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

The anatomical relationship between the roots of erupted permanent teeth and the mandibular canal: a systematic review

PURPOSE

This study reviewed the literature on the position of the mandibular canal (MC) relative to the root apices (RA) of neighbouring teeth using cone beam computed tomography (CBCT).

METHODS

The authors searched the PubMed, Scopus, EBSCO Dentistry and Oral Sciences Source, Cochrane and Lilacs databases for relevant English-language articles with no year limitations published through January 25, 2018.

RESULTS

The search identified 888 articles, 12 of which met the inclusion criteria. Three groups were found based on the measuring method: the shortest distance from the RA to the MC, the vertical distance from the RA to the MC, or the distance from the RA to the superior cortical bone of the MC. In the first and second groups, the shortest distances to the canines, first premolars, second premolars, first molars, second molars, and third molars were 3.8 mm, 4.76 mm, 1.65 mm, 1.23 mm, 0.64 mm, and 1.28 mm, respectively. In the third group, the shortest distances to the second premolars, first molars, and second molars were 2.71 mm, 3.82 mm, and 1.4 mm, respectively.

CONCLUSIONS

The distance from the MC to the RA was generally shorter in females and younger people, with decreasing distances in patients over 60 years old, and depended on the tooth type.

TRIAL REGISTRATION

The protocol for this systematic review was registered on PROSPERO (CRD42018085478).

Accuracy of in vitro mandibular volumetric measurements from CBCT of different voxel sizes with different segmentation threshold settings

Background

To determine the accuracy of volumetric measurements of the mandible in vitro by cone-beam computed tomography (CBCT) and to analyze the influence of voxel sizes and segmentation threshold settings on it.

Methods

The samples were obtained from pig mandibles and scanned with 4 voxel sizes: .125 mm, .20 mm, .30 mm, and .40 mm. The minimum segmentation thresholds in Hounsfield units (HU) were set as 0, 100, 200, 300, and 400, respectively, for each voxel size for 3D reconstruction. Laser scanning as the reference, the volumes of each CBCT scanning, the mean iterative distances of superimposition and total positive and negative deviations were recorded and compared.

Results

The volumes of CBCT-scan deviated from those of laser-scan by + 7.67% to − 3.05% with different HU and voxel sizes. The deviation increased with the voxel size. There was a more suitable minimum HU threshold of segmentation (HU100 for .125 mm, 200 for .20 mm, 300 for .30 mm, and 400 for .40 mm) for each voxel size.

Conclusions

Voxel sizes and Hounsfield unit thresholds influence the accuracy of volumetric measurements in CBCT scanning. The volume increase with the voxel size, and different voxel sizes correspond to different optimal Hounsfield unit thresholds.

The impact of different voxels and exposure parameters of CBCT for the assessment of external root resorptions: A phantom study

This study aimed to compare the effectiveness of the different voxel sizes and imaging parameters of cone beam computed tomography (CBCT) on the determination of external root resorption (ERR). ERRs were created in coronal, middle and apical regions. Depths (0.62-0.73 mm) and diameters (0.68-0.81 mm) of ERRs were measured using a digital calliper. Images were obtained in 0.125, 0.2, 0.25, 0.3 and 0.4 mm³ voxel sizes and at different currents. Data were analysed using Friedman and Wilcoxon signed-rank tests at a level of P < 0.05. There was a difference between the parameters in determining the size of the ERR in coronal and middle regions (P < 0.05), but there was no difference in the apical region (P > 0.05). The change in current and exposure time did not make a difference in determining the dimensions of the ERRs (P > 0.05). Some voxel dimensions were more reliable in determining the depth and diameter of ERR in the coronal and middle region.

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.

Cone-beam computed tomography imaging of dentoalveolar and mandibular fractures

Three-dimensional imaging methods have an important role in the diagnosis of dentomaxillofacial fractures that can not be seen on the plain films. Cone-beam computed tomography (CBCT) is one of the three-dimensional imaging methods and has facilitated dental professionals' access to cross-sectional imaging. CBCT units allow different technical parameters and the data acquired by CBCT, can be reformatted. Osseous structures are correctly examined with this technique but the technique is not useful for the examination of soft tissues. Therefore, the purpose of its use should be based on the expected diagnostic gain. The aim of this review is to present the use of CBCT with different multi-planar reformatted sections and three-dimensional reconstructions of dentoalveolar and mandibular fractures.

Cone Beam Computed Tomography

In the last several decades, the need for 3D images in dentistry have developed. Computerized tomography was first introduced mainly with the advent of implantology, but its use remained limited to a small number of specialists, due to its indications, access and dose radiation. In the late 90's, a new technology using a cone-shaped beam and a reciprocating detector, which rotates around the patient 360 degrees and acquires projected data in a single rotation, namely the cone beam computerized tomography (CBCT), invaded dentistry, making the perception of 3D easily acceptable to dentists and their patients.

Cone Beam Computed Tomography Evaluation of the Artery in the Lateral Wall of the Maxillary Sinus: Retrospective Analysis of 602 Sinuses

PURPOSE

This retrospective study evaluates the location of the arteries in the maxillary sinus, particularly in the middle portion, using cone beam computed tomography (CBCT) scans that can detect the lateral arteries with high reliability.

METHODS

In this retrospective study, 2 experienced independent examiners evaluated 602 sinuses on CBCT scans.

DISCUSSION

No significant correlation was found between the location of arteries and the patient's age, sex, or dentition. In 92.0% (P ≤ 0.001) of the sinuses, at least 1 arterial branch was detectable.

CONCLUSION

Based on the CBCT scans, we found that a very high proportion of patients have the maxillary artery in their lateral sinus wall, which is important information for sinus augmentation or sinus surgery.

Impact of voxel size and scan time on the accuracy of three-dimensional radiological imaging data from cone-beam computed tomography

PURPOSE

Three-dimensional (3D) radiological imaging plays an important role in surgical planning used in modern dentistry. The aim of this study was to optimize imaging parameters with a special focus on voxel size and scan time.

MATERIAL AND METHODS

A virtual 3D master model of a macerated human skull was generated using an industrial optical noncontact white light scanner. The skull was X-rayed with cone-beam computed tomography that was applied using different settings for voxel size and acquisition time (voxel edge length of 0.3 mm, scan times 4.8 s and 8.9 s; voxel edge length of 0.2 mm, scan times 14.7 s and 26.9 s). The scan was repeated 10 times at each setting. The CBCT scans were converted into 3D virtual models (actual value), which were superimposed with the 3D master model (reference value) to detect absolute differences.

RESULTS

The mean value of deviation increased with increasing voxel size and decreasing scan time. For a voxel edge length of 0.3 mm, the mean values of deviation were 0.33 mm and 0.22 mm with scan times of 4.8 s and 8.9 s, respectively. For a voxel edge length of 0.2 mm, the mean deviations were 0.16 mm and 0.14 mm with scan times of 14.7 s and 26.9 s, respectively.

CONCLUSIONS

When using small voxel sizes, the scan time does not have a significant impact on image accuracy and therefore the scan time can be shortened. However, for larger voxel sizes, shorter scan times can lead to increased inaccuracy.

CBCT assessment of gubernacular canals in relation to eruption disturbance and pathologic condition associated with impacted/unerupted teeth

OBJECTIVES

The aim of this study was to demonstrate the imaging characteristics of gubernacular canals (GCs) in impacted/unerupted permanent teeth and to determine whether these characteristics differ as a result of the presence of eruption disturbances or pathologic conditions associated with impacted/unerupted teeth.

STUDY DESIGN

GCs were retrospectively analyzed by using cone beam computed tomography in 250 patients with 753 impacted/unerupted permanent teeth (105 males, 145 females; mean age, 21.09 ± 14.45 years; range 6-70 years).

RESULTS

The rate of detection of GCs was significantly lower in cases with eruption disturbances than in those without eruption disturbances. An inverse correlation was observed between age and detection of GCs. Similarly, root resorption of adjacent teeth and resorption of impacted/unerupted teeth were associated with lower rates of detection of GCs. However, no association was found for widening of the follicular space. Regression analysis determined disturbed eruption pattern as the most important factor for the absence of GCs.

CONCLUSIONS

The absence of GC may indicate a disturbed eruption pattern of the tooth and may increase the risk of complications related to impaction resulting in a tooth that is more likely to remain unerupted.

Role of Computed Tomography Scan in Dental Trauma: A Cross-Sectional Study

Background:

Dental trauma is caused by fracture(s) in the vertical plane and the horizontal plane of roots. The objective of this study is to perform multiple diagnostic modalities for the diagnosis of horizontal root fracture(s) of the tooth.

Methods:

A total of 250 patients with dental complaints were subjected to intraoral radiography, multidetector helical computed tomography (MDHCT), and limited cone beam computed tomography (LCBCT). The suspected tooth was extracted, visually inspected, and subjected to microcomputed tomography (micro-CT). Images were observed in the lightbox, and a fracture was considered if it had been directly visualized as radiolucent line traversing tooth root. Wilcoxon test/Tukey post hoc test was performed at 99% of confidence level.

Results:

With respect to visual inspection, for LCBCT, intraoral radiography, MDHCT, and micro-CT, sensitivities were 0.988, 0.972, 0.967, and 0.979; accuracies were 0.956, 0.785, 0.905, and 0.888; false-positive values were 5, 21, 12, and 11; and false-negative values were 3, 24, 3, and 11, respectively. The area of the image visible at one time was in the order of treatment without radiography < intraoral radiography < MDHCT < micro-CT < LCBCT.

Conclusion:

The LCBCT had the highest sensitivity and accuracy for diagnosis of horizontal tooth root fracture(s).

Level of Evidence:

I.

Trial Registry:

researchregistry3647, dated December 31, 2016 (www.researchregistry.com).

Evaluation of Threshold Values for Root Canal Filling Voids in Micro-CT and Nano-CT Images

While several materials and techniques have been used to assess the quality of root canal fillings in micro-CT images, the lack of standardization in scanning protocols has produced conflicting results. Hence, the aim of this study was to determine a cutoff voxel size value for the assessment of root canal filling voids in micro-CT and nano-CT images. Twenty freshly extracted mandibular central incisors were used. Root canals were prepared with nickel titanium files to an ISO size 40/0.06 taper and then filled with a single cone (40/0.06 taper) and AH Plus sealer. The teeth were scanned with different voxel sizes with either micro-CT (5.2, 8.1, 11.2, and 16.73 μm) or nano-CT (1.5 and 5.0 μm) equipment. Images were reconstructed and analyzed with the NRecon and CTAn software. Void proportion and void volume were calculated for each tooth in the apical, middle, and coronal thirds of the root canal. Kruskal-Wallis and post hoc Mann-Whitney U tests were performed with a significance level of 5%. In micro-CT images, significantly different results were detected among the tested voxel sizes for void proportion and void volume, whereas no such differences were found in nano-CT images (p > 0.05). Micro-CT images showed higher void numbers over the entire root length, with statistically significant differences between the voxel size of 16.73 μm and the other sizes (p < 0.05). The values of the different nano-CT voxel sizes did not significantly differ from those of the micro-CT (5.2, 8.1, and 11.2 μm), except for the voxel size of 16.73 μm (p < 0.05). All tested voxel sizes enabled the detection of root canal filling voids except for the voxel size of 16.73 μm. Bearing in mind the limitations of this study, it seems that a voxel size of 11.2 μm can be used as a reliable cutoff value for the assessment of root canal filling voids in micro-CT imaging.

Diagnostic performance of cone beam computed tomography in assessing peri-implant bone loss: A systematic review

OBJECTIVES

To evaluate the diagnostic performance of cone beam computed tomography (CBCT) in the assessment of peri-implant bone loss and analyze its influencing factors.

MATERIALS AND METHODS

Clinical and preclinical studies reporting diagnostic outcomes of CBCT imaging of peri-implant bone loss compared to direct reference measurements were sought by searching five electronic databases, PubMed, MEDLINE, EMBASE, Web of Science, and CINAHL Plus, and OpenGrey. QUADAS-2 criteria were adapted for quality analysis of the included studies. A qualitative synthesis was performed. Two meta-analysis models (random-effects and mixed-effects) summarized the area under receiver operating characteristic (AUC) curve observations reported in the selected studies. The mixed-effects meta-analysis model evaluated three possible influencing factors, "defect type," "defect size," and "study effect."

RESULTS

The initial search yielded 3,716 titles, from which 18 studies (13 in vitro and 5 animal) were included. Diagnostic accuracy of CBCT was fair to excellent in detecting in vitro circumferential-intrabony and fenestration defects, but moderate to low for peri-implant dehiscences, and tended to be higher for larger defect sizes. Both, over- and underestimation of linear measurements were reported for the animal models. The meta-analyses included 37 AUC observations from eight studies. The random-effects model showed significant heterogeneity. The mixed-effects model exhibited also significant but lower heterogeneity, and "defect type" and "study effect" significantly influenced the variability of AUC observations.

CONCLUSION

In vitro, CBCT performs well in detecting peri-implant circumferential-intrabony or fenestration defects but less in depicting dehiscences. Influencing factors due to other site-related and technical parameters on the diagnostic outcome need to be addressed further in the future studies.

The effect of varying cone beam computed tomography image resolution and field-of-view centralization on effective radiation dose

OBJECTIVES

To investigate changes in the effective radiation dose (E) in relation to variations in voxel (VOX) size settings and the field-of-view (FOV) centralization. Methods: This cross-sectional dosimetry study used nanoDot OSLD dosimeters placed at 25 pre-determined sites in the head and neck slices of a RANDO male phantom to measure the absorbed radiation. The imaging scans took place at King Abdulaziz University Dental Hospital, Jeddah, Saudi Arabia between September 2016 and May 2017 using the i-CAT classic cone beam computed tomography (CBCT)  unit. Three VOX size setting were examined: 0.2 mm, 0.3 mm and 0.4 mm. The FOV was alternatively eccentrically centered on the maxillary and mandibular arches while holding all other factors constant. Effective radiation doses were calculated for each VOX size and FOV centralization setting. Results: An inverse and indirect relation was found between E and the VOX size setting with smaller VOX yielding higher E. CBCT scans centered on the mandible resulted in higher E than scans centered on the maxilla. Conclusion: Effective radiation doses are significantly affected by changes in VOX size settings and FOV centralization options. This reflects on the potential radiation risk to patients and highlights the importance of choosing exposure parameters carefully.

Diagnostic accuracy of cone-beam computed tomography scans with high- and low-resolution modes for the detection of root perforations

Purpose

This study compared the diagnostic accuracy of cone-beam computed tomography (CBCT) scans obtained with 2 CBCT systems with high- and low-resolution modes for the detection of root perforations in endodontically treated mandibular molars.

Materials and Methods

The root canals of 72 mandibular molars were cleaned and shaped. Perforations measuring 0.2, 0.3, and 0.4 mm in diameter were created at the furcation area of 48 roots, simulating strip perforations, or on the external surfaces of 48 roots, simulating root perforations. Forty-eight roots remained intact (control group). The roots were filled using gutta-percha (Gapadent, Tianjin, China) and AH26 sealer (Dentsply Maillefer, Ballaigues, Switzerland). The CBCT scans were obtained using the NewTom 3G (QR srl, Verona, Italy) and Cranex 3D (Soredex, Helsinki, Finland) CBCT systems in high- and low-resolution modes, and were evaluated by 2 observers. The chi-square test was used to assess the nominal variables.

Results

In strip perforations, the accuracies of low- and high-resolution modes were 75% and 83% for NewTom 3G and 67% and 69% for Cranex 3D. In root perforations, the accuracies of low- and high-resolution modes were 79% and 83% for NewTom 3G and was 56% and 73% for Cranex 3D.

Conclusion

The accuracy of the 2 CBCT systems was different for the detection of strip and root perforations. The Cranex 3D had non-significantly higher accuracy than the NewTom 3G. In both scanners, the high-resolution mode yielded significantly higher accuracy than the low-resolution mode. The diagnostic accuracy of CBCT scans was not affected by the perforation diameter.

Cone Beam Computed Tomography (CBCT) in General Dental Practice

Cone beam computed tomography (CBCT) can be a useful adjunct to conventional plain film radiography, but its use must be carefully justified as the radiation dose is generally higher. Factors affecting the dose include the field of view (FOV) size, the exposure factors, the angle of rotation and voxel size. Once justified, the exposure should be fully optimised to ensure the dose to the patient is kept as low as possible while ensuring there is no reduction in the diagnostic yield. The European Commission (EC) and the Faculty of General Dental Practice (FGDP)(UK) have published selection criteria on the use of CBCT in dentistry. This article provides an overview of CBCT and summarises the latest guidance on selection criteria relevant to the general dental practitioner.

Comparison of the accuracy of periapical radiography with CBCT taken at 3 different voxel sizes in detecting simulated endodontic complications: an ex vivo study

OBJECTIVES

To compare the accuracy of a photostimulable phosphor plateP sensor with cone beam CT (CBCT) images in the detection of simulated endodontic complications.

METHODS

Following simulated endodontic complications were created in 40 extracted human mandibular molar teeth: Group 1, Instrument separation (N = 10); Group 2, Strip perforation (N = 10); Group 3, Underfilling of root canals (N = 10); Group 4, Overfilling of root canals (N = 10). Intraoral and CBCT images (voxel size: 0.075 , 0.1 and 0.2 mm) were taken. Images were scored by 4 observers according to a 5-point scale. Weighted kappa and intraclass correlation coefficients were calculated. Receiveroperating characteristic analysis was performed and DeLong test was used to compare areaunder curve values. Significance level was set at p < 0.05.

RESULTS

Intraobserver kappa ranged from moderate (0.417) to excellent (0.918). Intraclass correlation coefficients ranged from moderate (0.482) to excellent (0.855). For Group 1 (instrument separation) the highest Az values were obtained for intraoral images and the lowest for CBCT (0.2 mm voxel size) (p < 0.05). The highest Az values were obtained for Group 2 (strip perforation) among all groups. With all CBCT image settings, observers performed similarly and better than intraoral images (p < 0.05) in detection of strip perforation. For Group 3 (underfilling), higher Az values for CBCT images were obtained compared to intraoral images without statistically significant difference (p > 0.05). For Group 4 (overfilling), higher Az values for CBCT images were obtained when compared to digital intraoral for observer 1 and 2 (p < 0.05).

CONCLUSIONS

CBCT images may be useful as an adjunct to periapical imaging in the detection of endodontic complications, such as strip perforation and overfilled root canals.

Incidence of Dentinal Crack Formation Using ProTaper Universal and WaveOne Systems in Straight and Curved Root Canals

Introduction

This study aimed to compare dentinal micro crack formation following root canal instrumentation with ProTaper Universal (PTU) and WaveOne (WO) rotary systems in straight and curved root canals.

Methods and Materials

One hundred mesiobuccal (MB) straight and curved canals of mandibular molars meeting inclusion criteria were divided into two control (n=10) and four experimental groups (n=20). After mounting the teeth and simulating the periodontal ligament, all the MB canals were coronally flared using Gates-Glidden drills #3 and 2 respectively. Then, in the experimental groups, the canals were instrumented with either PTU files (S_x, S₁, S₂, F₁, F₂), or Primary WO (25/0.08). Afterwards, roots were horizontally sectioned at 2, 4, and 6 mm from the apices, and evaluated under a microscope under 20× magnification. Data were analyzed with the Chi-Square and Kruskal-Wallis tests. The significance level was set at 0.05.

Results

The control groups showed no cracks. There was no significant difference between the two systems in the straight root canals (P>0.05). But in the curved root canals, PTU produced significantly more cracks (P<0.05) with the complete crack type which was dominant (P=0.013) compared to WO.

Conclusions

This in vitro study showed that in curved root canals, instrumentation with reciprocal WO system may be safer than full rotational PTU instruments regarding crack formation.

Influence of patient position and other inherent factors on image quality in two different cone beam computed tomography (CBCT) devices

•

Patient head position can affect the image quality in CBCT-examinations.

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CNR values can be used to evaluate image quality.

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Inherent factors influence effective dose variations between CBCT-devices.

Objectives

The aim of this in vitro study was to evaluate how a deviation from the horizontal plane, affects the image quality in two different CBCT-devices.

Methods

A phantom head SK150 (RANDO, The Phantom Laboratory, Salem, NY, USA) was examined in two CBCT-units: Accuitomo 80 and Veraviewepocs 3D R100 (J. Morita Mfg. Corp. Kyoto, Japan). The phantom head was placed with the hard palate parallel to the horizontal plane and tilted 20 ° backwards. Exposures were performed with different field of views (FOVs), voxel sizes, slice thicknesses and exposure settings. Effective dose was calculated using PCXMC 2.0 (STUK, Helsinki, Finland). Image quality was assessed using contrast-to-noise-ratio (CNR). Region of interest (ROI) was set at three different levels of the mandibular bone and soft tissue, uni- and bilaterally in small and large FOVs, respectively. CNR values were calculated by CT-value and standard deviation for each ROI. Factor analysis was used to analyze the material.

Results

Tilting the phantom head backwards rendered significantly higher mean CNR values regardless of FOV. The effective dose was lower in small than in large FOVs and varied to a larger extent between CBCT-devices in large FOVs.

Conclusions

Head position can affect the image quality. Tilting the head backward improved image quality in the mandibular region. However, if influenced by other variables e.g. motion artifacts in a clinical situation, remains to be further investigated.

Advances in knowledge

Image quality assessed using CNR values to investigate the influence of different patient positions and FOVs.

Comparison of cone beam computed tomography and digital intraoral radiography performance in the detection of artificially induced recurrent caries-like lesions

OBJECTIVES

The aim of this study was to compare the performance of cone beam computed tomography (CBCT) and digital radiography in the detection of artificial recurrent caries-like lesions under amalgam and composite fillings.

STUDY DESIGN

The study included class II cavities in 30 molars that had been filled with amalgam. Fifteen of those molars had the restoration-enamel interface artificially demineralized. Phantoms were prepared, and CBCT images were acquired with 2 units in 3 voxel sizes (K9000, 0.076 mm; i-CAT, 0.2 mm and 0.4 mm). Intraoral radiographs were obtained with 3 systems (Digora, VistaScan, and RVG-6100). Amalgam fillings were then replaced by composite, and new images were obtained. Three examiners assessed all of the images. Sensitivity, specificity, accuracy, and receiver operating characteristic curve were calculated and verified through analysis of variance and the Tukey test.

RESULTS

There were no significant differences in sensitivity and specificity when the same restorative material was present or when the restorative materials were compared with the imaging technique as a constant. As for accuracy and receiver operating characteristic curve, there were statistically significant differences when the 2 materials were compared, and there were differences in the amalgam group when the imaging modalities were compared.

CONCLUSIONS

CBCT performed similarly to intraoral radiography in detecting demineralization under restorations. However, the voxel size and the type of restorative material influenced its performance.

Impact of cone-beam computed tomography scan mode on the diagnostic yield of chemically simulated external root resorption

INTRODUCTION

The aim of this in-vitro study was to evaluate the influence of cone-beam computed tomography scans on the diagnosis of chemically simulated external root resorption.

METHODS

One hundred extracted anterior teeth were selected. Subsurface demineralization was induced on a limited area of the apical third of the root of 49 teeth. Each tooth was placed in an empty socket of a partially edentulous dry mandible. Cone-beam computed tomography images were obtained according to 3 protocols: (1) half scan, 0.40-mm voxel size; (2) full scan, 0.40-mm voxel size; and (3) full scan, 0.125-mm voxel size. Three observers evaluated the images. Sensitivity, specificity, accuracy, and area under the curve were compared with the Cochran Q and Mann-Whitney U tests.

RESULTS

Protocol 3 had the highest sensitivity (81.63%), accuracy (80.67%), and area under the curve (0.807). There were statistically significant differences between protocol 3 and the other 2 protocols (P <0.001). The specificity of protocol 1 (84.97%) was greater than that of protocols 2 (69.93%) and 3 (79.74%); however, a statistically significant difference was found only between protocols 1 and 2 (P = 0.005).

CONCLUSIONS

A more dedicated, high-resolution scan should be acquired when one intends to investigate the early stage of external root resorption during orthodontic treatment. However, this does not imply that all orthodontic patients should be subjected to high-dose cone-beam computed tomography scans.

Feasibility of Cone-beam Computed Tomography in Detecting Lateral Canals before and after Root Canal Treatment: An Ex Vivo Study

INTRODUCTION

The study objective was to evaluate the effectiveness of cone-beam computed tomographic (CBCT) imaging for the detection of lateral canals (LCs) in endodontically treated premolars.

METHODS

Two evaluators classified 80 extracted premolars into 2 groups based on the absence (n = 40) or presence (n = 40) of LCs according to micro-computed tomographic analysis. The extracted teeth were fixated in a human mandible and scanned with CBCT imaging. Subsequently, each tooth was endodontically treated, and CBCT scans were repeated. Three experienced examiners evaluated all images randomly. Receiver operating characteristic curves were compared using the McNemar test, and sensitivity, specificity, positive predictive value, and negative predictive value (NPV) were obtained.

RESULTS

The area under the receiver operating characteristic curve values were 0.58 and 0.49 before and after root canal treatment, respectively. These values were statistically significantly different (P < .001). Before root canal treatment sensitivity, specificity, positive predictive value, and negative predictive value were 55%, 52%, 55%, and 56%, whereas after root canal treatment the values were 33%, 61%, 46%, and 48%, respectively.

CONCLUSIONS

LC detection in nontreated teeth presented low accuracy, whereas among treated teeth CBCT imaging showed no efficacy. The results suggest that CBCT imaging is not an effective diagnostic tool for LC detection.

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.

Influence of acquisition parameters on the evaluation of mandibular third molars through cone beam computed tomography

OBJECTIVES

The aim of the study was to assess the influence of cone beam computed tomography (CBCT) acquisition parameters on the evaluation of mandibular third molars and their relationship to the mandibular canal.

STUDY DESIGN

Eight dry human mandibles with 13 mandibular third molars were scanned with one CBCT unit. Voxel size (0.2 and 0.3 mm), field of view (FOV) size (12 × 8.5 cm and 5 × 5 cm), and number of basis images (450 and 720) were the variables studied. Two examiners evaluated the images, and the resulting data were compared through McNemar, McNemar-Bowker, and Student t tests. Additionally, dosimetry was determined for all protocols tested, and radiation doses were compared through analysis of variance.

RESULTS

The variables did not influence evaluation of mandibular third molars, except for voxel size, when assessing contact between the tooth and the mandibular canal (P = .021). Although FOV and number of basis images affected radiation dose, voxel size did not.

CONCLUSIONS

FOV size and number of basis images did not influence the evaluation of mandibular third molars and their relationship to the mandibular canal in the CBCT unit used. Conversely, smaller voxel size affected the assessment of contact between the tooth and the mandibular canal. In units in which voxel size does not influence radiation dose, the most appropriate CBCT protocol is the one using a smaller voxel size and delivering the lowest radiation dose to the patient.

Effect of Field of View on Detection of Condyle Bone Defects Using Cone Beam Computed Tomography

In maxillofacial imaging, cone beam computed tomography (CBCT) is currently the modality of choice for assessment of bony structures of the temporomandibular joint (TMJ). Factors affecting the quality of CBCT images can change its diagnostic accuracy. This study aimed to assess the effect of field of view (FOV) and defect size on the accuracy of CBCT scans for detection of bone defects of the TMJs. This study was conducted on 12 sound TMJs of 6 human dry skulls. Erosions and osteophytes were artificially induced in 0.5, 1, and 1.5-mm sizes on the anterior-superior part of the condyle; CBCT scans were obtained with 6, 9, and 12-inch FOVs by NewTom 3G CBCT system. Two maxillofacial radiologists evaluated the presence/absence and type of defects on CBCT scans. The Cohen kappa was calculated to assess intra- and interobserver reliability. The Mann-Whitney U test was applied to compare the diagnostic accuracy of different FOVs.In comparison of 6- and 12-inch, 9- and 12-inch FOVs in detection of different sizes of erosive lesions, difference was significant (P <0.05), whereas difference between 6- and 9 inch just in 0.5-mm erosive lesion was significant (P = 0.04). In comparison of 6- and 12-inch FOVs in detection of different sizes of osteophyte lesion, difference was significant (P < 0.05), whereas between 6- and 9-inch FOVs statistically significant difference was not observed (P > 0.05). The highest and the lowest diagnostic accuracy of CBCT scans for condyle defects were obtained with 6-inch and 12-inch FOVs, respectively. Diagnostic accuracy of CBCT scans increased with an increase in size of bone defects.

Effect of Field Of View on Detection of External Root Resorption in Cone-Beam Computed Tomography

INTRODUCTION

Conventional methods for diagnosis of external root resorption (ERR) are based on clinical findings and x-ray observations which are not appropriate for early diagnosis. The present study assessed the effect of different sizes and field of views (FOVs) in the diagnosis of simulated external root resorption by cone-beam computed tomography (CBCT).

METHODS AND MATERIALS

In this diagnostic in vitro trial, 100 human extracted mandibular central incisors were collected and marked in 3 apical, middle and coronal areas. Cavities with different sizes were created in buccal and lingual surfaces of each area. Following this procedure, CBCT images were taken in 2 different 6 × 6 cm and 12 × 8 cm FOVs with the same voxel size of 0.2 mm. Absence or presence of cavities in CBCT images were assigned by 3 radiologists and compared with gold standard results which were obtained by measurement of the size of cavities using a digital caliper. Sensitivity and specificity values, positive predictive value (PPV) and negative predictive value (NPV), A_Z value and Kappa values were calculated and reported.

RESULTS

Amounts of sensitivity in 6 × 6 cm FOV with voxel size of 0.2 mm for small, medium and large cavities were 95.93%, 96.03% and 97.1%, respectively. Amounts of sensitivity in 12 × 8cm FOV with the same voxel size for small, medium and large cavities were noted as 94.4%, 96.03% and 98.5%, respectively. However, specificity in FOV of 6 × 6 cm and FOV of 12 × 8 cm was calculated as 93.03% and 90.83%, respectively.

CONCLUSION

Both used FOVs show nearly same performances in the case of detection of ERR; therefore, smaller FOV should be preferably used for detection of ERR in order to decrease the amount of imposed radiation dose given to patients.

3D reconstruction images of cone beam computed tomography in dental medicine application: A case study and mini-review

Dental cone beam computed tomography (CBCT) is a new approach in diagnosis and predication of various dental diseases, including trauma, congenital defects, tumors and inflammatory. In this study, we reported the outcome of CBCT for a complicated case of malocclusion, accompanied with tooth loss and periodontitis. A combined application of CBCT with 3D-static images and rotated reconstruction images is reviewed as a systematic model in diagnosis, treatment and progonsis of a complex malocclusion.

Effect of Voxel Size and Object Location in the Field of View on Detection of Bone Defects in Cone Beam Computed Tomography

OBJECTIVES

This study aimed to assess the effect of voxel size and object location in the field of view (FOV) on diagnostic accuracy of cone beam computed tomography (CBCT) for detection of simulated bone defects.

MATERIALS AND METHODS

In this in vitro study, bone defects were drilled in four sections of a dry human mandible. Bone blocks were fixed on a platform parallel to the horizontal plane and CBCT images were acquired using 0.2mm and 0.3mm resolutions and five locations of FOV (anterior, posterior, left, right and center). Three reviewers viewed the images twice and the presence or absence of simulated bone defects was determined in positive and negative cases.

RESULTS

Sensitivity in different locations of FOV ranged between 0.25-1.0 and 0.75-1.0 in low and high resolutions, respectively. These values were 0.625-1.0 and 0.69-1.0, respectively for specificity. Intra-observer agreements were in the range of 0.84-1.0 and 0.75-1.0 and inter-observer agreements were in the range of 0.3-0.61 and 0.46-0.69 in high and low resolutions, respectively. The highest sensitivity was seen at the center of the FOV and with an increase in resolution from 0.3mm to 0.2mm, the sensitivity increased specially in the posterior region of the FOV while image resolutions and FOV locations did not affect specificity.

CONCLUSIONS

The highest sensitivity values were obtained at the center of the FOV and lowest values were seen in images acquired in the posterior region in low resolution. Diagnostic accuracy improved with increased resolution.

Factors affecting the possibility to detect buccal bone condition around dental implants using cone beam computed tomography

OBJECTIVES

To evaluate factors with impact on the conspicuity (possibility to detect) of the buccal bone condition around dental implants in cone beam computed tomography (CBCT) imaging.

MATERIAL AND METHODS

Titanium (Ti) or zirconia (Zr) implants and abutments were inserted into 40 bone blocks in a way to obtain variable buccal bone thicknesses. Three combinations regarding the implant-abutment metal (TiTi, TiZr, or ZrZr) and the number of implants (one, two, or three) were assessed. Two CBCT units (Scanora 3D - Sc and Cranex 3D - Cr) and two voxel resolutions (0.2 and 0.13 mm) were used. Reconstructed sagittal images (2.0 and 5.0 mm thickness) were evaluated by three examiners, using a dichotomous scale when assessing the condition of the buccal bone around the implants. A multivariate logistic regression was performed using examiners' detection of the buccal bone condition as the dependent variable. Odds ratio (OR) were calculated separately for each CBCT unit.

RESULTS

Implant-abutment combination (ZrZr) (OR Sc = 19.18, OR Cr = 11.89) and number of implants (3) (OR Sc = 12.10, OR Cr = 4.25) had major impact on buccal bone conspicuity. The thinner the buccal bone, the higher the risk that the condition of the buccal bone could not be detected. The use of lower resolution protocols increased the risk that buccal bone was not properly detected (OR Sc = 1.46, OR Cr = 2.00). For both CBCT units, increasing the image reconstruction thickness increased the conspicuity of buccal bone (OR Sc = 0.33, OR Cr = 0.31).

CONCLUSIONS

Buccal bone conspicuity was impaired by a number of factors, the implant-abutment material being the most relevant. Acquisition and reconstruction factors had minor impact on the detection of the buccal bone condition.

Registration of cone beam computed tomography data and intraoral surface scans - A prerequisite for guided implant surgery with CAD/CAM drilling guides

OBJECTIVES

Guided implant surgery (GIS) is performed with drilling guides that are produced on the virtual tooth model using CAD/CAM technology. The prerequisite for this workflow is the alignment of patients cone beam computed tomography CBCT and surface scan (registration). Dental restorations may cause deteriorating imaging artifacts in CBCT data, which in turn can have an impact on the registration process. The influence of the user and the preprocessing of data and of image artifacts on the registration accuracy were examined.

MATERIAL AND METHODS

CBCT data and intraoral surface scans of 36 patients were used for virtual implant planning in coDiagnostiX (Dentalwings, Montreal, Canada). CBCT data were reconstructed to a three-dimensional anatomical model with the default settings provided by the software and also manually by four different examiners. Subsequently, the CBCT and intraoral surface models were registered by each examiner with the help of anatomical landmarks. Patients' data were subdivided into four groups (A-D) according to the number of metallic restorations: A = 0-2 restorations, B = 3-5 restorations, C = 6-8 restorations and D > 8 restorations. After registration, the distances between CBCT and dental surface models were measured. Linear regression models were used to assess the influence of the segmentation, the examiner and to the number of restorations (P < 0.05).

RESULTS

The deviations between surface scan and CBCT models accounted to 0.54 mm (mean). The mean deviations were 0.69 mm (max. 24.8 mm) and 0.4 mm (max. 9.1 mm) for default and manual segmentation, respectively. Mean deviations of 0.36 mm (Group A), 0.43 mm (Group B), 0.67 mm (Group C) and 1.01 mm (Group D) were recorded. The segmentation (P = 0.000), the user (P = 0.0052) and the number of restorations (P = 0.0337) had a significant influence on the registration accuracy.

CONCLUSIONS

The deviation between CBCT and surface scan model resulting from inaccurate registration is transferred to the surgical field and results in a deviation between the planned and actual implant position. The registration accuracy in commercial virtual implant planning software is significantly influenced by the preprocessing of imported data, by the user and by the number of restorations resulting in clinically non-acceptable deviations encoded in drilling guides.

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.

Use of micro-computed tomography for the assessment of periapical lesions in small rodents: a systematic review

This systematic review aimed to evaluate the literature on the acquisition-, reconstruction- and analysis parameters of micro-computed tomography (micro-CT) for the assessment of periapical lesions in rats and mice, and to illustrate the effect of variation in these parameters. The PubMed database was searched from 2000 to January 2015 (English-language publications) for reports on the use of micro-CT to evaluate periapical lesions in rats and mice. QUADAS criteria were used to rate the quality of the studies. To illustrate the effect of variations in acquisition-, reconstruction-, and analysis parameters on images of periapical lesions, micro-CT examination of two hemi-mandibles of mice, with periapical lesions around the first molar was undertaken. Twenty-one studies were identified, which analysed periapical lesions in rats or mice using micro-CT. According to the QUADAS, no study was classified as high-, seven were classified as moderate-, and 14 as low quality. The effect of variation in parameters was that voxel size may interfere with image sharpness, reconstruction may interfere with image sharpness and contrast, and inadequate plane orientation may alter the size of the periapical lesion. Nonpersonalized ROIs resulted in areas that were not part of the periapical lesion. Changing the limits of the threshold for bone-tissue visualization increased lesion size. There is no defined protocol for acquiring and analysing micro-CT images of periapical lesions in rats and mice. Furthermore, acquisition-, reconstruction- and analysis parameters are not adequately explained, which may compromise the scientific impact of the studies.

Investigation on slice direction dependent detectability of volumetric cone beam CT images

We investigate the detection performance of transverse and longitudinal planes for various signal sizes (i.e., 1 mm to 8 mm diameter spheres) in cone beam computed tomography (CBCT) images. CBCT images are generated by computer simulation and images are reconstructed using an FDK algorithm. For each slice direction and signal size, a human observer study is conducted with a signal-known-exactly/background-known-exactly (SKE/BKE) binary detection task. The detection performance of human observers is compared with that of a channelized Hotelling observer (CHO). The detection performance of an ideal linear observer is also calculated using a CHO with Laguerre-Gauss (LG) channels. The detectability of high contrast small signals (i.e., up to 4-mm-diameter spheres) is higher in the longitudinal plane than the transverse plane. It is also shown that CHO performance correlates well with human observer performance in both transverse and longitudinal plane images.

Evaluation of diagnostic accuracy and dimensional measurements by using CBCT in mandibular first molars

Background

This study aimed to assess the diagnostic accuracy of cone beam computed tomography (CBCT) and quantitatively evaluate the morphology of mandibular first molars using CBCT.

Material and Methods

Twenty-four double-rooted mandibular first molars were evaluated by NewTom VGi CBCT. The distance from the furcation and apex to the cementoenamel junction (CEJ), diameter and thickness of canal walls, the buccolingual (BL) to mesiodistal (MD) ratio (ΔD), prevalence of oval canals at different sections and taper of the canals were all determined. In order to assess the diagnostic accuracy of CBCT, distance from the furcation and apex to the CEJ and thickness of canal walls at the CEJ and apex were compared with the gold standard values (caliper and stereomicroscope). Statistical analyses were carried out using intraclass correlation coefficient (ICC), paired t-test and repeated measures ANOVA.

Results

A high correlation existed between the CBCT and gold standard measurements (P<0.001). In dimensional measurements, length of mesial root was higher than the distal root and lingual furcation was farther from the CEJ than the buccal furcation (P<0.001). An important finding of this study was the mesiodistal taper of the mesiobuccal (MB) and mesiolingual (ML) canals; which was equal to 0.02.

Conclusions

CBCT has acceptable diagnostic accuracy for measurement of canal wall thickness. Cleaning and shaping of the canals should be performed based on the unique anatomy of the respective canal; which necessitates the use of advanced imaging techniques for thorough assessment of root canal anatomy in a clinical setting.

Key words:Permanent mandibular first molar, accuracy, cone-beam computed tomography, dimensional measurement.

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.

Comparing 2 Cone Beam Computed Tomography Devices for the Transfer Accuracy of a Laboratory-Based Guided Surgery System In Vitro

PURPOSE

Using surgical templates for guided placement increases accuracy and decreases patient's discomfort, therefore optimizing the functional, aesthetic, and prosthetic outcomes. Cone Beam computed tomography (CBCT) devices differ in their resolution and geometric accuracies and have been recently demonstrated to influence the measurements of guided surgery. The study aim is to investigate the potential influence of CBCT device selection on the transfer accuracy of guided surgery.

MATERIALS AND METHODS

Thirty-two Straumann implants placed in 8 acrylic models were implanted using digital planning and guided surgery. Preoperative and postoperative CBCT scans of 2 different devices (AccuiTomo 170, Morita and NewTom 5G; QR Verona) were made. Post-op implant position was compared with the digital planning and linear and angular deviations at the implant tip and base were compared between both devices.

RESULTS

Mean linear and angular deviations were (0.53 mm/0.96 degree) and (0.66 mm/1.04 degree) for the Newtom and AccuiTomo, respectively. The differences were statistically insignificant (P = 0.615).

CONCLUSION

In our sample, CBCT device selection did not influence the transfer accuracy of guided surgery. More research is needed to evaluate the accuracy of other systems.

Dental cone beam CT: A review

For the maxillofacial region, there are various indications that cannot be interpreted from 2D images and will benefit from multiplanar viewing. Dental cone beam CT (CBCT) utilises a cone- or pyramid-shaped X-ray beam using mostly flat-panel detectors for 3D image reconstruction with high spatial resolution. The vast increase in availability and amount of these CBCT devices offers many clinical benefits, and their ongoing development has potential to bring various new clinical applications for medical imaging. Additionally, there is also a need for high quality research and education. European guidelines promote the use of a medical physics expert for advice on radiation protection, patient dose optimisation, and equipment testing. In this review article, we perform a comparison of technical equipment based on manufacturer data, including scanner specific X-ray spectra, and describe issues concerning CBCT image reconstruction and image quality, and also address radiation dose issues, dosimetry, and optimisation. We also discuss clinical needs and what type of education users should have in order to operate CBCT systems safely. We will also take a look into the future and discuss the issues that still need to be solved.

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.

Interforaminal hemorrhage during anterior mandibular implant placement: An overview

Implant surgery in mandibular anterior region may turn from an easy minor surgery into a complicated one for the surgeon, due to inadequate knowledge of the anatomy of the surgical area and/or ignorance toward the required surgical protocol. Hence, the purpose of this article is to present an overview on the: (a) Incidence of massive bleeding and its consequences after implant placement in mandibular anterior region. (b) Its etiology, the precautionary measures to be taken to avoid such an incidence in clinical practice and management of such a hemorrhage if at all happens. An inclusion criterion for selection of article was defined, and an electronic Medline search through different database using different keywords and manual search in journals and books was executed. Relevant articles were selected based upon inclusion criteria to form the valid protocols for implant surgery in the anterior mandible. Further, from the selected articles, 21 articles describing case reports were summarized separately in a table to alert the dental surgeons about the morbidity they could come across while operating in this region. If all the required adequate measures for diagnosis and treatment planning are taken and appropriate surgical protocol is followed, mandibular anterior region is no doubt a preferable area for implant placement.

Efficacy of CBCT for assessment of impacted mandibular third molars: a review - based on a hierarchical model of evidence

A radiographic examination of mandibular third molars is meant to support the surgeon in establishing a treatment plan. For years panoramic (PAN) imaging has been the first choice method; however, where an overprojection is observed between the third molar and the mandibular canal and when specific signs suggest a close contact between the molar and the canal, CBCT may be indicated. The present review provides an evaluation of the efficacy of CBCT for assessment of mandibular third molars using a six-tiered hierarchical model by Fryback and Thornbury in 1991. Levels 1-3 include studies on low evidence levels mainly regarding the technical capabilities of a radiographic method and the diagnostic accuracy of the related images. Levels 4-6 include studies on a higher level of evidence and assess the diagnostic impact of a radiographic method on the treatment of the patient in addition to the outcome for the patient and society including cost calculations. Only very few high-evidence studies on the efficacy of CBCT for radiographic examination of mandibular third molars exist and, in conclusion, periapical or PAN examination is sufficient in most cases before removal of mandibular third molars. However, CBCT may be suggested when one or more signs for a close contact between the tooth and the canal are present in the two-dimensional image-if it is believed that CBCT will change the treatment or the treatment outcome for the patient. Further research on high-evidence levels is needed.

Effect of voxel size on accuracy of cone beam computed tomography-aided assessment of periodontal furcation involvement

OBJECTIVE

To assess the accuracy of cone beam computed tomography (CBCT) images obtained at different voxel sizes in detecting ligature-induced furcation involvement.

STUDY DESIGN

Furcation lesions were prepared in 36 molar teeth in rats, and 24 intact teeth served as controls. CBCT Kodak 9000 images at three different voxel sizes were acquired: 0.076 mm, 0.100 mm, and 0.200 mm. Four observers assessed 3 sets of images using a 5-point evaluation scale. κ-Coefficients were calculated for intra- and interobserver agreement. Receiver operating characteristic analysis measured the true positive rate (TPR), true negative rate (TNR), and area under the curve (AUC). Accuracy values were compared by using Mood's Median Chi-Square (α<0.05).

RESULTS

Intra- and interobserver agreement ranged from 0.600 to 0.999 and from 0.366 to 0.573, respectively. Highest median AUC and true positive rate (TPR) values were obtained for voxel size of 0.076 mm. The highest median TNR values were obtained for the voxel size 0.1 mm. There were no significant differences (P≥.05) among the median AUC, TPR, or TNR values for the 3 different CBCT voxel sizes.

CONCLUSIONS

Given the limitations of this study, all voxel sizes performed similarly in the detection of furcation involvement.