ABSTRACT
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
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.
ABSTRACT
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