with high-resolution Cone Beam Computed Tomography CBCT (0.1 mm voxel size) using I CAT next Generation Machine (Imaging Science International, Hatfield, PA, USA), to provide the highest possible accuracy of linear measurements. Finally, the specimens were vertically sectioned parallel to the long axis of the tooth in a mesiodistal direction splitting the cavity into two halves through its center. Then, the actual RDT of each half will be measured in the same three points using a digital caliper. The outcome of one-way ANOVA revealed that there was no significant difference in RDT values measured by prepometer device, CBCT, or histological sectioning methods (p > 0.05). Within the limitations of this laboratory study, prepometer seems to be a potential non-invasive accurate measuring tool for RDT. Based on the findings of this study, the Prepometer can be considered as an easily handled and less-expensive method compared to CBCT to evaluate the RDT. Also, it can be used in dental schools and with less-experienced operators to avoid traumatic exposures of the dental pulp.

Influence of Voxel Size on CBCT Images for Dental Implants Planning

Objective  This study was developed to evaluate the influence of voxel size on bone measurements for implant planning.

Materials and Methods  The research was performed by using edentulous synthetic human mandibles with different levels of bone resorption. For each mandible, height and bone thickness were measured with a digital caliper. The PaX-i3d device was used to acquire the volumes of the five mandibles, with 50kVp, 4 mA, and a voxel size of 0.08 mm. After the acquisition, the images were reconstructed in the software CS three-dimensional Imaging, with four different sizes of voxels: 0.1, 0.2, 0.3, and 0.4 mm. All volumes were analyzed by a single evaluator who performed measurements to obtain bone height and thickness, using the reference points that were considered in obtaining the gold standard. The data were analyzed by ANOVA with a significance level of 5%.

Results  There was no significant difference in the measurements obtained with different voxel sizes, both for bone height measurements and bone thickness. There was no statistically significant difference in measurements in thickness in comparison to the gold standard.

Conclusion  When necessary, to measure height and bone thickness, it is possible to recommend voxel images of larger size (0.40 mm) without compromising the quality of the patient's clinical planning.

Evaluation of the accuracy of buccal bone thickness measurement from cone beam computed tomography compared with histologic analysis

STATEMENT OF PROBLEM

Three-dimensional radiographic assessment of buccal bone thickness and its integrity from cone beam computed tomography (CBCT) plays an essential role in immediate implant placement. However, the accuracy of CBCT measurements for the assessment of buccal bone thickness adjacent to maxillary anterior teeth is not well understood.

PURPOSE

The purpose of this observational study was to evaluate the accuracy of measuring the buccal bone thickness of maxillary anterior teeth from CBCT compared with direct measurement from histologic sections. A secondary objective was to analyze whether a minimal level of buccal bone thickness of maxillary anterior teeth can be detected from the CBCT scan.

MATERIAL AND METHODS

Five embalmed human cadavers with a complete anterior dentition were included in this study, providing 30 teeth for evaluation. After preparing reference notches at the gingival margin of each tooth, the anterior segments were scanned. The buccal bone thickness at 3, 5, and 7 mm from the notches was measured on the cross-sections obtained from the CBCT and histomorphometric images for a total of 90 sites. The CBCT measurements were compared with the histomorphometric measurements, and their agreement was assessed by using the Bland-Altman plots and intraclass correlation coefficients. The sensitivity and specificity of buccal bone detection were calculated from the CBCT scan.

RESULTS

Histologic examination showed absence of the buccal bone in 29 sites (32%). The mean ±standard deviation thickness of the buccal bone was 0.52 ±0.05 mm (range: 0 to 1.97 mm) from the CBCT analysis and 0.40 ±0.05 mm (range: 0 to 1.67 mm) from histology. Measurements obtained from the CBCT sections significantly overestimated the buccal bone thickness when compared with the histologic evaluation (P=.001). The intraclass correlation coefficient of buccal bone thickness between the CBCT and histology was ≤0.53, an agreement considered as poor. The sensitivity of the CBCT as a diagnostic tool to detect the presence or absence of the buccal bone was 75.4%, and the specificity was 65.5%.

CONCLUSIONS

The buccal bone thickness of maxillary anterior teeth was less than 2 mm at all sites as measured with both CBCT and histology evaluations. CBCT measurements had relatively low accuracy and reliability for the measurement of buccal bone thickness. These findings should be considered when using CBCT as a measuring tool for thin bone structures.

Three-Dimensional Classification of Lower Third Molars and Their Relationship to the Mandibular Canal

PURPOSE

To develop a novel classification making full use of radiographic three-dimensional (3D) information to describe the position, geometric configuration of a mandibular third molar (M3M) and its spatial relation to neighboring structures such as the mandibular canal (MC). The classification presented in this study helps to establish a common language and serves as a framework for further studies, for example, on 3D parameters influencing prognosis of the M3M and level of difficulty associated with its removal.

MATERIAL AND METHODS

A total of 8 parameters were included in the classification including position, the cranio-caudal height, the number of roots of the M3M as well as its spatial relationship to the MC, its course, its deformation, and distance to the M3M. The classification was retrospectively applied to a sample of 483 patients and these data were statistically evaluated.

RESULTS

The most commonly observed categories were the (+) vertical position (39.8%); the cranio-caudal height A (38.7%); 2 roots (83.2%); and the spatial relationship no contact caudal (37.5%). Contact between the M3M and inferior alveolar nerve was observed in 58% of all cases. A deformation of the MC was found in 81% of cases.

CONCLUSIONS

Our novel classification aims to provide a more holistic description of parameters defining 3D M3M position, as well as its spatial relation to relevant neighboring structures. It creates a uniform terminology that can be applied in practice by surgeons and radiologists, and also serves as a foundation for further research projects, such that results from similarly designed studies could be compared.

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.

Linear measurement accuracy of CBCT panoramic reconstructions: experimental study with dry human mandibles

INTRODUCTION

Studies on software accuracy of reformatted panoramic computed tomography (CT) images are scarce.

OBJECTIVES

The aim of this study was to evaluate the software accuracy of reformatted panoramic views from cone-beam computed tomography (CBCT).

METHODS

Ten dry mandibles were scanned using CBCT with different voxel sizes. Following the reconstruction of panoramic views with three different software, horizontal and vertical linear measurements were performed using the electronic rules of each software. Measurements of the corresponding dry mandibles were taken with a digital caliper and defined as the gold standard.

RESULTS

There were no statistically significant differences in linear distances among the dry mandibles and reformatted panoramic CT views. The relative error ranged from 1.3 to 8.0%, depending on the software and voxel size.

CONCLUSIONS

The linear measurements on reformatted panoramic views are reliable.

Effect of CBCT dose reduction on the mandibular canal visibility: ex vivo comparative study

OBJECTIVES

To compare the difference in mandibular canal (MC) visibility using three different cone beam computed tomography (CBCT) acquisition protocols: high resolution (HR), standard resolution (ST) and Quick scan+ (QS+).

METHODS

Twenty-five human dry mandibles were scanned by one CBCT machine; i-CAT FLX (Imaging Sciences International, Hatfield, PA, USA), using three different acquisition protocols: high-resolution (HR), standard (ST) and Quick scan+ (QS+). DICOM data were transferred to a third party software Ondemand 3D (Cybermed Co., Seoul, Korea). The fusion module was used to superimpose images derived from different acquisition protocols to standardize the areas to compare the MC visibility. Comparison was performed at nine selected cross sections extending from an area distal to the third molar posteriorly to the first premolar anteriorly. Two expert radiologists evaluated the degree of MC visibility using five-scale scoring system.

RESULTS

There was a statistically significant difference between the three acquisition protocols (HR, ST, QS+) at all investigated areas regardless of dentition status (p value < 0.001-0.034) except at the MR1M area where there was no statistically significant difference (p value = 0.094). HR protocol showed the highest prevalence of fully and partially corticated MC at almost all investigated areas while QS+ protocol showed the highest prevalence of invisible MC and clear and unclear non-corticated MC at almost all investigated areas.

CONCLUSIONS

QS+ protocol of i-CAT FLX CBCT machine is a recommended low-dose CBCT acquisition protocol for MC visibility at dentulous posterior mandibular regions while ST protocol is recommended at edentulous areas.

Accuracy of the measurements from multiplanar and sagittal reconstructions of CBCT

OBJECTIVES

The purpose of this study was to assess the accuracy of linear measurements performed in multiplanar reconstructions (MPR) and sagittal reconstructions (SR) of the left hemiface obtained from cone-beam computed tomography (CBCT) with 3D^® Dolphin Imaging software by comparing them with the same measurements made on lateral cephalograms and on dry skulls.

SETTING AND SAMPLE POPULATION

Lateral cephalograms and CBCT (with voxels of 0.25, 0.3 and 0.4 mm) were taken of 10 dry skulls.

MATERIALS AND METHODS

Linear distances were measured using the software's electronic rulers. Measurements performed on dry skulls using a digital caliper were considered the gold standard. The measurements were performed twice by two evaluators.

RESULTS

No significant difference was found in the measurements performed with the different imaging modalities and on the dry skulls. The highest mean error was observed in the lateral cephalograms, followed by MPR and SR.

CONCLUSIONS

Cephalometric measurements performed on multiplanar and sagittal reconstructions from CBCT, with different spatial resolutions, are accurate when compared with the measurements obtained in lateral cephalograms.

In vivo accuracy of tooth surface reconstruction based on CBCT and dental MRI-A clinical pilot study

OBJECTIVES

Guided implant surgery (GIS) requires alignment of virtual models to reconstructions of three-dimensional imaging. Accurate visualization of the tooth surfaces in the imaging datasets is mandatory. In this prospective clinical study, in vivo tooth surface accuracy was determined for GIS using cone-beam computed tomography (CBCT) and dental magnetic resonance imaging (dMRI).

MATERIALS AND METHODS

CBCT and 3-Tesla dMRI were performed in 22 consecutive patients (mean age: 54.4 ± 15.2 years; mean number of restorations per jaw: 6.7 ± 2.7). Altogether, 92 teeth were included (31 incisor, 29 canines, 20 premolars, and 12 molars). Surfaces were reconstructed semi-automatically and registered to a reference standard (3D scans of stone models made from full-arch polyether impressions). Reliability of both methods was assessed using intraclass correlation coefficients. Accuracy was evaluated using the two one-sided tests procedure with a predefined equivalence margin of ±0.2 mm root mean square (RMS).

RESULTS

Inter- and intrarater reliability of tooth surface reconstruction were comparable for CBCT and dMRI. Geometric deviations were 0.102 ± 0.042 mm RMS for CBCT and 0.261 ± 0.08 mm RMS for dMRI. For a predefined equivalence margin, CBCT and dMRI were statistically equivalent. CBCT, however, was significantly more accurate (p ≤ .0001). For both imaging techniques, accuracy did not differ substantially between different tooth types.

CONCLUSION

Cone-beam computed tomography is an accurate and reliable imaging technique for tooth surfaces in vivo, even in the presence of metal artifacts. In comparison, dMRI in vivo accuracy is lower. Still, it allows for tooth surface reconstruction in satisfactory detail and within acceptable acquisition times.

Role of Cone-Beam Computed Tomography in the Management of Periodontal Disease

The goal of this paper was to review the current literature surrounding the use of cone beam computed tomography (CBCT) related to the diagnosis, prognostic determination, and treatment of periodontal diseases. A literature review was completed to identify peer-reviewed articles related to CBCT and periodontics. The results were filtered to pool only articles specific to CBCT and periodontal diagnosis, prognosis, and treatment/outcomes. The articles were reviewed and findings summarized. Author’s commentary on technological advances and additional potential uses of CBCT in the field of periodontics were included. There is evidence to suggest that CBCT imaging can be more accurate in diagnosing specific periodontal defects (intrabony and furcation defects), and therefore be helpful in the prognostic determination and treatment planning. However, at this time, CBCT cannot be recommended as the standard of care. It is up to the individual clinician to use one’s own judgment as to when the additional information provided by CBCT may be beneficial, while applying the As Low As Reasonably Achievable (ALARA) principle. With continued technological advances in CBCT imaging (higher resolution, reduced imaging artifacts, lower exposure, etc.) the author’s believe that CBCT usage will become more prominent in diagnosis and treatment of periodontal diseases.

Should Cone Beam Computed Tomography Be Routinely Obtained in Implant Planning?

Clinical assessment and conventional 2-D radiographs often provide inadequate diagnostic data for proper implant placement. Cone beam CT (CBCT) enables 3-D visualization of the alveolar ridge, aiding clinicians with identification of anatomic structures and pathologies. CBCT provides accurate linear measurements at low radiation dose compared with conventional CT scan, which helps in diagnosis and treatment planning, particularly in complex implant cases. Even though straightforward implant surgery can be performed with careful clinical and 2-D radiographic assessment, CBCT should be considered. It provides the unparalleled benefit of computer-aided implant planning, leading to improved clinical outcomes and reduced complications.

Novel low-dose protocols using cone beam computed tomography in dental medicine: a review focusing on indications, limitations, and future possibilities

OBJECTIVES

A narrative review on the potential use of low-dose protocols for cone beam computed tomography (CBCT) was conducted to identify indications and their relevance for various dental disciplines.

MATERIALS AND METHODS

Google Scholar was searched using the words "low-dose CBCT". Reviews, consensus papers, clinical studies, and experimental studies were eligible for the initial screening process, but for data extraction only original articles were selected. Similar search procedures were then performed with the additional search words "pedo," "ortho," "endo," "implant," "perio," and "oral surgery." Furthermore, references of included articles were examined to identify further relevant articles.

RESULTS

After screening, 27 publications remained for the data extraction process. Low-dose protocols have been reported for specialties such as pediatric dentistry (evaluating orofacial clefts, periapical lesions, impacted teeth, and autotransplantation), orthodontics (cephalometric analysis and interim assessment of treatment results), endodontics (detecting root fractures, resorptions and periapical bone loss), implant dentistry (planning implant insertion, evaluating peri-implant fenestration and dehiscence), periodontology (assessing periodontal structures), and oral and maxillofacial surgery (assessing mandibular third molars and TMJs). Nevertheless, most of the literature available is related to non-clinical studies. Furthermore, there is a lack of position statements or guidelines from authoritative bodies regarding the use of low-dose protocols in dental medicine.

CONCLUSIONS

Low-dose protocols for CBCT imaging seem to have potential in various disciplines in dental medicine ranging from pediatric dentistry to oral and maxillofacial surgery. Dose reduction is usually achieved by mAs reduction, use of partial rotations, reduced number of projections, and larger voxel sizes, but seldom by kV reduction.

CLINICAL RELEVANCE

Albeit low-dose protocols have potential to result in a reduction of dose exposure for 3D imaging due to dental indications, there is a need to more clearly specify indications and limitations to avoid indiscriminate use of standard and high-dose CBCT scans in the future on the lines of ALARA/ALADA principles.

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.

Three-dimensional treatment outcomes in Class II patients with different vertical facial patterns treated with the Herbst appliance

INTRODUCTION

The aims of this study were to evaluate, using 3-dimensional superimposition techniques, the skeletal changes in Class II subjects with different vertical facial patterns treated with the Herbst appliance and to compare these skeletal changes to those of Class II controls treated with elastics.

METHODS

Sixteen Herbst patients who met the inclusion criteria were divided into 2 equal groups based on vertical facial pattern as determined by the Frankfort mandibular plane angle (brachyfacial, ≤22°; mesofacial, 23°-29°) and had cone-beam computed tomographs taken before treatment, 8 weeks after Herbst appliance removal, and after subsequent fixed appliance treatment. Eleven Class II control patients treated with fixed appliances and elastics had cone-beam computed tomographs taken before and after treatment. Three-dimensional models were generated from the cone-beam computed tomography images, registered on the anterior cranial bases, and analyzed using color maps and point-to-point measurements.

RESULTS

There were minimal differences in treatment response between the 2 Herbst groups across all skeletal parameters measured. The Herbst subjects showed a greater inferior displacement of anterior nasal spine compared with the Class II controls (Herbst brachyfacial, -1.44 mm; Herbst mesofacial, -1.95 mm) with other maxillary changes being clinically insignificant. The Herbst subjects showed greater inferior displacement of B-point compared with the Class II controls (Herbst brachyfacial, -2.59 mm; Herbst mesofacial, -2.75 mm). There were no statistically significant differences in mean linear mandibular measurements. All groups showed a trend toward posterior displacement of the condyles and glenoid fossae from the start to the end of treatment, with no significant differences across the 3 groups. There were minimal differences in the changes in gonial angle and Frankfort mandibular plane angle across all groups.

CONCLUSION

Approximately 2 years after Herbst treatment, the Herbst subjects with different vertical facial patterns showed similar patterns of skeletal change compared with the Class II controls treated with elastics.

Diagnostic ability of limited volume cone beam computed tomography with small voxel size in identifying the superior and inferior walls of the mandibular canal

Background

The aim of this study was to evaluate the visibility of the superior and inferior walls of the mandibular canal separately using limited volume cone beam computed tomography (CBCT) with small voxel size.

Methods

CBCT cross-sectional images of 86 patients obtained by 3D Accuitomo FPD and reconstructed with a voxel size of 0.08 mm were used for the evaluation. A 30-mm range of the mandible just distal to the mental foramen was divided into three equal areas (areas 1, 2, and 3, from anterior to posterior). Each area contained 10 cross-sectional images. Two observers evaluated the visibility of the superior and inferior walls of the mandibular canal on each of the cross-sectional images in these three areas. The visibility ratio in each area was determined as the number of cross-sectional images with a visible wall divided by 10.

Results

In all areas, the visibility ratio of the superior wall was significantly lower than that of the inferior wall. As for variance among the three areas, the ratio was highest in the most posterior area (area 3) and tended to decrease gradually towards the mental foramen for both walls. Cases in which more than two thirds of the superior wall could be identified (visibility ratio of 0.7 or more) in areas 1, 2, and 3 were 44, 62, and 66%, respectively.

Conclusions

The superior wall was significantly more poorly visualized than the inferior wall in all areas examined. The visibility of the superior wall on CBCT images was limited even when a limited volume device with small voxel size was used.

Use of cone beam computed tomography in implant dentistry: current concepts, indications and limitations for clinical practice and research

Diagnostic radiology is an essential component of treatment planning in the field of implant dentistry. This narrative review will present current concepts for the use of cone beam computed tomography imaging, before and after implant placement, in daily clinical practice and research. Guidelines for the selection of three-dimensional imaging will be discussed, and limitations will be highlighted. Current concepts of radiation dose optimization, including novel imaging modalities using low-dose protocols, will be presented. For preoperative cross-sectional imaging, data are still not available which demonstrate that cone beam computed tomography results in fewer intraoperative complications such as nerve damage or bleeding incidents, or that implants inserted using preoperative cone beam computed tomography data sets for planning purposes will exhibit higher survival or success rates. The use of cone beam computed tomography following the insertion of dental implants should be restricted to specific postoperative complications, such as damage of neurovascular structures or postoperative infections in relation to the maxillary sinus. Regarding peri-implantitis, the diagnosis and severity of the disease should be evaluated primarily based on clinical parameters and on radiological findings based on periapical radiographs (two dimensional). The use of cone beam computed tomography scans in clinical research might not yield any evident beneficial effect for the patient included. As many of the cone beam computed tomography scans performed for research have no direct therapeutic consequence, dose optimization measures should be implemented by using appropriate exposure parameters and by reducing the field of view to the actual region of interest.

Zygomaticomaxillary suture maturation: A predictor of maxillary protraction? Part I - A classification method

OBJECTIVE

The aim of this study was to present a method of classifying the maturational level of the zygomaticomaxillary sutures (ZMSs).

METHODS

Cone-beam CT (CBCT) images from 74 subjects (5.6-58.4 years) were examined to define the radiographic stages of ZMS maturation. Five stages of maturation of the ZMS were identified and defined: Stage A-uniform high-density sutural line, with no or little interdigitation; Stage B-scalloped appearance of the high-density sutural line; Stage C-two parallel, scalloped, high-density lines, separated in some areas by small low-density spaces; Stage D-fusion in the inferior portion of the suture; and Stage E-complete fusion. Intra- and inter-examiner agreements were evaluated by weighted kappa tests.

RESULTS

The intra- and inter-examiners reproducibility values demonstrated substantial to almost perfect agreement. No fusion of ZMSs was observed in patients up to 10 years of age. From 10 to 15 years, all maturational stages were identified. After 15 years of age, the majority of patients showed fusion of ZMSs.

CONCLUSIONS

The classification of ZMS maturation using CBCT is a reliable method that allows the assessment of the morphology of the ZMSs in the individual patient.

Localization of mandibular canal and assessment of the remaining alveolar bone in posterior segment of the mandible with single missing tooth using cone-beam computed tomography: a cross sectional comparative study

Objectives

Localization of the mandibular canal (MC) and measurement of the height and width of the available alveolar bone at the proposed implant site in the posterior segment of the mandible using cone-beam computed tomography (CBCT) in patients with a single missing tooth.

Materials and Methods

A cross-sectional study was performed where CBCT scans of the patients with a single missing tooth in the posterior segment of the mandible—premolar, I (1st) molar, and II (2nd) molar were used. The scans were assessed using OnDemand3D software (version 1.0; CyberMed Inc., Seoul, Korea) for localization of the MC asnd remaining alveolar bone both vertically (from the superior position of the MC to the crest of the alveolar ridge) and horizontally (buccolingual, 3 mm below the crest of the alveolar ridge). The findings were statistically analyzed using independent t-test.

Results

A total of 120 mandibular sites (40 sites for each of the three missing premolar, I molar, and II molar) from 91 CBCT scans were analyzed. The average heights (from the alveolar crest to the superior margin of the MC) at the premolar, I molar, and II molar areas were 15.19±2.12 mm, 14.53±2.34 mm, and 14.21±2.23 mm, respectively. The average widths, measured 3 mm below the crest of the alveolar ridge, at the premolar, I molar, and II molar areas were 6.22±1.96 mm, 6.51±1.75 mm, and 7.60±2.08 mm, respectively. There was no statistically significant difference between males and females regarding the vertical and horizontal measurements of the alveolar ridges.

Conclusion

In the study, the measurements were averaged separately for each of the single missing teeth (premolar, I molar, or II molar), giving more accurate information for dental implant placement.

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.

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.

Assessment of mandibular posterior regional landmarks using cone-beam computed tomography in dental implant surgery

The aim of this study has been to evaluate and correlate the anatomical features of the posterior mandibular region (submandibular fossa depth, bone height and thickness, and mandibular canal corticalization) to improve accident prevention and allow safe planning in implantology. Four parasagittal sections of cone-beam computed tomography (CBCT) from 100 patients were bilaterally analyzed. Linear measurements of the submandibular fossa depth, bone height and thickness were performed. The submandibular fossa was also classified into non-influential undercuts and influential undercuts for implant placement. Mandibular canal corticalization was also evaluated and classified according to the visualization. Data on patient age and gender were also collected. Forty-one scans (41%) were from male patients, and 59 (59%) were from female patients. Patient age ranged between 18 and 84 years, with an average age of 51.37 years. The submandibular fossa depth and implant bone thickness had a significant effect on the variability of the sample (46.1% and 22.3%, respectively). The submandibular fossa depth was quite variable, and the highest values were observed in the posterior regions. In 18.27% of the cases, the presence of the fossa directly influenced implant placement, considering a bone height of 10mm (standard implant). A significant correlation was observed between fossa depth and bone thickness. Thus, greater attention should be paid to thick ridges; although thick ridges are favorable, they may be associated with deeper submandibular fossae. The mandibular canal was the most influential anatomical structure in the premolar region due to the reduced bone height in this region and the greater difficulty in viewing the canal, and the submandibular fossa was the most influential structure in the molar region due to lower bone height leading up to the fossa and the greater fossa depth in this region. Therefore, CBCT is an important tool for assessing the mandibular region and planning for safe implant installation in the posterior mandible. Furthermore, comprehensive evaluation of the characteristics of this region is necessary, as the variables - submandibular fossa depth, bone height and thickness, and mandibular canal corticalization - are related and must be considered together when planning.

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.

Dose optimization by altering the operating potential and tube current exposure time product in dental cone beam CT: a systematic review

OBJECTIVES

Current guidelines highlight the need to optimize exposure parameters on CBCT equipment to levels that are as low as diagnostically acceptable. This systematic review aimed to answer the question "Can altering operating potential (kV) and tube current exposure time product (mAs) on CBCT machines reduce radiation dose to patients undergoing dental and/or maxillofacial scans without a detrimental impact on image quality/diagnostic accuracy?"

METHODS

Studies were selected and results reported following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) method. For each individual study, two authors (RG and JD or KH) independently extracted data using a specifically designed collection form, and an overall quality value was assigned using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system. Any disagreements in the overall quality value of a study were resolved by discussion between the current authors.

RESULTS

Nearly 75% of studies were considered to be of low or very low methodological quality using the GRADE system, and more studies stated that their results applied only in the specific situations they had investigated. However, most studies demonstrated that patient dose reduction is possible without a clinically relevant reduction in image quality.

CONCLUSIONS

For many CBCT machines, it should be possible to optimize one, or more, of the investigated exposure parameters and therefore reduce patient radiation dose, while maintaining diagnostic image quality for some diagnostic tasks. However, more rigorous research is still required.

Availability of Software-Based Correction of Mandibular Plane for the Vertical Measurement of the Mandible in Cone Beam Computed Tomography

Objectives. To investigate the availability of correction of mandibular plane using software for vertical measurements in cone beam computed tomography (CBCT) according to the sites of the mandible. Methods. CBCT scans of six dry mandibles were performed at 0-, 5-, 10-, 15-, and 20-degree angles relative to CBCT scanning table. Using the imaging software, mandibular planes of the different angles were corrected to that of 0-degree angle on the CBCT images. Before and after correction of the mandibular planes, the distance from the mandibular canal to the alveolar crest was measured at M1, M2, and M3 areas of the mandible and vertical measurements were statistically compared with those of 0-angle location using the paired t-test. Results. Prior to correction, the vertical measurements increased as the angle increased. The greatest differences of measurements were observed in M3 areas (P < 0.05). After correction, a strong correlation was found in measurements between the 0-degree angle and the other angles in all sites of the mandible (P > 0.05). Conclusions. The vertical measurements of CBCT were significantly influenced by mandibular positioning. When CBCT scans are performed at angles other than 0-degree angle, software-based correction of the mandibular plane can be a reliable tool for the accurate vertical measurements in CBCT.

Comparative evaluation of mandibular canal visibility on cross-sectional cone-beam CT images: a retrospective study

OBJECTIVES

The purpose of this study was to determine the visibility of the mandibular canal (MC) in CBCT images and if the visibility of the MC is affected by gender, location and/or age.

METHODS

CBCT images were evaluated for the visibility of the MC by a board-certified oral and maxillofacial radiologist, a board-certified periodontist and a periodontics resident. Representative slices were examined for the first premolar (PM(1)), second premolar (PM(2)), first molar (M(1)) and second molar (M(2)) sites by all examiners. The visibility of the MC was registered as either present or absent.

RESULTS

360 total CBCT cross-sectional images were examined, with the MC identified in 204 sites (56%). Age had a significant effect on MC visibility, but it differed by location: for PM(1), age 47-56 had lower visibility than age 65+ (p = 0.0377). Gender also had a significant effect on canal visibility, where females had lower visibility than males overall (p = 0.0178) and had the most pronounced difference for PM(1) (p = 0.0054). Location had a significant effect on visibility, but it differed by age and by gender: for age 65+, M(2) had lower visibility than PM(1) (p = 0.0411) and PM(2) (p = 0.0180), while for females, PM(1) had lower visibility than M(1) (p = 0.0123) and M(2) (p = 0.0419).

CONCLUSIONS

The MC was visualized only in just over half of the CBCT images. Age, gender and location had significant effects on the visibility.

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.

Development of a low-dose protocol for cone beam CT examinations of the anterior maxilla in children

OBJECTIVE

The aim of this study was to develop a low-dose protocol suitable for cone beam CT (CBCT) examination of an impacted maxillary canine in children by using a combination of dosimetry with subjective and objective image quality assessment.

METHODS

Radiation dose and image quality measurements were made using a dental CBCT machine. An image quality phantom was used to investigate the relationship between objective image quality and dose-area product (DAP) for a broad range of exposure settings. Subjective image quality assessment was achieved using a paediatric skull phantom submerged in a water bath for the same range of exposure settings. Eight clinicians assessed each CBCT data set for nine aspects of image quality using a five-point rating scale of agreement.

RESULTS

Acceptable image quality, defined using subjective judgements by the clinicians of the skull phantom images, was achievable with DAP values of 127 mGy cm(2) or greater and a polytetrafluoroethylene (PTFE) contrast-to-noise ratio (CNR) of 4.8 or greater. A cautious choice was made to recommend a low-dose protocol of 80 kV and 3 mA for implementation into clinical practice, corresponding to a DAP value of 146 mGy cm(2) and a PTFE CNR of 5.0.

CONCLUSION

A low-dose protocol for this particular CBCT machine was established which represents as much as a 50% reduction compared with manufacturer's recommendations.

ADVANCES IN KNOWLEDGE

To the authors' best knowledge, this is the first study that addresses dose optimization in paediatric clinical protocols in dental CBCT. Furthermore, this study explores the relationship between radiation dose, objective and subjective image quality.

Evaluation of the anterior mandibular donor site one year after secondary reconstruction of an alveolar cleft: 3-dimensional analysis using cone-beam computed tomography

The aim of this study was to analyse changes in the volume of the chin after harvest of a bone graft for secondary reconstruction of an alveolar cleft. Cone-beam computed tomographic (CT) scans of 27 patients taken preoperatively, and immediately and one year postoperatively, were analysed, and 3-dimensional hard-tissue reconstructions made. The hard-tissue segmentation of the scan taken one year postoperatively was subtracted from the segmentation of the preoperative scan to calculate the alteration in the volume of bone at the donor site (chin). A centrally-orientated persistent concavity at the buccal side of the chin was found (mean (range) 160 (0-500) mm(3)). At the lingual side of the chin, a central concavity remained (mean (range) volume 20 (0-80) mm(3)). Remarkably, at the periphery of this concavity there was overgrowth of new bone (mean (range) volume 350 (0-1600) mm(3)). Re-attachment of the muscles of the tongue resulted in a significantly larger central lingual defect one year postoperatively (p=0.01). We also measured minor alterations in volume of the chin at one year. Whether these alterations influence facial appearance and long term bony quality is to be the subject of further research.

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.

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.

Three-dimensional treatment outcomes in Class II patients treated with the Herbst appliance: a pilot study

INTRODUCTION

The aims of this study were to analyze 3-dimensional skeletal changes in subjects with Class II malocclusion treated with the Herbst appliance and to compare these changes with treated Class II controls using 3-dimensional superimposition techniques.

METHODS

Seven consecutive Herbst patients and 7 Class II controls treated with Class II elastics who met the inclusion criteria had cone-beam computed tomographs taken before treatment, and either after Herbst removal or at posttreatment for the control subjects. Three-dimensional models were generated from the cone-beam computed tomography images, registered on the anterior cranial bases, and analyzed using color maps and point-to-point measurements.

RESULTS

The Herbst patients demonstrated anterior translation of the glenoid fossae and condyles (right anterior fossa, 1.69 ± 0.62 mm; left anterior fossa, 1.43 ± 0.71 mm; right anterior condyle, 1.20 ± 0.41 mm; left anterior condyle, 1.29 ± 0.57 mm), whereas posterior displacement predominated in the controls (right anterior fossa, -1.51 ± 0.68 mm; left anterior fossa, -1.31 ± 0.61 mm; right anterior condyle, -1.20 ± 0.41 mm; left anterior condyle, -1.29 ± 0.57 mm; P <0.001). There was more anterior projection of B-point in the Herbst patients (2.62 ± 1.08 mm vs 1.49 ± 0.79 mm; P <0.05). Anterior displacement of A-point was more predominant in the controls when compared with the Herbst patients (1.20 ± 0.53 mm vs -1.22 ± 0.43 mm; P <0.001).

CONCLUSIONS

Class II patients treated with the Herbst appliance demonstrated anterior displacement of the condyles and glenoid fossae along with maxillary restraint when compared with the treated Class II controls; this might result in more anterior mandibular projection.

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.