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| Dincer Bozkaya (MS, June 2003), e-mail: bozkaya@coe.neu.edu |
| Click here for a powerpoint presentation of the research about the mechanics of dental implants.
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| Stress Distribution Characteristics of Various Implant Systems
due to Non-Central Occlusal Loads (PDF)
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Bozkaya, Dinçer+; Müftü, Sinan+; Müftü, Ali*: +Northeastern University, Department of Mechanical, Engineering, 334 SN, MA 02115; * Tufts, University, School of Dental Medicine, Boston, MA, 02111 |
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Long-term stability of the dental implants strongly depends on the stress distribution characteristics of the implant-bone interface. The occlusal and masticatory loads acting on the prosthesis are transferred to the implant by means of abutment and result in non-uniform stress distribution in the bone. In order to maintain a healthy bone, stresses should be in the range of 1.4-5 MPa. Stresses outside this range have been reported to cause resorption of the bone tissue1. In this study, the stress distribution characteristics of five different implants from Bicon, Ankylos, Astra, ITI and Nobel Biocare subjected to an occlusal load located off the central axis are investigated. The dimensions of the implants were comparable in size; however the thread profiles were considerably different from each other.
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The 2-D axisymmetric finite element models were loaded by 100 N vertical, 20 N lateral forces and 100 N.mm moment, separately and then the results are superposed to combine the effect of these loads to obtain the stress distribution due to a 102 N occlusal load 1 mm offset to the symmetry axis. The Youngs modulus of the bone was varied between 1 GPa (soft trabecular bone) and 16 GPa (hard cortical bone) in order to be able to investigate the success of the implants in different bone densities.
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The Bicon and Ankylos implant systems seem to distribute the stresses more evenly when compared to Astra, ITI and Nobel Biocare implants in all bone densities. High localized stresses were found at the tip of the Astra, ITI and Nobel Biocare implants that can lead to crestal bone loss, however stresses generated at the other sites of implant-bone interface were low enough to prevent bone resorption.
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1. Rieger M. R, Mayberry M, Brose M. O. Finite element analysis of six endosseous implants. J Prosthet Dent. 1990;63:671-6
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This work was supported by Bicon Dental Implants, Boston, MA.
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| Mechanics of Tapered Interference Fit in Dental Implants (PDF)
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Bozkaya, Dinçer; Müftü, Sinan, Northeastern University, Department of Mechanical, Engineering, 334 SN, MA 02115 |
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In evaluation of the long-term success of a dental implant, the reliability and the stability of the implant-abutment interface plays a great role. Tapered interference fits provide a reliable connection method between the abutment and the implant. In this work, the mechanics of the tapered interference fits was analyzed using a closed-form formula and the finite element (FE) method. An analytical solution, which is used to predict the contact pressure in a straight interference, was modified to predict the contact pressure in the tapered implant-abutment interface. An elastic-plastic finite element model was used to simulate the material non-linearity of the implant and abutment material. The validity and the applicability of the analytical solution were investigated by comparisons with the FE model for a range of problem parameters. It was shown that the analytical solution could be used to determine the pull-out force and loosening-torque with 5-10% accuracy. Detailed analysis of the stress distribution due to tapered interference fit, in a commercially available, abutment-implant system was carried out. This analysis shows that plastic deformation in the implant limits the increase in the pull-out force that would have been otherwise predicted by higher interference values.
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Keywords: Dental implants; Taper lock; Morse taper; Conical interference fit; Tapered interference fit; Connection mechanism; Pull-out force; Loosening torque
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