Numerical and experimental study on steady flow in the model of internal carotid artery siphon / 医用生物力学

Objective To investigate the hemodynamic factors in internal carotid arteries (ICA) with different shapes, and analyze the relationship between the arterial geometry and atherosclerotic stenosis to provide the hemodyanmic basis for the risk prediction and early diagnosis of ICA stenosis. Methods The flow field in the most two common types of ICAs, U and V-shaped ICA, were investigated by numerical simulation and particle image velocimetry (PIV) experiment under the condition of steady flow. Results At the upstream bend of ICA, the hemodynamic factors were monotonically associated with the curvature of the bend. As a result, the risk for stenosis here was smaller in the V-shaped ICA, as compared to U-shaped ICA. But at the downstream bend, such monotonic relationship didn’t exist due to the synergistic effect of the two bends. ConclusionsThe curvature of the artery is positively related to the risk for stenosis, but the synergistic effect of bends needs to be considered for studying arteries with the serial bends. The research on the synergistic effect may explain why the stenosis is frequently observed in arteries with multiple bends.

Finite Element analysis on space closure of central incisors using invisible appliance with different material hardness / 医用生物力学

Objective To analyze the mechanical effect of invisible appliances with different material hardness and provide theoretical basis for selecting the suitable material for invisible appliance and its clinical application. Methods Three different three-dimensional (3D) finite element models of invisible appliance were established, of which the elastic modulus was chosen as 415.6, 816.308 and 2 400 MPa, respectively. In these models, the upper central incisors were all designed to move 0.3 mm mesially. Then 3D nonlinear finite element method was used to analyze the stress-distribution in invisible appliance, teeth and periodontal ligament and the instant displacement of every tooth. The comparative study was made among three invisible appliances with different hardness． Results Under experimental condition, the most instant stress and displacement of teeth was the upper central incisor, with initial displacement greater in crown section than that in apical section and the greatest displacement was 0.17 mm. The tendency of central incisor movement was tipping in all situations. The movement of lateral incisor had the second greatest distance (the greatest displacement was 0.10 mm) and the tendency of its movement was in the opposite directions of aimed teeth. When elastic modulus of material decreased, the stress on the invisible appliance increased. The stress in periodontal ligament and the displacement of aimed teeth were also increased. Conclusions If the hardness of invisible appliance increases, the displacement of the designed tooth and treatment efficacy increases, but the appliance with more hardness couldn’t provide better ability in controlling of orthodontic tooth movement. The study suggested clinicians should use attachments or cooperate with fixed appliance to help move teeth bodily.

A computer aided design approach of all-ceramics abutment for maxilla central incisor / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To establish the computer aided design (CAD) software platform of individualized abutment for the maxilla central incisor.</p><p><b>METHODS</b>Three-dimentional data of the incisor was collected by scanning and geometric transformation. Data mainly included the occlusal part of the healing abutment, the location carinae of the bedpiece, the occlusal 1/3 part of the artificial gingiva's inner surface, and so on. The all-ceramic crown designed in advanced was "virtual cutback" to get the original data of the abutment's supragingival part. The abutment's in-gum part was designed to simulate the individual natural tooth root. The functions such as "data offset", "bi-rail sweep surface" and "loft surface" were used in the process of CAD.</p><p><b>RESULTS</b>The CAD route of the individualized all-ceramic abutment was set up. The functions and application methods were decided and the complete CAD process was realized.</p><p><b>CONCLUSIONS</b>The software platform was basically set up according to the requests of the dental clinic.</p>

Research and development of computer aided design and rapid prototyping technology for complete denture / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To explore a computer aided design (CAD) and rapid prototyping (RP) approach for fabrication of complete denture and to develop relevant programs for implementing it.</p><p><b>METHODS</b>Automatic crossing section scanner was used to scan artificial teeth and 3D graphic database of artificial teeth that could be aligned with parameters was established. A 3D laser scanner was used to scan upper and lower edentulous jaw casts and rims made in clinic. The vertical and horizontal relations were recorded before scanning with a patient instrument. Based on Imageware 11, tooth-arrangement curves, coordinate system, and landmark points for positioning were created, and construction cure and shape-controlling curve for base plate were constructed as well. Three-dimensional integrated design of complete denture, including artificial tooth automatic arrangement, aesthetic and individualized design of base plate, and artificial gingival, were finished. The programs were developed following the approach and the CAD platform was established. The virtual molds of complete dentures were constructed according to the above data in design and RP technology was used to make the plaster molds. Finally, the teeth were inserted and the complete denture was finished by dental technician.</p><p><b>RESULTS</b>The approach for the complete denture CAD/RP was confirmed and the CAD software platform was developed. A complete denture was manufactured.</p><p><b>CONCLUSIONS</b>The rules for complete denture in textbooks were expressed in design process with the CAD program developed by researcher. The 3D data of rims were utilized in design so that the digital, intelligentized and individualized design and manufacture process for complete denture was implemented.</p>

The inlay computer aided design based on reverse engineering technology / 中华口腔医学杂志

<p><b>OBJECTIVE</b>This study was to explore a CAD method for constructing occlusal and proximal surfaces of inlays using reverse engineering (RE) software and to develop a CAD software for the inlay fabrication.</p><p><b>METHODS</b>The dentition model of a volunteer with individual normal occlusion was scanned with a 3D mechanical scanner. The scanned objects were prepared teeth with G. V. Black class I, class II and class VI (MOD) cavities, neighbor teeth, intercuspal position (ICP) record, and functional bite record (or functional generate path, FGP). Inlays were constructed based on RE technology using the database of Chinese normal teeth.</p><p><b>RESULTS</b>The technique guideline of inlay CAD was developed based on RE softwares. Inlays designed with CAD technique showed smooth and continuous contours. The occlusal and proximal contacts of inlay met physiologic demands.</p><p><b>CONCLUSIONS</b>It is a feasible method to develop a CAD software for inlay fabrication based on RE software.</p>