Anibal M. Silveira

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 Students 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.

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.

The Safety and Effectiveness of an Er:YAG Laser for Caries Removal and Cavity Preparation in Children

Summary Purpose: The Erbium:YAG laser has been shown to be safe and effective for caries removal and cavity preparation in adults. In this study, we report a prospective parallel controlled randomized multicenter clinical trial of this laser for dental caries removal and cavity preparation in children. Methods: At two separate sites, a total of 124 patients from 4 to 18 years old, having at least one tooth with caries requiring restoration, were randomized for treatment in a 2:1 ratio, laser to conventional dental drill. Caries were removed, the teeth were restored and follow-up evaluations were completed after 3 months. Determination of safe and effective treatment included four criteria: 1) acceptable caries removal, 2) acceptable cavity preparation, 3) pulp vitality, and 4) intact and serviceable restoration. Results: All 42 drill procedures and 81 out of 82 laser procedures were found to be successful in terms of safety and effectiveness. No significant difference in pain reported was found between drill or laser treatments, and no complications or adverse events were reported after treatment or at any other time during the study. Subject satisfaction with treatment procedures as reported was equivalent in the laser and drill groups. The only significant difference found between treatment groups was in the greater use of anesthesia during drilling procedures. Conclusions: The Erbium:YAG laser is safe and effective for both caries removal and cavity preparation in children.

Longitudinal predictability of AF-BF value in Angle Class I patients

AF-BF is a linear cephalometric measure of the anteroposterior jaw relationship in the sagittal plane. A retrospective, longitudinal study was made to determine the mean Caucasian American AF-BF values at ages 8 and 18 years for 30 male and 32 female participants of the Bolton Growth Study. Mean AF-BF values (+/- s.d.) for males were 7.3 +/- 2.7 mm at 8 years and 6.5 +/- 4.2 mm at 18 years. Mean AF-BF values (+/- s.d.) for females were 6.7 +/- 2.1 mm at 8 years and 5.2 +/- 2.9 mm at 18 years. No significant difference was found between the mean AF-BF values for males and females at either age group (P < 0.05). The decrease in AF-BF mean values with increasing age both for males and females was statistically significant. The correlation (r) for the AF-BF values was 0.49 (P < 0.05) for females and 0.86 (P < 0.05) for males. With increasing age, the mean difference between ANB values for females was 1.40 +/- 1.60 and 1.10 +/- 1.40 for males. The correlation of ANB angle and AF-BF provides a clinically useful tool for the cephalometric assessment of anteroposterior sagittal discrepancies of maxillary and mandibular denture bases.

Diagnostic Accuracy of Film-Based, TIFF, and Wavelet Compressed Digital Temporomandibular Joint Images

The purpose of this research was to determine if digitization and the application of various compression routines to digital images of temporomandibular joint (TMJ) radiographs would diminish observer accuracy in the detection of specific osseous characteristics associated with TMJ degenerative joint disease (DJD). Nine observers viewed 6 cropped hard-copy radiographic films each of 34 TMJs (17 radiographic series). Regions of interest measuring 2 in × 2 in were digitized using an 8-bit scanner with transparency adapter at 300 dpi. The images were placed into a montage of 6 images and stored as tagged image file format (TIFF), compressed at 4 levels (25∶1, 50∶1, 75∶1, and 100∶1) using a wavelet algorithm, and displayed to the observers on a computer monitor. Their observations regarding condylar faceting, sclerosis, osteophyte formation, erosion, and abnormal shape were analyzed using ROC. Kappa values were determined for relative condylar size and condylar position within the glenoid fossa. Indices were compared using ANOVA at a significance level ofP<.05. Although significant and substantial observer variability was demonstrated, there were no statistically significant differences between image modalities, except for condylar position, in which TIFF and wavelet (at all compression ratios) performed better than the original image. For faceting, wavelet 100∶1 performed better than radiographic film images. Little actual image file reduction was achieved at compression ratios above 25∶1.

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Cephalometric landmark clarity in photostimulable phosphor images using pseudo-color and emboss enhancements

AbstractObjective The conspicuity of cephalometric landmarks may be improved by pseudo color and emboss enhancements of 8 and 16 bit photostimulable phosphor (PSP) cephalograms reviewed by orthodontists. Methods PSP cephalograms of orthodontic patients were obtained. These 8 bit and 16 bit images were viewed in random order in baseline “for processing,” emboss, pseudo color and emboss/pseudo color states. Ten observers viewed the images simultaneously and idependently. Selected soft tissue and hard tissue cephalometric landmarks and of overall image clarity were rated. Repeat images were included to determine intra observer reliability in making ratings. Results Statistically significant differences were found in the preferred image state for both specific cephalometric landmark evaluation and image bit depth. The emboss state was most frequently rated highest for clarity of hard tissue landmarks. Pseudo color state was rated best for soft tissue landmarks. Interrater agreement varied between landmarks but was not altered significantly by bit depth. Intrarater agreement was high. Conclusions Post-processing enhancement of PSP cephalograms is perceived to improve clarity of selected anatomic landmarks in PSP cephalograms.

Solid-state temporomandibular joint imaging: accuracy in detecting osseous changes of degenerative joint disease and determining condylar spatial relations

The purpose of this study was to evaluate the off-label use of an intraoral charge-coupled device (CCD) for extraoral transcranial radiography of the temporomandibular joint. Corrected linear tomograms and transcranial images made with conventional screen-film combinations and a CCD detector were compared with sectioned cadaver specimens. Radiation dosage, qualitative assessment of condylar degenerative features, and condylar position within the glenoid fossa of the 3 modalities were assessed and compared. The CCD method required special adjustments to achieve adequate quality, and it involved greater exposure than the other methods. This use of this intraoral system for extraoral imaging cannot now be recommended, but future refinements might make it more viable.

Image post-processing for optimization of photostimulable phosphor cephalograms

To evaluate 16-bit PSP cephalogram images for orthodontist-perceived quality of cephalometric landmark clarity at baseline and with three different image enhancements (emboss, inverse, and inverse/emboss). This presentation concerns results limited for detection of Porion and Pronasale. These two landmarks were evaluated in view of being extremes in contrast requirements. A Sectagraph (Denar Corporation, CA) was used with the DenOptix storage phosphor system (Dentsply/Gendex, IL). Images from 48 patients (plus 12 repeats) were presented randomly and simultaneously to 10 observers engaged in orthodontics. Each observer independently rated Porion and Pronasale detection (1 = poor; 2 = satisfactory; 3 = excellent). Equal numbers of images having single and double peak histograms were included. Enhancements used in the study were: (1) emboss; (2) inverse; and (3) inverse/emboss.

RadioVisioGraphy of the temporomandibular joint: comparisons with transcranial radiography.

RadioVisioGraphy (RVG), a new digital imaging technique, is compared to conventional transcranial radiographic imaging of the temporomandibular joint. The results of this study using fixed human cadaver specimens revealed an excellent correlation between the recorded images and the actual anatomic specimens. Dosimetry, using a beryllium-windowed ionization chamber, showed a 64% dose reduction with charge-coupled device (CCD) when compared to standard film-screen combination.