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Michael Liebschner
06-02-1998, 07:37 AM
Dear Subscribers,

Thanks to all who responded to my request for information. You have been
extremely helpful. After trying several of the suggested methods following
procedure works best in order to get a gas tight bond between casting
material and cortical bone:

1.) remove any fatty tissue on the surface you are interested in
2.) defat the bone surface with acetone
3.) apply at least three thin coatings of cyanoacrylate adhesive (i.e.,
Super Glue)
4.) let it dry in between each coating process
5.) cast specimens in poly methyl methacrylate (PMMA, or dental plastic)

Below is a summarized compilation of your responses.

ORIGINAL REQUEST:

Several months ago I posted a request for some information regarding the
hydraulic conductivity (hydraulic permeability coefficient) of bone tissue.
The response I got was somewhat confusing since some researchers used
different methods resulting in quite different outcomes. Because of that, I
want to verify some of the results found by applying an ASTM standard
procedure used in groundwater engineering for determining hydraulic
conductivity of stones.

I want to measure the hydraulic conductivity of a femur which will be casted
into a plastic tube, to avoid surface error effects, and then subject it to
fluid pressure on one end. So far, I had no luck finding the proper casting
material. I tried the commonly used PMMA (better known as Dental Plastic) as
well as Ultra Mount (Buehler, high performance mounting kit, Lake Bluff,
IL), but both materials didn't stick well enough to the bone surface. A
coworker of mine gave me the tip to use minimal expanding foam sealant
(nasty yellow stuff, that usually sticks to everything, even to places where
you don't want it), but that didn't work either.

What I am looking for is a casting material that bonds very well to bone and
a plastic (PVC) tube. Does anyone have experience with other kind of casting
materials? Does anybody know a commercially available casting material which
I could use?

Assistance on any of these questions would be very helpful. A summary of the
results of this query will be posted.


SUMMARY OF RESPONSE:

================================================== ========
Hello,

Just as a suggestion, have you tried defatting the surface of your bone (as
done in mounting strain gages) before using the materials you suggested for
potting or casting the bones? If not, it would probably help a great deal.
If this still doesn't work, you might try defatting the bone surface, then
applying a thin coating of cyanoacrylate adhesive (i.e., Super Glue) and
letting this dry before casting the bone in other materials. The
cyanoacrylate acts as a sealant from further release of blood and fat
(especially during the exothermic reaction in polymerization of the dental
cements) and should help the other materials stick better.

Hope these ideas help! Good luck.

Lisa Friis, Ph.D.
Orthopaedic Research Institute
Via Christi Regional Medical Center
Wichita, KS

================================================== ========

The adhesion problem may be fat and/or water. The region to be contacted
may have to be prepared using solvents such as ether or acetones to remove
fats and dehydrated with alcohols to replace interstitial water. These
methods are much the same as for embeddening bone before sectioning for
microscopy It may only be necessary to prepare the surfaces rather than
the deep interior in this case.

Joe Spadaro
=========================
Joseph A. Spadaro, Ph.D.
Research Associate Professor
Department of Orthopedic Surgery
S.U.N.Y. Health Science Center at Syracuse
750 East Adams St. Syracuse, NY,13210 U.S.A.
e-mail: spadaroj@hscsyr.edu
Fax: 315-464-6638
=========================

================================================== ========

Dear Michael Liebschner:

> You recently wrote: " PMMA (better known as Dental Plastic) " on the
> biomechanics list server and that leaves me with the question:

Are you sure that you used polymethyl methacrylate "PMMA"?

We use it here in our orthpaedic research lab often and it seems to work quite
well to adhereing to cadaver bones. You might have used a substance known as
"dental stone" which is drastically different than PMMA. PMMA goes through a
highly exothermic reaction. Too hot to hold with your hands. The fumes that are
produced are toxic and are very acrid smelling. PMMA is also transparent when
solidified. It also is expensive to purchase.

If you still think you used PMMA, then did you prep the cadaver bone? You will
need to remove any fatty tissue on the surface you are interested in and
possibly wipe it down with an alchol solution. Any soft tissue on the bone will
interfere with bonding.

I do not fully understand your application of the PMMA, but I hope this
information will help you out.

Sincerely,

- Nick

--
Nicholas A. Plaxton, M.S.
Orthopaedic Research Lab, Inc.
Mt. Sinai Medical Center
Cleveland, Ohio, 44106, USA
email: nick@orl-inc.com
website: http://orl-inc.com
Phone: (216) 421-4334
Fax: (216) 421-4843

================================================== ========

Hi Michael,

We have used glass-ionomer to bond bone samples in metallic molds for
tensile testing. I don't remember the commercial name of the product but it
is 2-component material used by dentists.

Timo Jamsa

------------------------------------------------------------------
Timo Jamsa, Lic.Tech. e-mail timo.jamsa@oulu.fi
Laboratory Manager tel +358-8-537 5982
University of Oulu fax +358-8-330 687
Faculty of Medicine
Kajaanintie 52 D
FIN-90220 Oulu, FINLAND http://cc.oulu.fi/~tjamsa/
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================================================== ========

We reached good results with Araldit D and a hardener.
If you contact Dow Chemicals, they can tell you the right hardener to get
(we got ours here in Germany).

Thomas Pandorf

================================================== ========
Dr.-Ing. Thomas Pandorf
Institut für Allgemeine Mechanik
Templergraben 64
52056 Aachen
Germany

Phone: ++49 241 804592
Fax: ++49 241 8888 231
email: pandorf@iam.rwth-aachen.de

================================================== ========





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,------------------vvvV----Vvvv------------------.
| V^V |
| Michael Liebschner |
| mliebsch@emba.uvm.edu |
| Biomechanics Laboratory |
| University of Vermont |
| Phone (802)656-1432 |
`-----------------------------------------------------'
You can not solve problems with the same level of
thinking that existed when the problems were created.
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