hello and welcome to chair side lies I'm your host Megan strong thanks for joining us today in
this episode we're talking about the reinvention of the pfm it's a city impressed to metal and it
has the potential to be a game-changer for your practice in this presentation dr. cheese at CDA
anaheim discussing unique characteristics of this revolutionary lithium silicate ceramic
material and laser centered copings and he's showing us how it outperforms traditional
PFN so let's check it out good afternoon how's everyone doing good you look comfortable we've
got something really exciting to share with you today we've got pfm and you're probably
thinking why are we here listening about such an old material old restoration an old technique and
that is in fact the case CSM's have been around for a very long time for several decades it came
into inception in the 60s and certainly to fill a void in dentistry to create something that was
aesthetic to get away from metallic restorations obviously as Dennis we like to hear about gold
and useful restorations but certainly can't use that everywhere and that's part of the reason
why there's been such a recent surge in all ceramic restorations recently with zirconia
and glass ceramics but here at Glide well we are always innovating and we identify problems
and we look at tsm's and we know that there are several clinicians that they'll enjoy you can
see our pens and because it has such a proven track record for so many years but there is a
fact with the attempts they have issues primarily with the way that they're being fabricated and as
a technician - I've made several and I'm aware of some of those issues in the workflow there's
number one several steps involved with it from the time you pour the impression and create
that metal sub structure all the way to adding the layered forcement on top and to have all of those
components fit together to create a reliable and long-term restoration for your patients is
extremely challenging so what we've done is taking a look at some of those issues that in fact are
some of the cases with TSM especially we're going to start off with the sub structure so with Tia
tailings porcelain fused to metal restorations the metal the metal coping certainly has issues
because with any restoration in dentistry you want to try to restore it similar to a to a natural
contour like the natural tooth but that transition between the tooth and the restoration often with
TSM has an over contoured area certainly if the dentist doesn't reduce enough that's an
issue but because whenever we use a lost-wax technique we have to have a certain thickness
with the wax up for the coping in order for it to cast properly so that's why a lot of designs
with tsm's with the traditional fabrication you end up with a lot thicker coping than you might
really want and then you add your opaque layer and then you're added feldspathic porcelain on
top you end up with the big stuff and what I've seen with a lot of restorations the ones that
I've replayed for service you see a lot of general inflammation because patients have
a very challenging time keeping that transition clean so that's the big issue with the way the
coatings are fabricated and then I've also seen several issues with the ceramic that's on top the
very part of the restoration that provides the aesthetic areas that's actually the weaker link
for these restoration so the Celtic foursome the ones that you mix with liquid and it's a
powdery thing you have to fire it that porcelain that's used on top is simply very weak it's about
eighty to a hundred mega tops of the flexural train so Pia films get its strength its full
strength from the metal substructure but the combination is - you have to work together but
because of the weaker porcelain when they fail it's always the portion that fails and that'll
never really has any issues with it other than it being in some cases too thick so with the
weaker porcelain you often see chipping you often see the ceramic shearing off and certainly that's
an issue and I've had several patients actually come to meet and have piaf ends and they said
the porcelain actually checked off when the debt is delivered it is that normal certainly it's not
that's not what we wanted here as clinicians we want to be able to have a long-term restoration
for our patients and certainly with this case here on the upper-left not the best aesthetic
that's also one of the issues to the porcelain if it's not applied properly or if there's not
enough rope or you end up getting very opaque looking restorations and certainly you can see
that issue with the transition between the tooth and the restoration for that fit is and then
what ends up happening is gingival recession that's just a natural process if restorations
are not fabricated ideally to the tooth so we've identified these issues and we sought up to find
ways to improve upon the manufacturing process so this is just a little preview of what we do
starting off with the metal substructure so we use these concepts centering machines and it actually
has a vat of powdered metal we have non precious semi-precious and precious alloys that we can use
to use an additive process and it basically wells together these powders of metal into
these sub structures and because we're using an additive technique instead of the lost wax
technique we're not casting anything anymore we can create metal substructures extremely thin in
areas that are under Concord or under reduced and that in turn helps to create a very very smooth
feel and transition from the preparation to that PSM restoration so this is an extremely unique
process we can do this for single units multiple units all of our bridge restorations and what we
found is by creating the sub structures using this method you have you don't have to solder
as much to sometimes during that casting process the metal substructure doesn't fit properly so
there's less cutting and less working of that sub structure because we certainly want that to
be as strong as possible for our porcelain to go on top so that's what we started off
with for the substructure so you can see some cross-sections of traditional Pia films again
keeping in mind that that metal substructure has to be a certain thickness for it to cast properly
if you are using the lost wax technique and again that transition is less than ideal and you can see
here this is just the metal substructure certainly the technicians go through the process that they
shift and finish that down but it's a certainly a challenging process to have to go back and finish
that after it passes so what you end up with is a very thick margin for those restorations
for the ceramic that's used on top our R&D department has developed a lithium silicate
glass so traditional PSM sicily use a felt Pathak for sand that's layered on top we've
already talked about some of those issues with it being weaker our lithium silicate is called
obsidian and this material is 385 mega Pascal's of flexural strength and this was manufactured
and engineered to have a coefficient of thermal expansion that matches that of the metal so
that's extremely important whenever you're using by layered materials we have two different types
of materials that go through a heating process so we pressed the metal on top the metal is heated
I'm sorry the ceramic is heated to a liquid form and it's pressed into a mold where the
restoration is was created and that fuses to that metal sub structure and so the combination
of the two you have a very strong core in that metal centered coking and then you have that
extremely strong ceramic that's pressed on top so what we end up with is something that's four
times stronger and traditional ceramic that's layered on to TFM and when we look at the when
we look at the flexural strength again its 385 almost 400 mega Pascal's of flexural strength
much much greater than typical feldspathic and the chipping resistance is a lot higher as well
so what we end up with is a restoration that's not only extremely strong it fits really well to the
patient's tooth and of course being able to form a great barrier from any openings and bacteria but
really the key difference is being able to create that very smooth transition and ultimately we have
transitions that are similar to monolithic restorations like a monolithic zirconia were
ceramic that's really the most important aspect in restorative dentistry creating a smooth transition
a margin that's undetectable whenever we check it and so that's what we found with our reengineered
P FM's and when we take a look at it we're able to mill down to a thickness of only 20 microns
using that additive laser standard process and those restorations that we've replaced that you
saw earlier here on the left we had those two key items that were failing and we redid that with a
CDN restorations so not only can we get something that's much much stronger it's also extremely
aesthetic as well you can see here with multiple unit in this case it's per unit bridge here on the
lower you get great aesthetics and some people may wonder okay you're now using a stronger ceramic on
top of your copings how does that affect the opposing intuition we have to consider how it
wears what the opposing dentition we now know in dentistry that the rate of wear caused by
restoration has nothing to do with the strength of the material or how hard it is it's all about
the surface roughness and telepathic porcelains the force and that's used on PSM typically is
extremely rough it has a lot of porosity zin it and the porosity is what actually causes the wear
so because the lithium silicate glass when it seed is melted and pressed into place it's an extremely
smooth surface porosity free and you have something that's extremely gentle and it wears
very similarly - enamel so the acidic an be used for anterior-posterior single units or multiple
unit cases for bridges other indications would be if you prescribe something like a zirconia
or Brooks or bridge and the connector height if you're doing a posterior bridge the connector
height can't be high enough to accommodate for what we call the rule of 27 then that's a great
opportunity to use the PSM as a bridge option and certainly to cover and mask out dark preparations
as well we thank you for your time if anyone has questions we'll be around to answer those for you
thank you thanks dr. cheese and to learn more about obsidian Preston metals visit our website
at wwlp.com well that about wraps it up for this episode of chairside live on that of everyone here
at global laboratories thank you for watching and I'll meet you right back here next time