Hello all!
I need to dissect the inner ear from a cadaver.  Plan to excise the petrous bone with a rotary saw and hand drill, then soak in nitric acid.  Any suggestions for concentration/duration?  Thanks, as always, Maureen Loomer, East Carolina University

-----Original Message-----
From: Paul Bradbury <histopathology@shaw.ca>
To: HistoNet Server <histonet@pathology.swmed.edu>, "P. Emry" <emry@u.washington.edu>
Sent: Mon, 12 May 2003 21:03:41 -0700
Subject: Re: edta

This is a good question, but I doubt if you will
get an answer to it. You are asking the
histological version of the old question "How long
is a piece of string". There are so many
variables, a simple answer is not possible.

EDTA is a slow acting decalcifier (compared to
decalcifiers that incorporate hydrochloric acid or
nitric acid). The surface area of the bone is less
significant than the thickness of the sample.
Cortical bone will take considerably longer to
decalcify than cancellous bone. The concentration
of the EDTA solution will have a major effect,
stronger solutions will act more quickly than very
dilute solutions. However, very strong solutions
will not give additional speed. The temperature
will also have a significant effect on the speed
of decalcification;  warming the solution will
increase the reaction rate, but again, there is
limit to the amount heat that is beneficial.
Gentle agitation is also very effective in
speeding up the process.

Assuming your bone sample is cancellous bone (not
dense, cortical bone) about 4-5 mm thick, using 5%
EDTA at 37 degrees with a little agitation, I
would guess you are looking at 48-72 hours (give
or take a day or two).

Testing to determine the completion of
decalcification is a good idea. But, don't "test"
your sample by squeezing it or bending it. These
are very subjective estimations and cause all
kinds of distortion and damage to the tissues. A
simple chemical test or X-ray is far better.

Hope this is of some help. Good luck with your
bones!

Paul

Paul Bradbury, FIMLS, ART
Kamloops Canada

Paul Bradbury, FIMLS, ART
Kamloops Canada