Three-dimensional Superimposition Research Articles

Change in condylar position in posterior bending osteotomy minimizing condylar torque in BSSRO for facial asymmetry

During the correction of an asymmetric mandible with sagittal split ramus osteotomy (SSRO), bony interference between the proximal and distal segments inevitably occurs. This results in positional change of the condyle. In order to avoid this, a posterior bending osteotomy (PBO) has been introduced. This is an additional vertical osteotomy posterior to the second molar after SSRO. To investigate the change in condylar position after SSRO with PBO, 22 patients with facial asymmetry were enrolled and divided into two groups based on the surgical method used to remove the bony interference after SSRO: PBO (n = 13) and the grinding method (n = 9). Each group was subdivided into large and small bony interference groups by estimating the volume of bony interference with simulation surgery. Condylar displacement was evaluated by three-dimensional superimposition and the amount of condylar displacement was calculated. The positional changes of the condyles were variable in each patient. When comparing patients with large bony interference in the PBO and grinding groups, the condyles were significantly inwardly rotated in the grinding group (p < 0.05). The grinding method can be used to remove small bony interferences with tolerable condylar torque. However, PBO would be beneficial in correcting large bony interferences while minimizing condylar torque.

Three-dimensional analysis of the change in the curvature of the smiling line following orthodontic treatment in incisor class II division 1 malocclusion

To investigate the different effects of changes in the occlusal plane, incisors inclination, and maxillary intercanine width on the curvature of the smiling line. Records of 46 subjects (28 females and 18 males, mean age 16.6 ± 4.2 years) with incisor class II division 1 malocclusions were selected. All subjects had four premolar extractions and were treated with preadjusted edgewise appliances. Pre- and post-treatment maxillary dental digital models were virtually aligned via corresponding landmarks to the respective lateral cephalograms. Subsequent two-dimensional superimposition of the aligned cephalograms facilitated the three-dimensional superimposition of the pre- and post-treatment models. This process allowed the quantification of the curvature from a frontal perspective of the models. The change in curvature was then correlated with changes in the cephalometric inclination of the anterior occlusal plane (AOP), functional occlusal plane (FOP), maxillary central incisor (U1), and the intercanine width. Orthodontic correction in this sample resulted in the clockwise rotation of the anterior occlusal plane (5.84 degrees), reduction in proclination of the incisors (-14.39 degrees), increase in intercanine width (2.48mm), and a corresponding increase in the curvature of the smiling line (6.83 degrees). The change in curvature of the smiling line in these subjects was found to be related more significantly to the magnitude of difference in the inclination between the pre-treatment AOP and FOP than to the change in the inclination of the maxillary incisors. With orthodontic treatment, the smiling line can be correlated with cephalometric data to improve or maintain the curvature.

MARS: Computing Three-Dimensional Alignments for Multiple Ligands Using Pairwise Similarities

The three-dimensional (3D) superimposition of molecules of one biological target reflecting their relative bioactive orientation is key for several ligand-based drug design studies (e.g., QSAR studies, pharmacophore modeling). However, with the lack of sufficient ligand-protein complex structures, an experimental alignment is difficult or often impossible to obtain. Several computational 3D alignment tools have been developed by academic or commercial groups to address this challenge. Here, we present a new approach, MARS (Multiple Alignments by ROCS-based Similarity), that is based on the pairwise alignment of all molecules within the data set using the tool ROCS (Rapid Overlay of Chemical Structures). Each pairwise alignment is scored, and the results are captured in a score matrix. The ideal superimposition of the compounds in the set is then identified by the analysis of the score matrix building stepwise a superimposition of all molecules. The algorithm exploits similarities among all molecules in the data set to compute an optimal 3D alignment. This alignment tool presented here can be used for several applications, including pharmacophore model generation, 3D QSAR modeling, 3D clustering, identification of structural outliers, and addition of compounds to an already existing alignment. Case studies are shown, validating the 3D alignments for six different data sets.

Affidabilità delle sovrapposizioni trimensionali nel trattamento distalizzante dei molari superiori

ObjectivesThe aim of the study was to establish an easy method to obtain three-dimensional superimposition of Cone Beam tomographies on stable anatomical landmarks in growing patients. Materials and methodsTwo patients in Class II molar relationship were selected and subjected to the tomographic exam before and immediately after the distalization of the first upper molars with two different appliances: the Hilgers’ Pendulum and the MGBM System. The results were compared with bidimensional superimposition, done with two methods: the “Best Fit” and the structural method by Bjork. The exam consists in a Cone Beam tomography at low radiation dose with the ILUMATM tomography machine, set at 0.3mm3 voxel dimension. The realization process was divided in three steps. The first is the image orientation, in order to orient each volume at the same position. The second step is the volume segmentation, to reconstruct the three-dimensional images of every anatomical structure that will be superimposed. The last process is the localization of the same landmarks on the two volumes. ResultsThe result obtained by the superimposition method proposed may be considered acceptable since the variation between the two volumes corresponds to the dental and skeletal changes induced by treatment with the appliances used. Further confirmation comes from the comparison with the two-dimensional superimposition. The final result is not completed because it cannot be used to quantify the extent of growth or displacement induced by treatment. The comparison with the two-dimensional superimposition has also highlighted the limitations of the conventional teleradiography and the great advantage of the CBCT. The teleradiography has some basical errors that do not permit an accurate and unique landmarks localitazion. CBCT, instead, allow to evaluate every anatomical structure at 360° with no images superimposition and no magnification, the sagittal and vertical variations in the two different patient's sides, the condilar position and the dental root position in the alveolar bone. ConclusionsThe progress is trying to convert all the diagnostic tools in three-dimensions and this method can be a starting point to create a system accessible to all the orthodontists.

Tip and torque changes in maxillary buccal segment after orthodontic treatment: a three-dimensional study

To investigate three-dimensional imaging registration and superimposition techniques in measuring the tip and torque change of upper canine, premolar and first molar after orthodontic treatment. Twenty-eight subjects (14 extraction cases and 14 non-extraction cases) with full records were randomly selected from the Department of Orthodontics, Peking University School and Hospital of Stomatology. The pre-and post-treatment upper dental casts were digitized with three-dimensional spot laser scanner and superimposed with reverse engineering software. The facial axis of the clinical crown (FACC) was transferred from post-treatment teeth to the pre-treatment teeth using three-dimensional imaging registration. The occlusal plane was constructed on the post-treatment upper digital cast and the tip and torque values were measured. In the non-extraction group, the tip of the second premolar decreased by 1.5° (P < 0.05). The buccal crown torque of the first and second premolars increased by 5.1° and 4.2° (P < 0.05), respectively. In the extraction group, the lingual crown torque of upper canine increased by 3.8° (P < 0.05). Non-extraction orthodontic treatment tended to tip the upper second premolar distally and increased the buccal crown torque of the upper premolars while extraction treatment increased the lingual crown torque of the upper canine.

A Novel Method for the Assessment of Three-Dimensional Tooth Movement during Orthodontic Treatment

To (1) evaluate the stability of palatal rugae as landmarks for superimposition of dental casts and (2) establish a three-dimensional superimposition method of maxillary dental casts for analyzing orthodontic tooth movement. The sample consisted of dental casts obtained from 10 patients treated with extraction of bilateral maxillary first premolars and placement of three palatal miniscrews as anchorage for retraction of the anterior teeth. Dental casts were measured by means of laser surface scanning system, and three-dimensional images were reconstructed. Serial dental casts were superimposed on the three miniscrews as registration landmarks (miniscrew-superimposition method), and the displacement of each palatal ruga point during the closure of extraction spaces was measured. Displacement of the central incisors was measured by the miniscrew-superimposition method and the proposed superimposition technique (ruga-palate-superimposition method). Correlation analysis and paired t-tests were performed to determine whether a significant difference existed between the measurements of the two superimposition methods. The medial points of the third palatal rugae and the shape of the palatal vault were stable throughout the treatment. The displacement of the central incisors measured using the ruga-palate-superimposition method showed no significant difference with that measured using the miniscrew-superimposition method. The maxillary dental casts can be reliably superimposed on the medial points of the third palatal rugae and the palatal vault as reference landmarks.

Large‐Scale Vector Modes and the First CMB Temperature Multipoles

Recent observations have pointed out various anomalies in some multipoles (small l ) of the cosmic microwave background (CMB). In this paper, it is proved that some of these anomalies could be explained in the framework of modified concordance model, in which there is an appropriate distribution of vector perturbations with very large spatial scales. Vector modes are associated with divergenceless (vortical) velocity fields. Here, the generation of these modes is not studied in detail (it can be done a posteriori); on the contrary, we directly look for the distributions of these vector modes which lead to both alignments of the second and third multipoles and planar octopole. A general three-dimensional (3D) superimposition of vector perturbations does not produce any alignment, but we have found rather general 2D superimpositions leading to anomalies similar to the observed ones; in these 2D cases, the angular velocity has the same direction at any point of an extended region, and moreover, this velocity has the same distribution in all the planes orthogonal to it. Differential rotations can be seen as particular cases, in which the angular velocity only depends on the distance to rotation axis. Our results strongly suggest that appropriate mixtures of scalar and vector modes with very large spatial scales could explain the observed CMB anomalies.

An Analysis of Core Deformations in Protein Superfamilies

An analysis is presented on how structural cores modify their shape across homologous proteins, and whether or not a relationship exists between these structural changes and the vibrational normal modes that proteins experience as a result of the topological constraints imposed by the fold. A set of 35 representative, well-populated protein families is studied. The evolutionary directions of deformation are obtained by using multiple structural alignments to superimpose the structures and extract a conserved core, together with principal components analysis to extract the main deformation modes from the three-dimensional superimposition. In parallel, a low-resolution normal mode analysis technique is employed to study the properties of the mechanical core plasticity of these same families. We show that the evolutionary deformations span a low dimensional space of 4–5 dimensions on average. A statistically significant correspondence exists between these principal deformations and the ∼20 slowest vibrational modes accessible to a particular topology. We conclude that, to a significant extent, the structural response of a protein topology to sequence changes takes place by means of collective deformations along combinations of a small number of low-frequency modes. The findings have implications in structure prediction by homology modeling.

Scattering of Radiation on Rough Surface Modelled by Three-Dimensional Superimposition Technique.

This work is one of the fundamental steps in the study of thermal radiation characteristics of metallic materials in actual industrial or natural environments. A new algorithm is presented for modelling the microstructure of a rough surface. A superimposition technique is introduced to realize the concept of three-dimensional continuous self-similar microgeometry. Scattering of radiation on the surface is described on the basis of an electromagnetic theory of diffraction. The proposed method is examined by means of a numerical calculation and a bidirectional reflectance measurement.

Scattering of Radiation at a Rough Surface Modelled by a Three-Dimensional Super-Imposition Technique.

Scattering of Radiation at a Rough Surface Modelled by a Three-Dimensional Super-Imposition Technique.