1,721,027 research outputs found
Laser scanner compared with stereophotogrammetry for measurements of area on nasal plaster casts
No full textImplant-Supported Immediately Loaded Full-Arch Rehabilitations: Comparison of Resin and Zirconia Clinical Outcomes in a 5-Year Retrospective Follow-Up Study
No full textPURPOSE:
We analyzed complications and failures of final full-arch implant-supported rehabilitations, comparing resin and zirconia prosthesis materials. Prostheses were retrospectively followed up for 5 years.
MATERIALS AND METHODS:
One hundred twenty-five patients who received one or two four to six implant-supported immediately loaded full-arch rehabilitations in resin (166 prostheses) or zirconia (48 prostheses) were analyzed.
RESULTS:
One hundred thirteen patients (53 men, 60 women), with 214 full-arch prostheses (105 maxillary, 109 mandibular), were analyzed. During the follow-up interval, the prosthesis annual complication rate was 6.6%, free complications survival was 75.5% (60 months). Age, number of implants, and prosthesis material did not influence complication risk. Men had a higher risk of complications than women. Prosthesis annual failure rate was 4.6%, free survival was 85.5% (60 months). Age, number of implants, and prosthesis material did not influence failure risk. Men and maxillary arch prostheses had a higher risk of failures than women and mandibular arch prostheses.
CONCLUSION:
Implant-supported, immediately loaded full-arch rehabilitations supporting resin or zirconia based prostheses were clinically successful in a 5-year follow-up. Prosthesis material did not influence complication risk
Validation of a technique for integration of a digital dental model into stereophotogrammetric images of the face using cone-beam computed tomographic data
No full textWe wanted to find and validate a new way to visualise patients’ faces and their dental arches non-invasively. The stereophotogrammetric images of the faces and the digitised dental casts of seven healthy subjects were analysed. Point-based and surface-based recording techniques matched the facial image with those of the mandibular and maxillary dental arches in their relative positions. The cone-beam computed tomographic (CT) images of the same subjects were analysed retrospectively. Twenty-eight dentofacial distances were obtained on cone-beam CT images and on the recorded facial and dental surfaces. The median (IQR) distances of more than 96% of the measurements did not differ significantly
Automatic cephalometric landmarks estimation in Cone Beam CT
Full text linkForensic medicine, craniofacial surgery and orthodontics make wide use of cephalometric analysis in identification, diagnosis and surgical planning. In order to measure linear distances, angular apertures and geometric features of the individual skull bones, an expert usually annotates by hand a set of cephalometric landmarks onto two-dimensional radiographic images or three-dimensional surface renderings of CT or Cone Beam CT volumes. Currently, the development of CBCT scanners has led the 3D cephalometric analysis to become a normal procedure, due to the improvement in the evaluation of three-dimensional morphology of subjects. Accuracy and repeatability of this manual approach are limited by intra-and inter-subject variability in landmark identification, even if an expert user takes care of the task. In order to improve the manual annotation, we propose a nearly-automatic method that gives the user an estimate of the positions of nine selected landmarks and a confidence region for each point, using as reference an accurate, manually annotated, single-subject CBCT volume. The method is based on intensity-based registration, on segmentation and on surface extraction of the CBCT target volumes. The confidence regions for each landmark have been preliminary estimated by testing the method on 21 CBCT volumes and by calculating Euclidean three-dimensional distances between the automatically annotated point and a standard manual cephalometric annotation done by an expert user. The obtained results are promising, annotation errors are acceptable for most points and the algorithm has good performances even in the presence of metal artifacts. Method improvements and a strong validation are currently in preparation
In-vitro quantification of the impact of artifacts on metal segmentation and image quality with varying CBCTs, materials and field of views
No full textObjective: To quantify the amount of metal artifact in CBCT images in varying CBCT devices, metal materials and FOVs.
Materials and Methods: Three phantoms made with acrylic resin and containing each one 3 metal cylinders of different materials (titanium, cupper-aluminum alloy and amalgam) were imaged scanned using 3 different CBCT devices and 2 FOVs, with a spatial resolution of 0.2 mm. DICOM images were exported for further image processing with MATLAB software.
After the segmentation of the metal cylinders and registration of the image volumes, the same ROI was defined for each pair images acquired with different FOV.
The difference between the segmented and the real volume of the metal cylinder was evaluated. Moreover, artifacts on the background were assessed by measuring the normalized standard deviation of voxel values in three different ROIs around the metal object. Results: Overestimation of the segmented volume was observed for all CBCTs devices and materials. Within the materials, amalgam and titanium generated, respectively, more and less artifacts in all images. Standard deviation values varied differently between the three ROIs in each device.
Conclusion: Different CBCT devices, materials and FOVs should be considered while evaluating CBCT images when metal objects are scanned. In particular, the segmentation of the metal object is highly influenced by the device and material factor. Regarding the background noise, the CBCT devices and the FOV size have more influence on the amount of artifact then the materials
A Quantitative Assessment of Lip Movements in Different Facial Expressions Through 3-Dimensional on 3-Dimensional Superimposition: A Cross-Sectional Study
No full textPurpose: The quantitative assessment of facial modifications from mimicry is of relevant interest for the rehabilitation of patients who can no longer produce facial expressions. This study investigated a novel application of 3-dimensional on 3-dimensional superimposition for facial mimicry.
Materials and Methods: This cross-sectional study was based on 10 men 30 to 40 years old who underwent stereophotogrammetry for neutral, happy, sad, and angry expressions. Registration of facial expressions on the neutral expression was performed. Root mean square (RMS) point-to-point distance in the labial area was calculated between each facial expression and the neutral one and was considered the main parameter for assessing facial modifications. In addition, effect size (Cohen d) was calculated to assess the effects of labial movements in relation to facial modifications.
Results: All participants were free from possible facial deformities, pathologies, or trauma that could affect facial mimicry. RMS values of facial areas differed significantly among facial expressions (P = .0004 by Friedman test). The widest modifications of the lips were observed in happy expressions (RMS, 4.06 mm; standard deviation [SD], 1.14 mm), with a statistically relevant difference compared with the sad (RMS, 1.42 mm; SD, 1.15 mm) and angry (RMS, 0.76 mm; SD, 0.45 mm) expressions. The effect size of labial versus total face movements was limited for happy and sad expressions and large for the angry expression.
Conclusion: This study found that a happy expression provides wider modifications of the lips than the other facial expressions and suggests a novel procedure for assessing regional changes from mimicry
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
VALIDATION OF AN AUTOMATIC HARD TISSUE SEGMENTATION ALGORITHM FOR CONE BEAM CT DATA
Full text linkAn automatic algorithm for hard tissue segmentation in CBCT data is presented and validated on 30 subjects. Bone segmentation threshold was set after voxel clustering through a sub-set of slices and the elimination of outliers with teeth and metal artifacts. Comparison with manual thresholding by experts gave no significant difference
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