Objectives: Conventional two-dimensional (2D) cephalometric radiography is an integral part of orthodontic patient diagnosis and treatment planning. One must be mindful of its limitations as it indeed is a 2D representation of a vaster three-dimensional (3D) object. Issues with projection errors, landmark identification, and measurement inaccuracies impose significant limitations, which may now be overcome with the advent of cone-beam computed tomography (CBCT). A systematic review of the reliability of different 3D cephalometric landmarks in CBCT imaging was conducted. Materials and Methods: Electronic database searches were administered until October 2017 using PubMed, MEDLINE via OvidSP, EBMR and EMBASE via OvidSP, Scopus, and Web of Science. Google Scholar was used as an adjunctive search tool. Results: Thirteen articles considering CBCT scans of human subjects from preexisting data sets were selected and reviewed. Most of the studies had methodological limitations and were of moderate quality. Because of their heterogeneity, key data from each could not be combined and were reported qualitatively. Overall, in 3D, midsagittal plane landmarks demonstrated greater reliability compared with bilateral landmarks. A minimum number of dental landmarks were reported, although most were recommended for use. Conclusions: Further research is required to evaluate the reliability of 3D cephalometric landmarks when evaluating 3D craniofacial complexes.

Objectives: To compare fixed appliances and clear aligner therapy in correcting anterior open bite and in controlling the vertical dimension in adult patients with hyperdivergent skeletal patterns. Materials and Methods: In this retrospective study, two treatment groups of adult (≥18 years old) hyperdivergent patients (mandibular plane angles of ≥38°) with anterior open bites were included: 17 fixed appliance patients and 36 clear aligner patients. Thirteen cephalometric measurements representing the vertical dimension were reported for each group. A two-sample t-test was used to assess differences in changes in mandibular plane angle and overbite between the two treatment groups. Results: There were no statistical differences found in the magnitude of overbite correction and the changes in any of the cephalometric measurements for vertical control. The clear aligner group showed a slightly greater amount of lower incisor extrusion (P = .009). The main mechanism of open bite correction was similar between the two treatment groups and was accomplished through retroclination of the upper and lower incisors while maintaining the vertical position of the upper and lower molars. Conclusions: Cephalometric comparison of anterior open bite correction and changes in the mandibular plane angle associated with use of clear aligners and fixed appliances did not demonstrate statistically significant differences in adult hyperdivergent patients.

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Objectives: To quantify reliability of three-dimensional skeletal landmarks and a comprehensive set of dental landmarks in cone-beam computed tomography (CBCT) and to determine the shapes of envelope of error. Materials and Methods: Three judges located 31 skeletal landmarks and 60 dental landmarks on the pre- and posttreatment CBCT images of 22 patients. Landmark error was determined by calculating the distance of deviation of landmark locations around their average. Standard deviation and mean radial spherical error were calculated. Scatterplots were constructed to characterize envelope of error. Results: The midline landmarks of the cranial base were highly reliable. Bilateral skeletal landmarks tended to have larger error than midline landmarks. Among the nonconventional landmarks, fronto-zygomatic suture, condyle, and mental foramen showed relatively high reliability. However, foramen spinosum and temporal fossa showed larger errors. Gonion was the least reliable landmark. Most dental landmarks were located more reliably than skeletal landmarks. The highest reliability was found at incisal edges. Mesiobuccal cusp of first molars also showed high reliability. Conclusions: There were differences in the size and shape of the distributions of errors of different landmarks. Most landmarks showed elongated envelopes. Bilateral structures tended to show greater errors than midline structures. Most dental landmarks were more reliable than skeletal landmarks.

Objective: To examine changes in the airway and cephalometric measurements associated with orthodontic treatment of adults with and without premolar extractions. The study investigated whether extractions had a direct or indirect effect on the airway and examined selected skeletal and dental features. Materials and Methods: This retrospective study used pre- (T1) and posttreatment (T2) cone-beam computed tomography scans of 83 adult patients matched for age and sex. A total of 15 airway and 10 skeletal and dental measures were analyzed by means of repeated-measures analysis of variance. Results: There were no results showing that extractions affected airway dimensions that could not be accounted for as reflections of measurement error. There was no evidence that extractions affected the airway indirectly through skeletal and dental changes. There were strong and consistent findings that patients with small airways showed larger ones after treatment and that patients with large airways showed smaller ones later. These effects were independent of whether or not extractions were part of treatment. The measurement phenomena of regression toward the mean and of differential unfolding of natural changes over time could have accounted for the results observed. Conclusions: There was no evidence that extractions in nongrowing patients have negative consequences on the size of various airway measures in the nasopharynx, retropalatal, or retroglossal regions.

Structured Abstract Objectives To assess the potential of predicting adult facial types at different stages of mandibular development. Setting and Sample Population A total of 941 participants from the Bolton‐Brush, Denver, Fels, Iowa, Michigan and Oregon growth studies with longitudinal lateral cephalograms (total of 7166) between ages 6‐21 years. Material and Methods Each participant was placed into one of three facial types based on mandibular plane angle (MPA) from cephalograms taken closest to 18 years of age (range of 15‐21 years): hypo‐divergent (MPA < 28°), normo‐divergent (28°≤ MPA ≤ 39°) and hyper‐divergent (MPA > 39°). Cephalograms were categorized into 13 age groups 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17 and 18‐21. Twenty‐three two‐dimensional anatomical landmarks were digitized on the mandible and superimposed using generalized Procrustes analysis, which projects landmarks into a common shape space. Data were analysed within age categories using stepwise discriminant analysis to identify landmarks that distinguish adult facial types and by jackknife cross‐validation to test how well young individuals can be reclassified into their adult facial types. Results Although each category has multiple best discriminating landmarks among adult types, three landmarks were common across nearly all age categories: menton, gonion and articulare. Individuals were correctly classified better than chance, even among the youngest age category. Cross‐validation rates improved with age, and hyper‐ and hypo‐divergent groups have better reclassification rates than the normo‐divergent group. Conclusions The discovery of important indicators of adult facial type in the developing mandible helps improve our capacity to predict adult facial types at a younger age.

Objectives To evaluate the accuracy and reliability of a fully automated landmark identification (ALI) system as a tool for automatic landmark location compared with human judges. Materials and Methods A total of 100 cone-beam computed tomography (CBCT) images were collected. After the calibration procedure, two human judges identified 53 landmarks in the x, y, and z coordinate planes on CBCTs using Checkpoint Software (Stratovan Corporation, Davis, Calif). The ground truth was created by averaging landmark coordinates identified by two human judges for each landmark. To evaluate the accuracy of ALI, the mean absolute error (mm) at the x, y, and z coordinates and mean error distance (mm) between the human landmark identification and the ALI were determined, and a successful detection rate was calculated. Results Overall, the ALI system was as successful at landmarking as the human judges. The ALI's mean absolute error for all coordinates was 1.57 mm on average. Across all three coordinate planes, 94% of the landmarks had a mean absolute error of less than 3 mm. The mean error distance for all 53 landmarks was 3.19 ± 2.6 mm. When applied to 53 landmarks on 100 CBCTs, the ALI system showed a 75% success rate in detecting landmarks within a 4-mm error distance range. Conclusions Overall, ALI showed clinically acceptable mean error distances except for a few landmarks. The ALI was more precise than humans when identifying landmarks on the same image at different times. This study demonstrates the promise of ALI in aiding orthodontists with landmark identifications on CBCTs.