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Research Papers

A Dynamic Analytical Model for Impact Evaluation of Percutaneous Implants

[+] Author and Article Information
R. Swain, G. Faulkner, D. Raboud, J. Wolfaardt

 University of Alberta, Mechanical Engineering Building, Edmonton, AB, T6G 2G8, Canada

J Biomech Eng 130(5), 051013 (Sep 10, 2008) (13 pages) doi:10.1115/1.2970061 History: Received January 17, 2007; Revised September 26, 2007; Published September 10, 2008

The ongoing need for a clinically effective noninvasive technique for monitoring implant stability has led to a number of testing methods based on the concept of resonant frequency. Resonant frequency measurements are an indirect measure of the bone-implant interface integrity and do not provide any specific measures of the physical properties of the interface itself. In this study, an analytical model has been developed to interpret the measurement results of an impact testing method based on the Periotest® handpiece. Model results are compared to a variety of in vitro tests to verify model predictions and to gain an understanding of the parameters influencing the measurements. Model simulations are then used to predict how changes in the supporting stiffness properties, material loss around the neck of the implant, and the presence of an implant flange will affect the measurements. The developed analytical model, in conjunction with the impact measurements, allows direct estimation of the bone properties that support implants. Model simulations show the impact testing technique to be sensitive to bone loss and stiffness changes that would correspond to poorly integrated implants (ones which may be in danger of failing). Similarly, for implants with very stiff support, little useful quantitative data can be obtained about the bone supporting the implant, as the stiffness of the other components of the system dominate the response. However, such implants are generally considered healthy.

Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Raw accelerometer signal collected from the Periotest® handpiece and conditioned accelerometer signal used to calculate PTV

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Figure 2

Typical implant-abutment system being impact tested by the Periotest®

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Figure 3

Experimental setup

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Figure 4

Four degree of freedom model

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Figure 6

Damped model acceleration response compared to measurement for a 10mm intraoral implant with a 10mm abutment

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Figure 7

Damped model acceleration response compared to measurement for 4mm implant with a 10mm abutment. (a) 4mm flangeless extraoral implant. (b) 4mm flanged extraoral implant.

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Figure 8

Modal acceleration components for a 10mm implant with a 10mm abutment and k of 7.5GPa

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Figure 9

Comparison of model to measurement values for two implants at different heights along a 10mm abutment. (a) 10mm intraoral implant. (b) 4mm extraoral flanged implant.

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Figure 10

Model results compared to measurements for a 10mm intraoral implant and a 10mm abutment struck at different points along the abutment. (a) Abutment struck at the top. (b) Abutment struck 2mm from the top. (c) Abutment struck 3mm from the top. (d) Abutment struck 4mm from the top.

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Figure 11

Comparison of model using changing KI values to measurements for two implants with different length abutments. (a) 10mm intraoral implant. (b) 4mm extraoral flanged implant.

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Figure 12

Model results compared to measurements for a 10mm implant with different sized abutments. (a) 10mm abutment. (b) 7mm abutment. (c) 5.5mm abutment. (d) 4mm abutment.

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Figure 13

Effects of varying the support stiffness (k) on the first mode frequency for two abutment lengths. (a) 10mm intraoral implant. (b) 4mm extraoral flanged implant.

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Figure 14

Effects of changing the damping coefficient on the model acceleration response for a 10mm intraoral implant with a 10mm abutment

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Figure 15

Effects on the first mode resonant frequency of bone loss from the top of the implant towards base. (a) 10mm intraoral implant. (b) 4mm extraoral flanged implant.

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Figure 16

Model results with and without a flange at two different first mode frequencies. (a) p1=1500Hz. (b) p1=1300Hz.

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Figure 5

Impact test acceleration compared to model output for a 10mm intraoral implant with a 10mm abutment. (a) Estimated KT from Eq. 4. (b) KT modified to match second mode frequency in Eq. 5.

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