Mechanics of the tapered interference fit in dental implants

Abstract

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.

Mechanics of the taper integrated screwed-in (TIS) abutments used in dental implants

“…The mechanics of the attachment method using the retainingscrew can be analyzed based on classical power screw formulas 2 and the finite element method 3 . The mechanics of the TIF type attachment method has been investigated with approximate closed form formulas by the authors 4 . The subject of this paper is the mechanical analysis of the TIS type attachment m ethod, which has been previously investigated using the finite element method 5 .…”

“…27,28 The mechanics of the purely TIF type implants was first explained by O'Callaghan et al 29 and then by Bozkaya and Müftü. 4,30 Approximate analytical solutions for the contact pressure, the pull-out force and loosening torque acting in a tapered interference were developed by modeling the tapered interference as a series of cylindrical interferences with variable radii. These formulas compared favorably with non-linear finite element analyses for different design parameters.…”

“…4 In this paper, approximate closed-form formulas are developed for estimating the tightening and loosening torque magnitudes for the TIS type abutment connections. The closed form equations for the tapered interference fit 4 are combined with screw mechanics equations to determine the loosening and tightening torque as a function of various design parameters. The efficiency of the system, defined as the ratio of the loosening torque to the tightening torque, is investigated.…”

Strain analysis of different diameter Morse taper implants under overloading compressive conditions

“…3,6 The tapered interference fit relies on a large contact pressure and the resulting frictional resistance in the mating region of the implant-abutment interface to provide a secure connection. 7 In general, interference fit implants have a hub and shaft that connect to each other and do not require a third member, such as a key, pin, bolt, or screw. The connection allows for load transmission due to the frictional forces between the mating surfaces where the shaft has a slightly larger diameter than the hub.…”

“…The dependent characteristics of the interference fit, including the pullout/insertion forces and the stress distribution in the members, depend on the taper angle, contact length, inner and outer diameters of the members, depth of insertion, material properties and coefficient of friction. 7 Clinically, straight and wide diameter implants are used in many clinical scenarios, including the use of single dental implants. In Morse taper implants, the measurements of the internal cone are the same, regardless of the implant diameter.…”