The current status of cone beam computed tomography imaging in orthodontics

Comparison of observer reliability of three-dimensional cephalometric landmark identification on subject images from Galileos and i-CAT cone beam CT

OBJECTIVES

Recently, there has been increasing interest in the use of cone beam CT (CBCT) for three-dimensional cephalometric analysis and craniofacial reconstruction in orthodontic and orthognathic surgical treatment planning. However, there is a need to redefine the cephalometric landmarks in three dimensional cephalometric analysis and to demonstrate the reproducibility of landmark identification on the type of CBCT machine being used.

METHODS

CBCT images of 20 subjects aged 15-25 years were selected, ten each from Galileos(®) (Sirona Dental Systems Inc., Bensheim, Germany) and Next Generation i-CAT(®) (Imaging Sciences International, Hatfield, PA). 2 observers located 18 landmarks on each subject twice using Dolphin-3D v. 11 software (Dolphin Imaging and Management Systems, Chatsworth, CA). Inter- and intraobserver reliability was assessed using Euclidean distances and linear mixed models.

RESULTS

Overall, the intra- and interobserver reliability was excellent for both machines. The landmarks Gonion, Nasion, Orbitale and Anterior Nasal Spine (ANS) showed the greatest median Euclidean distances for both intra- and interobserver measurements. There were significant observer effects in the unified models for Sella, Menton and all six dental landmarks. For Sella, the distances between the measures were significantly smaller (more closely spaced) on the i-CAT machine than on the Galileos in both intra- and interobserver measurements.

CONCLUSIONS

The intra- and interobserver reliability was excellent for both machines. Some of the landmarks were not as reproducible as others. Which machine produced the highest reliability depended on the landmark considered.

Cone-beam computed tomography: time for an evidence-based approach

Cone-beam computed tomography (CBCT) is an imaging technology that has revolutionised dental imaging in the last decade. Although of particular value to specialists performing implant treatment, it is increasingly being adopted by general dental practitioners. As the radiation dose is higher than that of conventional radiography, it is important to consider its diagnostic efficacy for the common tasks performed in general dental practice, such as caries diagnosis, endodontics and the detection of periapical pathosis. Any new imaging technique needs to have proven advantages over existing techniques before it is adopted, yet the evidence remains quite limited. Furthermore, image quality and radiation doses vary enormously between different manufacturers' equipment, so that extrapolating results of one piece of research from one CBCT machine to another is fraught with pitfalls. Radiation doses with CBCT are typically an order of magnitude higher than conventional radiography. There is scope, however, for reducing these doses by judicious adjustment of exposure factors and limiting the field of view to the smallest dimensions consistent with the clinical situation. There is still a long way to go before we understand the value of CBCT in dentistry. High quality research evidence is needed, particularly with regard to assessing whether using BCT improves patient outcomes.

Effect of mandibular advancement on the natural position of the head: a preliminary study of 3-dimensional cephalometric analysis

Our aim was to investigate the potential effect of advancement by bilateral sagittal split osteotomy (BSSO) on the natural position of the head by using 3-dimensional cephalomentric analysis. Seven consecutive patients who had had only BSSO advancement, and had had preoperative and 6-week postoperative cone beam computed tomography (CT) scans, were recruited to this retrospective study. Two variables, SNB and SNC2, were used to indicate the craniomandibular alignment and craniocervical inclination, respectively, in the midsagittal plane. Using 3-dimensional cephalometric analysis software, the SNB and the SNC2 were recorded in volume and measured in the midsagittal plane at 3 independent time-points. The reliability was measured and a paired t test used to assess the significance of differences between the means of SNB and SNC2 before and after operation. The 3-dimensional cephalometric measurement showed good reliability. The SNB was increased as planned in all the mandibles that were advanced, the cervical vertebrae were brought forward after BSSO, and the SNC2 was significantly increased in 6 of the 7 patients. Three-dimensional cephalometric analysis may provide an alternative way of assessing cephalometrics. After BSSO advancement, the natural position of the head changed by increasing the craniocervical inclination in an anteroposterior direction.

Assessment of skeletal maturation based on cervical vertebrae in CBCT

Diagnosis of skeletal age in adolescents helps orthodontists select and time treatments. Currently this is done using lateral cephalometric radiographs. This study evaluates the application of the conventional method in cone-beam computer tomographic (CBCT) images to bring forth assessment of skeletal maturation in three-dimensions. Ninety-eight lateral cephalometric radiographs and CBCT scans were collected from orthodontic patients between 11 to 17 years of age over an 18-month period. CBCT scans were examined in seven sagittal slices based on cervical vertebral maturation staging (CVMS). Collected CVMS values were compared with those from corresponding lateral cephalometric radiograph. CVMS measured from CBCT and lateral cephalometric radiographs were the same on average. However, they were not consistent with each other and scored interclass correlation coefficient of 0.155 in validity test. Interoperator reliability was weak (0.581). Adaptation of cervical vertebrae maturation staging in CBCT requires further clarifications or modifications to become consistent with lateral cephalometric examinations and to become a reliable method. Alternatively, a completely new method may be developed consisting of maturational indicators or landmarks unique to CBCT imaging.

Hausdorff Distance evaluation of orthodontic accessories' streaking artifacts in 3D model superimposition

The aim of this study was to determine whether image artifacts caused by orthodontic metal accessories interfere with the accuracy of 3D CBCT model superimposition. A human dry skull was subjected three times to a CBCT scan: at first without orthodontic brackets (T1), then with stainless steel brackets bonded without (T2) and with orthodontic arch wires (T3) inserted into the brackets' slots. The registration of image surfaces and the superimposition of 3D models were performed. Within-subject surface distances between T1-T2, T1-T3 and T2-T3 were computed and calculated for comparison among the three data sets. The minimum and maximum Hausdorff Distance units (HDu) computed between the corresponding data points of the T1 and T2 CBCT 3D surface images were 0.000000 and 0.049280 HDu, respectively, and the mean distance was 0.002497 HDu. The minimum and maximum Hausdorff Distances between T1 and T3 were 0.000000 and 0.047440 HDu, respectively, with a mean distance of 0.002585 HDu. In the comparison between T2 and T3, the minimum, maximum and mean Hausdorff Distances were 0.000000, 0.025616 and 0.000347 HDu, respectively. In the current study, the image artifacts caused by metal orthodontic accessories did not compromise the accuracy of the 3D model superimposition. Color-coded maps of overlaid structures complemented the computed Hausdorff Distances and demonstrated a precise fusion between the data sets.

Nasolabial aesthetics correlates poorly with skeletal symmetry in unilateral cleft lip and palate

OBJECTIVE

To evaluate the correlation between symmetry of the craniofacial skeleton and aesthetics of the nose and upper lip in children with complete unilateral cleft lip and palate (CUCLP).

MATERIAL AND METHODS

Craniofacial symmetry was evaluated on postero-anterior (PA) cephalograms of 54 children (37 boys and 17 girls; mean age = 11.0 years, SD 1.6) with CUCLP repaired with a one-stage closure (Cleft group). Treated subjects were age- and gender-matched with 54 untreated subjects taken from the University of Michigan Growth Study (Control group). Fourteen coefficients of asymmetry (CAs) were calculated and four angles were measured. Four raters assessed the nasolabial appearance on cropped facial and profile photographs with the 5-grade aesthetic index of Asher-McDade (grade 1 means the most aesthetic and grade 5 the least aesthetical outcome) in the Cleft group only. Independent t-tests were used to evaluate the inter-group differences for CAs. Pearson's correlation coefficients were calculated to examine a relationship between particular components of the aesthetical index and CAs. Multiple regression analyses were carried out to explain the nasolabial aesthetics on the basis of craniofacial symmetry.

RESULTS

In the Cleft group, most cephalometric variables demonstrated asymmetry not exceeding 10%. The Cleft and Control groups differed regarding three angular measurements (Se, Ism, and ANS) and 1 CA (Mo-V). Three of the four nasolabial components demonstrated correlation with some cephalometric variables. However, the correlation coefficients were low (range: -0.309 to 0.305).

CONCLUSIONS

There is a weak correlation between craniofacial skeletal symmetry and aesthetics of the nose and upper lip in children with CUCLP.

Efficacy of identifying maxillofacial lesions in cone-beam computed tomographs by orthodontists and orthodontic residents with third-party software

INTRODUCTION

The purpose of this study was to determine the ability of orthodontists and orthodontic residents to identify nonorthodontic incidental findings and false positives in cone-beam computed tomography scans.

METHODS

Two groups of 10 cone-beam computed tomography scans containing equal numbers of scans with no, 1, or several abnormal nonorthodontic lesions were selected from a database. Eight orthodontists and 8 orthodontic residents screened the 2 groups of scans before and after a basic cone-beam computed tomography training course. The paired t test was used for statistical analyses.

RESULTS

In the initial screening, the orthodontists and residents correctly identified 41.1% of the lesions. This lesion-detection rate improved significantly to a mean of 56.7% after the training course (P <0.0005). In parallel with these findings, the mean percentage of correctly identified extragnathic lesions improved significantly, from 22% to 48% (P <0.0005), and correctly identified temporomandibular joint lesions improved from 20% to 55% (P = 0.01) after the training. In contrast, the rate of correctly identified dentomaxillofacial lesions remained largely unchanged before and after the training. Both groups of evaluators had approximately 5 false positives per 10 scans before training and demonstrated significant decreases in false positives after training.

CONCLUSIONS

Relative to known error rates in medical radiology, both groups of evaluators had high error rates for missed lesions and false positives before and after training. Given these findings and since the most frequent cause of medical radiology malpractice litigation is due to missed lesions, it is recommended that an appropriately trained radiologist should be involved in reading and interpreting cone-beam computed tomography scans.

The reliability of cone-beam computed tomography (CBCT) - generated frontal cephalograms

BACKGROUND

The purpose of this study was to evaluate the reliability of measurements from cone-beam computed tomography (CBCT)-generated frontal cephalogram.

MATERIALS AND METHODS

CBCT and conventional posteroanterior (PA) cephalograms were taken from 30 adult patients. CBCT image was set according to the Frankfurt-Horizontal (FH) plane as the horizontal plane and the midsagittal reference (MSR) plane. The CBCT frontal cephalograms were generated using the orthogonal Raycast method (group CT(raycast)), the orthogonal maximum intensity projection (MIP) method (group CT(MIP)) after the head reorientation according to the reference planes, and the generator tool provided by the employed 3-dimensional (3D) imaging software (group CT(generator)), respectively. The differences between the CBCT-generated frontal cephalograms and conventional PA cephalograms (group PA(ceph)) were compared by paired t-test (p<0.05).

RESULTS

The significant differences were shown in two measurements for group CT(raycast), in 12 measurements for group CT(MIP), and in eight measurements for group CT(generator). It was confirmed that the CBCT frontal cephalograms, generated by means of the Raycast method (Group CT(raycast)), were more comparable to the conventional PA cephalograms in their measurements than were the others (Groups CT(MIP), CT(generator)).

CONCLUSION

This study may well suggest that frontal cephalograms derived by 3D CBCT reorientation can be effectively employed in clinical applications.

The KPG index--a novel 3D classification system for maxillary canine impactions

INTRODUCTION

Advancements in Cone Beam Computed Tomography (CBCT) have improved localization of impacted canines. The KPG index is the first 3-D classification system for classifying the position of canines based on their distance from the norm (1). The aim of this study was to determine if this index provides an estimate of the time necessary to treat an impacted canine using closed eruption.

MATERIALS AND METHODS

CBCT scans of 28 impacted canines at The University of Texas School of Dentistry at Houston Department of Orthodontics were classified using the KPG index. The scores and categories were compared to the time from surgical exposure to proper positioning.

RESULTS

Four canines were classified as "Easy," 11 as "Moderate," 9 as "Difficult," and 4 as "Extremely Difficult." Average treatment times associated in months were: "Easy"--11.23, "Moderate"--11.36, "Difficult"--12.76, and "Extremely Difficult"--13.23.

CONCLUSIONS

The KPG index currently cannot be confirmed as an accurate means of estimating treatment time for an impacted canine. Further verification studies should include larger sample sizes and compare differing mechanics. However, there are limitations to 2-D imaging; therefore, the 3-D CBCT images and the KPG index, with further validation, will become increasingly valuable to orthodontists.

Cone-beam computed tomography: a new low dose, high resolution imaging technique of the wrist, presentation of three cases with technique

Cone-beam computed tomography (CBCT) is a relatively new technique. It generates a 3D image by emitting a pulsed cone-shaped X-ray beam. CBCT has become a very useful and widely used technique for dentomaxillofacial imaging over the last decade. It provides clear, high resolution multiplanar reconstruction images. Previously, the images could only be generated while the patient was sitting with his/her head fixed in position. With the presented new generation CBCT (NewTom 5G, QR, Verona, Italy), a more free positioning of the patient, either lying or sitting, is possible. In this way, skeletal imaging of various body parts becomes possible. In this article we present three clinical cases of CBCT imaging of the wrist, describe the background of the technique, and discuss the advantages and disadvantages of CBCT imaging.

Cone-beam computed tomography evaluation of relationship between tongue volume and lower incisor irregularity

The aim of this study was to evaluate the relationship between the tongue volume and lower incisor irregularity, using cone-beam computed tomography (CBCT), and to identify the possible gender differences. CBCT images of 60 patients between 16 and 36 years of age were selected from 1400 sets of images in the database. Tomography was carried out using iCAT® (Imaging Sciences International, Hatfield, Pennsylvania, USA) and segmentation was carried out by using Mimics 10.1 software (Materialise NV, Leuven, Belgium). The tongue volume was calculated by using the volume of the voxels from the scan and the number of voxels selected for a given mask. Lower incisor crowding was measured with the Little's irregularity index and divided into three groups: mild, moderate, and severe. Independent samples t-test, analysis of variance (ANOVA), and Tukey test were used at P < 0.05 level. Pearson correlation coefficients and linear regression model were calculated to determine the correlation between tongue volume and incisor irregularity. No significant gender dimorphism was found for the tongue volume (females: 28.13 ± 8.54 cm(3) and males: 31.02 ± 9.75 cm(3)). According to ANOVA, there was statistically significant difference in the tongue volume measurements among subjects with different levels of irregularity. Tukey analysis indicated that mild irregularity group (33.97 cm(3)) showed higher values for tongue volume than severe irregularity group (26.60 cm(3); P = 0.025). The relationship between incisor irregularity and tongue volume was evaluated for both genders and significant inverse correlation (r = -0.429; P = 0.029) was determined between lower incisor irregularity and tongue volume in males. In female group, no significant correlation was determined between tongue volume and incisor irregularity.

Diagnostic accuracy studies needed for cone beam computed tomography

DATA SOURCES

Medline, Embase, CENTRAL and the reference lists of identified studies.

STUDY SELECTION

Studies had to describe diagnostic accuracy efficacy, diagnostic thinking efficacy, therapeutic efficacy or any combination for CBCT in the diagnosis of impacted teeth or of important features associated with impactions. Criteria for the diagnosis had to be described in detail or referenced. For studies elucidating only observer performance, the analysis had to be based on a minimum of two observers.

DATA EXTRACTION AND SYNTHESIS

Data were extracted with the aid of protocol based on critical appraisal of diagnostic studies. Two authors independently assessed the quality and internal validity of studies using the QUADAS tool,(1) with disagreements being resolved by discussion. The results were described narratively as meta-analyses could not be conducted.

RESULTS

The search yielded 96 titles, of which seven were included. There was only limited evidence for diagnostic efficacy expressed as sensitivity, specificity and predictive values. Only two studies compared CBCT and panoramic radiographs with a valid reference method and presented the results in terms of percentage of correct diagnoses.

CONCLUSIONS

There is a need for diagnostic accuracy studies on CBCT where accepted methodological criteria for diagnostic thinking, efficacy and therapeutic efficacy are incorporated.