Re: [CAD_CAM_EDM_DRO] Re: New trend - CNC in Dentistry

Hi Andrew:
The material is actually a Zirconium based ceramic that's not really
porcelain, but is tooth coloured and can be cut with diamond plated points
and wheels.
I know this technology well; I was a dentist for a good stretch before I
went back to my first love.
It's kind of neat in terms of the gadgetry that was developed for it, but it
makes pretty crappy restorations.
The fit is terrible, and the adhesive is routinely used to fill the gaps,
making for a much higher incidence of postoperative problems including
intractable sensitivity and recurrent tooth decay.
"Tis a great gimmick though, and really brings 'em in the door.
I'm not a fan, and I'd certainly never accept one in my mouth or inflict one
on a patient.
If you're interested in reading the hype, do a search for Siemens
Cerec...that's the company and the product.
They make it sound like the next wonder of the world...but then, they want
to move plenty of those $100,000.00 machines!!

The technique you refer to, is the time honoured Porcelain Fused to Metal,
or PFM crown.
When properly made, this is a very reliable restoration, and is still the
treatment of choice for full crown restorations in visible areas of the
mouth.
The metal base gives it some ductility, the casting process is FAR more
precise than CNC milling on such an irregular shape, and the tooth doesn't
need to be hacked into nearly as aggressively.
It's also impervious to cracking, even though the porcelain can become
detached, leading to a cosmetic problem but not a functional problem.
The alloy used for the base is a high noble alloy with gold, copper,
palladium, and some other stuff in it to help make the porcelain fuse to it.
The porcelain is sculpted and baked on and glazed...very demanding work to
do really well.
Dental technicians are among the most underappreciated craftspeople around!!

Cheers

Marcus

----- Original Message -----
From: "Andrew Werby" <andrew@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Tuesday, February 08, 2005 12:17 PM
Subject: [CAD_CAM_EDM_DRO] Re: New trend - CNC in Dentistry


>
> [I read this article with interest. But one thing puzzles me. It refers to
a
> "small porcelain block" as the material carved to be used as a crown. But
> this doesn't make a lot of sense to me. Is it fired porcelain, like
toilets
> are made from? This, besides being rather difficult to carve, would be
> rather brittle in use, no? Or is it carved in the green state and quickly
> fired? As far as I know (and my knowledge may be dated) crowns are cast in
> gold first, then coated with "porcelain" enamel, a glass powder which is
> carefully matched to the color of adjacent teeth, and fired onto the metal
> to form an opaque and impervious coating. It seems more likely that a
metal
> tooth was actually carved by this machine, and the enamelling was done
> before showing it to the patient, although the time-frame seems short for
> that. No URL was attached for futher reference - is there a little more
> detail on this anywhere?]
>
> Andrew Werby
> www.computersculpture.com
>
>
> "jjfear" <jjfear@...> wrote:
> Subject: New trend
>
>
> I haven't posted for months, since my vision has deteriorated to the
> point I no longer do shop work. But I ran across this post from
> Andrew Tobias, author and investment, "expert?" But I immediately
> thought of this group. So here it is:
>
>
> empty.gif (854 bytes) empty.gif (854 bytes)
> Daily Column
>
> Ah, Brave New World of Dentistry
> (And with this ring . . . )
> Published on February 07, 2005
>
> How I cracked half my molar eating a slice of tomato will go down in
> The Annals of Dental Mystery as its own separate chapter. But when I
> settled into his chair, my dentist announced that I needed a new
> crown, which I always modestly accept, being the King of Patience.
> Because we dental patients know the drill: First visit is for
> preparing the tooth and making that delicious and oddly cold playdough
> impression to send to the lab, and for installing the awful ill-shapen
> and bad-tasting aluminum "temporary." The following week is for
> getting that awful biting-the-inside-of-your-cheek deal going. Second
> visit is for finding out that the lab didn't make the crown quite
> right. Third visit is for - ta-da! - successfully fitting the crown
> and handing over $1,000, give or take, for your regality.
>
>
>
> No more.
>
>
>
> Without even bragging, my dentist (who - a little journalistic probing
> revealed once I was allowed to talk - is just one of 40 out of 7,000
> in Florida to have this technology) wheeled over a cart with a control
> panel and computer screen, displaying the 3D image of my tooth and
> designing the crown right in front of me, like Leonardo Da Dentist.
> Then, when it was perfect - get this - he clicked GO and sent the
> instructions to a milling machine in the backroom, which set about
> sculpting a small porcelain block into the precise crown that had been
> specified.
>
>
>
> Anyone under 30 will know this as "CAD/CAM" - computer-aided design /
> computer-aided manufacture. But instead of milling the prototype for
> a new carburetor, they were milling my tooth #14 (which I call Herbie).
>
>
>
> (As you probably know, your teeth are numbered. You start with the
> top right wisdom tooth way in the back, which is #1, and go all the
> way around to #16; then drop down to #17, the wisdom tooth right under
> #16, and back around to the right. Those of us whose wisdom teeth now
> hang on leather bands around our necks [to intimidate potential
> adversaries] count from #2 to #31, skipping #16 and #17. William "the
> Refrigerator" Perry, who needs nothing around his neck to intimidate,
> and is available to appear at your next event, seems to be missing #6
> thru #11 and #22 thru #27.)
>
>
>
> Within a second or two of my dentist's clicking GO, the computer
> reported that milling would take 17 minutes - the way your browser
> estimates the length of a download - which gave me time to return some
> phone calls ("I'm at the dentist, but I have 13 minutes and 12 seconds
> left to talk") and my dentist time to go out for a beer, or whatever
> dentists do in these circumstances. (Call their brokers, more likely.)
>
>
>
> In he came 17 minutes later, bing, bang, boom . . . and then . . .
> after the ritual "bite down, chop-chop" so many of us are familiar
> with ("No, it's still too high," you say, ten or twelve consecutive
> times, feeling increasingly embarrassed and guilty for being so
> difficult, when, really, what have you done wrong? But what if he
> keeps drilling deeper and deeper to make the fit and goes all the way
> through the crown to your nerve or - worse - breaks the crown and you
> have to start all over again? Could it be you are just being
> difficult? Or are setting your bite funny because of the Novocain?) .
> .. . it was perfection.
>
>
>
> A crown in a single visit.
>
>
>
> To find a dentist near you who's made the $100,000 investment and
> taken the training to master this system, click here. (The link's in
> the box at lower right.) Despair not if you don't find one; the
> listing is incomplete. Your own dentist may be off at CAD/CAM school
> as we speak. Thank you, Dr. Nassery.
>
>
>
>
>
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