Linear accuracy of cone beam CT derived 3D images.

OBJECTIVE: To compare the in vitro reliability and accuracy of linear measurements between cephalometric landmarks on cone beam computed tomography (CBCT) 3D volumetric images with varying basis projection images to direct measurements on human skulls. MATERIALS AND METHODS: Sixteen linear dimensions between 24 anatomic sites marked on 19 human skulls were directly measured. The skulls were imaged with CBCT (i-CAT, Imaging Sciences International, Hatfield, Pa) at three settings: (a) 153 projections, (b) 306 projections, and (c) 612 projections. The mean absolute error and modality mean (+/- SD) of linear measurements between landmarks on volumetric renderings were compared to the anatomic truth using repeated measures general linear model (P < or = .05). RESULTS: No difference in mean absolute error between the scan settings was found for almost all measurements. The average skull absolute error between marked reference points was less than the distances between unmarked reference sites. CBCT resulted in lower measurements for nine dimensions (mean difference range: 3.1 mm +/- 0.12 mm to 0.56 mm +/- 0.07 mm) and a greater measurement for one dimension (mean difference 3.3 mm +/- 0.12 mm). No differences were detected between CBCT scan sequences. CONCLUSIONS: CBCT measurements were consistent between scan sequences and for direct measurements between marked reference points. Reducing the number of projections for 3D reconstruction did not lead to reduced dimensional accuracy and potentially provides reduced patient radiation exposure. Because the fiducial landmarks on the skulls were not radio-opaque, the inaccuracies found in measurement could be due to the methods applied rather than to innate inaccuracies in the CBCT scan reconstructions or 3D software employed.

Linear accuracy and reliability of cone beam CT derived 3-dimensional images constructed using an orthodontic volumetric rendering program.

OBJECTIVE: To compare accuracy of linear measurements made on cone beam computed tomographic (CBCT) derived 3-dimensional (3D) surface rendered volumetric images to direct measurements made on human skulls. MATERIALS AND METHODS: Twenty orthodontic linear measurements between anatomical landmarks on 23 human skulls were measured by observers using a digital caliper. The skulls were imaged with CBCT and Dolphin 3D (version 2.3) software used to generate 3D volumetric reconstructions (3DCBCT). The linear measurements between landmarks were computed by a single observer three times and compared to anatomic dimensions using Student's t-test (P < or = .05). The intraclass correlation coefficient (ICC) and absolute linear and percentage error were calculated. RESULTS: The ICC for 3DCBCT (0.975 +/- 0.016) was significantly less than for skull (0.996 +/- 0.007) measurements. Mean percentage measurement error for 3DCBCT (2.31% +/- 2.11%) was significantly higher than replicate skull measurements (0.63% +/- 0.51%). Statistical differences between 3DCBCT means and true dimensions were found for all of the midsagittal measurements except Na-A and six of the 12 bilateral measurements. The mean percentage difference between the mean skull and 3D-based linear measurements was -1.13% (SD +/- 1.47%). Ninety percent of mean differences were less than 2 mm, and 95% confidence intervals were all less than 2 mm except for Ba-ANS (3.32 mm) and Pog-Go(left) (2.42 mm). CONCLUSIONS: While many linear measurements between cephalometric landmarks on 3D volumetric surface renderings obtained using Dolphin 3D software generated from CBCT datasets may be statistically significantly different from anatomic dimensions, most can be considered to be sufficiently clinically accurate for craniofacial analyses.

Application of distance learning to interactive seminar instruction in orthodontic residency programs.

INTRODUCTION: A series of experiments involving 3 orthodontic departments has shown that distance learning can be acceptable to residents and effective in teaching concepts that are fundamental to orthodontic practice. METHODS: Residents in each department participated in distance seminars, clinical conferences, and clinical seminars via high-speed Internet connections. The acceptability of this form of instruction was judged from evaluation forms completed by the residents. Its effectiveness was judged from pretests and posttests on the seminar topics. RESULTS: The improvement from pretest to posttest scores after observing a sequence of distance seminars was similar to that with direct instruction. Orthodontic residents rated the educational experiences positively. Live participation in seminars via video conferencing was preferred to live observation or later observation of a recording, but observation provided similar improvement in test scores. CONCLUSIONS: The acceptability of the distance seminars appeared to be influenced by the instructor's personality and teaching style in facilitating interaction, the seminar subject, the residents' comfort level in dealing with this technology, and the sequence for interaction vs observation. Further development of recorded seminars with live follow-up discussions has the potential to supplement instruction in graduate orthodontic programs and help with the impending shortage of experienced full-time orthodontic faculty.

Accuracy of cone-beam computed tomography imaging of the temporomandibular joint: comparisons with panoramic radiology and linear tomography.

INTRODUCTION: Cone-beam computed tomography (CBCT) is increasingly being used as an imaging modality, particularly in the assessment of the temporomandibular joint (TMJ). A blinded observational cross-sectional in-vitro study was conducted to compare the diagnostic accuracy of observers viewing images made with CBCT, panoramic radiography, and linear tomography. The task was to detect cortical erosions affecting the mandibular condylar head. METHODS: The sample consisted of 37 TMJ articulations from 30 skulls with either normal condylar morphology (n = 19) or erosion of the lateral pole (n = 18). The articulations were imaged by using corrected angle linear tomography (TOMO), normal (Pan-N) and TMJ-specific (Pan-TM) panoramic radiography, and CBCT. Digital images were obtained with photostimulable phosphor plates for all modalities except CBCT. The CBCT detector used an amorphous silicon flat-panel array combined with cesium iodide. Images and 10 rereads were presented to 10 observers on a flat-panel display at a pixel-to-monitor ratio of 1:1. CBCT multi-planar images were presented both statically (CBCT-S) and interactively (CBCT-I). The observers were permitted to scroll through axial (0.4 mm) and para-sagittal (1 mm) sections and then independently rate their confidence about the presence or absence of cortical erosion. Intraobserver reliability was determined by weighted kappa and diagnostic accuracy by the fitted area under the ROC curve. Means were compared by using ANOVA (P < or =.05). RESULTS: Intraobserver reliability was moderate (0.57 +/- 0.22; range, 0.34-0.78). Pan-N (0.72 +/- 0.15), CBCT-I (0.65 +/- 0.21), and CBCT-S (0.65 +/- 0.17) reliability was significantly greater than TOMO (0.44 +/- 0.25). The diagnostic accuracy of CBCT-I (0.95 +/- 0.05) and CBCT-S (0.77 +/- 0.17) was significantly greater than all other modalities (Pan-N [0.64 +/- 0.11], Pan-TM [0.55 +/- 0.11], TOMO [0.58 +/- 0.15]). CBCT-I was also more accurate than CBCT-S, and Pan-N was more accurate than Pan-TM and TOMO. CONCLUSIONS: CBCT images provide superior reliability and greater accuracy than TOMO and TMJ panoramic projections in the detection of condylar cortical erosion.

Accuracy of linear measurements from imaging plate and lateral cephalometric images derived from cone-beam computed tomography.

INTRODUCTION: As orthodontic practice moves toward 3-dimensional cephalometric analyses, a solution is required to ensure sustained availability of well-established projected treatment outcomes based on 2-dimensional analyses. This ex-vivo study was conducted to compare the accuracy of linear measurements made on photostimulable phosphor cephalograms with 3 methods for simulating lateral cephalograms with cone-beam computed tomography (CBCT). METHODS: The linear distances between anatomical landmarks on dentate dry human skulls were measured by observers using digital calipers for S-N, Ba-N, M-N, ANS-N, ANS-PNS, Pog-Go, Go-M, Po-Or, and Go-Co. The skulls were imaged with CBCT with a single 360 degrees rotation, producing 306 basis images and achieving 0.4 mm isotrophic voxel resolution on volumetric reconstruction for making ray-sum reconstructed cephalograms. Two other cephalogram approaches were used with the CBCT system--a single transmission image generated as a scout image designed to check patient positioning before CBCT, and a single-frame lateral basis image. Conventional digital lateral cephalograms (LCs) were acquired with the photostimulable phosphor system. Images were imported into a cephalometric analysis program (Dolphin Imaging Cephalometric and Tracing Software, Chatsworth, Calif) to compute the included linear measurements. Analyses were repeated 3 times and statistically compared with measured anatomic truth with ANOVA (P < or =.05). The intraclass correlation coefficient was determined as an index of intra- and interobserver reliability. RESULTS: The intraclass correlation coefficient for the LCs was significantly less than for the measured anatomic truth and for all CBCT-derived images. CBCT images either produced with individual frames or reconstructed from the volumetric data set were accurate for all measurements except Pog-Go and Go-M. CBCT scout images had the second highest accuracy for all measurements except Pog-Go, Go-M, and Go-Co. Conventional LCs had the least accuracy; they were accurate only for Po-Or and ANS-N. CONCLUSIONS: CBCT-derived 2-dimensional LCs proved to be more accurate than LCs for most linear measurements calculated in the sagittal plane. No advantage was found over single-frame basis images in using ray-sum generated cephalograms from the CBCT volumetric data set.

Childhood obesity and skeletal maturation assessed with Fishman's hand-wrist analysis.

INTRODUCTION: The purpose of this study was to determine whether increased body mass index is associated with accelerated skeletal maturation. METHODS: The skeletal ages of 107 children, aged 9 to 16 years, were determined by using Fishman's hand-wrist analysis. The difference between chronologic age and dental age was analyzed against body mass index, sex, and age. RESULTS: The mean differences between chronologic and skeletal ages for normal weight, overweight, and obese subjects were 0.51 years, 0.44 years, and 1.00 years, respectively. Although there was a trend for obese subjects to have accelerated skeletal maturation compared with overweight and normal-weight subjects, the difference was not statistically significant. Skeletal age differences significantly decreased with increasing age. The mean skeletal age differences were 0.90 year for 9- to 13-year-olds and 0.26 year for 13- to 16-year-olds. Mean skeletal age did not differ significantly by sex. CONCLUSIONS: Overweight or obese children did not have significantly accelerated skeletal maturation after adjusting for age and sex.

Correlation between carotid area calcifications and periodontitis: a retrospective study of digital panoramic radiographic findings in pretreatment cancer patients.

OBJECTIVES: The objective of this study was to examine the prevalence of carotid area calcifications retrospectively detected on digital panoramic radiographs of pretreatment cancer subjects, and to correlate the finding of such calcifications with radiographic evidence of periodontal bone loss in the same subjects. STUDY DESIGN: Digital panoramic radiographs of 201 subjects were evaluated for calcifications projected in the carotid artery bifurcation area as well as for alveolar bone loss as a result of periodontal disease. Inclusion criteria were unobscured carotid artery bifurcation regions bilaterally and sufficient index teeth present with a definable cemento-enamel junction and alveolar crest. Radiographs were independently observed for carotid area calcifications and for periodontal status. Image enhancements permitted for detection of calcifications projected in the carotid area included window/level, inverse, and emboss. Periodontal measurements were made on index teeth using proprietary imaging software and a mouse-driven measurement algorithm. A 3-factor analysis of variance was performed with 3 between-subjects comparisons. Percentage of bone loss was the dependent variable. Independent variables were age, subject sex, and the presence or absence of carotid area calcifications. RESULTS: Differences measured in percentage of bone loss between sexes were not statistically significant. While bone loss did increase with age, comparison of the mean bone loss of each age category revealed no statistical significance. There was a highly significant correlation between carotid artery area calcifications visible on panoramic radiographs and percent alveolar bone loss. Radiographs showing unilateral and bilateral calcifications had a mean percent bone loss of 24.2% +/- 12.6% and 25.7% +/- 13.0% respectively, compared to those with no calcification at 10.4% +/- 9.9%. CONCLUSIONS: Nearly 1 in 4 subjects in this study evidenced calcifications projected in the carotid bifurcation region. The finding of such calcifications was significantly related to the calculated percentage of alveolar bone loss.

Orthodontic treatment provided by general dentists who have achieved master's level in the Academy of General Dentistry.

INTRODUCTION: The purposes of this study were to document orthodontic treatment currently provided by general dentists for comparison with past and future studies and to ascertain variables that influence practitioners' orthodontic treatment patterns. METHODS: A 21-item survey was mailed to 750 master's level members of the Academy of General Dentistry. Surveys returned within 8 weeks were included for statistical analysis. RESULTS: The response rate was 62%. Most practitioners spent less than 10% of their practice time providing orthodontic treatment and reported that this would not change in the future. Many provided orthodontic treatment in the permanent dentition, and the most common conditions or malocclusions treated were space maintenance, anterior crossbite, rotation, habits, molar uprighting, and posterior crossbite. The most common orthodontic appliances used were removable Hawley appliances with finger springs, straight wire orthodontic therapy, rapid palatal expanders, and functional appliances. CONCLUSIONS: The number of general dentists providing comprehensive orthodontic treatment has not changed since previous surveys; practitioners also do not expect a change in the next 5 years. Factors that influenced the orthodontic treatment provided included the primary source of orthodontic training, the number of orthodontic continuing education hours earned per year, the practitioner's location, and the proximity to the nearest orthodontist.

Graduate orthodontic education: the residents' perspective.

INTRODUCTION: The purpose of this study was to identify current demographic trends of orthodontic residents, their goals for the future, and their perspectives on orthodontic training. METHODS: A 26-item survey was conducted at the Graduate Orthodontic Residency Program (GORP) at Harvard University in August 2003. Questionnaires were distributed to residents representing 51 orthodontic programs (of 58 in the United States). Surveys were sent to 5 of the 7 programs whose residents did not attend GORP. RESULTS: Of the 380 questionnaires distributed, 295 were completed and returned at the meeting for a 77% response rate. Additionally, 35 of the 50 mailed questionnaires were completed and returned, for a total response rate of 77% (330 completed/430 distributed). Most residents stated that clinical education was the most important factor when choosing a residency. Most residents planned to publish their research, complete American Board of Orthodontics certification requirements, and work 4 days a week after program completion. CONCLUSIONS: Several trends were identified since orthodontic residents were last surveyed in 1992. The most significant change reported was an increase in the number of those who plan to complete American Board of Orthodontics certification requirements.

Do pediatric dentists practice the orthodontics they are taught?

PURPOSE: The purpose of this study was to determine whether the orthodontic treatment provided by pediatric dentists reflects the orthodontic training received in pediatric dental residency programs. METHODS: Five questions from a survey of the American Academy of Pediatric Dentistry (AAPD) diplomates in August 2002 and a survey of pediatric dental residency program directors in June 2002 were statistically analyzed to compare the orthodontic treatment provided by diplomates to that provided within pediatric dental residency programs. RESULTS: Patient populations differed financially between pediatric dental residencies and diplomates of the AAPD. Residents treated significantly more public assistance patients. The residents were more likely than diplomates to use most orthodontic appliances and treat most stages of dental development and most conditions/malocclusions with orthodontics. Diplomates anticipated a decrease in the amount of orthodontic treatment provided in the next 5 years, while program directors anticipated an increase. CONCLUSIONS: The majority of the orthodontic treatment provided by pediatric dental residents and diplomates was similar, although the residents were exposed to more diverse orthodontic treatment modalities than those used by diplomates. The residencies were also more likely than the diplomates to increase the amount of orthodontic treatment provided in the next 5 years.

Three-dimensional computerized tomographic scanning of craniofacial anomalies / Tomografia computadorizada tridimensional em anomalias craniofacial

Three-dimensional images were reconstructed from conventional CT scans with the use of special software. These reconstructed images did not exhibit magnification nor superimpositioning of structures. Quantitative measurements of three-dimensional craniofacial structures were very precise, and their form and continuity could be evaluated. The application of this technique will be demonstrated in three cases involved with craniofacial anomalies