Assessment of integration of titanium to bone using acoustic emission transmission
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Date
31/07/2021Author
Bodbbos, Zinab
Metadata
Abstract
Increasingly, titanium is being used as an implantable material to make best
use of its ability to integrate with bone. The replacement of missing teeth is
likely the most widespread use of this technology but there is an increasing
number of uses in orthopaedics and audiology. One of the challenges with this
technique is being able to assess whether the bone-titanium interface is intact
or is being subject to breakdown. Currently there is not a reliable and sensitive
instrument able to monitor changes in bone-titanium interface.
This study sought to develop a reliable and simple-to-use test for monitoring
osseointegration using dental implants as a model system with an approach
that would allow early detection of compromise to the bone to implant interface.
A series of systematic investigations were conducted to examine the reliability
of the acoustic emission technique (AE) for measuring changes in the
osseointegration of dental implants using an in vitro model system. The model
system involved dental implants installed into bovine rib bones with models for;
primary stability, partial and full osseointegration, and degraded osseointegrated
interfaces.
The AE (a high-frequency ultrasonic wave) was produced by a simple source
and was injected into the abutment of the implant. The transmitted energy was
measured on the surface of the rib bone using a proprietary sensor. Some
energy is lost at the implant-bone interface, but also in transmission along and
through the bone.
The effect of bone micro- and macro-structure on acoustic transmission through
and along bone has been measured in the primary stability model and a
quantitative relationship developed to allow this patient-specific aspect to be
taken into account in a clinical situation.
The primary stability model simply involved installing the implant using the
normal surgical procedure. For secondary stability, glass ionomer cement was
used as a model interfacial material giving partial and full coverage. It has been
found that the transmitted energy could distinguish between primary stability
and partial and full integration.
Finally, to gauge how effective the acoustic emission technique could be in
detecting early changes in the marginal bone around osseointegrated implants,
simulated circumferential and vertical peri-implant bone defects of various
vertical and circumferential extent were tested. It was found that the acoustic
energy could effectively detect small changes in marginal bone level around
osseointegrated implants. Changes in transmission of the AE signal were able
to show both circumferential and narrow vertical bone defects including the
most coronal 1 mm of the marginal bone.
These findings suggest a role for AE in monitoring the development of
osseointegration in the weeks following implant placement and could be
coupled with an assessment of bone density on an individual patient basis.
The technique could also have a potential application in the early diagnosis of
the peri-implantitis in the oral environment or other forms of loss of integration
when used elsewhere in the body.
These findings are promising, although a number of practical issues need to
be resolved before the technique can be validated in the clinical setting.
Whereas the dental application is a useful model system, a clinical validation
could lead to more general application in cases of monitoring bone-implant
integration.