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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: Reverse engineering modeling has been widely used in previous studies. However, there are a few studies on implantation modeling, especially in aspects of mandibular molar implantation. The mandibular molar has high miss rate in dentition. Thus, to establish three-dimensional finite element models of a jaw bones with mandibular molar implant denture using reverse engineering shows a great parameter value for research of mandibular molar implantation repair. OBJECTIVE: To establish a three-dimensional finite element model of a mandibular molar with dental implant inserted in mandibular molar area using reverse engineering, and to provide mathematical model basis for biomechanics researches of stomatology.METHODS: Establish three-dimensional model, divide mesh and calculate by Solidworks 2007 through scanning mandible by screw jaw using helix CT, obtaining data from images, separating data, rebuilding three-dimension using Mimics software,optimizing the design of mesh by Magics software, and dealing with solid model by Pro/E preprocessor.RESULTS AND CONCLUSION: A three-dimensional finite element model of mandibular first molar implant with regular depth was established, which has high geometrical similarity, good properties of mechanics and mesh, and can be easily modified. This can provide excellent model support for studying the stress analysis of different designs on restoring mandibular first molar implant.
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@#Objective To evaluate the accuracy of Intraoperative Iso-C3D navigation guiding cervical pedicle screw fixation. Methods Twenty-two cases adopted cervical pedicle screw fixation of cervical spine, including 9 cervical spine fractures, 4 cervical tumors, 6 cervical destabilizing, 3 cervical syndrome. The cervical pedicle screw position were assessed with post-operative CT by grade. Results One hundred and twelve screws were fixed in 22 cases successfully. Grade: 107 in A grade (95.5%); 3 in B grade: 1 in C grade; 1 in D grade. There were not any complication. Conclusion Intraoperative Iso-C3D navigation can improve precision of cervical petiole screw fixation distinctively.
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Mandibular molar loss, which is in a high ratio, is found accompanying with alveolar bone resorption frequently while being restored in clinic. Therefore, due to the existence of mandibular neural canal, the success ratio of implant denture in this area can be directly affected by the height reduction of alveolar bone. In clinic, there are some achievements obtained to improve the survival rate of implant denture, such as increasing the implant support area, enhancing alveolar bone height through surgery, optimizing the design of the superior part of implant. This article summarizes the research progress on the mandibular molar implant denture with alveolar bone absorbed and aims to search a selective design of mandibular molar implant denture under the high absorption of alveolar bone.
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Objective:To determine the shear bond strength and analyze the bonding mechanism of home-made and imported nickel-based alloys to resin-veneers.Methods: Home-made and imported alloy disks were cast by lost-wax technique and embedded in acrylic resin fabricating cylinders.Sixteen specimens of each alloy were divided into 2 subgroups: thermocycling group and non-thermocycling group.Specimens in thermocycling groups were submitted to thermocycling(300 cycles) and those in non-thermocycling groups were just stored in water at 37?C for 24 h(0 cycles).Then the shear bond strength values were determined by universal testing machine.The highest shear bond strength values were recorded and metallurgical analysis was performed on the interface between alloys and resin-veneers.Results: The shear bond strength values of both alloys to resin-veneers were relatively high either before or after thermocycling.The shear bond strength values of home-made alloy+thermocycling group,imported alloy+thermocycling group,home-made alloy+non-thermocycling group and imported alloy + non-thermocycling group were(10.50?2.72),(13.12?2.82),(15.51?3.04) and(18.44?3.15) MPa,respectively.The bond strength was significantly different before and after thermocycling for both alloys(P
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Objective:To observe the consistence of the color and optical parameters of metal-ceramic, all-ceramic and composite resin with Vita Classical shade guides. Methods:Specimens of VITA VMK95 metal-ceramic, In-Ceram all-ceramic and Artglass composite resin according to the same area with Vita Classical shade guide were made respectively. ?E_ ab ,L,a,b between specimens and shade guide were calculated. Results:The mean ?E between shade guide and all-ceramic or composite resin was less than 3 NBS. The mean ?E between shade guide and metal-ceramic material was 13.78 NBS, the significant difference could be identified by visual determination (P
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Objective:To compare the root filling results of 2 thermoplasticized gutta-percha filling techniques(Ultrafil 3D and ObturaⅡ) with cold lateral condensation of gutta-percha.Methods: Sixty freshly extracted maxillary mandibular single-rooted teeth were instrumented and randomly divided into 3 groups: Ultrafil 3D,ObturaⅡ and cold lateral condensation groups.The root canal was routinely prepared and the obturation time was recorded.Three days later,10 teeth of each group were randomly stained and the micro effusion length was subsequently measured.The micro-chink between filling materials and the wall of root canal were measured with scanning electron microscope in the other 10 teeth of each group.The data were analyzed using unpaired Student's t-test.Results: The longest obturation time was in cold lateral condensation group,then ObturaⅡ and Ultrafil 3D group in order,with significant difference found between the cold lateral condensation group and the latter 2 groups((P