[Histonet] Plastic Embedding Molds

[Morken, Tim - Labvision]

Dr. Hessler wrote: "...what advantages do these have over traditional steel
other than you don't clean them? As steel basically has an unlimited
lifespan, are the disposable molds really cost effective in a clinical
laboratory."
 
Plastic molds:
Disadvantages:
Very high cost (although they can be reused for a while - just don't store
in the heated space of the embedding center or they get warped)
Hard to orient fragments due to some kind of electrostatic forces that move
the pieces around.
Slow to cool - again hard to work with small fragments and skin when you
want to orient them a certain way. (though some may see as an advantage)
Not as flat on the face as metal, so more trimming - bad for very small
specimens.
Do not hold heat the way metal does, so cools faster on the sides when time
is spent orienting tissue. I see many more mis-oriented tissues in plastic
molds, and mis-oriented mold/cassette problems (block face is mis-oriented
to the cassette back, which means the block face is at an angle in the
microtome chuck...= more trimming).
 
Advantages:
The sides of the mold are more vertical than the metal mold so a bit easier
to cut (smaller face, sharper edge)
Easy to take off the block (metal molds are often difficult to remove)
 
 
Metal:
Advantages
Very low cost, last forever
Flat face
Cool fast
 
Disadvantage
Sometimes difficult to remove - use mold release (but that does take time
and requires cleaning the molds daily in xylene/alcohol - we put them in the
tissue processor and run the clean cycle)
Cracked blocks? I haven't seen that as a problem. It is mainly in large
blocks. You can put them on a piece of paper over the cooling plate to avoid
that.
 
It seems the only real advantage of the plastic is the shorter time spent
taking the mold off the block and avoiding the time it takes to clean the
metal ones (about 15 min/day max)
If I was paying the bills I wouldn't get the plastic - they are far more
expensive and do not give as good quality face as the metal. 
But...I haven't done a cost analysis of the plastic molds vs time spent to
clean metal molds and then soak in mold release every day.
 
 
Tim Morken
 
-----Original Message-----
From: Richard Hessler [mailto:RHESSLER <@t> mail.mcg.edu] 
Sent: Tuesday, December 16, 2003 7:56 AM
To: histonet <@t> lists.utsouthwestern.edu
Subject: [Histonet] Plastic Embedding Molds
 
I would like advise about disposable plastic embedding molds. Was wondering
if any clinical labs had experienced problems with delays and uneven tissue
alignment due to static and slow heat transfer. Also, what advantages do
these have over traditional steel other than you don't clean them? As steel
basically has an unlimited lifespan, are the disposable molds really cost
effective in a clinical laboratory.
 
Thanks
 
Richard B Hessler, MD
Chief, Section of Anatomic Pathology
Associate Professor of Pathology and Neurology
The Medical College of Georgia
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