3-dimensional finite element analysis on stress distribution in maxillary with All-on-4 implants in different arch forms / 吉林大学学报(医学版)

Objective To explore the effect of different arch forms of maxillary models on stress distribution of peri-implant of All-on-4 implants with 3-dimensional finite element, and to provide evidence for the improvement of implant achievement ratio in clinic. Methods 3-dimensional finite element analysis models of Tapered,Square and Ovoid arch form maxillary based on the MBTTM Arch Form Templates were constructed by using Solidworks software.The cortical bone thickness was defined as 2 mm at all points.The implants with 13 mm in length were inserted between the mental foramina.The 2 posterior implants were set at 4 inclination angle,from 0°to 45°.All implants were splinted with superstructure.A 100 N pressure was applied to 2 kinds of loading positions on the superstructure models. The maximum Von-Mises stress on cortical bone around the implants was measured by using Abaqus software.Results The maximum Von-Mises value in maxillary cortical bone with All-on-4 implants in 3 arch forms showed significant differences. In Square model the concentration of stress was advanced with the increasing of implant inclination angle;In Ovoid model, the maximum Von-Mises value was observed at 1 5°in posterior region,and was increased significantly by pasted 15°in anterior region;In Tapered model,the Maximum Von-Mises value was increased greatly at 45°. Conclusion Arch forms have appreciable impact on stress distribution of peri-implant.In Square arch form,the inclination of implant should be avoided;in Ovoid arch form, the inclination angle should be under 15°;in Tapered arch form,the inclination should be under 30°.

Finite element analysis on the connection types of abutment and fixture / 대한치과보철학회지

PURPOSE: This study was performed to compare the stress distribution pattern of abutment-fixture connection area using 3-dimensional finite element model analysis when 5 different implant systems which have internal connection. MATERIALS AND METHODS: For the analysis, a finite element model of implant was designed to locate at first molar area. Stress distribution was observed when vertical load of 200 N was applied at several points on the occlusal surfaces of the implants, including center, points 1.5 mm, 3.0 mm away from center and oblique load of 200 N was applied 30degrees inclined to the implant axis. The finite element model was analyzed by using of 3G. Author (PlassoTech, California, USA). RESULTS: The DAS tech implant (internal step with no taper) showed more favorable stress distribution than other internally connected implants. AS compare to the situations when the loading was applied within the boundary of implants and an oblique loading was applied, it showed higher equivalent stress and equivalent elastic strain when the loading was applied beyond the boundary of implants. Regardless of loading condition, the abutments showed higher equivalent stress and equivalent elastic strain than the fixtures. CONCLUSION: When the occlusal contact is afforded, the distribution of stress varies depending on the design of connection area and the location of loading. More favorable stress distribution is expected when the contact load was applied within the diameter of fixtures and the DAS tech implant (internal step with no tapering) has more benefits than the other design of internally connected implants.

3-D Finite element stress analysis in screw-type, cement-type, and combined-type implant fixed partial denture designs / 대한치과보철학회지

STATEMENT OF PROBLEMS: Stress analysis on implant components of the combined screw- and cement-retained implant prosthesis has not investigated yet. PURPOSE: The purpose of this study was to assess the load distribution characteristics of implant prostheses with the different prosthodontic retention types, such as cement-type, screw-type and combined type by using 3-dimensional finite element analysis. MATERIAL AND METHODS: A 3-dimensional finite element model was created in which two SS II implants (Osstem Co. Ltd.) were placed in the areas of the first premolar and the first molar in the mandible , and three-unit fixed partial dentures with four different retention types were fabricated on the two SS II implants. Model 1 was a cement-retained implant restoration made on two cement-retained type abutments (Comocta abutment; Osstem Co. Ltd.), and Model 2 was a screw-retained implant restoration made on the screw-retained type abutments (Octa abutment; Osstem Co. Ltd.). Model 3 was a combined type implant restoration made on the cement-retained type abutment (Comocta abutment) for the first molar and the screw-retained type abutment (Octa abutment) for the first premolar. Lastly, Model 4 was a combined type implant restoration made on the screw-retained type abutment (Octa abutment) for the first molar and the cement-retained type abutment (Comocta abutment) for the first premolar. Average masticatory force was applied on the central fossa in a vertical direction, and on the buccal cusp in a vertical and oblique direction for each model. Von-Mises stress patterns on alveolar bone, implant body, abutment, abutment screw, and prosthetic screw around implant prostheses were evaluated through 3-dimensional finite element analysis. RESULTS: Model 2 showed the lowest von Mises stress. In all models, the von Mises stress distribution of cortical bone, cancellous bone and implant body showed the similar pattern. Regardless of loading conditions and type of abutment system, the stress of bone was concentrated on the cortical bone. The von-Mises stress on abutment, abutment screw, and prosthetic screw showed the lower values for the screw-retained type abutment than for the cement-retained type abutment regardless of the model type. There was little reciprocal effect of the abutment system between the molar and the premolar position. For all models, buccal cusp oblique loading caused the largest stress, followed by buccal cusp vertical loading and center vertical loading. CONCLUSION: Within the limitation of the FEA study, the combined type implant prosthesis did not demonstrate more stress around implant components than the cement type implant prosthesis. Under the assumption of ideal passive fit, the screw-type implant prosthesis showed the least stress around implant components.

Influence of implant-abutment interface design, implant diameter and prosthetic table width on strength of implant-abutment interface: three-dimensional finite element analysis / 대한치과보철학회지

STATEMENT OF PROBLEM: Higher incidence of prosthetic complications such as screw loosening, screw fracture has been reported for posterior single tooth implant. So, there is ongoing research regarding stability of implant-abutment interface. One of those research is increasing the implant diameter and prosthetic table width to improve joint stability. In another part of this research, internal conical type implant-abutment interface was developed and reported joint strength is higher than traditional external hex interface. Purpose. The purpose of this study is to compare stress distribution in single molar implant between external hex butt joint implant and internal conical joint implant when increasing the implant diameter and prosthetic table width : 4mm diameter, 5mm diameter, 5mm diameter/6mm prosthetic table width. MATERIAL AND METHOD: Non-linear finite element models were created and the 3-dimensional finite element analysis was performed to see the distribution of stress when 300N static loading was applied to model at 0., 15., 30.off-axis angle. RESULTS: The following results were obtained: 1. Internal conical joint showed lower tensile stress value than that of external hex butt joint. 2. When off-axis loading was applied, internal conical joint showed more effective stress distribution than external hex butt joint. 3. External hex butt joint showed lower tensile stress value when the implant diameter was increased. 4. Internal conical joint showed lower tensile stress value than external hex butt joint when the implant diameter was increased. 5. Both of these joint mechanism showed lower tensile stress value when the prosthetic table width was increased. CONCLUSION: Internal conical joint showed more effective stress distribution than external hex joint. Increasing implant diameter showed more effective stress distribution than increasing prosthetic table width.

THREE-DIMENSIONAL FINI6E ELEMENT ANALYSIS OF THE ENDOSSEOUS IMPLANT DESIGNS / 대한치과보철학회지

The stress distribution generated in the surrounding bone was calculated and compared for various geometry of the dental implants by means of the finite element methods. The models were designed to represent the screw type endosseous implants (varing the size, shape, direction of the screw thread and the angle of the body) with supporting bone and the cylinder type endosseous implants (varing the lower portion-Round type, tapered type) with supporting bone. Static mean bite forces were applied 100N vertically and 25N horizontally on the center of the implant and three dimensional finite analysis was undertaken using software ANSYS 5.1 Version. The result demonstrated that different implant shape leads to significant variations in stress distribution in the bone. In the case of variation of the screw size, direction and shape the implant model with normally directional and triangular screw implied lower stress than with upper directional or lower directional and quadrangular screw but among models a different screw size, within a variation of 0.2mm there was no meaningful difference in maximum stress. In the case of variation of angle of body the straight implied lower stress than the tapered. As a result of analysis of cylinder type, the implants with larger radius of curvature of the round form and larger diameter of the tapered form implied lower stress.