|
Pros Class
Notes for December 14 2001 Didactic Exam
Nov.
5 | Nov. 9 (1) | Nov.9
(2 | Nov. 12 (Lindquist) | Nov.
12 (Schneider) | Nov. 16 (1) | Nov.
16 (2) | Nov 26 | Nov. 30
| Dec. 3 | Dec. 7
Pros, 11/5/01 7:58 am
Dental
Ceramics
ceramics have been around around a long time.
ceramics and porcelain in
dentistry around since 19th
century....
ceramo metal restorations began to really be
usable in the 1950s.
pocelain is in a powder. we"stack"
it on, then bake it.
we'll mix the porcelain initially ith
glass slab and stack in that
manner.
Porcelain for
metal bonding (some extra things that might not be in
handout)
crystalline solids
glasses
silica
porcelain
-- crystalline islands wihin a matrix of glass (usually fudes
silica)
comment on physical properties -- por. has
30-48 psi compressive
strength, that's good. but it has a low
tensile strength. and a low
sheer strength -- this is because
of its lack of ductility (not
flexible)
classifications
of dental porcelain:
- high temp maturing 1288-1371 degrees
-
medium temp maturing: 1093-1260 deg. por. denture teeth, some
jacket
porcelains.
- low temp maturing: 871-1066 deg. most
ceramo metal restorations
requirements for a ceramometal
porcelain
1. physical, chemical, and optical properties
cannot change
substantiallly with repeated firings -- BUT....
SiO2 glass is really the
basic structure of a ceramometal
porcelain.
2. he por must fuse at a temp that is somewhat
lower than the melting
temp of the alloy.
BUT - Fusion
temp for most med and high temp porcelains are greater tan
that
of mopst ceramometal alloys.
3. coefficients of thermal
expansion (alpha) of the porcelain must be
closely
matched.
BUT - coefficients of thermal lexpansion for medium
and high temp pors
are much lower than tose of ceramometal
allloys. The addn of oxides
increase CTE by the "loosening"
of the atomic structure -- you want a
10% mismatch -- por.
has a 10% lower CTE than the metal.
However -- the
disruption of the glass by the addition of oxides maeks
crystallization more likely. called deitrification. the more
crystals
you have, the more opacity you have, so the more
less esthetic it is.
So - it is crucial to follow
manufacture requirements.
chatr: how temp temp on the
physical properties of porcelain
takes more energy to
break more crystalne structure -- igher modulus of
rupture
with more crystals. but there is a compormise between strength
and esthetics.
4. the por must be capab;e of bonding t
the alloy....
Porcelain-alloy bond:
1. mecahnical
2.
compressive - not part of the physical bod mechanism oer se, but
rather palcement of the por ..... missed it....
3,
molecular components -
a. van der wals
b.
chemical - oxide bonding between elemets in the alloy and the
SiO2
network.
Need: diffusin of trace elements
take
care whn you form initial bond to oxide layer, creating the
opaque
por.
por. manufacturing...
materials"
-
quartz (SiO2), feldspar clays, additional modifying
oxides
Fritting
- repeatedly melting and rapidl cooling the
raw materials to achieve a
homogeneous powdered glass
"frit."
por. types (low fusng)
opaquw, body
(denting) and incisal (enamel), modifiers and stains.
if
staining doesn't wor k to well, ou can just sandblast it and try
again.
opaque:
- the basic glass to which
tetravalent, realitively insoluble woops --
couldn;t get it
all.
body and incisal:
- basic glass to whihc small
amounts are addded for opacity -- very
little in
incisal
modifiera and stain
larger amounts of colorant.
can be sed internally or on the surface...
In addition,the
viscosity, thermal expansion, and f temp differs
slightly
between the different types of porcelain. don't want opauque to
move....
single central incisor is one of the toughest
restoration ou can do....
case -- diag cast , wax cutback,
invested and cast, with sf52 metal.....
then it is fitted to
die.... you use disappearing margin....
lab
considerations:
- degassing (oxidation)
- opaque
application
- condensation of percelain
degassing...
opaque
pplication - brush a noce thin layer on, this gives o2 access to
the metal, enhances strenght. gotta add coats till you see no
grey
underneath.
body and incisal por. addition -- pnk
is body...
mix por with water initially. it is aplied to
the crown ina slurry --
but it still needs to hold its shape.
liquid is mostly water, but also
might conmtain binders to
ais in molding the por.
mechanisms:
capillary,surface
tension, mechanical agitation.
the better the
condensation, the better the strength qualities.
uncondensed
opor has more shrinlaage (crystall shrink after every
firing)
effect of condensation is
unclear>
firing:
drying, sintering (bring to firing
temp), vacuum firing, releasing
vacuum at end of cycle,
glazing (gives shiny surface)
Dryiing:
- not all water
is removed by condensation. Slow introduction of the
condensed
por. into the oven is necessary to avoid steam production and
explosion of the por. mass. Don't wat por. t bust. gotta get
all the
water out.
vacuum friring
- decreases
porposity of por. by drawing out air incorporated during
stacking and condensation. (porposity leads to decreased,
increase
opacity.)
vacuum firing geives etter
esthr=etics
sintering: fusinf particles.....
common
to use graphite pencil to mark line angles -- this is while crown
is on cast...
glazing..
manytimes we get crown back
in bis baked stage - it look s roughened or
chalky. in this
state you can check occlusion.
autoglaze vs. overglase.
auuto is almost the always used.
alminous percelain is
high crystalline .. see h.o. ground = bis baked.
glazed =
glazed...
porcelain can be pretty abrasive to opposing
dentition....
project:
perp it.
do
registration
custom tray for pvs impression - put adhesiveon
tray. use nonlatex fre
impression fill tray with brown, blue
around tooth.... (light vs hea vy
ody). impressio needs to be
deepo and wide enough. need good
buccolingual room. bevel.
clip interprox
- box it
- pur it with tpe 4 - silky rock.
pour slowly . wait 45 min before yu
seperate. ese it out.
bffal kniofe. trim on model trimmer. careful not
to trim
facial surface of anterior teeth. 1012mm from te margin tot eh
tissue (impression should be that high) has to be thin enough
to mounton
cast. 10-12 from the tissue. 20mm wide is enough
for pins and
strength... on internal lingual surface....
slight bevel so you can
remove.
- pindex. do good with
countersink. make sure pins fit before gluing.
short pins on
lingual. grey on smal, white on long.
- box it. pour. don't
forget supersep. sep after 45 min.
- section. 5 removable
sections
- trim die. emergence profile. abrd parker works
well. some like
weidelstat.
- mount to mandib model.
(already mounted....
Barry Hillam
barry@hillam.net
Pros,
11/9/01 8:05 am
Esthetic
Considerations
we'll bring in knowledge of dental anatomy for this....
list all problems
- sequence tx
- diagnostic wax up
communication:
-patient education
- dentist's education
Choices of Esthetic restorations
- 3/4 crown
- copmosit
- veneers
- resin bonded bridges
- pfm
- pjc
- implnats
Team approach
- restorative dentist
- periodontist
- orthodontist
- oral surgeon
- endodontist
the general dentist is the one in charge. The ortho needs to do what
fits into our tx plan. same with surgeons and periodontists.
case -- inapropriate enso access: remaining pulp: discoloration. You
can
go in and do some internal bleaching. teeth were also tweaked, ortho
was
best option, although could try restorative. tx: accessed chambers
better, got necrotic stuff out, bleached. straightened....
Perpectives of dental esthetics
1. ginigival hx and architecture
2. harmony within the dental arch
3, individual tooth contour
4. surface textre
5. color
6. prep and fabrication variables
Gingival hx and ar.
- perio hx
- marginal tissue recession
- loss of interdental papilla (black triangle - tough to fix)
-?
gingival hx - look at whole perspective. check for general vs. local
problems. address this early in d. control of tx plan.
"disruption of the gradation of perspective compromises the continuity
of the patient's smile." (PPAD 19999;11(6):721-28
cae - gold based veneer wiith acrylic facing...
pictures -- differring smile lines -- varying amount of goingival
display can be due o different factors.. can be skeletal ....
Harmon within the dental arch
- Incisal edge relationships
prox contact..
- ?
Incisal edge relationships
- varied: natural (youthful)
- Uniform: aged or artificial. makes patient look older.
Prox contactlocation
- teeth approx a trapezoidal shape.
" the location of the anterior contact points that should be
referenced."
prox contact goes more gingival as ou go posterior.
OPen contacts: some
Embrasure forms
- should be even on both sides...
as you go post, the ging embrasure gets smaller, occlusal gets bigger.
embrasures on FPD's need to be sufficiently opeed up. We tend to
com[promise a little more on lingual embrasure for srength, but on the
facial we need to make it look good.
Long axis Angulation
- incisal edge
- ging contour
-crest of concavity
- embrasures
"The axiakl inclinations are referenced from the midline."
(PPAD)
Mesio distal width considerations
- ortho correction
- modified tooth contours and embrasures
- surface texture alteration
- overlapping or spacing
- value change
Relative tooth widths
- "Golden proposrion -- width of central has a relation to width
of the
lateral and cuspid. Same proportions exist elsewhere in nature.
Adjstnig line angles canmake teeth appear wider.
playing with line angles and embrasures can compensate for discrepancies
in space size.
Inciso gingival length problesm:
- incorporatin a cervical line angle
- surface texture alteration
- surgical correction
- use of gingiva; colored porcelainporcelain or stain
regarding long narrow teeth, a little more mesiodistal surface texture
ehlps (?).
Short teeth -- can do crown lengthening, highlighting surface texture
individual tooth contour
- what does easch tooth look like (from your dental anatom)? apply this
to restorations. consider indviual charactersics -- distal embrsre,
incisal embrasre, creating symmmetry with thee components
probably th emost challenging restoration is central incisor. symettry
has to be perfect. elps to get crown in bis baked stage. defect
incisally was added to match the other, slight staining, gl;azing.
overal very nice result.
Tere is an ada code for staining and gl;azing procedures in our office.
case: 8&9 look to round.
Surface Texture
- Macroscopic
-Developmental depressions and grooves
- microscopic
- galze
some teeth are very very smooth, snd some have a lot of surface texture.
Surface reflectance
textured surface has ??? missed the rest....
case: single crown on 9. Color is decent, but the surface is way to
smooth. it needed more striations. stands out too much. in another mouth
that smoothness might be fine.
Surface Texture
vertical highlights - illusion of a
horizontal highlights -- illusion of a
G;aze: there is soft, medium, hard
Hard glaze has a very high luster (looked gross to me)
Color -- Hue, chroma, value...
value:
- increased value gives illusio of larger crown -- Dang it!! can't keep
up -- slide went too fast.
case: white crowns, but no opacity... gross! But patient wanted this.
didn't understand the ned for color andn opacity gradations. Certain
teeth have more chroma o gingival 3rd. gotta educate a patient on
appearance of natural teeth.
Esthetics and fx
- harmon between face, lips, teeth
- conducinve to porper phometic fx
- compatible with occlsal requirements
prep and fabrication variables
- prep design
-? (too fast)
Actually went withth ecrossbite and restred it that way....
tetracx staining -- crown unfortnatelyaveto beopaqued more to mask
staining
To summarize, you must: Evaluate, Diagnose, and resolve esthetic
problem.
---------
Onto project - mount, die hardener and spacer, die lube, wax up. get
embrasures, line angles, etc. same as adjacent tooth. in other words,
full contour wax up.
Barry Hillam
barry@hillam.net
Fixed Pros Student
Notes
Nov
9, 2001
Klint
Butler
Esthetics
Communication:
a.
Patient Education - They need to know what tx options are available
b.
Dentist Education - Need to know what the pt expectations are
Team
approach:
a.
Restorative dentist is in charge
b.
Ortho, perio, pros, omfs, endo
Perspectives
of Dental Esthetics:
a.
Gingival health + architecture
b.
Harmony within the dental arch
c.
Individual tooth contour
d.
Surface texture
e.
Color
f.
Preparation + fabrication variable/methods
Essentially
we are looking at how the perceptive shape of an individual tooth can
be altered, and how the elements of esthetic composition affect one
another.
Gingival
health + architecture:
a.
Periodontal health, patient’s home care, need to start with that
b.
Marginal tissue recession (prognosis affected by grade of rec. (1-4))
c.
Loss of interdental papilla, this is probably the toughest thing to
deal with, the ‘Black Triangle Effect’. Very difficult to
regenerate lost papilla.
d.
Localized alveolar ridge deficiency
e.
Excessive gingival display
f.
Gingival health, bone loss, localized gingivitis, etc.
Patient’s
smile line should portray a nice, even relationship of the gingival
height of contour.
Harmony
within the dental arch:
a.
Incisal edge relationship
b.
Proximal contacts
c.
Embrasure forms
d.
Long axis
e.
M-D width considerations
f.
Relative tooth widths
Incisal
edge relationship:
a.
Varied look is more youthful/natural. Centrals a little bit longer,
laterals a little shorter than centrals; the cuspids are typically approximately
the same length as the centrals. (Maxilla of course)
b.
Teeth all the same length, patient looks older, teeth look more worn
Proximal
contact location:
a.
Teeth are trapezoidal, creates the proximal contacts
b.
As you go posterior proximal contact goes more gingival
Embrasure
forms:
a.
Should be symmetrical on both sides
b.
As you go posterior the gingival embrasure gets smaller, the incisal
embrasure gets larger (both maxilla + mandible)
c.
FPD embrasures are opened up, close to normal; we compromise on the
lingual embrasure to have adequate strength for the connector, open
on facial so that it looks good.
Long
axis location:
a.
Looking at the incisal edge, this affects the gingival contour, the
crest of convexity, and the embrasures. How they relate to one another
will affect all of these things.
b.
Incisal ‘picket fence’ look isn’t natural, slight variations
Axial
inclinations:
a.
Referenced from the midline, anterior teeth have a slight mesial inclination
in natural teeth, should carry over to restorative work.
M-D
width considerations:
a.
Ortho correction, sometimes not utilized as much as should
b.
Modifying tooth contours and embrasures can be done chair side as we
are looking at fitting restorations, doing this as you are doing composite
restorations too
c.
Surface texture alteration to fit in with the surrounding dental tissue
d.
‘Golden Proportion’, as you are looking straight on in an
anterior situation the width of the central has a mathematical relationship
to the width of the lateral to the smaller width of the cuspid
e.
When adjusting widths of teeth that are too small, or too large we can
adjust the line angles to alter perception of space
Incisogingival
problems:
a.
More challenging to deal with.
b.
Incorporate cervical line
c.
Surface texture alteration
d.
Surgical correction
e.
Use of gingival colored porcelain or stain
Individual
tooth contour:
a.
The most difficult restoration as far as esthetics is the single central
incisor
Surface
texture:
a.
Macroscopic = depressions, grooves, etc.
b.
Microscopic = Glaze
c.
Textured surface diffuse reflectance
d.
Smooth surface specular reflectance
e.
Vertical highlights = illusion of narrower, longer tooth
f.
Horizontal highlights = illusion of wider, shorter tooth
Color:
a.
Hue = Tint
b.
Chroma = intensity of Hue
c.
Value = Light and darkness (grayscale), if value is increased it gives
an illusion of a larger crown. If value is decreased it gives an illusion
of a smaller crown
Pros,11/12/01
7:58 am (Dr. Lindquist)
Esthetic
limitations of the pfm crown...
strength limitations of PFM
crowns....
Methods of strengthening dental
porcelain...
currently available and experimentatl all
porcelain systems...
- comparative studies of all porcelain
restorations...
Return to the all porcelain
crown....
manufacturers concstant;y trying to ,ake a better
porcelain crown. They
are felt to be more esthetic than pfm.
this is becasue of transfer of
light -- por. just looks a
heck of lot like enamel.
limitation of the pfm
crown: a little less vbibrabt looking. Creates the
"metalceramic
smile."
Light transmisssiona...
Light goes
through ceramic much better than pfm. Depth of translucency
is wat really matters, thogh.
some of the nwere all
ceramics have a core material -- some of them are
almost as
opaque as pfm! Something to consider...
Limitations of
dental porcelain- weakness in tension
- brittleness
-
pyroplasticity and sintering shrinkage
Weakness in
tension
- concentration of stress at surface flawa (cracks)...
griffith flaws
come about as a result of cooling. stress is
concentrated at the tip of
flaws. glazing is meant to
minimize this.
- corrocion fatigue
Concentrationi of
stress at surface flaws
- residual stress = oral stress >
crack growth > eventual catastrophic
failure
- limits
tensile strength to 1/100 - 1/10000
"we masue by
weakness at surface." (/)
Corrosion fatigue
-
chemical reaction of water and glass > crack growth and
gradual
decrease in strength
- moist porcelain shows an
immediate decrease in strength of
approximately 1/3
ask
yourself how materilas were stored when they were tested during
studies that show porcelain qualities...
Brittleness
-
the critical strain to fracture all dental porcelains is
approximately
.1% (ium strain/1mm thickness of porcelain)...
so it must be propoerly
supported. choose cases
carefullly.
Proplasticity and shrinkage
- the sintering
shrinkage and flow of porcelain at high temperature make
attainment of accurate margins difficult. Any timne you
heeat the
porfcelain, the glass structure moves. you never
get that really sharp
lmargin like with metal.
Dental
porcelain
- glass matrix
Strengthenin porcelain
-
increase the modulsus of elasticity elasticit (stiffness)y
-
decrease the effect of surface flaws
Campbell 1989 --
study on porcelain strength..
increasing modulus of
elasticity
- current methods achieve this va the enhances
mechanical propoerties of
the crystalline
phase
strengthening via the crystalline phase
1.
dispersion hardening
2. enamiling to high strength profiles
3.
controlled crystallization
The dillemma boils down to:
strength vs. translucency.
Dispersion hardening (increase
crystalization ratio)
- aluminous porcelain
- cerestore
-
hi-ceram
- optec hsp
O'Brien (experimantal)
don't
worry about brands, but know methods of
strengthining.
Controlled Crystallizaition
- dicor
(cast glass)
- CeraPearl
method for dicor: wax up,
precerammed casting -- cerammed casting --
shaded crown. some
say this is almost too translucent
Enameling to a high
strength profile -- platinum foil is place upon
core. High
strength core porcelain as a sub structure. and this core is
very strong.
Decreasiig the effectg of the surface
flaws
- decreaseing frequency or size
- limiting crack
propogation
problem -- the ceramic core is also
susceptible to microcracks. you get
surface flaws on outside
and inside...
decreasing frequency and size of surface
flaws
- enamelling to metal foils
- fabrication
using
enameling to metal foils....
- bonded platinum
-
? (didn;t get it)
refractory die material... very porous
die material is used that soaks
up water. withstands high
heat....
Limiting vrack propogation
- enamielling
to metal foils
- dispersion hardening
- pre-stressing the
surface (experimental)
Flexural strength: what is
necessary?
anterior:
- 140-15- MPa (2.1% clinical failure
rtae of bonded platinum aluminous
orr. incosor crowns over a
7 yr perios)
Posterios:
- 450-55- MPa
Summary:
Presently
available all-ceramic crowns do not equal PFM crowns in
strength
Careful case selection is the KEY. usually
anteriors are used for
all-porcelain systems.
study --
repoted mean flexural strengths... we need to know what
"system"
we like to use the most... technicians are going to spend the
big bucks on a system, so they'll want to know what we are
using.
different studies look at different aspects... hard
to make side by side
comparison -- all studies have different
materials, measuring
techniques, etc. But all studies havve a
trend that boils down to this
-- once you get posterior to
the premolars, your strength reqwuirement
is so much
higherthat you need to be wary of porcelain.
Marginal
adaptation: wat is clinicallly acceptible?
- 40um is the
smallest detectable aginakl opening
- 120um is the max
clinically acceptible marginal opening.
Summary:
Margins
Marginal fit of newer porcelains is better than
traditional pjc's, but
still not as good as pfm. All ceramics
are getting a little better,
though...
Lab studies vs.
clinical performance.... observed srength and marginal
fit is
affected by: tooth preparation, fabrication variables, and test
conditions. All three of these thingsa re measures much
better with
clinical performance studies. keep thatin
mind.
Wide variationin strength and fit are ingerent
fot eh all-porcelain
crown... therefore, ? (dind't get)
noe
that some systems have very specific cementationi techniques...
all
ceramicsystems all differ from wach other in terms of
manufacturing,
srength, cementatin, etc....
THE
BOTTOM LINE:
- case selection is critical
- prep design is
critical, critical to mechanial success
- technical supprt
from the labis critical.
--------------------------
project
-- waxingtoday. check protrusives.... get embrasure and line
angle symmetry.
make a matrix based upon wax up. half
a scoop weach of base and
catylist. this will guide you
during cutback. regarding cutback, ou can
use a t3 or
explorer. need a 1mm collar. In the end it will be
colarless.ceramometal jnction will be ust above lingula, in
folla -- as
long as contact area is in ginnival 1/3. Collar
format goes at least to
prox contact. take 1.5mm off inciasl
edge. after taking incisal edge, do
dept uts facially of 1
mm. do same off prox and lingaul surfaces. eep
internalaspect
nice and rounded. ceramometal jctino line is very
distinct.
wax
cutback: looking for:
- uniform reduction (depth cutes --
incisal and axial)
- eval with matrix
- keep neat and
smooth as possibnle
- form rounded internal line
angles
- por/metal junctino is 90 degrees.
Barry
Hillam
barry@hillam.net
Pros
11/12/01 8:46 am (Dr. Schneider)
Common
Sense Evaluation of Currently Available All Ceramic Fixed
Restorations
Dr. Schneider has concerns with this
stuff...
is all ceramic the new standard? (picture of
woman with missing incisor)
all ceramics is a very hip
topic.. but dr. s still has questions that
have not been
answered yet.
Most esthietic failures with anterior
restorations are a result of
immproper soft i=tisue
mamagement rather than deficiencies in the
materials utilized
in the restoration..
pfm advantages:
- good margins
-
controlled occlusal contacts
- easily polished when adjusted
-
good esthetics
- metal coping give s good spurrot and
strength
- metal contacts minimize enamel wear. especially on
posterioir .
Porcelain wears enamel.
Advancess
in PFM technilolgy tha have imporc=oved esthetics:
- inernal
color addition
- segmental buikld up of various tooth colo
compoents
- accurate all porcelain margin fabrication.. today
we can get darng
good margins.
Many new all ceramic
system (you'l be barraged with these) are promoted
for their
high strength...
assming that streggtendn porcelains will
result inimporoved clincal
performance lacks clinical
valisity
with current techniques it is not possible to
produce any ceramic
restoration without griffith
flaws.
sekectin all ceramic stuff based on contrlolled
clininal studies.
there is anl one 5 year study on
all ceramic available .. "I'm not
goung to try stuff on
patients -- show me the data.
all ceramic systems,
clinical trials show that alll porcelains have a
faiklure tae
of 33 % in posteriors.
it seems prudent, then, to keep all
porcelains off of molars. Dr. S has
big
scneiders
concerns for all ceramic restoratinos:
1. lab trials don't
determine clinical performance.
2. controlled clinical trials
are crucial -- there are almost none
3. all ceramics should
not be used indiscriminately to restore
posteriorteeth and
occlusion. -- show me the restoration in 5 years....
4. no all
ceramic system provides inherently superior marginal
integrity.
procera: "you get perfect margins...
how about them" they are only open
100 microns. that's
stupid! that's way too open.
5. alll ceramic sstems
uutilizing refractory dies will be technique
sensitive unless
each batch of refractory material is identical. ... any
system
that requires rafratory type investmemnts: stay awa from it.
6.
all ceramic systems as currentl =ty designed require more tooth
reduction than pfm's. prblem if small tooth to begin with
7.
very tough to comensate for lack of ideal preparation.. all preps
must be based up and ideal
8. all types of porcelain
will cause attrition of opposing dentition
9.
currentlyinidicated for single unit. no studies for
bridges
10. optimal results are obtained with standardized
procedures. systems
classified as technique sensitive will
haea lack of predictably... these
are farfrom simple... too
many variables to haver a million steps...
11. ther are no
economic advantages with all porcelain... so why are we
doing
it? for esthetics...
12. all ceramics are less biologicall
active than those using metal
alloys. so may be uselful
for those with metal allergies. but this is
almost a non
issue. Dr. S. has inly teated 1 patient with this.
13. if
it hasan internal opaque core, the esthetics will be no different
(better) than pfm.
14. pressables... when
internal characterization isn't possible, you
have to
colorize on external surace. in this case it will look
unnatural. color can wear off. they ca look liike a piece of
chalk.
15. excellent esthetic results may be achieved by
talented (not gifted)
technicians IF you give them enough
reduction. that's their bigest
complaint
1
what
is the status of these restorations after endo is done? lots of
times you can restore the acces with an alloy, and you don't
have to
scrap th ecrown. you just can't do this with all
ceramic... most of the
time the will explode. approx 25% --
woops, 10-17% of all fixed
restoratioons will need endo
therapy.
conservation of tooth structure determines
long term rognosis -- this
is a huge factor.
dr
s. uses all ceramic, just not indiscriminately.
current
litaruter ahows pfm lasting WAY longer.
conservation of
toooth structure with preps is still an absolute
cornerstone
don't fall forall the stuff at trade
shows, like about cad cams, etc...
go to back of jada.
find what's for sale. you'll see cad cams for sale.
people
always getting rid of them.
gold and alloys last decades
(pics)...
case -- guy insisted on all ceramic. dr s.
didn't wasnt to . patient
won. but it started to crack in 2
yrs...
a good technicial=n can match shade gide very well
with pfm.
BOTTOM LINE:
patient selectin: bruxer,
oclusion, pros design (long span, etc)
- prep design (critical
to success fo all ceramic)
- technical support (should lab
invest in it?)
Barry Hillam
barry@hillam.net
Pros 11/16/01
8:00 am
Ceramometal
Restorations -- Framework Design
dentists will
be designing framework. technician will be fabricated, but
YOU
DA MAN.
ceramometal framework
- material properties
-
anterior vs. posterior
-fpd considerations
- steps of
fabrication
- evaluation
the framework gives the
strength. the porcelain just makes it pretty.
connectors in
the porcelain are critical.
you can't really evaluate
framework when porcelain is on.
The ulktimate goals of the
frameqork
- esthetics
- function
- predictable success.
(on't want patient to ome back in a ear with
fractured
porcelain -- they should last for a predictable amount of
time.)
who's in charge?
- the dentist?
- the
labratory technician?
we design it, they make it.
collaborate and agree re: materials,
fabrication
methods.
Material properties
- Porcelain
-
metal
base metal alloy. porcelain must meet coefficient of
thermal expansion.
Metal properties
- metal choices
- high noble alloy (what we use at the school - we'll use
sf52 for
our project)
- noble alloy
- basealloy
- ceramometal bond
-
pysalproperties
Porcelain properties
- strong im
compression
- weak in tension
- brittle
- abrasive
(where to put ceramometal junction?)
knowing these things
efects youir design.
Framework COnsiderations
-support
forporcelain
- marginal integrity
- framework rigitity
0
wear potentian
- final stess state
-
- esthetic
conseiderations
Porcelain support
- por thickness shoul
dnot exceed 2 mmm
- wrap porcelain
- lingual
surface of anterior
- buccal cusp wrap of
posterior
pic: bad prep. lost tooth structure. metal makes
up for deficiency. ten
everyhing is okay. but if you g and
try and stack more than 2 mm of
porcelain, the material
fatiggues -- ou get micro cracks, and then,
**POW!**
catastrophic failure!! Nobody wants that kind of
anguish.
sometimes you may want to brin lingual all the
way up in metal. nice for
strength, bad for esthetics.
avoid
having ceramometal jnctn the same heightsh as incisal edge
support. too much potential for fracture.
Marginal
Integrity
- Metal Margin
-entire circumference
of restoration
- 0.5 mm or greater when present
-
Esthetic considerations
-disappearing margin
- porcelain shoulder
know what accomodates what.
shoulder bevel means ou must have collar,
for wxample. heavy
chamfir gives you more options.
Framework Rigisity
-
metal allo
- metal thickness (this is the usual culprit)
- 0.3-0.5mm
- dependent upon preparation
-
Non-esthetic surface left in metal
-
occlusal, lingual
east and west coast -- ou'll see very
littel metal on pfm's. Only a
slight lingual
colllar
flex=length cubed or 1/depth cubed
or
1/width
picture -- bad design
anterior vs.
posterior -- the connector design is different according to
tooth shape. we compromise a little with lingual areas so we
can good
esthetics with facial (?)
Wear Potential of
Porcelain
- evaluate overall occlusal scheme
- centric
contact on metal when possible
- location
- opposing dentition
sometimes over time the
porcelain ends up looking way out of place
becasue of how
much the neighboring teeth wear...
putting contact in
porcelain is smart if porcelain restoration is
opposing.
Final
stress state of porcelain
- relatively uniform por thickness
-avoid extrememly thin or thick
- round internal
framework line angles
- minimize the number of surfaces
veneered with porcelain
- butt-joint porcelain-metal
junction
- Occlusal loas away from porcelain metal junction
we
do a full contoured wax up so that we can get uniform thickness
of
porcelain.
don't make the incisal edge point on the
framwework.
Don't put occlusal contacts on the ceramometal
junction. It should be
1.5mm away.
FPD connector
design
- maximize occlusogingival dimensioin
- unencumbered
gingival, facial, incisal/oclusal embrasures
-
esthets
-perio heallth
- compromise lingual
embrasures
- flex + length cubed (Etc, from above)
Lingual
embrasures aren't as sharply defines as they would be in an all
metal restoration.
You can get frameworks back in the
wax cutback stage... (You all go
ahead and do that...)
FPD
cPontic design'
- appearance zone
- modified ridge
lap
- illusion of tooth
- convex
surface
- lingual deflective contour
- non
appearcnce zone
- bullet of conical
Anterior
Restorations
- prox contacts not blocked by metal (so light
can pass through)
- incisal edge not bloced by metal
-
marginal design
-disappearing margin
-porcelain shoulder
badpic - framework contacts are
in metal between central incisors. there
will be no
transmission pf light...
understand (use book) how winged
design plasinto this (?)
Post restoration
prox contacts
- metal or porcelain
- full coveralge por
- marginal
design
some people like prox contacts in porcelain on
posteriors. In this way
it is easier to to tweak
contacts if ou want to change them.
Steps of framework
fabrication
1. full contoured wax up
2. cut back of wax
pattern (design framework
3. cast, and if
necessary,
solder
4. try-in framework
you can
have labsend back wax up and matrix so you can see if they did
fulll contour (then you can plant an ultra-small tracking
device in the
wax so that ou can trace their every move when
you send the wax up back)
"Finessing the collar..."
(referring to the wax cut-back)
Evaluation of the
Framework
- full contoures wac up
- cut back of wax
pattern
- metal farmework prior to porcelaini
application
Potential Ceramometal Failers
- Materials
-metal
-porcelain
- Oral Conditions
(bruxing, etc)
- Improper famework design (picture: WAY too
little pontic supprt in
framework
Physical porcelain
fractures casues, reparing and prevention
- potential for
fracture
- resognize during fabrication
-
before repair
Physical fracture casues
- thin metal
substructure (thick enough, location, fx rewuirements)
-
improper metal design...
(didn't get all of the last three
slides)
"the ceramometal framework needs to satisfy
all the esthetic and fx
demans,...."
Project--
matrix..... draw framework design... do depth cuts. good to
use cleoid. takek small amoutns off at once. sharp
ceramometal juncture,
but rounded intenal line anlges.
Wax
cutbazck
- uniform reduction
- eval with matrix
]- keep
neat and smooth as possible
Couple changes -- phosphate
boded investments on monday. seniors need
benchlab ny 12:30
on monday. schedule -- december 21 -- id practical.
takes 20
min per rotation. that will be changed to dec 7, during
class.
Barry Hillam
barry@hillam.net
Fixed
Pros
11-16-01
Corrinn
Cosaert
PFM
framework Design and PFM Cutback
Phosphate
bonded investments
Phosphate
Bonded Investments
-used with alloys requiring casting temperature in excess of 2100
-Expansion varied by the proportions of silica solution in water
increase silica, decrease water = Increased expansion
-Gypsum
bonded investment carried out over 2100 F have decomposition of calcium
sulfate releasing contaminating sulfur in the mold. (silica solution
is special solution we will be using with powder)
-Power Cast will be used with Power Plus Liquid
11ml of liquid and 3 ml of water.
-Completely wet powder by hand mixing 20 sec.
-Vacuum mix for 90 sec (b/c setting reaction will release gas into investment
so takes longer to release all gas from mixture)
-Let
set for 45 min (no submergence of investment into water) expansion controlled
by proportion of liquid/powder we use
-1250 C oven---need about 45 min to an hour to reach 1250 burnout temp
-Heat soak for 45min at 1250C
-Crucible
should be new (no contamination)
-Cast-let
cool (DO NOT QUENCH-b/c might cause distortion, want it to be stronger
and harder,
don’t
want alloy to be in soften state)
-Remove investment (can use air abrasion)
-Remove internal positives
-Fit onto die
disclosing agent (occlude)
-Evaluate overall fit and marginal adaptation
-cut sprue off w/ a joe dandy
METAL
PREPARATION
-done to prepare metal before porcelain is added
*pink stone---use for gross removal of metal
*green stone---finer details
make sure to use new set of stones so to
eliminate any chance of contamination
-use caliper before adjusting!
NEED INCISAL CLEARANCE OF AT LEAST 1.5mm\
Facial clearance -want thickness of metal to be .3mm to have at least
1.2mm porcelain
Metal
Finishing
-Finish in one direction
Mesial-Distal---never ever ever overlap direction of finishing
Pick a direction and stay with it
Prevents overlapping of metal and trapping contaminates
Reduce metal to
.3mm for HIGH NOBLE METAL
.2mm for BASE METAL
metal surface should be smooth with a satin finish this can be achieved
using green stone
Framework
necessities
Develop rounded internal line angles
Create distinct metal-porcelain junction
Reduce metal collar to desired thickness
Disappearing margin
.5mm
is the smallest collar for polishing (it can be larger depending on
location)
REVIEW
OF INVESTMENT MATERIALS by Clark Stanford
This lecture was a review of a previous lecture on 3/21/01. IF by chance
you can’t
Find yours you can copy mine.
Pros
objectives
I
compiled these from book, old notes, and old objectives
1. Know and
understand the first step in a well designed PFM framework
Can
only be achieved by waxing to full contour the restoration and then
cutting back
the
correct amount of wax so that there is an even thickness of reduction
allowing
for
even thickness of porcelain application, good connector design, and
optimally placed occlusal contacts.
2. In a PFM
framework how do anterior and posterior designs compare in relation
to: proximal contacts, connector designs, wrapping over onto occlusal/lingual
surface, marginal design?
Anterior
-Proximal contacts are both in porcelain allowing for max esthetics.
-Winged -minimizes the amount of translucency in interproximal area
-Wingless-better esthetics
-Connector design- narrower buccal lingually than posterior, there for
maximize occlusal gingivally (connectors should be placed so they do
not impede on oral hygiene, lingual embrasures may be compromised at
times
to
allow for max esthetics)
-wrapping over occlusal/lingual surface for anteriors-the design of
the lingual portion is very much dependent upon the dentition that is
opposing the restoration.
-Make
sure that your centric contact is 1.5mm away from the metal/porcelain
junction.
Posterior
-Proximal contacts -mesial in porcelain while distal in metal (a distal
contact
In porcelain allows for a more conservative tooth preparation)
-Connectors
This is directly from book pg 496
If
only a facial veneer is involved, make the connectors identical to those
for a conventional restoration. If the incisal or occlusal aspect is
involved in the porcelain veneer, don not displace the connector cervically,
because access for oral hygiene will be impeded.
3. What is
the relationship of the occlusal contact to the metal ceramic junction?
The
occlusal contact must be 1.5 mm away from the metal ceramic junction
or else
Porcelain FRACTURE.
4. How does
the porcelain stress state relate to the number of surfaces covered
with porcelain?
Covering
more surfaces in porcelain is going to increase your stress state and
lead to fracture.
5. What is
the optimal thickness of PFM coping (wax vs. metal)
Wax:
.5mm thick so that you can get proper casting as well as most of the
necessary reduction for adequate porcelain addition.
Make
sure to reestablish the collar before investing to about .5mm thickness
to ensure an undistorted complete casting.
6. What are
the purposes of a full contoured wax-up?
-to
arrive at a substructure that will support a relatively even thickness
of porcelain
-If
the retainer is to serve as part of a FPD it must allow for proper connector
configuration
and
location
-The
restoration must conform to the normal anatomic configuration of the
tooth that is being replaced.
If
this technique is not followed your bound to screw up : ) But we’re
all used to this because it’s pros which by very definition means
your bound to screw up somewhere along the line meaning you’ll
have to start all over again! Oh, no, I’m not bitter.
7. Optimum
porcelain thickness in the PFM restoration
1mm
at cavosurface margin (heavy chamfer)
axial
reduction so that 1.5mm of porcelain can be added.
Incisal
edge reduction of 2.0mm.
8. What design
considerations should be taken into account with a PFM long span FPD?
(the
following is from the book pages527-528, 535
There
are many things to be considered when making a long span PFM FPD one
of which is
MECHANICAL
Long span FPD are inevitably susceptible to mechanical problems
(Remember
Law of Beams that the amount of flexure varies inversely with the cube
of the depth, and directly with the cube of the length)
Metal Ceramic FPD are more susceptible to fracture but with adequate
Framework design and porcelain thickness they can be successful.
-need
at least 1.2mm porcelain thickness ( if too thick then it can lead to
fracture)
-make sure that the metal surface is free of pits and irregularities
this helps prevent incomplete wetting by the porcelain leading to
voids at the porcelain metal interface that reduces bond strength and
increases
the possibilities of failure
-sharp angles need to be rounded
-the location
and design of the centric contacts requires
1.5mm distance from metal ceramic junction
excursive contacts must be watched closely.
FPD pontic design
Anterior appearance Zone -typically use the modified ridge lap pontic
Non-appearance Zone-Typically use a bullet or conical pontic. Can’t
Use hygienic pontic with a PFM FPD because you don’t have enough
Room for all the material.
Advantages of PFM FPD
-esthetics and Biocompatable
Disadvantages of PFM FPD
-Difficult if an abutment is not metal-ceramic
-weaker than all-metal
Indications
-Most situations
Contraindications
-long span with high stress
9.What
factors are considered in relation to occlusal contacts?
Metal
contacts are preferred because less abrasive to opposing teeth, can
withstand more stress than porcelain, can adjust contacts if needed.
Make sure that all occlusal contacts are 1.5mm away from ceramo-meatal
junction.
10. Know and
understand what framework design feature help to decrease the stress
state of Porcelain.
-Rounded internal line angles
-Adequate, uniform thickness of porcelain as mentioned above
-Porcelain
thickness not to exceed 2.0mm (If you have a tooth with a lot of reduction
you can make up the difference in the metal substructure. )
-Occlusal contacts at least 1.5mm away from Ceramo-metal junction
-Metal should be smooth without pitting so that the ceramo-metal bond
is
maximized
-Need at least .5mm of metal for collar design inorder to be able to
adequately polish
the metal.
-limit
number of surfaces with porcelain
-90
degree butt join at porcelain metal junction.
-
What
factors are necessary to optimum esthetics?
Student
Notes
Fixed
Pros
11/26/01
Nicole
Eberle
Porcelain
Application
1st
step = oxidation cycle in the oven. Holds the temp for 5 min in order
to oxidize the surface to bring up trace metals to the surface so that
it will bond with the porcelain.
Opaque
= off-white/egg-shell
Pink=body
Incisal=white
(used on middle to incisal 1/3)
Stains/modifiers
applied externally after have everything fitted and shaped the way you
want. This is the last and final step before finishing metal.
Body
makes up most of the crown surface. Incisal goes mainly on middle to
incisal 1/3, has a gradual transition. Modifiers can also be placed
internally, which makes the tooth look much more vital. We will be placing
stains externally. Can use the stains in clinic too.
Opaque
Creates 1st metal-porcelain
bond
Masks color of metal/grayness
Primary source of color for
the crown (many colors go together to create color chosen on the shade
tab)
Should not exceed 0.1mm (therefore
do not need a lot of opaque to mask metal and create bond)
Make
sure metal prepared to 0.3mm, especially on facial. May have more on
incisal, interproximal, and lingual depending on what prep looks like,
but try not to exceed 0.1 with opaque.
Clamp
lingual collar of framework with hemostat after metal prepared with
green stone (final step). Then sand blast, steam clean to rinse, then
ready to go into oven for oxidation cycle. Sandblaster should take less
than 30 sec and want to keep moving around as not to perforate the framework.
Do not touch coping with fingers (even with gloves) after sandblasted
because fingers have oil and gloves will contaminate surface. Sagger
tray (ceramic tray) used in porcelain oven. Pillow put on tray and coping
put on pillow and tray put in oven. When comes out of oven, grab coping
with hemostat. If you oxidize, you need to put on at
least one layer of opaque. Other layers can do one at a time and
leave it. Put opaque on glass slab. Two different liquids can be used
to mix porcelain: 1. distilled water, 2. special modeling liquid (primarily
water with a few extra ingredients that make the water evaporate a little
slower) Both do the exact same thing, no problem using either one. Mix
till it flows fairly easily. As long as you keep clean, can reuse powder
mixture if you add water. Once oxidized, framework has a little more
charcoal color. Number of ways to apply porcelain to framework: 1. glass
instrument, 2. sable brushes (#1=small, #6=large). Place thin layer
of opaque with #1 sable brush. Make sure coping is cool when place opaque,
otherwise water will evaporate too quickly and you can’t move opaque.
If blotchy, even out opaque by tapping with another instrument. Will
not necessarily get full masking of metal with 1st layer
of opaque. May need 3 layers to completely mask. Judge this after porcelain
has been baked in the oven. Do not just set hot Sagger trays on plastic
or will melt. Ovens normally run in night mode. Low glaze better for
us for glazing step. Need a dry time for each layer of porcelain, and
this is programmed into the oven. Can reuse brushes, just rinse them
out. We will use the same brushes for the stain. Should have egg shell
texture when opaque comes out of oven. Want to mask grayness of metal
with opaque. Use same glass slab for body/incisal porcelain. Use small
and large brush for this.
Body
Provides basic color of restoration
May shrink as much as 20%
of their volume during 1st firing, so tend to overbuild just
a little bit to compensate (this has to do with how well you are condensing
the porcelain)
Incisal
Enhances translucency of restoration
May shrink as much as 20%
of their volume during 1st firing, so tend to overbuild just
a little bit to compensate
Incisal
put on over body to enhance esthetic result. Put coping on working cast
now, then place porcelain. After opaque, now can handle with fingers,
but keep it at a minimum because want to try to keep it as clean as
possible. Want tissue handy to control water adding to porcelain. Want
more consistency with body and incisal than with opaque when mixing.
When tissue placed next to porcelain it will absorb to get to right
consistency. Also want new Bard Parker blade and cup of water to rinse
brush off as going through the addition process. Dr. L likes to wet
the surface 1st before she adds porcelain.
Holding tissue behind helps absorb some of the water. Build up a general
shape. Not worried about interproximal contacts at this point. If too
much liquid, the porcelain will slump pretty easily. If dry, can’t
move it around and it’s hard to blend in. Use large sable brush
to shape. Add body and incisal at the same time to get a better blend.
Incisal primarily in incisal edge and interproximal. Use Bard Parker
to take off incisal edge and to bevel toward the facial aspect to get
gradual transition from body to incisal from middle to incisal 1/3.
Also take some out of interproximal area. Gently wet porcelain 1st
then add incisal. Smooth it out with a brush. Use tissue to absorb some
of the water. Need to take off of working cast to get proximal contacts.
Grab with hemostat on lingual collar. Work with it initially on working
cast to get F-L and I-G aspect of incisal edge. Shape a little bit with
brush in general so looks like well rounded porcelain anterior crown.
Take small wet brush to wipe away excess porcelain at metal-ceramic
junction so porcelain is not overlapping. Also be sure there is no porcelain
internally, because can see it now, but will not see it be able to see
it after you fire it (esp. incisal porcelain). Vibration condensing
- condense for a few minutes, but be sure to take water off with tissue
as soon as it comes to the surface. Do not tap so hard that all the
porcelain slumps. It you keep vibrating this, it will gradually turn
into a little ball. More than one crown can go on a pillow. After 1st
bake, it has a chalky look to it. We will not going to be looking at
the quality of the porcelain or the color of the porcelain, we will
only be graded on contours and embrasures. Usually, after it comes out
of the oven, will not go into place. Mark interproximal contacts with
marking paper, then shape with green wheel. Adjust incisal edge after
have adjusted proximal contacts. Can draw on porcelain Not unusual to
add porcelain in more than one bake. To do this, hold with hemostat
on lingual collar, then sandblast and steam clean, then add more porcelain.
Once everything is all shaped and clean, experiment with putting surface
texture in (horizontal and vertical). Stain and then put in final glaze
cycle (low glaze). Stains will be premixed with glycerin. There are
different hues and different levels of chroma to practice putting stain
on. After final glaze and not touching porcelain any more, then polish
metal collar on lingual. After porcelain completed, use small green
stone to identify ceramo-metal junction so no flash of porcelain over
90 degree butt joint. Then go over same polishing sequence as you do
with full cast crown.
Fixed
Pros
11/30/01
Mike
Franzman
Factors
influencing Esthetics
Tooth and embrasure form
Surface texture
Color - it is harder to detect
problems with color (the eye is less discriminating with color)
Tooth size
Preparation and fabrication
variables
Tooth
and embrasure form and tooth size are the easiest to see when there’s
a problem.
Color
is generated by waves of electromagnetic energy - there is no such thing
as an exact color match, only a limited range of acceptable variability.
Energy
Distribution x Reflectance x Response = Color Stimulus
(more
reflectance with natural teeth)
Factors
involved in final color: light->modifier->observer (eye)
Dimensions
of Color - These three allow you to communicate the color you want in
the restoration:
1. Hue - The quality of the
color determined by the wavelength.
2. Chroma - The concentration,
intensity, or strength of the hue.
3. Value - The relative whiteness
or blackness of a color (grayscale) - the most challenging aspect of
color.
The
Munsell Color Notation: A color wheel that is good for color comparisons.
Chroma and value tend to have greater spectrum of variability than hue.
The
Vita Shade Guide: used in clinic. There is not enough material out there
to match the variability we see in teeth clinically.
Shade
Matching
1. Clean tooth to be matched
- pumice first, don’t dehydrate the tooth, do the shade selection
at the beginning of appointment.
2. Select guide tab based
on general appraisal of value of hue. Hold the whole shade guide up
to the teeth to pick the right tab range.
3. Moisten the tooth and guide
tab, hold it in direct apposition (same plane) as the tooth you’re
looking at.
4. Squint to appraise the
value - rod cells in the eye are used for this and squinting facilitates
their use.
5. Appraise the hue - is the
tooth more yellow or red? (this is the range of tooth colors yellow
to yellow-red)
6. Appraise the chroma - is
it more intense (gingival) or less intense (incisal)?
7. Limit viewing to 5 second
spurts, use a blue card (or coat) to look away because rods and cones
tire very quickly. (Remember the flag example she used?)
8. View female patients (or
male if they’re into that…) with and without lipstick.
9. Use multiple light sources
- different hues can be given by different light sources, this is called
metamerism. A partly cloudy day is the best source.
The
spectral curve measures the apparent color temperature. It is a color
rendering index. (?)
10. Use the shade guide recommended
by the porcelain manufacturer.
11.
If modification is possible, pick a shade higher in value
and lower in chroma.
When
you stain a restoration it decreases the value and increases the chroma.
12. If modification is not
possible, pick a shade lower in value (so it won’t stand out in
the mouth)
13. If you use modified shade
guides, submit the guide tab to the laboratory.
Final
step of shade:
Communicating
the color appearance to the dental lab.
Accurate
shade matches begin with adequate tooth reduction.
We
need:
Framework 0.3 mm
Porcelain:
Opaque 0.3 mm
Dentin (body) 0.7 mm
Enamel (incisal) 0.2 mm
Essentials
for color prescription:
Proper shade selection
Shade reference to a specific
tab (guide)
Enamel/Dentin blend
Color characterization
-reference to a specific stain
-placement (draw a picture for the lab tech)
Completing
the prescription:
Surface Characterization -
allows the restoration to blend in with natural teeth
Glaze - high, medium, or low
Patient information - young
person, old fogey, where’s their smile line?
Color
is ambiguous (so is Fixed Pros) - People see colors differently
Value:
Decreased
by:
Applying a complementary hue
Applying brown
Using a lower glaze
Increased
by:
Applying yellow
Applying white
Using a higher glaze
Stains:
1. Lower the values
2. Give metameric responses.
Color
selection and matching is a learned process - we must practice.
Fixed
Pros. Student Notes: Monday, 12/3/01
Bob
Fuhrman
Work
Authorization (Dr. Lindquist)
Identify tooth
Shade (ie B3) and type of
Guide used (ie Vita)
Serial # of articulator
Condylar inclination: R= 30,
L= 30
Bennett angle: R= 0, L= 0
Type of Pontic if FPD
Example:
Please fabricate PFM restoration for #5. The master cast is mounted,
die is trimmed with margins marked in red.
--Please
wax #5 to full contour using adjacent teeth as guides.
--Cutback
for porcelain
Create disappearing margin
on facial (with a collar, you need it’s dimensions)
Mesial contact in porcelain,
distal contact in metal
Porcelain-metal junction should
end 1/2 way down lingual incline of buccal cusp. Establishing centric
contacts in metal. No lateral excursive contacts (or Protrusive)
Cast in High noble ceramo-metal
alloy (SF52), fit to die
****Option:
Coping/Framework try-in - this is especially important.
Single units vs. FPD - may
need to section and solder
If working with a new lab
--Prepare
metal for porcelain and apply Vita shade B3
--Shape
porcelain using adjacent teeth as guides
Options: 1) Return at bisbake stage
2) Return stained and glazed
with metal polished
--Draw
a Picture
Lab
Communication: (Todd Fridrich)
Why
is it essential?
1) We are constantly exposed
to new materials and technologies
2) We provide complex dental
treatment
3) High esthetic expectations
are demanded by patients
Enrollment:
only 34 Dental Technology schools now = fewer skilled technicians. Enrollment
has been down 66% in last 25 years, and down 25% in last 5 years.
Don’t
bitch at technicians…they don’t know why you want the restoration
made a certain way, they only make it!
Labs
do not want to stop the production line! In a big lab, if you don’t
specify shade it WILL be A2.
DDS
wants:
Quality product
Good esthetics
Consistency
On time delivery
Lab
wants:
Good impression
Completed work authorization
Adequate working time (1.5-2
weeks)
Timely payment
Write
a MEANINGFUL work authorization! It is a legal document that could save
your butt in court or be incriminating against you.
Work
authorization should include:
Restoration type and tooth
#(s) - scroll this right into the impression too
Procedure, check steps that
you want see the restoration returned before final finished product
Margin design (even implants
have margin designs)
Esthetic
margin options: deep chamfer - good for an all
purpose, porcelain margin. Deep shoulder - for a porcelain butt
margin.
With
the Procera porcelain restoration system, you need to use a diamond
the size of the probe which scans the prep. (This was a huge probe next
to the tooth.) Bad - no one wants to use this type of diamond to cut
a prep.
Framework design - easier
to see when porcelain is not on. If framework is too thick, porcelain
will be too thin. Have a metal collar on the lingual, and a metal occlusal
surface because this is stronger and easier to adjust in occlusion.
Want and even thickness of porcelain for color and strength.
Occlusion, Guidance - put
patient in progressive group function if you know they will wear down
their teeth. Want a balanced occlusion if you know dentures are involved.
Shade and characterization
- best if you can provide ONE shade tab to the lab technician. Now we
use ceramics to match/replace gingiva too. Make sure to compare the
completed restoration to the shade tab AND the written lab authorization
Personal Information - Franzman’s
mom or whomever gets it
Slides
and photos do give helpful characterization information regarding the
teeth and gingiva, but they cannot give shade information
Make
good provisionals! They will build your practice. The work authorization
goes hand-in-hand with a good provisional . . . make a crappy provisional,
you hurry lab tech to get restoration done because provisional looks
so bad . . . you get a crappy restoration back!
Improving
Communication:
Establish an open line of
communication
Relate on a personal level
to technician
Encourage and initiate input
- Technician has a mortgage, kids, etc. . . he won’t tell you you’re
doing things wrong. You must contact Technician for info!
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