G’day; I was very pleased to get the post by Skip Meister on
certain dental techniques, and I am sure I ‘speak’ for many
others when I reckon that he has enlightened quite a lot of us -
and not only we who have never done any casting either. I know
that dental technicians (hate the non-word, “techies”!) do a good
deal more than 'just ’ cast gold fillings and fire up crowns. I
am also (mildly) interested in the casting of vitallium dental
plates, (and in particular knees!) though I don’t think the
latter comes under the ‘dental technician’ umbrella. I believe
the alloy is of cobalt and chromium, and I’m certain that must be
a beast to cast, especially the precision jobs I’ve seen. So,
Skip, how do you go about vitallium casting - what is it’s
melting point for a start and what exactly is the alloy? And
being expensive, extremely durable, bright and shiny and most
certainly non-allergenic, why isn’t it used for jewellery? But
thanks a lot Skip, anyway. Cheers,
/\
/ / John Burgess,
/ /
/ //\ @John_Burgess2
/ / \ \
/ (___)
(_________)
Hi John,
The alloys of which you speak are used in removable bridgework
and also in oral and maxilofacial reconstruction. Vitallium is
a registered name of the Howmedica Corp. but there are a myriad
of similar alloys used. Here are the constituent metals and the
percentages used in various alloys. I got this info from the
U.S. Air Force dental technicians manual available from the U.S.
govt. printing office at a very reasonable cost. It has some
great sections on golds, casting, fabricating etc. in many
instances very valuable to jewelry making.
Here goes:
chromium 20-30%
cobalt 0-60%
nickel 5-60%
molybdenum 4.6-18.5%
tungsten 0-4%
iron 0-5%
manganese 0-0.5%
aluminum 0-0.7%
beryllium 0-1.8%
silicon 0.4-0.7%
carbon 0.2-0.4%
The casting range for these alloys ranges from 1600 degrees F to
over 3000 degrees F. Vitallium is in the 3000 deg. area. These
metals are EXTREMELY hard and are difficult to cast, finish,
and polish. The work is done on a special high speed bench
grinder with a quick change chuck. The work is constantly
dipped in water to cool it, but chrome finishers have calluses
on their fingers that have to be seen to be believed! The
metals cost from $50-$120 per lb. with fairly large 20-40% price
breaks if you buy 20 or more lbs. You need special investments
and the guys I know all use gas fired burnout(a treat on a
sweltering summer day) and cast with oxy/acetylene
I do not do chrome casting. Dental technicians specialize and
are certified in these areas:
-
Crown and Bridge- Create crowns, bridges, inlays, and onlays
for all-cast, plastic veneers, and precision attachment
work(attaches removable bridgework to fixed[glued-in] work
without the unsightly clasps)
-
Ceramist- Creates crowns and bridges veneered in dental
porcelain on a metal sub structure which is sometimes made by
the ceramist but usually the crown and bridge tech. He also
makes porcelain inlays, shells and porcelain jacket crowns which
are made on adapted platinum foil which is removed before
cementation.
-
Full Denture- Makes full dentures and usually puts the teeth
and acrylic(pink stuff) on the removable work.
-
Partial Denture- designs, waxes and casts removable
bridgework frames and applies the teeth and the acrylic(most
techs send the tooth and acrylic work to a denture lab and the
denture lab usually sends cast palate work to a partial denture
lab)
-
Orthodontic- Wire benders we call them. This is a dying
specialty due to the new modular orthodontic systems available
to the orthodontist. There are only a handful of rather large
labs left now. Chicago once had 30-40 ortho labs. I don’t
think there is even one left.
-
Generalist- This is a new specialty that knows a fair amount
about each specialty but probably can’t handle extensive
restorative work, complex occlusal problems (crossbites,
misaligned jaws, etc) precision attachments, etc. They are the
utility people that can be plugged into busy depts. or fill in
for vacations, doing the repetitive tasks like model work,
opaqueing for the ceramist, single all cast crowns, investing
and casting and such allowing those more skilled in a specialty
to spend more time on the complex work.
All techs know how to do case prep and model work.
I am a Crown and Bridge and Ceramic tech. These specialties
usually go together as do Denture and Removable but not always.
I don’t use nickel chrome alloys because I’m allergic to nickel.
My skin gets raw, my nose bleeds and my hands crack and bleed
from prolonged exposure.
I hope that this answers your question.
Regards,
Skip
Skip Meister
NRA Endowment and
Instructor
@Skip_Meister
11/01/9711:30:02