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After the application of project-based learning (PBL) and 3D printing in classroom and teaching, the integrating methods and principles of PBL and 3D printing and recent teaching resources were summarized, PBL-based 3D modeling combined with recent innovative practice of 3D printing teaching model, with the course of Computer-aided medicine as an example, showed that the new teaching mode can effectively stimulate the interests of students, and cultivate their innovative thinking.
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PURPOSE: To explore whether there is matching relation between the length and the tilting angle of terminal implants in the All-on-Four protocol by studying the effects of different implant configurations on stress distributions of implant, bone, and framework. MATERIALS AND METHODS: Four implants were employed to support a full-arch fixed prosthesis and five three-dimensional finite element models were established with CT images, based on the length (S and L) and distal tilt angle (0degrees, 30degrees and 45degrees) of terminal implants for an edentulous mandible, which named: Tilt0-S, Tilt30-S, Tilt30-L, Tilt45-S and Tilt45-L. An oblique 240 N was loaded at second molar. The von Mises Stresses were analyzed. The implants were consecutively named #1 to #4 from the loading point. RESULTS: 1) Tilt0-S had the greatest stress on the implants, with the other groups exhibiting variable reductions; the four implants of Tilt45-L demonstrated the greatest reduction in stress. 2) Tilt0-S had the greatest stress at bone around #1 implant neck, and Tilt45-L exhibited the least stress, which was a 36.3% reduction compared to Tilt0-S. 3) The greatest stress in the framework was found on the cantilevers distal to #1 implant. Tilt45-S exhibited the least stress. CONCLUSION: Matching different length and tilting angle of the terminal implants led to variable stress reductions on implants, bone and the superstructure. By optimizing implant configuration, the reduction of stress on implants and surrounding bone could be maximized. Under the present condition, Tilt45-L was the preferred configuration. Further clinical testings are required.
Subject(s)
Finite Element Analysis , Mandible , Molar , Neck , Prostheses and ImplantsABSTRACT
<p><b>OBJECTIVE</b>To study the effect of implant number and inclination on stress distribution in implant and its surrounding bone with three-dimensional finite element analysis.</p><p><b>METHODS</b>A special denture was made for an edentulous mandible cast to collect three-dimensional finite element data. Three three-dimensional finite element models were established as follows. Model 1: 6 paralleled implants; model 2: 4 paralleled implants; model 3: 4 implants, the two anterior implants were parallel, the two distal implants were tilted 30° distally.</p><p><b>RESULTS</b>Among the three models, the maximum stress values found in anterior implants, posterior implants, and peri-implant bone were modle 3<modle 1<modle 2 in turn. The effect of implant numbers on stress distribution was as follow: the maximum stress value of the anterior and posterior implant, and the peri-implant bone of model 2 were 126.8, 267.4, and 40.0 MPa, which was 35.8%, 3.8% and 7.8% higher than those in model 1 (93.4, 257.7, 37.1 MPa) respectively. The impact of implant inclination on stress distribution was as follow: when the distal implant titled 30° in model 3, the maximum stress value of the anterior and posterior implant, and the peri-implant bone were 82.0, 239.5 and 28.7 MPa, which was 35.4%, 10.5% and 28.2% lower than those in model 2 respectively.</p><p><b>CONCLUSIONS</b>Within the limitation of this study, when implants are placed parallel, the maximum stress of the distal implant can be reduced by increasing the number of implant.When the number of implant was decreased from six to four, the maximum stress around the implant can be reduced by tilting the distal implant. This design will provide a better prostheses effect than the design with six implants does.</p>
Subject(s)
Dental Implants , Dental Prosthesis Design , Dental Prosthesis, Implant-Supported , Dental Stress Analysis , Finite Element Analysis , Mandible , Prostheses and Implants , Prosthesis ImplantationABSTRACT
BACKGROUND:Studies on tibial plateau fractures had gradualy focused on “360° stereochemical structure” from medial and lateral “double track structure” nowadays. Scholars pay great attention on the stability and reposition of posterior plateau and functional recovery after reduction. The choice of fixation material of posterior plateau was controversial. OBJECTIVE:To discuss the biomechanical characteristics of posterolateral fracture of tibial plateau using three types of internal fixation. METHODS:Using three-dimensional finite element analysis, we simulated 1/2 and 1/4 posterolateral tibial plateau fractures. Three types of internal fixation were used: two anterior 6.5 mm lag screws, lateral 4.5 mm L-shape plate, and posterior 3.5 mm T-shape plate. 500 N was loaded at the center of the tibial plateau verticaly, and biomechanical status of three types of fixation was compared. RESULTS AND CONCLUSION: In 1/2 fracture model, anterior lag screw group and posterior plate group gained least displacement in al directions, as lateral plate group gained more. In 1/4 model, the advantage in displacement of anterior lag screw group was more apparent, the second was posterior plate group, and the last was lateral plate group. In 1/2 fracture model, the maximum stress of anterior lag screw was 36.523 MPa, which of lateral plate group was 153.372 MPa and posterior plate group was 115.922 MPa. The maximum stress left in the separate bone of lag screw group was 4.309 MPa, which of lateral plate group was 4.37 MPa and posterior plate group was 3.124 MPa. In 1/4 fracture model, the maximum stress of anterior lag screw was 36.803 MPa, which of lateral plate group was 153.336 MPa and posterior plate group was 104.234 MPa. The maximum stress left in the separate bone of lag screw group was 1.195 MPa, which of lateral plate group was 0.827 MPa and posterior plate group was 1.196 MPa. Results indicated that anterior lag screw could bear more stress and gained least displacement after loading, and the fixation was more stable. Posterior plate can give more stabilization when the separate bone was bigger (1/2), similar to anterior lag screw. When the separate bone was smaler (1/4), posterior plate model was less stable than anterior lag screw. Lateral plate model, with poor stabilization, was the worst choice in three types of fixation.
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BACKGROUND:Repair programs of posterolateral tibial plateau fracture included posterior plate screws, lateral plate screw and anterior and posterior lag screw fixation. To choose which fixation methods depends on clinical experiences of physicians. Study results are mainly clinical reports, and lack of mechanical evidence. OBJECTIVE:To compare biomechanical changes in three fixed manners (lateral plate screw group, posterior plate screw group and anterior and posterior lag screw group) in the repair of posterolateral fracture of tibial plateau from the angle of biomechanics. METHODS:A total of tibial specimens of six adult male antisepsis corpses (12 samples) were used for measuring bone mineral density of metaphysis. 1/2 posterolateral tibial plateau fracture model was established by electric pendulum saw. The model was randomly divided into three groups:lateral plate screw group, posterior plate screw group and anterior and posterior lag screw group. Finite element method and biomechanics were used to test axial displacement value and the maximal displacement distribution area under the axial loads of 250, 500, and 1 000 N. RESULTS AND CONCLUSION:There was no significant difference in average bone density in three groups of metaphysis (P>0.05). The minimum axial displacement of the fracture fragments was in the anterior and posterior lag screw group (0.013 521 mm), fol owed by posterior plate screw group (0.016 991 mm), and the maximum was visible in the lateral plate screw group (0.138 200 mm) under 250 N load. Displacement value was similar to the 250 N under 500 and 1 000 N. According to the results of biomechanics, displacement values of anterior and posterior lag screw was obviously less than the lateral plate screw group and posterior plate screw group (P0.05). The maximal displacement distribution area was proximal tibiofibular joint border zone in two methods. These data indicated that the biomechanical stability was most advantageous in the anterior and posterior lag screw group, and poorest in the lateral plate screw group. In the clinic, anterior and posterior lag screw fixation can be used as a first choice for repair of posterolateral tibial plateau fracture.