Objective-To evaluate reliability in 3D landmark identification using Cone-Beam CT.Study Design-Twelve pre-surgery CBCTs were randomly selected from 159 orthognathic surgery patients. Three observers independently repeated three times the identification of 30 landmarks in the sagittal, coronal, and axial slices. A mixed effects ANOVA model estimated the Intraclass Correlations (ICC) and assessed systematic bias.Results-The ICC was >0.9 for 86% of intra-observer assessments and 66% of inter-observer assessments. Only 1% of intra-observer and 3% of inter-observer coefficients were <0.45. The systematic difference among observers was greater in X and Z than in Y dimensions, but the maximum mean difference was quite small. Conclusion-Overall, the intra-and inter-observer reliability was excellent. 3D landmark identification using CBCT can offer consistent and reproducible data, if a protocol for operator training and calibration is followed. This is particularly important for landmarks not easily specified in all three planes of space.Three-dimensional cephalometry has long been proposed as the ideal for orthodontic diagnosis, treatment planning, and follow-up of the patients. 1 Diagnosis, treatment planning, and assessment of change over time have been routinely based on landmark based analysis in 2D cephalometry. 1 CORRESPONDING AUTHOR: Lucia H.S. Cevidanes, DDS, MS, PhD, UNC School of Dentistry, Assistant Professor, Department of Orthodontics, 201 Brauer Hall, UNC School of Dentistry, Chapel Hill, NC, 27599-7450, Phone: (919) 3578603, Email: cevidanl@dentistry.unc.edu. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. The use of Cone-Beam CT (CBCT) in dentistry offers great potential for 3D diagnosis and treatment planning compared to CT. 5-16 However, the development of three-dimensional landmark-based cephalometric analysis requires definition of 3D landmarks on complex curving structures, which is not a trivial problem. As Bookstein 16 noted, there is a lack of literature about suitable operational definitions for the landmarks in the 3 planes of space (coronal, sagittal, and axial). Practical considerations of identification errors, coupled with an essential need for biological relevance and a balanced representation of components of the craniofacial form, limit the number and nature of landmarks available for analysis. Historically landmarks, such as Articulare, were used because of the ease in landmark location on the 2D cephalometric projections, but these projected superimposed structures do not exist in the actual 3D facial structure. For these reasons, the...

No abstract

The recent emphasis on soft tissues as the limiting factor in treatment and on soft tissue relationships in establishing the goals of treatment has made 3D analysis of soft tissues more important in diagnosis and treatment planning. It is equally important to be able to detect changes in the facial soft tissues produced by growth and/or treatment. This requires structures of reference for superimposition, and a way to display the changes with quantitative information. This paper outlines a technique for quantifying facial soft tissue changes as viewed in CBCT data, using fully-automated voxel-wise registration of the cranial base surface. The assessment of change of soft tissues is done via calculation of the Euclidean surface distances between the 3D models. Color maps are used for visual assessment of the location and quantification of changes. This methodology allows a detailed examination of soft tissue changes with growth and/or treatment. Because of the lack of stable references with 3D photogrammetry, 3D photography and laser scanning, soft tissue changes cannot be accurately quantified by these methods.

Objective: To determine the reliability of obtaining two-dimensional cephalometric measurements using two virtual head orientations from cone-beam computed tomography (CBCT) models. Materials and Methods: CBCT scans of 12 patients (6 class II and 6 class III) were randomly selected from a pool of 159 patients. An orthodontist, a dental radiologist, and a third-year dental student independently oriented CBCT three-dimensional (3D) renderings in either visual natural head position (simulated NHP) or 3D intracranial reference planes (3D IRP). Each observer created and digitized four CBCT-generated lateral cephalograms per patient, two using simulated NHP and two using 3D IRP at intervals of at least 3 days. Mixed-effects analysis of variance was used to calculate intraclass correlation coefficients (ICCs) and to test the difference between the orientations for each measure. Results: ICC indicated good reliability both within each head orientation and between orientations. Of the 50 measurements, the reliability coefficients were Ն0.9 for 45 measurements obtained with 3D IRP orientation and 36 measurements with simulated NHP. The difference in mean values of the two orientations exceeded 2 mm or 2Њ for 14 (28%) of the measurements. Conclusions: The reliability of both virtual head orientations was acceptable, although the percentage of measurements with ICC Ͼ0.9 was greater for 3D IRP. This may reflect the ease of using the guide planes to position the head in the 3D IRP during the simulation process. (Angle Orthod. 2009;79:971-977.)

This prospective longitudinal study assessed the 3D soft tissue changes following mandibular advancement surgery. Cranial base registration was performed for superimposition of virtual models built from cone beam computed tomography (CBCT) volumes. Displacements at the soft and hard tissue chin (n=20), lower incisors and lower lip (n=21) were computed for presurgery to splint removal (4-6 week surgical outcome), presurgery to 1 year postsurgery (1-year surgical outcome), and splint removal to 1 year postsurgery (postsurgical adaptation). Qualitative evaluations of color maps illustrated the surgical changes and postsurgical adaptations, but only the lower lip showed statistically significant postsurgical adaptations. Soft and hard tissue chin changes were significantly correlated for each of the intervals evaluated: presurgery to splint removal (r=0.92), presurgery to 1 year postsurgery (r=0.86), and splint removal to 1 year postsurgery (r=0.77). A statistically significant correlation between lower incisor and lower lip was found only between presurgery and 1 year postsurgery (r=0.55). At 1 year after surgery, 31% of the lower lip changes were explained by changes in the lower incisor position while 73% of the soft tissue chin changes were explained by the hard chin. This study suggests that 3D soft tissue response to mandibular advancement surgery is markedly variable.

Purpose-To evaluate the association of 3-dimensional changes in the position of the condyles, rami, and chin at splint removal and 1 year after mandibular advancement surgery.Patients and Methods-This prospective observational study used preoperative and postoperative scans of 27 subjects presenting with a skeletal Class II jaw relationship with a normal or deep overbite. An automatic technique of cranial base superimposition was used to assess the positional and/or remodeling changes in the anatomic regions of interest. The displacements were visually displayed and quantified using 3-dimensional color maps. The positive and negative values of surface distances in the color maps indicated the direction of the displacements. Pearson correlation coefficients and a linear model for correlated data were used to evaluate the association between the regional displacements.Results-The postoperative adaptations in the chin position between splint removal and 1 year after surgery were significantly negatively correlated with changes in the borders of the posterior ramus (left, r = −0.73, P ≤ .0001; and right, r = −0.68, P = .00) and the condyles (left, r = −0.53, P = .01; and right, r = −0.46, P = .02), indicating that these structures tended to be displaced in the same direction. Even though the mean condylar displacement with surgery was less than 1 mm, individual displacements greater than 2 mm with surgery were observed for 24% of the condyles. The condylar displacements were maintained at 1 year after surgery for 17% of the condyles.Conclusions-The surface distance displacements indicated that the postoperative adaptations at different anatomic regions were significantly related.Although mandibular advancement surgery is considered a highly stable procedure,1 , 2 postoperative changes, such as rotation, transverse condylar displacements during surgery, 3 -5 and subsequent long-term condylar resorption have been suggested as factors leading to sagittal relapse and anterior bite opening.6 -8 Therefore, the postoperative instability of bilateral sagittal split ramus osteotomy due to displacement of the condyle from its seated position in the glenoid fossa in the 3 planes of space remains an area of concern.9 , 10Recent assessments of 3-dimensional (3D) skeletal changes 1 year after mandibular advancement surgery have shown individual variability in postoperative adaptations, with a greater than 2-mm relapse of the chin position in 28% of the patients, with additional advancement of the chin position in 20% of the patients.11 The use of cone beam computed tomography (CBCT) and 3D superimposition tools now allow assessment of the relationships of the surface adaptations among the dental, skeletal, and soft tissue components that was not possible with 2-dimensional landmark linear or angular measures. These methods have the potential to highlight the associations between the structural changes and the stability of surgical correction.12 , 13The present study investigated whether surface distance displacements with...

Objective: To evaluate the reliability of three-dimensional (3D) landmark identification in conebeam computed tomography (CBCT) using two different visualization techniques. Materials and Methods: Twelve CBCT images were randomly selected. Three observers independently repeated three times the identification of 30 landmarks using 3D reconstructions and 28 landmarks using multiplanar views. The values of the coordinates X, Y, and Z of each point were obtained and the intraclass correlation coefficient (ICC) was calculated. Results: The ICC of the 3D visualization was rated .0.90 in 67.76% and 45.56%, and #0.45 in 13.33% and 14.46% of the intraobserver and interobserver assessments, respectively. The ICC of the multiplanar visualization was rated .0.90 in 82.16% and 78.56% and #0.45 in only 16.7% and 8.33% of the intraobserver and interobserver assessments, respectively. An individual landmark classification was done according to ICC values. Conclusions: The frequency of highly reliable values was greater for multiplanar than 3D reconstructions. Overall, lower reliability was found for points on the condyle and higher reliability for those on the midsagittal plane. Depending on the anatomic region, the observer must choose the most reliable type of image visualization. (Angle Orthod. 2015;85:11-17.)

Objective: To evaluate the esthetic perception of upper dental midline deviation by laypersons and if adjacent structures influence their judgment. Methods:An album with 12 randomly distributed frontal view photographs of the smile of a woman with the midline digitally deviated was evaluated by 95 laypersons. The frontal view smiling photograph was modified to create from 1 mm to 5 mm deviations in the upper midline to the left side. The photographs were cropped in two different manners and divided into two groups of six photographs each: group LCN included the lips, chin, and two-thirds of the nose, and group L included the lips only. The laypersons performed the rate of each smile using a visual analog scale (VAS). Wilcoxon test, Student’s t-test and Mann-Whitney test were applied, adopting a 5% level of significance. Results: Laypersons were able to perceive midline deviations starting at 1 mm. Statistically significant results (p< 0.05) were found for all multiple comparisons of the values in photographs of group LCN and for almost all comparisons in photographs of group L. Comparisons between the photographs of groups LCN and L showed statistically significant values (p< 0.05) when the deviation was 1 mm. Conclusions:Laypersons were able to perceive the upper dental midline deviations of 1 mm, and above when the adjacent structures of the smiles were included. Deviations of 2 mm and above when the lips only were included. The visualization of structures adjacent to the smile demonstrated influence on the perception of midline deviation.