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The preparation of abutments for veneer retainers
A U G U S T 1956
V O L U M E 53
• NUMBER 2
MFÜICAJV /JAÆ ’ TAl ASSOCIATION
The preparation of abutments for veneer retainers
R o b e r t E . W il le y , D . D . S ., L o s A n g e l e s
It
h as
been
s a id ,
and
r ig h tfu lly ,
to
th a t
in su re
th e
u ltim a te
su ccess
of
th e
(F ig .
1)
fin is h e d r e s to r a tio n .
o p e r a t iv e d e n tis try o f th e h ig h e s t q u a lity
T h e v e n e e r ty p e o f re ta in e r
is m o r e e a s ily a tta in e d t o d a y th a n e v e r b e fo r e . T h e p r o p e r u se o f h ig h -s p e e d r e
h a s p r o v e d to b e b y f a r th e m o s t re lia b le
v o lv in g d i a m o n d a n d c a r b id e in stru m en ts,
m e t h o d o f a t t a c h m e n t t o a t o o t h . T h is
i m p r o v e d c o n t r o l o f w a x in p a t te r n m a k
c o n c lu s io n h a s b e e n r e a c h e d a ft e r yea rs
in g ,
t e c h n ic s , c o n
o f o b s e r v in g th e su ccesses a n d fa ilu re s o f
t r o lle d c a s tin g m e t h o d s , t o g e t h e r w it h a
f ix e d a n d r e m o v a b le ty p es o f b r id g e w o r k .
a ccu ra te
im p re s s io n
m o r e t h o r o u g h u n d e r s t a n d in g o f th e b i o
O v e r th e yea rs th e v e n e e r r e ta in e r h as
m e c h a n ic a l
show n
p r in c ip le s
in v o lv e d
in
th e
itse lf t o b e so w e ll q u a lifie d to
p r e p a r a t io n o f te e th , a re fa c t o r s e n a b lin g
w ith s ta n d h e a v y fu n c t io n a l stresses th a t
th e
a
fix e d b r id g e s so s u p p o r t e d a re c o n s id e r e d
s e rv ice o f e x c e lle n t s ta n d a r d . I t is n o t
c o m p a r a b le t o a n y o t h e r d e n ta l re s to r a
n e ce ssa ry to s e a rch v e r y lo n g , n o r su rv e y
tio n .
avera ge
p r a c t it io n e r
to
p r o v id e
to
F r o m th e s ta n d p o in t o f b io m e c h a n ic a l
re a liz e th a t th e r e is still a g r e a t n e e d f o r
e n g in e e r in g , th e v e n e e r r e ta in e r is f u n d a
r e -e m p h a s iz in g
m e n ta lly
th e
fie ld
very
d ilig e n tly , th e
h ow ev er,
p r in c ip le s
w h ic h
co rrect.
The
te r m
“ v e n e e r ,”
m a k e f o r g r e a t e r s e rv ice a n d d u r a b ility ,
u se d in p r e fe r e n c e t o
“ c r o w n ,”
p a r t ic u la r ly in th e fie ld o f fix e d a n d r e
th e o v e r la y in g o f th e c o r o n a l p o r t io n o f
im p lie s
m o v a b le p r o s t h o d o n t ic re sto ra tio n s. T h is
th e t o o t h w ith a th in la y e r o f g o ld a llo y ,
p a p e r w ill d e a l w ith th e s e p r in c ip le s in s o
th e s ta b ility o f w h i c h is o b t a in e d b y th e
f a r as th e y a re a p p lic a b le t o th e p r e p a r a
f r ic t io n a l
tio n o f te e th w h ic h a re t o se rv e as a b u t
v e r g e n t w a lls a n d g r o o v e s . T h e v e n e e r is
re te n tiv e n e s s
of
slig h tly
con
m e n ts f o r th ese t w o classes o f a p p lia n ce s .
p r im a r ily a s u r fa c e c o v e r in g o f a p a r t o r
O b v io u s ly , w h a t e v e r th e m e t h o d sele cte d t o r e p r o d u c e th e p r e p a r e d t o o t h , ce rta in
Professor o f fixed prosfhodontics., University o f South ern C alifornia School of Dentistry.
b a s ic p r in c ip le s o f d e s ig n m u s t b e a p p lie d 141
142 • THE JOURNAL OF THE AM ER IC AN DENTAL ASSOCIATION
a ll o f th e e n tire c r o w n . I f th e p r e p a r a t io n
u n w a r r a n t e d . S u c h p r e p a r a tio n s a re in
f o r th e v e n e e r is m a d e essen tia lly w ith in
h e r e n t ly w e a k
th e e n a m e l o f th e t o o t h , th e h a z a r d s to
a tta c h o n ly to th e lin g u a l e le m e n ts o f th e
a n d in v ite fa ilu r e . T h e y
th e p u lp a t t e n d a n t o n th e o p e r a t io n to
t o o t h , a n d fle x u r e o r e v e n f r a c t u r e o f th e
th e t o o t h a re g r e a tly m in im iz e d .
u n s u p p o r t e d p o r t io n o f th e t o o t h is p o s
The
d o m e lik e
fo rm
of
m e t a l,
aug
sib le. T h e fle x ib ilit y o f th e t o o t h s tru ctu re
m e n t e d b y th e tru sslik e s u p p o r t o f th e
s h o u ld
g r o o v e s , c o m p r is e s a m e c h a n ic a l d e s ig n
c h a r a c te r is t ic
h ig h ly
brok en
c a p a b le
of
resistin g
d is t o r tio n .
F o r c e s d ir e c t e d a g a in st th ese v e n e e r s te n d to
sea t
th e m
p r e p a r a tio n s .
m ore The
fir m ly
ven eer
on
a ls o
of
in m in d . T h is
d e n tin
c e m e n t jo in t s
m ay
and
go
le a d
to
u n recog
n iz e d as th e c a u s e o f fa ilu r e .
th e ir
O u t s t a n d in g as a ca u se f o r m a n y f a i l
th e
u res o f re ta in e rs a n d a s p e c ific in sta n ce
ties
s tr u c tu r a l e le m e n ts o f th e c r o w n
a lw a y s b e b o r n e
m ore
o f fa u lt y e n g in e e r in g is th e in d is c r im in a t e
tig h tly t o g e th e r , a n d th u s e lim in a te s th e
u se o f in la ys ( F ig . 4 ) . I f th e in la y p r in
p o s s ib ility o f fr a c t u r e d e n a m e l w a lls o r
c ip le is a n a ly z e d c a r e fu lly , it w ill b e seen
cu sp s. V e n e e r s s h o u ld a lw a y s b e d e s ig n e d
th a t b e c a u s e o f th e n a tu r e o f th e m e ta l
w it h
th is
im p o r t a n t
c o n s id e r a t io n
in
u se d a n d th e t o o t h s tru ctu re in to w h ic h
th e
of
c r o w n o f th e t o o t h , c o m p o s e d la rg e ly o f
even
d e n tin , a fle x ib le s u b s ta n ce , c o u ld h a r d ly
m in d . In
it is p la c e d , th e r e is in c o n s is te n c y . T h e m ost
in sta n ce s
dem ands
e s th e tics m a y b e a d e q u a t e ly m e t , th ou g h
a
c o n s id e r a b le
p o r t io n
of
th e
c r o w n m a y b e c o v e r e d w ith m e t a l. P r o p e r
be
c o n s id e r e d
a s u ita b le s tr u c tu r e in to
w h ic h t o in se rt a n o t h e r fle x ib le m a te r ia l,
d e s ig n a n d m i n im a l m a r g in a l e x te n s io n
th e m e t a l a llo y o f g o ld , t o resist th e severe
can
fo r c e s t o w h i c h th e in la y is e x p o s e d . F le x
fu lfill
e s th e tic
r e q u ir e m e n ts
under
o r d in a r y c o n d it io n s o f s p e a k in g , la u g h in g
in g , p a r t ic u la r ly in th e ca se o f reta in ers,
o r s m ilin g .
is in e v ita b le , a n d th e b r o k e n m a r g in s o o n
I n p r a c t ic a lly a ll teeth c a r r y in g a p a r
in d u c e s fa ilu r e .
tia l v e n e e r , th e e n tire f u n c t io n in g s u r fa c e ,
A fu r t h e r in a d e q u a c y o f th e in la y r e
in cis a l o r o c c lu s a l, is c o v e r e d . B y th e u se
ta in e r is th a t th e c u s p h e ig h t is t w o to
o f lo n g b e v e ls , th e m a r g in s a r e c a r r ie d
th r e e tim es in c r e a s e d w h e n e v e r th e o c
o u t b e y o n d th e fa c e ts o f w e a r , t o a c h ie v e
clu s a l g r o o v e is c u t in o r d e r t o r e c e iv e
th r e e d e fin ite en d s (F ig . 2 ) . F ir st, g r in d
th e in la y ; this cre a te s a w e d g i n g o r c r o w
in g o r w e a r is n e v e r a llo w e d t o e x e r t d e
b a r e ffe c t . W h ile th e t o o t h s u p p o r t in g an
s tr u c tiv e
in d iv id u a l in la y m a y w ith s ta n d s u c h
fo rce
on
th e m a r g in
b e tw e e n
a
m e t a l a n d t o o t h . S e c o n d ly , th e s w e e p o f
p r o c e d u r e , a f r a c t u r e o f th e u n p r o t e c t e d
f o o d o v e r th is m a r g in d u r in g f u n c t io n is
c u s p o r cu sp s is v e r y p o s s ib le u n d e r th e
s im ila r t o
the' s h e d d in g o f w a t e r b y
a
lo a d r e q u ir e d t o s u p p o r t a fix e d b r id g e
s h in g le r o o f ; th e a c t i o n te n d s t o c lo s e th e
or
m a r g in r a th e r th a n o p e n it. T h ir d ly , th e
stre n g th o f v e n e e r a n d in la y re ta in e rs is
s tr u c tu r a l e le m e n ts o f th e t o o t h a r e h e ld
w e ll
to g e th e r . O n u p p e r a n t e r io r te e th , th e re
v e n e e r c a s tin g s u p p o r ts th e t o o t h w h ile
need
be
no
undue
of
m e ta l.
th e
upper
t o o t h .”
m ay
be
w e ll h id d e n
a tta ch m en t.
d e s c r ib e d
T h e in c is a l m a r g in o f m e ta l o n a n t e r io r te e th
exp osu re
p r e c is io n
in la y
by
c a s tin g
th e is
The
rela tiv e
ph rase:
su p p orted
“The by
th e
by
W h e n te e th w h i c h h a v e s u ffe r e d e x
c a r e f u l r o u n d in g o f th e s u r fa c e in o r d e r
tr e m e c a r io u s in r o a d s a re t o b e r e s to r e d
t o c a s t th e r e fle c tio n s d o w n w a r d ( F ig . 3 ) .
o r u s e d as b r id g e a b u tm e n ts , a p p lic a t io n
A s a g e n e r a l r u le e ffo r t s t o a v o id in v o lv in g
th e
e n tire
o c c lu s a l
s u r fa c e
of
of
th e
s tre n g th
ven eer of
p r in c ip le
th e s e
te e th .
en h an ces The
th e
“ w rap
th r e e -q u a r t e r v e n e e rs in th e p o s t e r io r p o r
a r o u n d ” e f fe c t o f th is ty p e o f ca s tin g ties
tio n o f th e m o u t h f o r e s th e tic re a s o n s a re
th e w e a k e n e d p o r t io n o f th e t o o t h to th e
WILLEY . . . V O L U M E 53, AUGUST 1956 • M3
s tr o n g e r , th u s e lim in a t in g th e t e n d e n c y
q u a t e le n g th c o n s t it u t e th e g re a te st sin g le
o f f o r c e s t o ca u s e fr a c t u r e ( F ig . 5 ) . T h is
e le m e n t in t h e sta b ility o f a c a s tin g o n a
is o n e o f th e im p o r t a n t a p p lic a t io n s o f
t o o t h ; th a t is, p r o v id in g fr ic t io n a l r e t e n
th e v e n e e r a n d is f u n d a m e n t a l in a b u t
tio n . F r ic t io n a l r e t e n t io n c a n b e d e fin e d
m e n t d e s ig n .
as th a t r e s is ta n ce t o r e m o v a l o r d is p la c e
I n y o u t h fu l p e r so n s a n d o th e r s h a v in g
m e n t o f a c a s tin g o n a t o o t h w h i c h b e
te e th w ith e x t r e m e ly la r g e p u lp s a n d e x
c o m e s a c t iv a t e d b y fo r c e s t e n d in g t o d is
te n d e d
lo d g e it. T h is re s is ta n ce is b r o u g h t a b o u t
h orn s,
th e
veneer
p r in c ip le
r e c o m m e n d s its e lf b e c a u s e o f its g re a te r
b y th e f r ic t io n a l f o r c e b e t w e e n th e a lm o s t
s a fe ty
p a r a lle l in te r n a l w a lls o f th e ca s tin g a n d
(F ig . 6 ) . V e n e e r p r e p a r a t io n s o f
a d e q u a t e stre n g th m a y b e m a d e w it h o n ly
th e e x t e r n a l w a lls o f th e p r e p a r a tio n .
s lig h t p e n e tr a t io n s in t o th e d e n tin . I t is
A slig h t s p a c e a llo w e d f o r c e m e n t b e
w e ll in s u c h in sta n ce s t o u tiliz e o n e o f th e
t w e e n ca s tin g a n d t o o t h a ft e r p e r m a n e n t
h a r d e r c r o w n a n d b r id g e g o l d a lloys.
p la c e m e n t o f th e ca s tin g w ill n o t in te r fe r e
T h e a c c e p t e d ru les p e r t a in in g to e x
p e r c e p t ib ly w it h this r e t e n t io n , p r o v id e d
te n s io n f o r p r e v e n t io n a re o r d in a r ily a p
p r o p e r e n g in e e r in g h a s b e e n u se d in th e
p li e d t o th e v e n e e r ty p e o f c a s tin g f o r
p r e p a r a tio n .
re ta in e rs o r in d iv id u a l re s to r a tio n s . T h e
o v e r ly c o n v e r g e n t w a lls la c k f r ic t io n a l r e
S h ort
p r e p a r a tio n s
w ith
a d d it io n a l ru le o f a v o id in g d ir e c t f o r c e
te n tio n
o r a b r a s iv e c o n t a c t o n m a r g in s is a lo g ic a l
w o r k d e n ta l c e m e n t in th e m a in serves
s u p p le m e n t . A l l m a r g in s s h o u ld b e
o n ly as a s e a le r ; its p o w e r o f r e t e n t io n
ex
and
in v a r ia b ly fa il.
In
b r id g e -
te n d e d t o r e la tiv e ly im m u n e a rea s. W h e r e
is n e g lig ib le . I n te e th o f a v e r a g e e x p o s e d
it is d e s ir a b le to m in im iz e th e d is p la y o f
c o r o n a l le n g t h , th e g in g iv a l m a r g in o f th e
g o l d , m in im u m e x t e n s io n s h o u ld b e p r a c
p r e p a r a t io n w ill b e p la c e d s lig h tly s u b -
t ic e d (F ig . 7 ) . W h e r e th e r e is n o e s th e tic
g in g iv a lly . H e r e , v e r y o f t e n , w h e r e f o r c e
c o n s id e r a t io n ,
is t o b e h e a v y a n d th e o v e r - a ll le n g th o f
m a x im u m
e x t e n s io n
w ill
g iv e g r e a t e r a s su ra n ce o f s ecu rity .
th e t o o t h is s h o r t, th is m a r g in m u s t b e '
' i
c a r r ie d
w e ll b e lo w
th e f r e e g in g iv a in
o r d e r to p r o v id e s u fficie n t le n g th t o th e
PR E P A R IN G A V E N E E R R E T A IN E R
p r e p a r a t io n . O n th e o t h e r h a n d , w h e r e T h e th r e e -q u a r t e r v e n e e r r e s to r a t io n o n
g in g iv a l re ce s s io n h a s e x p o s e d c o n s id e r
a m a x illa r y a n t e r io r t o o t h t o s e rv e as a
a b le
r e t a in e r f o r a fix e d o r r e m o v a b le b r id g e
e x t e n s io n
p r o b a b ly d e m a n d s m o r e skill o f th e o p e r a
c h a n ic a l d e m a n d s . T h e g in g iv a , b e in g a
crow n is
o r root
le n g th , s u b g in g iv a l
u n n e ce s s a ry
to
fu lfill
m e
t o r th a n a n y o th e r p r o c e d u r e . H e r e th e
tr a n s ito r y tissu e, n e e d n o t b e th e f a c t o r
d e n tis t c o n fr o n t s a c o m b i n a t i o n
d e t e r m in in g th e lo c a t io n o f th e g in g iv a l
m e c h a n ic a l
and
es th e tic
o f b io
dem a n d s.
A
m a r g in o f a ca s tin g .
m i n im u m o f t o o t h s tru ctu re is a v a ila b le
T h e d e v e lo p m e n t o f p r o p e r ly c o n v e r
b y w h ic h a d e q u a t e a tt a c h m e n t m a y b e
g e n t w a lls w ill resu lt in v a r io u s f o r m a
o b t a in e d
tio n s o f th e fin is h in g lin e r e g io n
to
resist c o m p a r a t iv e ly
heavy
(F ig . 9 ,
fo r c e s . A d d e d to this is th e n e ce s s ity o f
a b o v e ) . A t tim es th e r e w ill b e ju s t th e
a v o id in g e s th e tic o f fe n c e . T h e r e a re fiv e
slig h test
c o n s id e r a tio n s
lin g u a l s u r fa c e o f th e lo w e r m o la r , w h e r e
in
to o th
w h ich
m ore
c a p a b le
can of
th e
p r e p a r a t io n
m ake
su ch
of
a
a
c a s tin g
w ith s ta n d in g
h o stile
as
on
s h o u ld e r
d e fin ite th e
fin is h
o th er
m ay
be
lin e ,
s u r fa c e s
as o n a
d e v e lo p e d .
th e
d e fin ite By
th e
fo r c e s . T h e s e p r in c ip le s m a y b e a p p lie d
p la c i n g o f a l o n g b e v e l, h o w e v e r , th e d e f i
to a n y t o o t h c a r r y in g a p a r t ia l v e n e e r .
n ite fin is h lin e p r in c ip le is still e m p lo y e d . T h e s h o u ld e r f o r m a t io n is o n ly in c id e n t a l
W a lls a n d G r o o v e s • W a lls a n d g r o o v e s
t o t h e p a r a lle lin g o f th e w a lls
( F ig . 8 ) o f p r o p e r c o n v e r g e n c e a n d a d e
b e lo w l e f t ) . T h i s p r in c ip le is a p p lie d t o
( F ig . 9 ,
• THE JOURNAL OFTHE AMERICAN DENTAL ASSOCIATION
F ig. I • T h r e e -q u a rte r v e n e e r p re p a ra tio n on u p p e r c u s p id , fu ll v e n e e r on lo w e r m o la r, h a lfc ro w n o n lo w e r m o la r a n d th r e e -q u a r te r ve n e e r on u p p e r b ic u s p id
F ig . 2 • P re p a ra tio n in v o lv in g fa c e t o f w e a r w ith m a rg in e x te n d e d to n o n fu n c tio n in g a rea , fo r "s h in g le d r o o f " e ffe c t
F ig . 3 • S e c tio n s h o w in g g o ld - to o th re la tio n s h ip . A rro w s in d ic a te d ir e c tio n o f lig h t rays r e fle c te d o ff f la t s u rfa c e and ro u n d e d su rfa c e , re s p e c tiv e ly
WILLEY . . . VOLUME 53, AUGUST 1956 • 145
F ig . 5 • The " w r a p a ro u n d " e ffe c t o f th e ve n e e r tie s th e p o rtio n s o f th e to o th to g e th e r, w ith o u t e s th e tic o ffe n c e . Shown a re a se ve n -e ig h th s v e n e e r on u p p e r fir s t m o la r, a nd th r e e -q u a rte r crow ns on lo w e r b ic u s p id and u p p e r cu spid
F ig . 6 • S e ctio n s sh o w in g e x tre m e ly la rg e p ulp s in r e la tio n t o d e p th o f a v e ra g e v e n e e r p re p a ra tio n s
146 • TH EJO U R N AL OF THE AMERICAN DENTAL ASSOCIATION
th e c in g u l a o f cu s p id s o r o t h e r a n t e r io r
and
te e th , w h e r e it is es s e n tia l th a t a c o lla r
g r in d in g s .
lik e f o r m a t io n b e d e v e lo p e d ( F ig . 9 , b e
th e
A
in s t r u m e n t
c a r e f u l s u rv e y
a re of
kept
fr e e
of
th e p r e p a r a t io n
lo w r i g h t ) . T h e g r e a t e r th e n e ce ss ity o f
s h o u ld b e m a d e b e f o r e s ta rtin g t o c u t.
s lo p in g
th e
T h e lo c a t io n o f g in g iv a l m a r g in s s h o u ld
lin g u a l f r o m th e l o n g a xis o f th e c r o w n ,
th e
p r e p a r a t io n
to w a rd
b e d e t e r m in e d . E x c e s s iv e s u b g in g iv a l e x
th e m o r e p r o n o u n c e d is th e f o r m a t io n o f
t e n s io n m ig h t b e c o n t r a in d ic a t e d u n less
th e s h o u ld e r a b o u t th e c in g u lu m . T h e
a d e q u a t e le n g t h o f th e p r e p a r a t io n c a n
d e v e lo p m e n t o f th e c o lla r lik e f o r m a b o u t
n o t b e o b t a in e d o th e r w is e . S u c h e x ce s s iv e
th e g in g iv a l a rea s g r e a t ly e n h a n c e s th e
e x te n s io n w o u l d o n ly a d d n e e d le s s g in g i
r e t e n t iv e fa c t o r s o f th e p r e p a r a tio n .
v a l tr a u m a a n d m a k e it d iffic u lt t o o b t a in
In
a n t e r io r
fin ish
lin e
te e th ,
m akes
th is
a ccen tu a te d
p o s s ib le ,
by
s lig h tly
o v e r c o n t o u r i n g th e c in g u lu m a r e a in th e
a n im p re s s io n o f th e t o o t h w it h e la s tic m a te ria ls . E s th e tic a lly ,
th e
in t e r p r o x im a l in itia l
w a x p a tte r n , a d e fin ite c o lla r o f m e t a l
“ s lice c u t ” o n a n a n t e r io r t o o t h is a m o s t
w h i c h p r o v id e s a d d e d
d e lic a t e
r e t e n t io n
o f th e
step ,
p a r t ic u la r ly
on
a
to oth
c a s tin g . I t a ls o p r o v id e s r ig id ity o n th e
w h i c h h a s n o t b e e n p r e v io u s ly re s to r e d o r
lin g u a l a s p e c t a g a in s t t h e f o r c e s o f o c c l u
w h e r e ca rie s is n o t p re se n t. I n this situ a
s io n w h ic h so o f t e n s p r in g o p e n th e ca s t
tio n in c lin a t io n o f th e s e p a r a tin g disks
in g m a r g in s
t o w a r d th e lin g u a l s u r fa c e , as illu s tra te d
in In
th e
(F ig .
1 0 ).
te e th ,
p a r t ic u la r ly
s h o u ld e r lik e
in t e r p r o x im a l
s h o rt-cro w n e d p o s t e r io r
fin is h in g
lin e
a re a
t a p e r in g on es,
o fte n
this
results
w h e n th e w a lls a re m a d e m o r e p a r a lle l. S u p p le m e n t a l g r o o v e s
cou n tersu n k
in to
in F ig u r e
12, w ill p r e s e r v e th e n a tu r a l
m e s io d is ta l c o n t o u r o f th e t o o t h , th e r e b y p r e v e n t in g
th e
d is p la y
of
g o ld
to
th e
ca s u a l o b s e r v e r . A c o m p a r is o n o f F ig u re s 12 a n d
13 illu stra tes this p o in t .
S lig h t
th e s h o u ld e r m a y b e u s e d in th ese i n
s e p a r a tio n o f th e te e t h o n th e d e n tu lo u s
s ta n ce s t o g r e a tly in c r e a s e th e r e te n tiv e
s id e o f th e a b u t m e n t w ill fa c ilita t e th e
p ow er.
p a s s a g e o f th e d is k th r o u g h th e c o n t a c t in g a rea . A c c e s s m a y a ls o b e g a in e d in
I n s tr u m e n ta t io n • A s te p -b y -s te p d e s c r ip
th is r a th e r c o n fin e d lo c a t io n b y u s in g a
tio n o f th e in s t r u m e n ta tio n o f th e v e n e e r
steel s a fe -s id e d lig h t n in g strip . T h e n , to
r e ta in e r is n o t in d ic a t e d in th is p a p e r .
re ite ra te , as th e d is k r e m o v e s th e in te r
T h e u se o f p r e s e n t -d a y d ia m o n d ston es
p r o x im a l s u r fa c e , it m u s t b e h e ld w e ll in
and
c a r b id e
burs
as
a d a p te d
to
th e
c lin e d t o w a r d t h e lin g u a l s u r fa c e w h e n
p r e p a r a t io n w ill b e p o in t e d o u t , h o w e v e r
v ie w e d f r o m
( F ig . 1 1 ) .
t w o slice cu ts c o n v e r g e s lig h tly in cis a lly .
I n s t r u m e n t a tio n
of
ven eer
a la b io lin g u a l p la n e . T h e
p repara
A x ia l s u rfa ce s a r e b est r e m o v e d w ith
tio n s m a y b e c a r r ie d o u t w ith a m in im u m
th e ty p e o f d ia m o n d s to n e illu s tra te d in
p o s s ib ility o f ir r it a tin g th e p u lp
tissue.
F ig u r e
14.
ca relessn ess so th a t e x ce s s iv e h e a t is p r o
th e lin g u a l s u rfa ce s o f a n t e r io r te e th , th e s m a lle r is f o r c a r r y in g th e fin is h in g lin e
s p ra y
a tta ch m en t
has
The proved
a v a ila b le of
in
s iz e ;
th e
d ia m o n d
du ced
g r in d in g .
in
ta p e r e d
ston es
w h i le
vary
T h ese
L o c a l a n e s th e tics m a y b e e m p lo y e d , b u t th e p a t ie n t ’ s a n e s th e s ia m u s t n o t le a d to
la r g e r
is
fo r
m o la r s , th e m e d iu m is f o r b ic u s p id s a n d
as f a r as p o s s ib le in to th e in te r p r o x im a l
e s tim a b le v a lu e a n d a ssista n ce in c u t t in g
a rea . T h is ty p e o f s n u b -n o s e d s to n e c a n
th e se p r e p a r a tio n s . W i t h th is d e v ic e h ig h
b e u s e d to d e v e lo p e ith e r a c le a n fin is h in g
s p e e d r e v o lv in g in stru m e n ts m a y b e u s e d
lin e o r a s h o u ld e r lik e a c c e n t u a t e d fin is h
w it h o u t
heat
p r o d u c t io n .
The
fie ld
is
in g lin e . T h i s a c c e n t u a t e d ty p e o f lin e
m a in ta in e d c le a r o f d e b ris a n d v is ib ility
w ill a u t o m a t ic a lly a p p e a r w it h in c r e a s e d
is fa c ilit a t e d . I n a d d it io n , b o t h th e t o o t h
p a r a lle lis m
on
th e b u c c a l s u r fa c e o f
a
W IL L E Y ... VOLUME 53, AUGUST 1954 • 147
lo w e r m o l a r (F ig . 1 5 ) , o r o n th e lin g u a l
ance
s u r fa c e
w h e r e a n a n t e r io r v e n e e r ca s tin g is c o n
of
an
a n t e r io r
veneer
w hen
of
0 .7 5
mm.
w o u ld
g r e a t e r b u lk o f m e t a l is u s e d t o g iv e th e
s tr u c te d o n
c o lla r lik e
th e h a r d e r ty p e s o f
e ffe c t
at
th e
c in g u lu m
as
p r e v io u s ly m e n t i o n e d . I n t e r p r o x im a l a c
be
a d eq u ate
a th in t o o t h , u s in g o n e o f crow n
and
b r id g e
g o ld . A t th e o t h e r e x t r e m e , in th e p o s
cess w h e r e a n a d ja c e n t t o o t h is p r e se n t
te r io r s e c tio n o f th e m o u t h w h e r e a m o la r
c a n b e g a in e d g e n e r a lly b y u s in g a th in
is t o se rv e as a lo n g s p a n a b u t m e n t, a n d
steel lig h tn in g disk. W h e r e n o p r o x im a l
w h e r e th e r e m a in in g te e t h in d ic a t e h e a v y
to o t h is p r e s e n t, this r e g io n m a y b e d e
w e a r , a c le a r a n c e o f 1.5 m m . w o u l d n o t
v e lo p e d
b e ex ce s s iv e . I n th e p o s t e r io r te e th , s u ffi
w ith
th e
ta p e r e d
s n u b -n o s e
d ia m o n d . T h e s e d ia m o n d s ton es a re a ll
c ie n t o c c lu s a l c le a r a n c e in a ll e x cu rs io n s
u sa b le
o f m a s t ic a tio n m u s t b e a c q u ir e d to a llo w
fo r
in t e r p r o x im a l
p e n d in g o n 1 5 ).
g r o o v in g
th e size o f th e t o o t h
de (F ig .
T h is fig u r e illu stra tes b e t t e r th a n
w o r d s c a n te ll, a b a s ic r u le in a b u t m e n t
f o r b u lk o f m e t a l a n d d e e p o c c lu s a l c a r v in g s. I t is w e ll t o f o l l o w
o u t th e b a s ic
c u s p a l f o r m o f th e s e s u rfa ce s in o r d e r t o
p r e p a r a tio n . T h e h a n d p ie c e is h e ld c o n
o b t a in m o r e o r less u n if o r m
s ta n tly in a p r e v io u s ly d e t e r m in e d lin e o f
D e e p , d e fin ite c a r v in g s a r e a n a t o m ic a lly
c le a r a n c e .
s h e d . I n th is w a y th e h a z a r d s o f u n d e r
c o r r e c t , a n d th e y p r o v id e f o r th e f u n c
c u t t in g a re g r e a tly r e d u c e d .
t io n in g p a r t o f th e ca s tin g t o b e f o r m e d
The
a n t e r io r
t h r e e -q u a r t e r
prepara
b y a series o f
s h a rp b la d e s
(F ig .
1 7 ).
tio n in v o lv e s th e m o s t d iffic u lt step in th e
T h e s e b la d e s e n c o u r a g e e ffic ie n t m a s t i
fie ld
c a t io n , a n d
of
p r e c is io n
o p e r a t iv e
d e n tis try —
w e a r m o r e u n if o r m ly w ith
th e c o n n e c t in g o f th e m a r g in le f t b y th e
th e r e m a in in g te e th th a n d o
s e p a r a t in g d is k in t e r p r o x im a lly w ith th e
fa c e ts . I t is o f t e n
g in g iv a l e n d o f th e g r o o v e o n th e sid e
b r id g e s c o n s t r u c t e d w it h la r g e , fla t o c
a p p r o x im a t in g r e la tiv e ly
a n a d ja c e n t t o o t h . T h is
in a c c e s s ib le
tr ia n g u la r -s h a p e d
n o te d
la rg e flat
th a t e x te n s iv e
clu s a l s u rfa ce s o f h a r d g o l d a llo y r e a c h a sta te o f h y p e r o c c lu s io n s im p ly b e ca u s e
a r e a o f t o o t h s tru ctu re c a n n o t b e r e a c h e d
th e m e t a l h as fa ile d t o w e a r a w a y a t th e
b y th e d is k ; u n til th e a d v e n t o f th e v e r y
s a m e r a te as th e o c c lu s a l s u r fa c e s o f th e
s m a ll d ia m o n d ta p e r e d s to n e th e o p e r a
r e m a in in g n a tu r a l te e th .
tio n
w as
a lw a y s
r a th e r
a
h it-a n d -m is s
p r o p o s itio n . F ig u r e 16 illu stra tes th e u se
I n s tr u m e n ta t io n
o f th is sm a ll sto n e , c o m p a r a b le t o a n o .
q u ic k ly w ith a w h e e l ty p e o f s to n e (F ig .
• B u lk m a y b e r e m o v e d
7 0 0 fissu re b u r in size. H ig h s p e e d a n d
1 8 ) , th e size o f th e s to n e a g a in d e p e n d
v e r y lig h t p re ssu re a re u s e d t o r e m o v e this
in g o n th a t o f th e t o o t h in v o lv e d . T h e
is la n d o f t o o t h s tr u c tu r e a n d e s ta b lis h a
g e n e r a l c u s p a l f o r m a t io n o f th e m o la r s
d e fin ite fin ish m a r g in b e t w e e n th e
m a y b e f o l l o w e d o u t w ith in v e r te d c o n e
end
o f th e g r o o v e a n d th e in t e r p r o x im a l slice
ston es.
c u t.
th e p r e p a r a t io n in th is m a n n e r a llo w s f o r
S h a p in g th e o c c lu s a l s u r fa c e o f
a u n if o r m c le a r a n c e as w e ll as s u fficie n t A d e q u a t e C le a r a n c e • I t is e x t r e m e ly d i f
d e p th
fic u lt t o p r o p o s e a n y d e fin ite a m o u n t o f
in th e fin is h e d ca s tin g .
fo r a cce n tu a te d
o c c lu s a l g r o o v e s
c le a r a n c e o n th e lin g u a l s u r fa c e o f a n te r io r v e n e e rs o r o n th e o c c lu s a l s u r fa c e
O ffs e t
o f p o s t e r io r v e n e e rs . T h e d e g r e e o f f o r c e
1 9 ) s erv e t o c o n n e c t th e p r o x im a l g r o o v e s
ex erted
w it h a th ic k b a r o f m e t a l, b o t h in th e
a g a in st v e n e e r s ,
th e
le n g th
of
G rooves
and
• O f fs e t g r o o v e s
p o s t e r io r
p a r t ia l
(F ig .
s p a n o f th e b r id g e , th e a m o u n t o f t o o t h
a n t e r io r
s tru ctu re a v a ila b le in t o w h i c h t o c u t th e
T h e i r u se is e n tir e ly co n s is te n t w it h th e
ven eer.
p r e p a r a tio n , a re fa c t o r s d e t e r m in in g th e
e n g in e e r in g p r in c ip le o f th e truss. W it h
c le a r a n c e . I t is c o n c e iv a b le th a t a c le a r
th e s a crifice o f a m in im u m
am ount o f
148 • THE JOURNAL OF THE AMERICAN DENTAL ASSOCIATION
Fig. 7 • View of upp e r cuspid show ing minimum extension of labial extension and go ld exposure
Fig. 8 • Three-quarter preparation on upper molar, full veneer on lower m olar and three-quar ter veneer on u p p e r cuspid, show ing quasiparalleling or slight convergence of walls and grooves to obtain maximum frictional force
WILLEY
F ig . 9 • A b o v e : The d e v e lo p m e n t o f p ro p e r ly c o n v e rg e n t w alls w ill re s u lt in v a rio u s fo r m a tio n s o f th e fin is h in g lin e . The sam e b lu n t-n o s e d ta p e re d d ia m o n d sto n e m a y b e used as show n. B elow le f t : A c c e n tu a te d fin is h in g lin e on lin g u a l su rfa c e fa d e s o u t t o a c o n v e n tio n a l fin is h in g lin e in th e in te r p ro x im a l a re a . Below r ig h t: A n even m o re p r o n o u n c e d s h o u ld e r on th e lin g u a l g in g iv a l m a rg in o f th e lo w e r a n te rio r to o th results fro m a lin e o f shed d ir e c te d lin g u a lly
F ig . 10 • A s h o u ld e rlik e fin is h in g lin e o fte n re sults on b u c c a l s u rfa ce w hen w alls a re m a d e m o re n e a rly p a ra lle l. S u p p le m e n ta l g ro o v e s im p ro v e th e r e te n tio n in s h o rt p o s te rio r te e th
F ig . I I • N os. I, 2 a n d 3 a re v a rio u s sizes o f b lu n t-n o s e d ta p e r e d d ia m o n d stones. N o . 4 is a v e ry sm all, fin e -ta p e re d d ia m o n d a p p ro x im a te ly th e size o f a no. 700 b u r. N o . 5 is a c a r b id e b ur, size n o. 700, f o r p la c in g in te rp ro x im a l g ro o ve s
. VOLUME 53, AUGUST 1956 • 149
150 • THE JOURNAL OF THE AMERICAN DENTAL ASSOCIATION
Fig. 12 • M esiodista! contour of upper cuspid is preserved when mterproximal surface is rem oved with a separating disk inclined lingually
Fig. 13 • W h e n initla! Interproxim al cuts are m ade without the lingual inclination of the disk, the entire m esiolingual contour of the cuspid is destroyed, resulting in needless disp lay of go ld and sacrifice o f tooth structure
WILLEY
Fig. 14 • O n lower m olar an accentuated finished line is autom atically de ve lo pe d by a snub-nosed diam ond on the buccal and lingual surfaces of an upp e r cuspid. A rrow s indicate position o f stone in relation to line of shed to establish definite wall to function in o pposition to grooves
Fig. 15 • A basic rule in abutm ent preparation is to m aintain the h andpiece in an established line o f shed, regardless of the direction of the long axis of the tooth being prepared
Fig. 16 • ’’Islan d " o f tooth structure left by slice cut and înterproxima! gro ove is rem oved by small tapered diam ond stone
.V O LU M E 53, AUGUST 1956 • 151
152 • THE JOURNAL OF THE AMERICAN DENTAL ASSOCIATION
of
m o r e a c c u r a t e ly a r o u n d in g o f th e in cis a l
m e t a l is m a d e a v a ila b le in a m o s t v u l
tooth
s tr u c tu r e ,
m a r g in . T h e in c is a l m a r g in o f a c a r e fu lly
n e r a b le
p repa red
r e g io n .
an
added
The
am ount
added
th ick n ess
t h r e e -q u a r t e r v e n e e r le a v e s a
g iv e s r ig id ity t o w ith s ta n d th e fu n c t io n a l
sh a rp , d e lic a te e n a m e l k n ife -e d g e . S lig h t
f o r c e e x e r t e d a g a in st it in th e r e g io n o f
r o u n d in g o f th is m a r g in n o t o n ly p r o te c t s
th e t o o t h w h e r e th e g re a te st w e a r o c c u r s ,
it a g a in st fr a y in g o r f r a c t u r e d u r in g th e
a n d a ls o p r o v id e s b u lk t o p r e v e n t o p e n
f a b r ic a t io n o f th e c r o w n , b u t p r o v id e s a
in g
m u c h ea sier e d g e a g a in st w h i c h t o fin ish
of
th e
in c is a l o r
o c c lu s a l
m a r g in ,
s p r in g in g o f th e c a s tin g , a n d s u b s e q u e n t
th e m a r g in o f th e ca s tin g . W it h o u t s u ch
fa ilu r e o f th e in t e r p r o x im a l m a rg in s .
r o u n d in g ,
one
is w o r k in g
w ith
a
b u tt
jo i n t , a n d as e v e r y o p e r a t o r k n o w s , it is M a r g in a l E x te n s i o n re s u lt
is
• W h e r e a n e s th e tic
im p o r t a n t ,
th e
te n s io n s a re lim it e d
(F ig .
m a r g in a l 2 0 ).
ex
T h is
is
p a r t ic u la r ly tr u e in th e m e s ia l a r e a o f th e
e x t r e m e ly d iffic u lt t o a d a p t a n d fin is h a g o l d ca s tin g t o a b u t t jo i n t . F u r t h e r m o r e , th e “ s h in g le d
ro o f”
r e la t io n
w h ich
th e
g o ld h as t o th e t o o t h in th is r e g io n a llo w s
a n t e r io r t h r e e -q u a r t e r c r o w n c a s tin g . T h is
th e f o r c e s d ir e c t e d a g a in st it t o c lo s e th e
m in im a l
m a r g in r a th e r th a n o p e n it.
e x te n s io n
can
be
a t t a in e d
by
c a r e fu l o p e r a t in g , r e ly in g o n th e u se o f s e p a ra to rs , th in s e p a r a t in g d isk s a n d fin e
I n s t r u m e n t a t io n
d ia m o n d
n oted ,
ta in e d w it h t h e w e t o r d r y t y p e o f p a p e r
th o u g h , e s p e c ia lly w ith c u s p id s , th a t a n y
disk. O n th e in c is a l m a r g in o f a n t e r io r
loss
s u ch
te e th it is b est d o n e w ith th e a ssista n ce o f
lim ite d e x te n s io n s h o u ld b e c o m p e n s a t e d
b in o c u la r lo u p e s . F o r e s th e tic h a r m o n y
f o r b y a s lig h t e x t r a e x te n s io n o n th e d is
th e in c is a l e d g e s h o u ld c o n f o r m in s h a p e
ta l s u r fa c e . T h is p r in c ip le is o f c a r d in a l
t o th a t o f th e a d ja c e n t a n t e r io r te e th . T h e
im p o r t a n c e , a n d a n y s a crifice o f e x te n s io n
e d g e c a n b e d e v e lo p e d w it h th e d isk a n d
f o r th e p u r p o s e o f e sth etics is a n in v it a
th e n c a r e fu lly r o u n d e d .
of
sto n e s. coron al
It
s h o u ld
g ra s p
be
ca u sed
by
• T h e bevel can b e o b
tio n to fa ilu r e . A s p r e v io u s ly s ta ted , all
A t this p o in t th e p r e p a r a t io n s h o u ld
fa c e ts o f w e a r s h o u ld b e c o v e r e d , a n d th e
b e r e a d y f o r fin a l c h e c k in g a n d in s p e c
m a r g in s e x t e n d e d
tio n . S c o u r in g t h e t o o t h w ith a p a s te o f
to
ju s t b e y o n d
th e ir
b o u n d a r ie s .
p u m ic e a n d p e r o x id e w ill r e m o v e d e b ris . A f o r c e f u l b la s t o f w a r m s p ra y f r o m th e
I n s tr u m e n ta t io n
• A re fin e d in s t r u m e n
a to m iz e r ,
fo llo w e d
by
d r y in g
of
th e
ta t io n o f th a t u se d in w a lls a n d g r o o v e s is
p r e p a r a t io n w it h w a r m a ir, w ill m a k e th e
u se d in m a r g in a l e x te n s io n . O n th e m e s ia l
p r e p a r a t io n r e a d y f o r e x a m in a t io n w ith
s u r fa c e o f a th r e e -q u a r t e r v e n e e r w h e r e
th e lo u p e s . I t is w e ll t o n o t e th e f o l l o w
th e e x t e n s io n , f o r e s th e tic re a s o n s , is t o
in g p o in t s :
b e lim ite d , th e m a r g in o f t e n m a y b e c o m p le t e d w ith fin e w e t o r d r y p a p e r disks. I n f a c t , th e se a re e x c e lle n t f o r fin is h in g
1.
T h e le n g t h o f w a lls a n d
s h o u ld
b e ob served
to m ak e
grooves
su re th a t
a ll m a r g in s a n d fla res w h e r e a cce s s ib le .
th e y a re a d e q u a t e in le n g th a n d fr e e o f
The
u n d e r c u ts .
d ista l
asp ect
of
th e
p r e p a r a t io n ,
u s u a lly c a r r ie d w e ll o n t o th e b u c c a l su r f a c e o f p o s t e r io r te e th w ith a b lu n t -n o s e d d ia m o n d , c a n a ls o b e fin is h e d w ith su ch
2. 3. fre e
disks.
C le a r a n c e in c e n t r ic a n d e c c e n t r ic
p o s itio n s s h o u ld b e c h e c k e d . E v e r y m a r g in m u s t b e s m o o t h a n d fro m
ra gged
e d g e s,
and
fla res
p o lis h e d . T h e la b io g in g iv a l a n g le s o f th e I n c is a l o r O c c l u s a l R e v e r s e B e v e l • T h e
t h r e e -q u a r t e r p r e p a r a t io n s h o u ld b e r e
s lig h t re v e rs e o r b a c k b e v e l ( F ig . 2 1 ) is a
c h e c k e d t o a s ce rta in th a t t h e fla re s b e
“ b e v e l”
c o m e c o n t in u o u s w it h t h e b e v e l a t th e
in a v e r y re s tr ic te d sense. I t is
F ig. 18 • Bulk is re m o v e d w ith a w he e l ty p e o f d ia m o n d sto n e
F ig . 19 • A n in v e rte d c o n e d ia m o n d sto n e is used to d e v e lo p o c c lu s a l o r in cisa l g ro o v e c o n n e c tin g in te rp ro x im a l g ro o ve s
F ig . 20 • M a r g in a l e xtensions a re e s th e tic reasons on th e u p p e r cu sp id
lim ite d
F ig . 21 • A s lig h t reverse o r " b a c k " in cisa l o r o cclu sa l m a rg in
fo r
b e v e l on
154 • THE JOURNAL OF THE AM ERICAN DENTAL ASSOCIATION
g in g iv a l e n d o f th e g r o o v e s . N o a b r u p t s h e lf s h o u ld b e le f t a t th is p o in t .
t o th e p o s t e r io r te e th . W h e t h e r it b e a h a lf c r o w n , th r e e -q u a r t e r , se v e n -e ig h th s ,
P r e p a r a tio n s p e r f o r m e d in th e m a n n e r
o r f u ll v e n e e r c r o w n , th e s a m e f u n d a
d e s c r ib e d in th is p a p e r a re n o t a lte r e d to
m e n ta ls s h o u ld b e o b s e r v e d . T h e a b s e n c e
c o n f o r m t o a n y p a r t ic u la r t e c h n ic o f r e
of
p r o d u c t io n , i f s u c h a lte r a t io n in a n y w a y
r e g io n o f th e m o u t h p e r m its e v e n m o r e
s e v e re
e s th e tic
r e q u ir e m e n ts
in
this
lessens th e a d v a n ta g e s g a in e d b y f o l l o w
e x te n s iv e
in g th e p r in c ip le s a d v o c a t e d . E a c h d e ta il
w h e n n e e d e d , a n d g r e a t e r b u lk o f m e ta l
in th e p r e p a r a tio n s is p e r f o r m e d
to resist d is p la c e m e n t a n d d e fle c t io n .
fo r a
coverag e,
a d d it io n a l
le n g th
d e fin ite re a s o n . T h e n e x t step in th e p r o ced u re
co n s titu te s
a
g e n u in e
c h a lle n g e
C O M M E N T
t o th e o p e r a t o r — b u ild in g a d ie o n w h ic h or,
R a r e ly d o e s a d e n tis t e x p e r ie n c e a g r e a te r
b e t t e r y e t, in th e ca se o f th e c o n s e r v a tiv e
to
con stru ct
a
s a tis fa c to r y
c a s tin g
s a tis fa c tio n f r o m d e n ta l o p e r a t io n s th a n
a n t e r io r th r e e q u a r t e r p r e p a r a t io n , b u il d
w h e n o b s e r v in g a r e s to r a t io n o f th is ty p e ,
in g a d ir e c t w a x p a t te r n f r o m w h i c h to
e s th e tic a lly a c c e p t a b le ,
c o n s t r u c t a s a tis fa c to r y c a s tin g . H e m u s t
a ft e r m a n y y ea rs, w it h p u lp u n d a m a g e d ,
p r o je c t , s o t o s p e a k , o n t o th e fin is h e d
and
r e s to r a t io n th o s e in h e r e n t q u a litie s b u ilt
q u o t e th e la te H a r r y P o t t e r :
w it h
h e a lt h y
still f u n c t io n in g
in v e s tin g tissues.
To
in to t h e p r e p a r e d t o o t h . T h e ca s tin g b e com es
th e
im p o r t a n t
c o n n e c t in g
lin k
w h i c h m a k e s th is p o s s ib le . P o s te r i o r P r e p a r a tio n s
• T h e p r in c ip le s
c o v e r e d in th e f o r e g o in g d is cu s s io n o f th e a n t e r io r v e n e e r c r o w n a re a ls o a p p lic a b le
W ith ordinary precautions in the design, preparation, guarding and cem entation of veneer types o f castings for fixed or removable types o f bridges constructed along proven principles, the placing of such work should represent one o f the finest services the dental profession can render.
Joy o f P erfection • A great deal o f the jo y o f life consists o f doin g perfectly, or at least to the best o f one’ s ability, everything w hich he attempts to do. Th ere is a sense of satisfaction, a pride in surveying such a work— a w ork w hich is rounded, full, exact, com plete in all its parts— which the superficial man, w h o leaves his w ork in a slovenly, slipshod, half-finished con dition, can never know. It is this conscientious completeness w hich turns w ork into art. T h e smallest thing, well done, becom es artistic. W illiam M athew s.
V O L U M E 53
• NUMBER 2
MFÜICAJV /JAÆ ’ TAl ASSOCIATION
The preparation of abutments for veneer retainers
R o b e r t E . W il le y , D . D . S ., L o s A n g e l e s
It
h as
been
s a id ,
and
r ig h tfu lly ,
to
th a t
in su re
th e
u ltim a te
su ccess
of
th e
(F ig .
1)
fin is h e d r e s to r a tio n .
o p e r a t iv e d e n tis try o f th e h ig h e s t q u a lity
T h e v e n e e r ty p e o f re ta in e r
is m o r e e a s ily a tta in e d t o d a y th a n e v e r b e fo r e . T h e p r o p e r u se o f h ig h -s p e e d r e
h a s p r o v e d to b e b y f a r th e m o s t re lia b le
v o lv in g d i a m o n d a n d c a r b id e in stru m en ts,
m e t h o d o f a t t a c h m e n t t o a t o o t h . T h is
i m p r o v e d c o n t r o l o f w a x in p a t te r n m a k
c o n c lu s io n h a s b e e n r e a c h e d a ft e r yea rs
in g ,
t e c h n ic s , c o n
o f o b s e r v in g th e su ccesses a n d fa ilu re s o f
t r o lle d c a s tin g m e t h o d s , t o g e t h e r w it h a
f ix e d a n d r e m o v a b le ty p es o f b r id g e w o r k .
a ccu ra te
im p re s s io n
m o r e t h o r o u g h u n d e r s t a n d in g o f th e b i o
O v e r th e yea rs th e v e n e e r r e ta in e r h as
m e c h a n ic a l
show n
p r in c ip le s
in v o lv e d
in
th e
itse lf t o b e so w e ll q u a lifie d to
p r e p a r a t io n o f te e th , a re fa c t o r s e n a b lin g
w ith s ta n d h e a v y fu n c t io n a l stresses th a t
th e
a
fix e d b r id g e s so s u p p o r t e d a re c o n s id e r e d
s e rv ice o f e x c e lle n t s ta n d a r d . I t is n o t
c o m p a r a b le t o a n y o t h e r d e n ta l re s to r a
n e ce ssa ry to s e a rch v e r y lo n g , n o r su rv e y
tio n .
avera ge
p r a c t it io n e r
to
p r o v id e
to
F r o m th e s ta n d p o in t o f b io m e c h a n ic a l
re a liz e th a t th e r e is still a g r e a t n e e d f o r
e n g in e e r in g , th e v e n e e r r e ta in e r is f u n d a
r e -e m p h a s iz in g
m e n ta lly
th e
fie ld
very
d ilig e n tly , th e
h ow ev er,
p r in c ip le s
w h ic h
co rrect.
The
te r m
“ v e n e e r ,”
m a k e f o r g r e a t e r s e rv ice a n d d u r a b ility ,
u se d in p r e fe r e n c e t o
“ c r o w n ,”
p a r t ic u la r ly in th e fie ld o f fix e d a n d r e
th e o v e r la y in g o f th e c o r o n a l p o r t io n o f
im p lie s
m o v a b le p r o s t h o d o n t ic re sto ra tio n s. T h is
th e t o o t h w ith a th in la y e r o f g o ld a llo y ,
p a p e r w ill d e a l w ith th e s e p r in c ip le s in s o
th e s ta b ility o f w h i c h is o b t a in e d b y th e
f a r as th e y a re a p p lic a b le t o th e p r e p a r a
f r ic t io n a l
tio n o f te e th w h ic h a re t o se rv e as a b u t
v e r g e n t w a lls a n d g r o o v e s . T h e v e n e e r is
re te n tiv e n e s s
of
slig h tly
con
m e n ts f o r th ese t w o classes o f a p p lia n ce s .
p r im a r ily a s u r fa c e c o v e r in g o f a p a r t o r
O b v io u s ly , w h a t e v e r th e m e t h o d sele cte d t o r e p r o d u c e th e p r e p a r e d t o o t h , ce rta in
Professor o f fixed prosfhodontics., University o f South ern C alifornia School of Dentistry.
b a s ic p r in c ip le s o f d e s ig n m u s t b e a p p lie d 141
142 • THE JOURNAL OF THE AM ER IC AN DENTAL ASSOCIATION
a ll o f th e e n tire c r o w n . I f th e p r e p a r a t io n
u n w a r r a n t e d . S u c h p r e p a r a tio n s a re in
f o r th e v e n e e r is m a d e essen tia lly w ith in
h e r e n t ly w e a k
th e e n a m e l o f th e t o o t h , th e h a z a r d s to
a tta c h o n ly to th e lin g u a l e le m e n ts o f th e
a n d in v ite fa ilu r e . T h e y
th e p u lp a t t e n d a n t o n th e o p e r a t io n to
t o o t h , a n d fle x u r e o r e v e n f r a c t u r e o f th e
th e t o o t h a re g r e a tly m in im iz e d .
u n s u p p o r t e d p o r t io n o f th e t o o t h is p o s
The
d o m e lik e
fo rm
of
m e t a l,
aug
sib le. T h e fle x ib ilit y o f th e t o o t h s tru ctu re
m e n t e d b y th e tru sslik e s u p p o r t o f th e
s h o u ld
g r o o v e s , c o m p r is e s a m e c h a n ic a l d e s ig n
c h a r a c te r is t ic
h ig h ly
brok en
c a p a b le
of
resistin g
d is t o r tio n .
F o r c e s d ir e c t e d a g a in st th ese v e n e e r s te n d to
sea t
th e m
p r e p a r a tio n s .
m ore The
fir m ly
ven eer
on
a ls o
of
in m in d . T h is
d e n tin
c e m e n t jo in t s
m ay
and
go
le a d
to
u n recog
n iz e d as th e c a u s e o f fa ilu r e .
th e ir
O u t s t a n d in g as a ca u se f o r m a n y f a i l
th e
u res o f re ta in e rs a n d a s p e c ific in sta n ce
ties
s tr u c tu r a l e le m e n ts o f th e c r o w n
a lw a y s b e b o r n e
m ore
o f fa u lt y e n g in e e r in g is th e in d is c r im in a t e
tig h tly t o g e th e r , a n d th u s e lim in a te s th e
u se o f in la ys ( F ig . 4 ) . I f th e in la y p r in
p o s s ib ility o f fr a c t u r e d e n a m e l w a lls o r
c ip le is a n a ly z e d c a r e fu lly , it w ill b e seen
cu sp s. V e n e e r s s h o u ld a lw a y s b e d e s ig n e d
th a t b e c a u s e o f th e n a tu r e o f th e m e ta l
w it h
th is
im p o r t a n t
c o n s id e r a t io n
in
u se d a n d th e t o o t h s tru ctu re in to w h ic h
th e
of
c r o w n o f th e t o o t h , c o m p o s e d la rg e ly o f
even
d e n tin , a fle x ib le s u b s ta n ce , c o u ld h a r d ly
m in d . In
it is p la c e d , th e r e is in c o n s is te n c y . T h e m ost
in sta n ce s
dem ands
e s th e tics m a y b e a d e q u a t e ly m e t , th ou g h
a
c o n s id e r a b le
p o r t io n
of
th e
c r o w n m a y b e c o v e r e d w ith m e t a l. P r o p e r
be
c o n s id e r e d
a s u ita b le s tr u c tu r e in to
w h ic h t o in se rt a n o t h e r fle x ib le m a te r ia l,
d e s ig n a n d m i n im a l m a r g in a l e x te n s io n
th e m e t a l a llo y o f g o ld , t o resist th e severe
can
fo r c e s t o w h i c h th e in la y is e x p o s e d . F le x
fu lfill
e s th e tic
r e q u ir e m e n ts
under
o r d in a r y c o n d it io n s o f s p e a k in g , la u g h in g
in g , p a r t ic u la r ly in th e ca se o f reta in ers,
o r s m ilin g .
is in e v ita b le , a n d th e b r o k e n m a r g in s o o n
I n p r a c t ic a lly a ll teeth c a r r y in g a p a r
in d u c e s fa ilu r e .
tia l v e n e e r , th e e n tire f u n c t io n in g s u r fa c e ,
A fu r t h e r in a d e q u a c y o f th e in la y r e
in cis a l o r o c c lu s a l, is c o v e r e d . B y th e u se
ta in e r is th a t th e c u s p h e ig h t is t w o to
o f lo n g b e v e ls , th e m a r g in s a r e c a r r ie d
th r e e tim es in c r e a s e d w h e n e v e r th e o c
o u t b e y o n d th e fa c e ts o f w e a r , t o a c h ie v e
clu s a l g r o o v e is c u t in o r d e r t o r e c e iv e
th r e e d e fin ite en d s (F ig . 2 ) . F ir st, g r in d
th e in la y ; this cre a te s a w e d g i n g o r c r o w
in g o r w e a r is n e v e r a llo w e d t o e x e r t d e
b a r e ffe c t . W h ile th e t o o t h s u p p o r t in g an
s tr u c tiv e
in d iv id u a l in la y m a y w ith s ta n d s u c h
fo rce
on
th e m a r g in
b e tw e e n
a
m e t a l a n d t o o t h . S e c o n d ly , th e s w e e p o f
p r o c e d u r e , a f r a c t u r e o f th e u n p r o t e c t e d
f o o d o v e r th is m a r g in d u r in g f u n c t io n is
c u s p o r cu sp s is v e r y p o s s ib le u n d e r th e
s im ila r t o
the' s h e d d in g o f w a t e r b y
a
lo a d r e q u ir e d t o s u p p o r t a fix e d b r id g e
s h in g le r o o f ; th e a c t i o n te n d s t o c lo s e th e
or
m a r g in r a th e r th a n o p e n it. T h ir d ly , th e
stre n g th o f v e n e e r a n d in la y re ta in e rs is
s tr u c tu r a l e le m e n ts o f th e t o o t h a r e h e ld
w e ll
to g e th e r . O n u p p e r a n t e r io r te e th , th e re
v e n e e r c a s tin g s u p p o r ts th e t o o t h w h ile
need
be
no
undue
of
m e ta l.
th e
upper
t o o t h .”
m ay
be
w e ll h id d e n
a tta ch m en t.
d e s c r ib e d
T h e in c is a l m a r g in o f m e ta l o n a n t e r io r te e th
exp osu re
p r e c is io n
in la y
by
c a s tin g
th e is
The
rela tiv e
ph rase:
su p p orted
“The by
th e
by
W h e n te e th w h i c h h a v e s u ffe r e d e x
c a r e f u l r o u n d in g o f th e s u r fa c e in o r d e r
tr e m e c a r io u s in r o a d s a re t o b e r e s to r e d
t o c a s t th e r e fle c tio n s d o w n w a r d ( F ig . 3 ) .
o r u s e d as b r id g e a b u tm e n ts , a p p lic a t io n
A s a g e n e r a l r u le e ffo r t s t o a v o id in v o lv in g
th e
e n tire
o c c lu s a l
s u r fa c e
of
of
th e
s tre n g th
ven eer of
p r in c ip le
th e s e
te e th .
en h an ces The
th e
“ w rap
th r e e -q u a r t e r v e n e e rs in th e p o s t e r io r p o r
a r o u n d ” e f fe c t o f th is ty p e o f ca s tin g ties
tio n o f th e m o u t h f o r e s th e tic re a s o n s a re
th e w e a k e n e d p o r t io n o f th e t o o t h to th e
WILLEY . . . V O L U M E 53, AUGUST 1956 • M3
s tr o n g e r , th u s e lim in a t in g th e t e n d e n c y
q u a t e le n g th c o n s t it u t e th e g re a te st sin g le
o f f o r c e s t o ca u s e fr a c t u r e ( F ig . 5 ) . T h is
e le m e n t in t h e sta b ility o f a c a s tin g o n a
is o n e o f th e im p o r t a n t a p p lic a t io n s o f
t o o t h ; th a t is, p r o v id in g fr ic t io n a l r e t e n
th e v e n e e r a n d is f u n d a m e n t a l in a b u t
tio n . F r ic t io n a l r e t e n t io n c a n b e d e fin e d
m e n t d e s ig n .
as th a t r e s is ta n ce t o r e m o v a l o r d is p la c e
I n y o u t h fu l p e r so n s a n d o th e r s h a v in g
m e n t o f a c a s tin g o n a t o o t h w h i c h b e
te e th w ith e x t r e m e ly la r g e p u lp s a n d e x
c o m e s a c t iv a t e d b y fo r c e s t e n d in g t o d is
te n d e d
lo d g e it. T h is re s is ta n ce is b r o u g h t a b o u t
h orn s,
th e
veneer
p r in c ip le
r e c o m m e n d s its e lf b e c a u s e o f its g re a te r
b y th e f r ic t io n a l f o r c e b e t w e e n th e a lm o s t
s a fe ty
p a r a lle l in te r n a l w a lls o f th e ca s tin g a n d
(F ig . 6 ) . V e n e e r p r e p a r a t io n s o f
a d e q u a t e stre n g th m a y b e m a d e w it h o n ly
th e e x t e r n a l w a lls o f th e p r e p a r a tio n .
s lig h t p e n e tr a t io n s in t o th e d e n tin . I t is
A slig h t s p a c e a llo w e d f o r c e m e n t b e
w e ll in s u c h in sta n ce s t o u tiliz e o n e o f th e
t w e e n ca s tin g a n d t o o t h a ft e r p e r m a n e n t
h a r d e r c r o w n a n d b r id g e g o l d a lloys.
p la c e m e n t o f th e ca s tin g w ill n o t in te r fe r e
T h e a c c e p t e d ru les p e r t a in in g to e x
p e r c e p t ib ly w it h this r e t e n t io n , p r o v id e d
te n s io n f o r p r e v e n t io n a re o r d in a r ily a p
p r o p e r e n g in e e r in g h a s b e e n u se d in th e
p li e d t o th e v e n e e r ty p e o f c a s tin g f o r
p r e p a r a tio n .
re ta in e rs o r in d iv id u a l re s to r a tio n s . T h e
o v e r ly c o n v e r g e n t w a lls la c k f r ic t io n a l r e
S h ort
p r e p a r a tio n s
w ith
a d d it io n a l ru le o f a v o id in g d ir e c t f o r c e
te n tio n
o r a b r a s iv e c o n t a c t o n m a r g in s is a lo g ic a l
w o r k d e n ta l c e m e n t in th e m a in serves
s u p p le m e n t . A l l m a r g in s s h o u ld b e
o n ly as a s e a le r ; its p o w e r o f r e t e n t io n
ex
and
in v a r ia b ly fa il.
In
b r id g e -
te n d e d t o r e la tiv e ly im m u n e a rea s. W h e r e
is n e g lig ib le . I n te e th o f a v e r a g e e x p o s e d
it is d e s ir a b le to m in im iz e th e d is p la y o f
c o r o n a l le n g t h , th e g in g iv a l m a r g in o f th e
g o l d , m in im u m e x t e n s io n s h o u ld b e p r a c
p r e p a r a t io n w ill b e p la c e d s lig h tly s u b -
t ic e d (F ig . 7 ) . W h e r e th e r e is n o e s th e tic
g in g iv a lly . H e r e , v e r y o f t e n , w h e r e f o r c e
c o n s id e r a t io n ,
is t o b e h e a v y a n d th e o v e r - a ll le n g th o f
m a x im u m
e x t e n s io n
w ill
g iv e g r e a t e r a s su ra n ce o f s ecu rity .
th e t o o t h is s h o r t, th is m a r g in m u s t b e '
' i
c a r r ie d
w e ll b e lo w
th e f r e e g in g iv a in
o r d e r to p r o v id e s u fficie n t le n g th t o th e
PR E P A R IN G A V E N E E R R E T A IN E R
p r e p a r a t io n . O n th e o t h e r h a n d , w h e r e T h e th r e e -q u a r t e r v e n e e r r e s to r a t io n o n
g in g iv a l re ce s s io n h a s e x p o s e d c o n s id e r
a m a x illa r y a n t e r io r t o o t h t o s e rv e as a
a b le
r e t a in e r f o r a fix e d o r r e m o v a b le b r id g e
e x t e n s io n
p r o b a b ly d e m a n d s m o r e skill o f th e o p e r a
c h a n ic a l d e m a n d s . T h e g in g iv a , b e in g a
crow n is
o r root
le n g th , s u b g in g iv a l
u n n e ce s s a ry
to
fu lfill
m e
t o r th a n a n y o th e r p r o c e d u r e . H e r e th e
tr a n s ito r y tissu e, n e e d n o t b e th e f a c t o r
d e n tis t c o n fr o n t s a c o m b i n a t i o n
d e t e r m in in g th e lo c a t io n o f th e g in g iv a l
m e c h a n ic a l
and
es th e tic
o f b io
dem a n d s.
A
m a r g in o f a ca s tin g .
m i n im u m o f t o o t h s tru ctu re is a v a ila b le
T h e d e v e lo p m e n t o f p r o p e r ly c o n v e r
b y w h ic h a d e q u a t e a tt a c h m e n t m a y b e
g e n t w a lls w ill resu lt in v a r io u s f o r m a
o b t a in e d
tio n s o f th e fin is h in g lin e r e g io n
to
resist c o m p a r a t iv e ly
heavy
(F ig . 9 ,
fo r c e s . A d d e d to this is th e n e ce s s ity o f
a b o v e ) . A t tim es th e r e w ill b e ju s t th e
a v o id in g e s th e tic o f fe n c e . T h e r e a re fiv e
slig h test
c o n s id e r a tio n s
lin g u a l s u r fa c e o f th e lo w e r m o la r , w h e r e
in
to o th
w h ich
m ore
c a p a b le
can of
th e
p r e p a r a t io n
m ake
su ch
of
a
a
c a s tin g
w ith s ta n d in g
h o stile
as
on
s h o u ld e r
d e fin ite th e
fin is h
o th er
m ay
be
lin e ,
s u r fa c e s
as o n a
d e v e lo p e d .
th e
d e fin ite By
th e
fo r c e s . T h e s e p r in c ip le s m a y b e a p p lie d
p la c i n g o f a l o n g b e v e l, h o w e v e r , th e d e f i
to a n y t o o t h c a r r y in g a p a r t ia l v e n e e r .
n ite fin is h lin e p r in c ip le is still e m p lo y e d . T h e s h o u ld e r f o r m a t io n is o n ly in c id e n t a l
W a lls a n d G r o o v e s • W a lls a n d g r o o v e s
t o t h e p a r a lle lin g o f th e w a lls
( F ig . 8 ) o f p r o p e r c o n v e r g e n c e a n d a d e
b e lo w l e f t ) . T h i s p r in c ip le is a p p lie d t o
( F ig . 9 ,
• THE JOURNAL OFTHE AMERICAN DENTAL ASSOCIATION
F ig. I • T h r e e -q u a rte r v e n e e r p re p a ra tio n on u p p e r c u s p id , fu ll v e n e e r on lo w e r m o la r, h a lfc ro w n o n lo w e r m o la r a n d th r e e -q u a r te r ve n e e r on u p p e r b ic u s p id
F ig . 2 • P re p a ra tio n in v o lv in g fa c e t o f w e a r w ith m a rg in e x te n d e d to n o n fu n c tio n in g a rea , fo r "s h in g le d r o o f " e ffe c t
F ig . 3 • S e c tio n s h o w in g g o ld - to o th re la tio n s h ip . A rro w s in d ic a te d ir e c tio n o f lig h t rays r e fle c te d o ff f la t s u rfa c e and ro u n d e d su rfa c e , re s p e c tiv e ly
WILLEY . . . VOLUME 53, AUGUST 1956 • 145
F ig . 5 • The " w r a p a ro u n d " e ffe c t o f th e ve n e e r tie s th e p o rtio n s o f th e to o th to g e th e r, w ith o u t e s th e tic o ffe n c e . Shown a re a se ve n -e ig h th s v e n e e r on u p p e r fir s t m o la r, a nd th r e e -q u a rte r crow ns on lo w e r b ic u s p id and u p p e r cu spid
F ig . 6 • S e ctio n s sh o w in g e x tre m e ly la rg e p ulp s in r e la tio n t o d e p th o f a v e ra g e v e n e e r p re p a ra tio n s
146 • TH EJO U R N AL OF THE AMERICAN DENTAL ASSOCIATION
th e c in g u l a o f cu s p id s o r o t h e r a n t e r io r
and
te e th , w h e r e it is es s e n tia l th a t a c o lla r
g r in d in g s .
lik e f o r m a t io n b e d e v e lo p e d ( F ig . 9 , b e
th e
A
in s t r u m e n t
c a r e f u l s u rv e y
a re of
kept
fr e e
of
th e p r e p a r a t io n
lo w r i g h t ) . T h e g r e a t e r th e n e ce ss ity o f
s h o u ld b e m a d e b e f o r e s ta rtin g t o c u t.
s lo p in g
th e
T h e lo c a t io n o f g in g iv a l m a r g in s s h o u ld
lin g u a l f r o m th e l o n g a xis o f th e c r o w n ,
th e
p r e p a r a t io n
to w a rd
b e d e t e r m in e d . E x c e s s iv e s u b g in g iv a l e x
th e m o r e p r o n o u n c e d is th e f o r m a t io n o f
t e n s io n m ig h t b e c o n t r a in d ic a t e d u n less
th e s h o u ld e r a b o u t th e c in g u lu m . T h e
a d e q u a t e le n g t h o f th e p r e p a r a t io n c a n
d e v e lo p m e n t o f th e c o lla r lik e f o r m a b o u t
n o t b e o b t a in e d o th e r w is e . S u c h e x ce s s iv e
th e g in g iv a l a rea s g r e a t ly e n h a n c e s th e
e x te n s io n w o u l d o n ly a d d n e e d le s s g in g i
r e t e n t iv e fa c t o r s o f th e p r e p a r a tio n .
v a l tr a u m a a n d m a k e it d iffic u lt t o o b t a in
In
a n t e r io r
fin ish
lin e
te e th ,
m akes
th is
a ccen tu a te d
p o s s ib le ,
by
s lig h tly
o v e r c o n t o u r i n g th e c in g u lu m a r e a in th e
a n im p re s s io n o f th e t o o t h w it h e la s tic m a te ria ls . E s th e tic a lly ,
th e
in t e r p r o x im a l in itia l
w a x p a tte r n , a d e fin ite c o lla r o f m e t a l
“ s lice c u t ” o n a n a n t e r io r t o o t h is a m o s t
w h i c h p r o v id e s a d d e d
d e lic a t e
r e t e n t io n
o f th e
step ,
p a r t ic u la r ly
on
a
to oth
c a s tin g . I t a ls o p r o v id e s r ig id ity o n th e
w h i c h h a s n o t b e e n p r e v io u s ly re s to r e d o r
lin g u a l a s p e c t a g a in s t t h e f o r c e s o f o c c l u
w h e r e ca rie s is n o t p re se n t. I n this situ a
s io n w h ic h so o f t e n s p r in g o p e n th e ca s t
tio n in c lin a t io n o f th e s e p a r a tin g disks
in g m a r g in s
t o w a r d th e lin g u a l s u r fa c e , as illu s tra te d
in In
th e
(F ig .
1 0 ).
te e th ,
p a r t ic u la r ly
s h o u ld e r lik e
in t e r p r o x im a l
s h o rt-cro w n e d p o s t e r io r
fin is h in g
lin e
a re a
t a p e r in g on es,
o fte n
this
results
w h e n th e w a lls a re m a d e m o r e p a r a lle l. S u p p le m e n t a l g r o o v e s
cou n tersu n k
in to
in F ig u r e
12, w ill p r e s e r v e th e n a tu r a l
m e s io d is ta l c o n t o u r o f th e t o o t h , th e r e b y p r e v e n t in g
th e
d is p la y
of
g o ld
to
th e
ca s u a l o b s e r v e r . A c o m p a r is o n o f F ig u re s 12 a n d
13 illu stra tes this p o in t .
S lig h t
th e s h o u ld e r m a y b e u s e d in th ese i n
s e p a r a tio n o f th e te e t h o n th e d e n tu lo u s
s ta n ce s t o g r e a tly in c r e a s e th e r e te n tiv e
s id e o f th e a b u t m e n t w ill fa c ilita t e th e
p ow er.
p a s s a g e o f th e d is k th r o u g h th e c o n t a c t in g a rea . A c c e s s m a y a ls o b e g a in e d in
I n s tr u m e n ta t io n • A s te p -b y -s te p d e s c r ip
th is r a th e r c o n fin e d lo c a t io n b y u s in g a
tio n o f th e in s t r u m e n ta tio n o f th e v e n e e r
steel s a fe -s id e d lig h t n in g strip . T h e n , to
r e ta in e r is n o t in d ic a t e d in th is p a p e r .
re ite ra te , as th e d is k r e m o v e s th e in te r
T h e u se o f p r e s e n t -d a y d ia m o n d ston es
p r o x im a l s u r fa c e , it m u s t b e h e ld w e ll in
and
c a r b id e
burs
as
a d a p te d
to
th e
c lin e d t o w a r d t h e lin g u a l s u r fa c e w h e n
p r e p a r a t io n w ill b e p o in t e d o u t , h o w e v e r
v ie w e d f r o m
( F ig . 1 1 ) .
t w o slice cu ts c o n v e r g e s lig h tly in cis a lly .
I n s t r u m e n t a tio n
of
ven eer
a la b io lin g u a l p la n e . T h e
p repara
A x ia l s u rfa ce s a r e b est r e m o v e d w ith
tio n s m a y b e c a r r ie d o u t w ith a m in im u m
th e ty p e o f d ia m o n d s to n e illu s tra te d in
p o s s ib ility o f ir r it a tin g th e p u lp
tissue.
F ig u r e
14.
ca relessn ess so th a t e x ce s s iv e h e a t is p r o
th e lin g u a l s u rfa ce s o f a n t e r io r te e th , th e s m a lle r is f o r c a r r y in g th e fin is h in g lin e
s p ra y
a tta ch m en t
has
The proved
a v a ila b le of
in
s iz e ;
th e
d ia m o n d
du ced
g r in d in g .
in
ta p e r e d
ston es
w h i le
vary
T h ese
L o c a l a n e s th e tics m a y b e e m p lo y e d , b u t th e p a t ie n t ’ s a n e s th e s ia m u s t n o t le a d to
la r g e r
is
fo r
m o la r s , th e m e d iu m is f o r b ic u s p id s a n d
as f a r as p o s s ib le in to th e in te r p r o x im a l
e s tim a b le v a lu e a n d a ssista n ce in c u t t in g
a rea . T h is ty p e o f s n u b -n o s e d s to n e c a n
th e se p r e p a r a tio n s . W i t h th is d e v ic e h ig h
b e u s e d to d e v e lo p e ith e r a c le a n fin is h in g
s p e e d r e v o lv in g in stru m e n ts m a y b e u s e d
lin e o r a s h o u ld e r lik e a c c e n t u a t e d fin is h
w it h o u t
heat
p r o d u c t io n .
The
fie ld
is
in g lin e . T h i s a c c e n t u a t e d ty p e o f lin e
m a in ta in e d c le a r o f d e b ris a n d v is ib ility
w ill a u t o m a t ic a lly a p p e a r w it h in c r e a s e d
is fa c ilit a t e d . I n a d d it io n , b o t h th e t o o t h
p a r a lle lis m
on
th e b u c c a l s u r fa c e o f
a
W IL L E Y ... VOLUME 53, AUGUST 1954 • 147
lo w e r m o l a r (F ig . 1 5 ) , o r o n th e lin g u a l
ance
s u r fa c e
w h e r e a n a n t e r io r v e n e e r ca s tin g is c o n
of
an
a n t e r io r
veneer
w hen
of
0 .7 5
mm.
w o u ld
g r e a t e r b u lk o f m e t a l is u s e d t o g iv e th e
s tr u c te d o n
c o lla r lik e
th e h a r d e r ty p e s o f
e ffe c t
at
th e
c in g u lu m
as
p r e v io u s ly m e n t i o n e d . I n t e r p r o x im a l a c
be
a d eq u ate
a th in t o o t h , u s in g o n e o f crow n
and
b r id g e
g o ld . A t th e o t h e r e x t r e m e , in th e p o s
cess w h e r e a n a d ja c e n t t o o t h is p r e se n t
te r io r s e c tio n o f th e m o u t h w h e r e a m o la r
c a n b e g a in e d g e n e r a lly b y u s in g a th in
is t o se rv e as a lo n g s p a n a b u t m e n t, a n d
steel lig h tn in g disk. W h e r e n o p r o x im a l
w h e r e th e r e m a in in g te e t h in d ic a t e h e a v y
to o t h is p r e s e n t, this r e g io n m a y b e d e
w e a r , a c le a r a n c e o f 1.5 m m . w o u l d n o t
v e lo p e d
b e ex ce s s iv e . I n th e p o s t e r io r te e th , s u ffi
w ith
th e
ta p e r e d
s n u b -n o s e
d ia m o n d . T h e s e d ia m o n d s ton es a re a ll
c ie n t o c c lu s a l c le a r a n c e in a ll e x cu rs io n s
u sa b le
o f m a s t ic a tio n m u s t b e a c q u ir e d to a llo w
fo r
in t e r p r o x im a l
p e n d in g o n 1 5 ).
g r o o v in g
th e size o f th e t o o t h
de (F ig .
T h is fig u r e illu stra tes b e t t e r th a n
w o r d s c a n te ll, a b a s ic r u le in a b u t m e n t
f o r b u lk o f m e t a l a n d d e e p o c c lu s a l c a r v in g s. I t is w e ll t o f o l l o w
o u t th e b a s ic
c u s p a l f o r m o f th e s e s u rfa ce s in o r d e r t o
p r e p a r a tio n . T h e h a n d p ie c e is h e ld c o n
o b t a in m o r e o r less u n if o r m
s ta n tly in a p r e v io u s ly d e t e r m in e d lin e o f
D e e p , d e fin ite c a r v in g s a r e a n a t o m ic a lly
c le a r a n c e .
s h e d . I n th is w a y th e h a z a r d s o f u n d e r
c o r r e c t , a n d th e y p r o v id e f o r th e f u n c
c u t t in g a re g r e a tly r e d u c e d .
t io n in g p a r t o f th e ca s tin g t o b e f o r m e d
The
a n t e r io r
t h r e e -q u a r t e r
prepara
b y a series o f
s h a rp b la d e s
(F ig .
1 7 ).
tio n in v o lv e s th e m o s t d iffic u lt step in th e
T h e s e b la d e s e n c o u r a g e e ffic ie n t m a s t i
fie ld
c a t io n , a n d
of
p r e c is io n
o p e r a t iv e
d e n tis try —
w e a r m o r e u n if o r m ly w ith
th e c o n n e c t in g o f th e m a r g in le f t b y th e
th e r e m a in in g te e th th a n d o
s e p a r a t in g d is k in t e r p r o x im a lly w ith th e
fa c e ts . I t is o f t e n
g in g iv a l e n d o f th e g r o o v e o n th e sid e
b r id g e s c o n s t r u c t e d w it h la r g e , fla t o c
a p p r o x im a t in g r e la tiv e ly
a n a d ja c e n t t o o t h . T h is
in a c c e s s ib le
tr ia n g u la r -s h a p e d
n o te d
la rg e flat
th a t e x te n s iv e
clu s a l s u rfa ce s o f h a r d g o l d a llo y r e a c h a sta te o f h y p e r o c c lu s io n s im p ly b e ca u s e
a r e a o f t o o t h s tru ctu re c a n n o t b e r e a c h e d
th e m e t a l h as fa ile d t o w e a r a w a y a t th e
b y th e d is k ; u n til th e a d v e n t o f th e v e r y
s a m e r a te as th e o c c lu s a l s u r fa c e s o f th e
s m a ll d ia m o n d ta p e r e d s to n e th e o p e r a
r e m a in in g n a tu r a l te e th .
tio n
w as
a lw a y s
r a th e r
a
h it-a n d -m is s
p r o p o s itio n . F ig u r e 16 illu stra tes th e u se
I n s tr u m e n ta t io n
o f th is sm a ll sto n e , c o m p a r a b le t o a n o .
q u ic k ly w ith a w h e e l ty p e o f s to n e (F ig .
• B u lk m a y b e r e m o v e d
7 0 0 fissu re b u r in size. H ig h s p e e d a n d
1 8 ) , th e size o f th e s to n e a g a in d e p e n d
v e r y lig h t p re ssu re a re u s e d t o r e m o v e this
in g o n th a t o f th e t o o t h in v o lv e d . T h e
is la n d o f t o o t h s tr u c tu r e a n d e s ta b lis h a
g e n e r a l c u s p a l f o r m a t io n o f th e m o la r s
d e fin ite fin ish m a r g in b e t w e e n th e
m a y b e f o l l o w e d o u t w ith in v e r te d c o n e
end
o f th e g r o o v e a n d th e in t e r p r o x im a l slice
ston es.
c u t.
th e p r e p a r a t io n in th is m a n n e r a llo w s f o r
S h a p in g th e o c c lu s a l s u r fa c e o f
a u n if o r m c le a r a n c e as w e ll as s u fficie n t A d e q u a t e C le a r a n c e • I t is e x t r e m e ly d i f
d e p th
fic u lt t o p r o p o s e a n y d e fin ite a m o u n t o f
in th e fin is h e d ca s tin g .
fo r a cce n tu a te d
o c c lu s a l g r o o v e s
c le a r a n c e o n th e lin g u a l s u r fa c e o f a n te r io r v e n e e rs o r o n th e o c c lu s a l s u r fa c e
O ffs e t
o f p o s t e r io r v e n e e rs . T h e d e g r e e o f f o r c e
1 9 ) s erv e t o c o n n e c t th e p r o x im a l g r o o v e s
ex erted
w it h a th ic k b a r o f m e t a l, b o t h in th e
a g a in st v e n e e r s ,
th e
le n g th
of
G rooves
and
• O f fs e t g r o o v e s
p o s t e r io r
p a r t ia l
(F ig .
s p a n o f th e b r id g e , th e a m o u n t o f t o o t h
a n t e r io r
s tru ctu re a v a ila b le in t o w h i c h t o c u t th e
T h e i r u se is e n tir e ly co n s is te n t w it h th e
ven eer.
p r e p a r a tio n , a re fa c t o r s d e t e r m in in g th e
e n g in e e r in g p r in c ip le o f th e truss. W it h
c le a r a n c e . I t is c o n c e iv a b le th a t a c le a r
th e s a crifice o f a m in im u m
am ount o f
148 • THE JOURNAL OF THE AMERICAN DENTAL ASSOCIATION
Fig. 7 • View of upp e r cuspid show ing minimum extension of labial extension and go ld exposure
Fig. 8 • Three-quarter preparation on upper molar, full veneer on lower m olar and three-quar ter veneer on u p p e r cuspid, show ing quasiparalleling or slight convergence of walls and grooves to obtain maximum frictional force
WILLEY
F ig . 9 • A b o v e : The d e v e lo p m e n t o f p ro p e r ly c o n v e rg e n t w alls w ill re s u lt in v a rio u s fo r m a tio n s o f th e fin is h in g lin e . The sam e b lu n t-n o s e d ta p e re d d ia m o n d sto n e m a y b e used as show n. B elow le f t : A c c e n tu a te d fin is h in g lin e on lin g u a l su rfa c e fa d e s o u t t o a c o n v e n tio n a l fin is h in g lin e in th e in te r p ro x im a l a re a . Below r ig h t: A n even m o re p r o n o u n c e d s h o u ld e r on th e lin g u a l g in g iv a l m a rg in o f th e lo w e r a n te rio r to o th results fro m a lin e o f shed d ir e c te d lin g u a lly
F ig . 10 • A s h o u ld e rlik e fin is h in g lin e o fte n re sults on b u c c a l s u rfa ce w hen w alls a re m a d e m o re n e a rly p a ra lle l. S u p p le m e n ta l g ro o v e s im p ro v e th e r e te n tio n in s h o rt p o s te rio r te e th
F ig . I I • N os. I, 2 a n d 3 a re v a rio u s sizes o f b lu n t-n o s e d ta p e r e d d ia m o n d stones. N o . 4 is a v e ry sm all, fin e -ta p e re d d ia m o n d a p p ro x im a te ly th e size o f a no. 700 b u r. N o . 5 is a c a r b id e b ur, size n o. 700, f o r p la c in g in te rp ro x im a l g ro o ve s
. VOLUME 53, AUGUST 1956 • 149
150 • THE JOURNAL OF THE AMERICAN DENTAL ASSOCIATION
Fig. 12 • M esiodista! contour of upper cuspid is preserved when mterproximal surface is rem oved with a separating disk inclined lingually
Fig. 13 • W h e n initla! Interproxim al cuts are m ade without the lingual inclination of the disk, the entire m esiolingual contour of the cuspid is destroyed, resulting in needless disp lay of go ld and sacrifice o f tooth structure
WILLEY
Fig. 14 • O n lower m olar an accentuated finished line is autom atically de ve lo pe d by a snub-nosed diam ond on the buccal and lingual surfaces of an upp e r cuspid. A rrow s indicate position o f stone in relation to line of shed to establish definite wall to function in o pposition to grooves
Fig. 15 • A basic rule in abutm ent preparation is to m aintain the h andpiece in an established line o f shed, regardless of the direction of the long axis of the tooth being prepared
Fig. 16 • ’’Islan d " o f tooth structure left by slice cut and înterproxima! gro ove is rem oved by small tapered diam ond stone
.V O LU M E 53, AUGUST 1956 • 151
152 • THE JOURNAL OF THE AMERICAN DENTAL ASSOCIATION
of
m o r e a c c u r a t e ly a r o u n d in g o f th e in cis a l
m e t a l is m a d e a v a ila b le in a m o s t v u l
tooth
s tr u c tu r e ,
m a r g in . T h e in c is a l m a r g in o f a c a r e fu lly
n e r a b le
p repa red
r e g io n .
an
added
The
am ount
added
th ick n ess
t h r e e -q u a r t e r v e n e e r le a v e s a
g iv e s r ig id ity t o w ith s ta n d th e fu n c t io n a l
sh a rp , d e lic a te e n a m e l k n ife -e d g e . S lig h t
f o r c e e x e r t e d a g a in st it in th e r e g io n o f
r o u n d in g o f th is m a r g in n o t o n ly p r o te c t s
th e t o o t h w h e r e th e g re a te st w e a r o c c u r s ,
it a g a in st fr a y in g o r f r a c t u r e d u r in g th e
a n d a ls o p r o v id e s b u lk t o p r e v e n t o p e n
f a b r ic a t io n o f th e c r o w n , b u t p r o v id e s a
in g
m u c h ea sier e d g e a g a in st w h i c h t o fin ish
of
th e
in c is a l o r
o c c lu s a l
m a r g in ,
s p r in g in g o f th e c a s tin g , a n d s u b s e q u e n t
th e m a r g in o f th e ca s tin g . W it h o u t s u ch
fa ilu r e o f th e in t e r p r o x im a l m a rg in s .
r o u n d in g ,
one
is w o r k in g
w ith
a
b u tt
jo i n t , a n d as e v e r y o p e r a t o r k n o w s , it is M a r g in a l E x te n s i o n re s u lt
is
• W h e r e a n e s th e tic
im p o r t a n t ,
th e
te n s io n s a re lim it e d
(F ig .
m a r g in a l 2 0 ).
ex
T h is
is
p a r t ic u la r ly tr u e in th e m e s ia l a r e a o f th e
e x t r e m e ly d iffic u lt t o a d a p t a n d fin is h a g o l d ca s tin g t o a b u t t jo i n t . F u r t h e r m o r e , th e “ s h in g le d
ro o f”
r e la t io n
w h ich
th e
g o ld h as t o th e t o o t h in th is r e g io n a llo w s
a n t e r io r t h r e e -q u a r t e r c r o w n c a s tin g . T h is
th e f o r c e s d ir e c t e d a g a in st it t o c lo s e th e
m in im a l
m a r g in r a th e r th a n o p e n it.
e x te n s io n
can
be
a t t a in e d
by
c a r e fu l o p e r a t in g , r e ly in g o n th e u se o f s e p a ra to rs , th in s e p a r a t in g d isk s a n d fin e
I n s t r u m e n t a t io n
d ia m o n d
n oted ,
ta in e d w it h t h e w e t o r d r y t y p e o f p a p e r
th o u g h , e s p e c ia lly w ith c u s p id s , th a t a n y
disk. O n th e in c is a l m a r g in o f a n t e r io r
loss
s u ch
te e th it is b est d o n e w ith th e a ssista n ce o f
lim ite d e x te n s io n s h o u ld b e c o m p e n s a t e d
b in o c u la r lo u p e s . F o r e s th e tic h a r m o n y
f o r b y a s lig h t e x t r a e x te n s io n o n th e d is
th e in c is a l e d g e s h o u ld c o n f o r m in s h a p e
ta l s u r fa c e . T h is p r in c ip le is o f c a r d in a l
t o th a t o f th e a d ja c e n t a n t e r io r te e th . T h e
im p o r t a n c e , a n d a n y s a crifice o f e x te n s io n
e d g e c a n b e d e v e lo p e d w it h th e d isk a n d
f o r th e p u r p o s e o f e sth etics is a n in v it a
th e n c a r e fu lly r o u n d e d .
of
sto n e s. coron al
It
s h o u ld
g ra s p
be
ca u sed
by
• T h e bevel can b e o b
tio n to fa ilu r e . A s p r e v io u s ly s ta ted , all
A t this p o in t th e p r e p a r a t io n s h o u ld
fa c e ts o f w e a r s h o u ld b e c o v e r e d , a n d th e
b e r e a d y f o r fin a l c h e c k in g a n d in s p e c
m a r g in s e x t e n d e d
tio n . S c o u r in g t h e t o o t h w ith a p a s te o f
to
ju s t b e y o n d
th e ir
b o u n d a r ie s .
p u m ic e a n d p e r o x id e w ill r e m o v e d e b ris . A f o r c e f u l b la s t o f w a r m s p ra y f r o m th e
I n s tr u m e n ta t io n
• A re fin e d in s t r u m e n
a to m iz e r ,
fo llo w e d
by
d r y in g
of
th e
ta t io n o f th a t u se d in w a lls a n d g r o o v e s is
p r e p a r a t io n w it h w a r m a ir, w ill m a k e th e
u se d in m a r g in a l e x te n s io n . O n th e m e s ia l
p r e p a r a t io n r e a d y f o r e x a m in a t io n w ith
s u r fa c e o f a th r e e -q u a r t e r v e n e e r w h e r e
th e lo u p e s . I t is w e ll t o n o t e th e f o l l o w
th e e x t e n s io n , f o r e s th e tic re a s o n s , is t o
in g p o in t s :
b e lim ite d , th e m a r g in o f t e n m a y b e c o m p le t e d w ith fin e w e t o r d r y p a p e r disks. I n f a c t , th e se a re e x c e lle n t f o r fin is h in g
1.
T h e le n g t h o f w a lls a n d
s h o u ld
b e ob served
to m ak e
grooves
su re th a t
a ll m a r g in s a n d fla res w h e r e a cce s s ib le .
th e y a re a d e q u a t e in le n g th a n d fr e e o f
The
u n d e r c u ts .
d ista l
asp ect
of
th e
p r e p a r a t io n ,
u s u a lly c a r r ie d w e ll o n t o th e b u c c a l su r f a c e o f p o s t e r io r te e th w ith a b lu n t -n o s e d d ia m o n d , c a n a ls o b e fin is h e d w ith su ch
2. 3. fre e
disks.
C le a r a n c e in c e n t r ic a n d e c c e n t r ic
p o s itio n s s h o u ld b e c h e c k e d . E v e r y m a r g in m u s t b e s m o o t h a n d fro m
ra gged
e d g e s,
and
fla res
p o lis h e d . T h e la b io g in g iv a l a n g le s o f th e I n c is a l o r O c c l u s a l R e v e r s e B e v e l • T h e
t h r e e -q u a r t e r p r e p a r a t io n s h o u ld b e r e
s lig h t re v e rs e o r b a c k b e v e l ( F ig . 2 1 ) is a
c h e c k e d t o a s ce rta in th a t t h e fla re s b e
“ b e v e l”
c o m e c o n t in u o u s w it h t h e b e v e l a t th e
in a v e r y re s tr ic te d sense. I t is
F ig. 18 • Bulk is re m o v e d w ith a w he e l ty p e o f d ia m o n d sto n e
F ig . 19 • A n in v e rte d c o n e d ia m o n d sto n e is used to d e v e lo p o c c lu s a l o r in cisa l g ro o v e c o n n e c tin g in te rp ro x im a l g ro o ve s
F ig . 20 • M a r g in a l e xtensions a re e s th e tic reasons on th e u p p e r cu sp id
lim ite d
F ig . 21 • A s lig h t reverse o r " b a c k " in cisa l o r o cclu sa l m a rg in
fo r
b e v e l on
154 • THE JOURNAL OF THE AM ERICAN DENTAL ASSOCIATION
g in g iv a l e n d o f th e g r o o v e s . N o a b r u p t s h e lf s h o u ld b e le f t a t th is p o in t .
t o th e p o s t e r io r te e th . W h e t h e r it b e a h a lf c r o w n , th r e e -q u a r t e r , se v e n -e ig h th s ,
P r e p a r a tio n s p e r f o r m e d in th e m a n n e r
o r f u ll v e n e e r c r o w n , th e s a m e f u n d a
d e s c r ib e d in th is p a p e r a re n o t a lte r e d to
m e n ta ls s h o u ld b e o b s e r v e d . T h e a b s e n c e
c o n f o r m t o a n y p a r t ic u la r t e c h n ic o f r e
of
p r o d u c t io n , i f s u c h a lte r a t io n in a n y w a y
r e g io n o f th e m o u t h p e r m its e v e n m o r e
s e v e re
e s th e tic
r e q u ir e m e n ts
in
this
lessens th e a d v a n ta g e s g a in e d b y f o l l o w
e x te n s iv e
in g th e p r in c ip le s a d v o c a t e d . E a c h d e ta il
w h e n n e e d e d , a n d g r e a t e r b u lk o f m e ta l
in th e p r e p a r a tio n s is p e r f o r m e d
to resist d is p la c e m e n t a n d d e fle c t io n .
fo r a
coverag e,
a d d it io n a l
le n g th
d e fin ite re a s o n . T h e n e x t step in th e p r o ced u re
co n s titu te s
a
g e n u in e
c h a lle n g e
C O M M E N T
t o th e o p e r a t o r — b u ild in g a d ie o n w h ic h or,
R a r e ly d o e s a d e n tis t e x p e r ie n c e a g r e a te r
b e t t e r y e t, in th e ca se o f th e c o n s e r v a tiv e
to
con stru ct
a
s a tis fa c to r y
c a s tin g
s a tis fa c tio n f r o m d e n ta l o p e r a t io n s th a n
a n t e r io r th r e e q u a r t e r p r e p a r a t io n , b u il d
w h e n o b s e r v in g a r e s to r a t io n o f th is ty p e ,
in g a d ir e c t w a x p a t te r n f r o m w h i c h to
e s th e tic a lly a c c e p t a b le ,
c o n s t r u c t a s a tis fa c to r y c a s tin g . H e m u s t
a ft e r m a n y y ea rs, w it h p u lp u n d a m a g e d ,
p r o je c t , s o t o s p e a k , o n t o th e fin is h e d
and
r e s to r a t io n th o s e in h e r e n t q u a litie s b u ilt
q u o t e th e la te H a r r y P o t t e r :
w it h
h e a lt h y
still f u n c t io n in g
in v e s tin g tissues.
To
in to t h e p r e p a r e d t o o t h . T h e ca s tin g b e com es
th e
im p o r t a n t
c o n n e c t in g
lin k
w h i c h m a k e s th is p o s s ib le . P o s te r i o r P r e p a r a tio n s
• T h e p r in c ip le s
c o v e r e d in th e f o r e g o in g d is cu s s io n o f th e a n t e r io r v e n e e r c r o w n a re a ls o a p p lic a b le
W ith ordinary precautions in the design, preparation, guarding and cem entation of veneer types o f castings for fixed or removable types o f bridges constructed along proven principles, the placing of such work should represent one o f the finest services the dental profession can render.
Joy o f P erfection • A great deal o f the jo y o f life consists o f doin g perfectly, or at least to the best o f one’ s ability, everything w hich he attempts to do. Th ere is a sense of satisfaction, a pride in surveying such a work— a w ork w hich is rounded, full, exact, com plete in all its parts— which the superficial man, w h o leaves his w ork in a slovenly, slipshod, half-finished con dition, can never know. It is this conscientious completeness w hich turns w ork into art. T h e smallest thing, well done, becom es artistic. W illiam M athew s.