Three-dimensional Cephalometric Analysis Research Articles

Automatic three-dimensional cephalometric annotation system using three-dimensional convolutional neural networks: a developmental trial

ABSTRACTAutomatic annotation for three-dimensional (3D) cephalometric analysis has been limited by computational complexity and computing performance. The purpose of this study was to evaluate the accuracy of our newly-developed automatic 3D cephalometric annotation system using a deep learning algorithm. Our model system mainly consisted of a 3D convolutional neural network and image data resampling. Discrepancies between the referenced and predicted coordinate values in three axes and in 3D distance were calculated to yield prediction errors of 3.26, 3.18, and 4.81 mm (for three axes) and 7.61 mm (for 3D). Moreover, there was no difference (p > 0.05) among the landmarks of three groups (midsagittal plane, horizontal plane and mandible). Although our 3D convolutional neural network-based annotation system could not achieve the level of accuracy demanded by immediate clinical applications, it can nevertheless serve as an initial approximate guide to landmarks, thus reducing the time needed for annotation.

Relationship Between Nostril, Nasal Valve and Minimal Cross-Sectional Area in Functional Upper Airway.

To propose a three-dimensional cephalometric analysis of upper airway (UA) related to its functionality, defining normal reference values in healthy individuals and the relationship between nostril, nasal valve, and minimal cross-sectional area (MCS) in functional upper airway. The UAs of 20 Class I patients were analyzed with CBCT using Nemoceph 3D-OS and HOROS software, determining linear distances, volumes and cross-sectional areas, including MCS. MCS was mostly located in the middle-upper oropharynx and high hypopharynx. MCS showed moderate correlation with the area of both nares (BNA) (r = 0.60, P = 0.004) and high correlation with the area of both internal nasal valves (BNV) (r = 0.66, P = 0.0016). BNA and BNV showed a moderate correlation (r = 0.445, P = 0.049). A total upper airway (TUA) and functional upper airway (FUA) volumes were established. TUA and FUA showed the strongest statistical correlation (r = 0.82, P = 0.00). A paired samples t test compared the measurement as absolute values of MCS with BNA (t = 0.781, P = 0.44), with BNV (t = -0.12, P = 0.90); and BNA with BNV (t = -0.76, P = 0.45), showed no significant differences. A functional cephalometric analysis of the UA with stable parameters in cervical spine and normal reference values has been proposed. BNA and BNV could be used as reference to establish the MCS compatible with respiratory health.

Three-dimensional cephalometric analysis of the maxilla: Analysis of new landmarks

Clinical evaluation of the midface including the paranasal and upper lip regions is highly subjective and complex. Traditional and 3-dimensional cephalometrics were not developed with the clinical appearance of these midfacial areas in mind and are therefore inappropriate surrogates for the clinical appearance of the midface, making them unsuitable as aids in diagnosing dentofacial deformities. The aim of this study was to evaluate traditional as well as newly defined landmarks and measurements and their correlation with clinical appearance of the midface. Fifty-two subjects who underwent full-field cone-beam computed tomography were recruited for this study. A single examiner assessed each subject's midfacial region (paranasal and upper lip), and a second examiner obtained traditional and newly defined cephalometric measurements for each subject. Both examiners were blinded to each other's data throughout the study. Statistical analysis was performed to assess the correlations of the traditional and novel cephalometric measurements with clinical midfacial findings. The impact of the soft tissue thickness in the paranasal region was also analyzed. The performance of any classification derived from statistically significant variables was analyzed with the use of micro-F scores and area under the receiver operating characteristic curve (AUC). Both traditional (SNA) and newly defined measurements (SNANS, SNPR, SNNP, SNh) had no statistically significant correlation with clinical paranasal diagnosis. However, in the absence of upper lip procumbency or protrusion, SNNP and SNh had statistically significant correlations with clinical paranasal diagnosis (P=0.047 and P=0.003, respectively). For upper lip analysis, both traditional (SNA) and newly defined measurements (SNCEJ) had strong correlations with clinical upper lip diagnosis (P<0.001). All statistically significant cephalometric variables had good intra- and interobserver reliability (correlation coefficients ≥0.972 and≥0.968, respectively) except SNA, which had a low interobserver reliability (correlation coefficient 0.739). Fitted models for paranasal and upper lip analyses showed low micro-F scores, indicating low precision and recall. However, AUC values of 0.7019 and 0.6362 for the paranasal and upper lip analysis, respectively, suggest improved performance of the model when properly trained with a larger sample size. Newly defined measurements SNh and SNNP correlated with clinical paranasal diagnosis only in the absence of upper lip procumbency and protrusion. SNA and SNCEJ were strongly correlated with clinical upper lip diagnosis. However, fitted models based on this study sample yielded low micro-F scores, making the fitted models currently unsuitable for anything besides correlation with clinical findings. A larger sample size will be necessary to further clarify the potential roles of these measurements, especially given the reasonable AUC values. The findings of this study demonstrate the highly subjective and relative nature of midfacial diagnosis and the importance of clinical judgment despite the potential utility of some traditional and new measurements.

Three-dimensional cephalometric analysis of the maxilla - analysis of new landmarks

Introduction Clinical evaluation of the midface including the paranasal and upper lip regions is highly subjective and complex. Traditional and 3-dimensional cephalometrics were not developed with the clinical appearance of these midfacial areas in mind and are therefore inappropriate surrogates for the clinical appearance of the midface, making them unsuitable as aids in diagnosing dentofacial deformities. The aim of this study was to evaluate traditional as well as newly defined landmarks and measurements and their correlation with clinical appearance of the midface. Methods Fifty-two subjects who underwent full-field cone-beam computed tomography were recruited for this study. A single examiner assessed each subject's midfacial region (paranasal and upper lip), and a second examiner obtained traditional and newly defined cephalometric measurements for each subject. Both examiners were blinded to each other's data throughout the study. Statistical analysis was performed to assess the correlations of the traditional and novel cephalometric measurements with clinical midfacial findings. The impact of the soft tissue thickness in the paranasal region was also analyzed. The performance of any classification derived from statistically significant variables was analyzed with the use of micro-F scores and area under the receiver operating characteristic curve (AUC). Results Both traditional (SNA) and newly defined measurements (SNANS, SNPR, SNNP, SNh) had no statistically significant correlation with clinical paranasal diagnosis. However, in the absence of upper lip procumbency or protrusion, SNNP and SNh had statistically significant correlations with clinical paranasal diagnosis (P = 0.047 and P = 0.003, respectively). For upper lip analysis, both traditional (SNA) and newly defined measurements (SNCEJ) had strong correlations with clinical upper lip diagnosis (P Conclusions Newly defined measurements SNh and SNNP correlated with clinical paranasal diagnosis only in the absence of upper lip procumbency and protrusion. SNA and SNCEJ were strongly correlated with clinical upper lip diagnosis. However, fitted models based on this study sample yielded low micro-F scores, making the fitted models currently unsuitable for anything besides correlation with clinical findings. A larger sample size will be necessary to further clarify the potential roles of these measurements, especially given the reasonable AUC values. The findings of this study demonstrate the highly subjective and relative nature of midfacial diagnosis and the importance of clinical judgment despite the potential utility of some traditional and new measurements.

Diagnosis and planning of complex aesthetic-functional rehabilitation of patients with asymmetrical dentoalveolar anomalies

Within the framework of the article, according to the literature, the available etiological factors for the occurrence of asymmetric dental-maxillary anomalies associated with the maxillary complex were analyzed. At the same time, the absence of an algorithm for the differential diagnosis of the morphological basis for the appearance of this kind of asymmetry was noted. In this context, a study was conducted in two groups of patients with the allocation of angular and linear parameters to assess the position of the middle palatal suture. As a result, a block of the algorithm of three-dimensional cephalometric analysis was formulated for the possibility of differential diagnosis of the morphological basis of asymmetric dentition.

Novel method of constructing a stable reference frame for 3-dimensional cephalometric analysis.

Three-dimensional (3D) cephalometric analysis has provided the ability to overcome the limitations of 2-dimensional cephalometrics. However, there is no international standard method for 3D cephalometric analysis yet. Determining the position of the midsagittal plane (MSP) practically is the most important step when constructing a 3D cephalometric reference frame. Recent studies have used several approaches to construct the MSP. In this study, we aimed to determine the true MSP of the skull to establish a stable reference frame for 3D cephalometric analysis. Cone-beam computed tomography data of 12 adult patients were divided into 2 groups: symmetry (n=6) and asymmetry (n=6). The anterior cranial base region model and its mirror model were registered and used to determine the MSP to prevent any influence of the degree of symmetry on the registration of other parts of the skull, particularly for subjects with severe facial or cranial asymmetry. Intraclass correlation coefficients were used to assess intraexaminer and interexaminer reliabilities of the x, y, and z coordinates of all landmarks measured by 2 investigators. The intraclass correlation coefficient values were greater than 0.9, indicating almost perfect agreement. The candidate reference planes constructed using this novel method were thought to be reliable for 3D cephalometric analysis and may expand its clinical applicability in patients with cranial asymmetry.

Bone and Soft Tissue Nasal Angles Discrepancies and Overlying Skin Thickness: A Computed Tomography Study.

The aim of this study was to derive the normal values for bone and soft tissue nasal angles as well as the overlying skin thickness and to attempt to determine the correlation between differences in bone and soft tissue angles and overlying skin thickness in Middle Eastern patients. Three-dimensional cephalometric analysis was performed for 100 patients who underwent computed tomography of the paranasal sinuses. The nasofrontal angle, pyramidal angle-nasal root, pyramidal angle-tip of the nasal bone, and overlying skin thickness were measured, and the results were analyzed according to sex, age, and body mass index (BMI). All soft tissue angles were significantly larger than the bone angles, with the mean difference being 11.62°, 30.80°, and 27.05° for the nasofrontal angle (P = 0.000), pyramidal angle-nasal root (P = 0.000), and pyramidal angle-tip of the nasal bone (P = 0.000), respectively. The mean overlying skin thickness was 3.89 ± 1.48mm at the nasion, 1.16 ± 0.6mm at the rhinion, and 2.93 ± .97mm at the nasal tip. Differences in the nasofrontal angle were strongly correlated with the skin thickness at the nasion (P = 0.001). A simple clinical exam of the soft tissue nasal angles does not reflect the underlying bone angles that will be encountered during rhinoplasty. BMI does not influence nasal shape, and rhinoplasty surgery should take into account the ethnic group, age, and sex of the patient. Surgeons should leave a minor skeletal hump at the end of the nasal bone for Middle Eastern patients. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Three-dimensional evaluation of mandibular asymmetry: a new classification and three-dimensional cephalometric analysis

Mandibular asymmetry is common among orthognathic patients and exhibits great variation. The aim of this study was to propose a new classification of mandibular asymmetry by anatomical regions; namely R (ramus), B (mandibular body) and C (chin), in conjunction with a corresponding ‘RBC’ three-dimensional (3D) cephalometric analysis. The cone beam computed tomography data of 65 patients with mandibular asymmetry was retrieved to perform the RBC 3D cephalometric analysis and to investigate the characteristics of mandibular asymmetry. It was found that the more posteriorly in mandible, the more pronounced was the vertical asymmetry. Significant transverse asymmetry was only noted in mandibular body. Both mandibular body and chin were significantly asymmetric in length. Seven significant morphologic predictors of menton deviation were identified, namely lower dental midline shift, difference in ramus height, difference in chin length, difference in body length, body height on contralateral side, coronoid height on deviated side and body width on contralateral side, confirming the complex nature of mandibular asymmetry. This simple and concise classification allows comprehensive assessment of mandible morphology by anatomical regions which also facilitates diagnosis, treatment planning and communication in both clinical and research settings.

A THREE-DIMENSIONAL EVALUATION OF THE EFFECTS OF DIFFERENT INCISOR INTRUSION MECHANICS TO THE PERMANENT MAXILLARY FIRST MOLAR TEETH BY USING CONE BEAM COMPUTED TOMOGRAPHY

Objective: The present study aims to evaluate the impacts of the upper incisor teeth intrusion in deepbite patients by two different techniques to the permanent maxillary first molar tooth using the three-dimensional cephalometric analysis in the individuals. Materials and Methods: The population of this study consists of 34 patients with >4 mm overbite and a ≥2 mm gummy smile during post-pubertal period. Patients who underwent intrusion of upper incisor teeth were randomized to receive Connecticut intrusion arch (CTA) or miniscrew anchorage intrusion system (MAIS) to compare the impacts on permanent maxillary first molar teeth. Cone Beam Computed Tomography (CBCT) data obtained before (T1) and after (T2) intrusion were evaluated through three-dimensional (3D) cephalometric analysis. Intragroup assessment of treatment-related variables were performed via “t-test in dependent samples” and intergroup comparisons were assessed by “t-test in independent samples”. Results: In patients who underwent intrusion of upper incisors, permanent maxillary first molar teeth became deviated distally (1.48 mm/7.63 degree) only in CTA group, a statistically significant difference was found between two groups (p<0.05). The distance between resistance centers of maxillary first molar teeth was only increased in CTA group (0.31 mm), which also statistically differed from MAIS group. Conclusion: CTA and MAIS techniques resulted in similar intrusive effects overall at the end of the treatment. While MAIS is recommended when anchorage from posterior region is not desired in patients with deep overbite, we believe that CTA may serve a suitable treatment alternative where miniscrew technique could not be performed.

MODERN METHODS OF DIAGNOSIS IN ORTHODONTICS

The paper presents the possibilities of the virtual planning of orthodontic treatment with programs In Vivo Anatomage and 3Shape Ortho Analyzer, which allows you to create an individual plan of orthodontic treatment. Using three-dimensional cephalometric analysis and cone-beam computed tomography eliminates the risk of complications during orthodontic tooth moving. Aim - to determine the main directions of application of three-dimensional cephalometric analysis in orthodontist’s practice Materials and methods. The study involved 20 patients aged between 18 and 35 years (women 85%, men 15%). All patients underwent cone-beam computed tomography of the facial region of the skull conducted on a tomograph with a matrix 16h10. To obtain the most objective data, a wide range of clinical and other diagnostic methods was used in the study: clinical (survey, visual examination of face and oral cavity, clinical functional tests), anthropometric (measurement of jaw models in the program 3Shape Ortho Analyzer), CBCT of the facial region of the skull and cervical part of the spine. The survey was conducted on every patient according to the developed protocol. 1. Assessment of the dental hard tissues (diagnosis of caries, pulpitis and periodontitis), periapical periodontal tissues, and the state of the cortical bone; construction of three-dimensional panoramic reconstruction to determine the parallelism of the roots and their position in the bone of the alveolar processes on the vestibular and lingual surfaces. 2. Assessment of the patency of airways. 3. Evaluation of the bone elements of the temporomandibular joint on both sides, determining the position of articular head in the glenoid fossa. 4. Three-dimensional cephalometric analysis. 5. Superimposition of the data of the facial skull computed tomography; analysis of the changes in the course of dental treatment. The results of research. The obtained CBCT of the facial skull, processed in the program In Vivo Anatomage version 5.2, allows specifying the status and location of the bony structures of the temporomandibular joint, sinuses, individual structural features of the upper and lower jaws, dental roots deep in the alveolar processes and their correlation to the cortical plate. Additional features of the program are the opportunity to study the airways, combination of the scanned plaster models in .Stl format and superimposition of one CT scan to the other to produce a report on the changes that occurred. Discussion. The computer program allows correction of congenital abnormalities of dentition, reducing the risk of complications to a minimum. Moreover, the expected result can be predicted at the initial stage of treatment. The main advantage of CBCT is the possibility to determine the exact anatomical parameters of a patient without overlapping of adjacent structures and projection distortion of the sizes of anatomical structures.

Temporomandibular joint ankylosis contributing to coronoid process hyperplasia

The purpose of this study was to investigate the association between coronoid process hyperplasia and temporomandibular joint (TMJ) ankylosis and to analyze the pathological mechanism and clinical significance of coronoid process hyperplasia. Forty-four patients treated for TMJ ankylosis between January 2007 and December 2014 were studied retrospectively; 176 patients with normal TMJs served as controls. The original DICOM data were used to reconstruct the jaw, and a three-dimensional cephalometric analysis (SimPlant Pro software version 11.04) was performed to assess the association between the severity of TMJ ankylosis and the height of the coronoid process. The height of the coronoid process was 20.41±5.00mm in the case group and 14.86±2.67mm in the control group; there was a significant difference between the two groups (P<0.001). Long-standing TMJ ankylosis contributes to coronoid process hyperplasia. Therefore, attention should be drawn to the coronoid process in patients with TMJ ankylosis. A coronoidectomy together with arthroplasty is recommended in patients with TMJ ankylosis.

Individualized Surgical Templates and Titanium Microplates for Le Fort I Osteotomy by Computer-Aided Design and Computer-Aided Manufacturing.

The authors report the use of novel individualized surgical templates and titanium miniplates for Le Fort I osteotomy and evaluate the accuracy of this technique in vitro. Nine three-dimensional stereolithographic skull models were used to design the templates and titanium microplates and to simulate the operation. Cone beam computed tomography (CBCT) scans of the skulls were acquired preoperatively and were used to generate virtual models. The surgical plans were made based on three-dimensional cephalometric analyses, and osteotomies were then performed virtually. Cylinder-shaped markers were placed to permit the correct location of titanium screws, and individualized surgical templates were designed. The bony segments were then repositioned virtually according to the surgical plans to correct the skeletal deformities. Resin surgical templates were produced by stereolithography rapid prototyping and the titanium miniplates by three-dimensional cutting. Le Fort I osteotomy was performed under the guide of the surgical templates and fixed with the titanium miniplates. Postoperatively, CBCT scans of each skull model were taken, and the differences between the actual and planned surgical outcomes were measured by superimposing the planned and postoperative virtual models generated from CBCT images. The authors demonstrated that the average linear difference between the planned and actual outcomes was <1 mm and the average orientation difference was <1°. The individualized surgical templates and titanium microplates designed in this experimental study permitted the repositioning of the maxillary segment to the correct planned positions during Le Fort I osteotomy, making this technique a promising alternative to the conventional split method.

Three-Dimensional Cephalometric Analysis of Orbital Morphology Modification for Midface Correction Surgery.

The aim of this study was to create an evidence-based three-dimensional cephalometric analysis of orbits in order to perform time-efficient measurements of postoperative orbital morphology changes. The authors used 23 (11 bilateral and 1 unilateral) anatomical landmarks. Based on these, 6 planes, 12 angular and 16 linear measurements were determined. A three dimensional analysis was performed twice by two observers on pre and post-operative computed tomography scans of six patients who had undergone midface advancement. The mean, minimal and maximal difference, as well as standard deviation (SD) and intraclass correlation coefficient (ICC) for the inter- and intra-observer landmark selection reliability were calculated. Additionally, the mean, minimal, maximal difference and standard deviation between pre- and post-operative angular and linear measurements were calculated to examine a connection between the established measurements and any morphological change. The inter and intra-examiner accuracy of all landmarks for three axes was >0.9 ICC. Despite excellent inter and intra-examiner agreement (<2.49mm±2.05mm SD) for the landmark selection, linear and angular measurements showed a mismatch, the mean SD for angular measurements was found to be 8.2° and the linear 3.04mm. The possible causes of linear and angular measurement discrepancies are discussed and the future direction for the development of three-dimensional cephalometric analysis of orbits proposed.

Two-dimensional to three-dimensional: A new three-dimensional cone-beam computed tomography cephalometric analysis

Objectives of the Study: were (1) to develop a three-dimensional cephalometric analysis scheme applicable to assessing dentofacial deformities; and (2) to create a normative database of three-dimensional cephalometric measurements for adult North Karnataka population. Materials and Methods: A cross-sectional study was conducted on 40 male and 40 female adults with normal balanced facial profile and occlusion. Cone-beam computed tomography (CBCT) images obtained in digital imaging and communications in medicine format and the anatomic Cartesian three-dimensional cephalometric reference system according to Swennen et al. was used to standardize the reference planes. Cephalometric analysis was performed using various landmarks. New three-dimensional cephalometric analyses appropriate for orthognathic surgery as well as new parameters were used in this study. Results: The cephalometric norms generated in this study were comparable with those reported in the literature for conventional two-dimensional cephalometric analysis and unique features of North Karnataka population. The results showed significant differences between males and females in most of the facial measurements (P < 0.0001). Conclusion: This is the first database of three-dimensional cephalometric norms based on CBCT of the North Karnataka population. Norms generated were comparable with those reported in the literature with the conventional two-dimensional cephalometry: More accurate and reliable. Moreover, three-dimensional cephalometric analysis has the potential of incorporating new measurement methods that are difficult if not impossible in two-dimensional cepholmetric analysis. This method of cephalometric analyses can be useful in diagnosis and treatment planning for patients with dentofacial deformities.

Three-dimensional Cephalometric Analysis of Adolescents With Cleft Lip and Palate Using Computed Tomography–Guided Imaging

To propose landmarks and a new coordinate system to aid three-dimensional cephalometric analysis of adolescent cleft lip and palate (CLP) using computed tomography (CT) imaging. Sixty-four-row CT images obtained from 52 adolescent patients were retrospectively analyzed with the MIMICS program (MIMICS 10.02; Materialise Technologies, Leuven, Belgium) to determine intrarater reliability of new landmarks for three-dimensional cephalometric analysis before surgery. Five points were located on each image including the midpoint between both uppermost external points of the external auditory meatus (EAM), the center of the sella turcica (sella, S), the most anterior point on the nasofrontal suture in the midline (nasion, N), and the right and left lowest points of the lower edge of the orbitale (r/l orbitale, r/l Or). The horizontal reference plane was then determined using EAM and bilateral Or. The sagittal reference plane was defined perpendicular to the horizontal plane, passing through N and S. The coronal reference plane included the EAM landmark and was perpendicular to the sagittal and horizontal planes. All 5 points had high intrarater reliability and proved easy to use in constructing the new coordinate system. The horizontal, sagittal, and coronal reference planes formed by these respective points improved the ease of performing three-dimensional cephalometric analysis of CLP adolescents with CT imaging. Our 5 landmarks provided reliable CT-guided three-dimensional cephalometric analysis of CLP, allowing for accurate quantitative assessment in adolescents before orthognathic surgery.

Reliability and reproducibility of landmarks on three-dimensional soft-tissue cephalometrics using different placement methods.

Affixing markers on the face in vivo with an optical surface imaging system and placing landmarks on a computed tomographic reconstructive facial model represent two helpful approaches prevailing in three-dimensional cephalometric analysis of facial aesthetics. In this study, the authors determine the suitability of these methods for soft-tissue evaluation along with the reproducibility and reliability of landmark placement. Thirty-seven soft-tissue landmarks were investigated in 35 normal healthy volunteers who underwent cephalometric analysis by direct and indirect placement methods. Two operators performed the analysis twice for each method at a 1-week interval. Landmark positions were measured on the three-dimensional coordinates, and data were standardized and converted into landmark placement errors for the estimation, by two-way random intraclass correlation coefficients. Using the direct method, 86.5 percent of the landmarks had a higher intraclass correlation coefficient than 0.75, and 67.6 percent were higher than 0.90. The authors found that 75.7 percent were higher than 0.75 and 43.2 percent were higher than 0.90 with the indirect method. Both methods showed good reliability in identifying midline-related structures, although the correlations of markers surrounding eyelashes and lips were better using the direct method. The direct method had a significantly smaller landmark placement error and better reproducibility than that identified indirectly (p<0.05). When evaluating well-defined contours and the natural texture of the face, the direct placement method shows better accuracy than the indirect method. The three-dimensional evaluation emphasizes the eye, lip, and some structures more laterally, therefore providing comprehensive analysis for clinical diagnosis. Diagnostic, II.

Comparison of two three-dimensional cephalometric analysis computer software.

Background:Three-dimensional cephalometric analyses are getting more attraction in orthodontics. The aim of this study was to compare two softwares to evaluate three-dimensional cephalometric analyses of orthodontic treatment outcomes.Materials and Methods:Twenty cone beam computed tomography images were obtained using i-CAT® imaging system from patient's records as part of their regular orthodontic records. The images were analyzed using InVivoDental5.0 (Anatomage Inc.) and 3DCeph™ (University of Illinois at Chicago, Chicago, IL, USA) software. Before and after orthodontic treatments data were analyzed using t-test.Results:Reliability test using interclass correlation coefficient was stronger for InVivoDental5.0 (0.83-0.98) compared with 3DCeph™ (0.51-0.90). Paired t-test comparison of the two softwares shows no statistical significant difference in the measurements made in the two softwares.Conclusions:InVivoDental5.0 measurements are more reproducible and user friendly when compared to 3DCeph™. No statistical difference between the two softwares in linear or angular measurements. 3DCeph™ is more time-consuming in performing three-dimensional analysis compared with InVivoDental5.0.

Reliability of anatomic structures as landmarks in three-dimensional cephalometric analysis using CBCT

To identify anatomic structures in three dimensions and examine their reliability to be used as landmarks in a three-dimensional coordinate cephalometric analysis, using cone-beam computerized tomography (CBCT). Thirty CBCT images were randomly selected for landmark location. Forty-two anatomic landmarks, which are not included in the traditional cephalometric landmarks, were chosen based on radiographic characteristics that make them pragmatic to mark in the CBCT image slices. The principal investigator marked the full set of landmarks on the software by navigating in the X, Y, and Z axes for every image three times, with each measurement trial being at least 1 week apart. One other investigator also located the landmarks once for each image for reliability purposes. Intraclass correlation coefficients (ICCs) were used to analyze the mean differences in landmark location in all axes. Intra- and interexaminer reliability for x, y, and z coordinates for all landmarks had ICC greater than 0.95 with confidence interval of 0.88-0.99. Mean measurement differences found were <1.4 mm for all landmarks in all three coordinates. Mean measurement error differences obtained in the principal investigator's trials were primarily <0.5 mm. The most reliable and reproducible landmarks tested for use in CBCT are mental foramina, infraorbital foramina, inferior hamulus, dens axis, foramina transversarium of atlas, medial and lateral condyles of the mandible, superior clinoid processes, and mid-clinoid.

“Black Bone” MRI: a potential non-ionizing method for three-dimensional cephalometric analysis—a preliminary feasibility study

CT offers a three-dimensional solution to the inaccuracies associated with lateral cephalogram-based cephalometric analysis. However, it is associated with significant concerns regarding ionizing radiation exposure. MRI offers a non-ionizing alternative, but this has been less well investigated. We present a novel gradient echo MRI sequence ("Black Bone") and highlight the potential of this sequence in cephalometric analysis. After regional ethics approval, "Black Bone" imaging was obtained in eight patients in whom lateral cephalograms were available. "Black Bone", T1 and T2 weighted spin echo imaging were obtained in the mid-sagittal plane, and measurements were compared with those obtained on the lateral cephalogram using both the Advantage Windows Workstation (GE Medical Systems, Buckinghamshire, UK) and the Dolphin(®) cephalometric software (v. 11.5.04.23, Premium; Dolphin Imaging, Chatsworth, CA) by one assessor. Further assessment was made by scoring the ease of landmark identification on a ten-point scale. "Black Bone" imaging surpassed T1 and T2 weighted imaging in terms of cephalometric landmark identification. A number of mid-sagittal cephalometric landmarks could not be clearly identified on T2 weighted imaging, making analysis impossible. Measurements on "Black Bone" demonstrated the smallest discrepancy when compared with those obtained on the lateral cephalogram. The discrepancy seen between measurements completed on mid-sagittal MRI and the lateral cephalogram was compounded by inherent inaccuracies of the lateral cephalogram. The overall mean discrepancy between distance measurements on "Black Bone" imaging and those on the lateral cephalogram was 1-2 mm. Overall, "Black Bone" MRI offered an improved method of cephalometric landmark identification over routine MRI sequences, and provides a potential non-ionizing alternative to CT for three-dimensional cephalometrics.

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.