rehabilitación de hexágono externo
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Anterior Single-Tooth
Implant Restorations
Steven
Lewis, DMD
he opptication af impiant dentistry to the treatment of partial edentulism
has necessitated the development afnew components and techniques.
his article reviews the various systems and techniques u sed to fabricate
success fui anterior single-tooth implant restorations Placement techniques
for nonsegmented, sarew-retoined abutments: segmented, screw-retained
abutm ents: and segmented , cement-retained abutm ents ore illustrated.
IntJ Periodont Rest Dent
1995;
15:31-41)
•Private Practice,
San
Antonio, texos.
Reprint requests; Dr Sleven Lewis, 7 Inwood Point, San Antonio,
Texas 782d8.
The successful t reatment
edentu l i sm wi th osseo in t
gra ted prostheses hos iead to
revolution in dentistry. With th
success ul t imateiy came th
desire to appiy the same tec
noiogy to the partiaiiy edent
lous popu ia t ion as
we
i-iowever, many different ciinic
chaiienges were encountere
when this adaptation was in
t ia i iy at tempted, ond i t soo
b e c a m e e v i d e n t t h a t n e
components and techn ique
were necessary to overcom
some of the probiems uniqu
to the par t ia i i y edentu iou
pct ient , Ohe of the greate
cha i ienge s was tha t o f th
anterior singie-impiant restor
tion and the abiiity to achiev
a stabie and esthetic impia
restorat ion. Var ious syste
designs and restorotive tec
niques used to create succes
fu i an ter io r s ing ie- imp ia
restorations are reviewed in th
articie.
One ciassification divid
impiant components and
tec
niques into those restorotio
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Fig 1 Nonsegmented single-tooth
implant restorations UCi-A abutment)
ñt directly to the implant fixfure and
must engage the hexagon of the
impiant tar antiratation
that are cement-retained and
those that are screw-retained,
Anather classificatian relates
to
fhe averall design, either non-
segmented Of segmented. The
nonsegmented design consists
of
a
restoration that connects
direofiy
fo
the impiant fixture,
while the segmented design
inciudes
a
restoration that fits
over
a
fitanium abutment. The
categories of single-tooth tech-
nique described in this artioie
are 1)
the
nonsegmented
sorew-retained abutment,
(2) the segmented screw-
retained abutment and
(3)
the segmented, cement-
retained abutment. Examples
of fhe nonsegmented, sorew-
retained,
and
segmented,
cement-retained types will
be
of the same clinicai restoration
to allow oomparison.
Nonsegmented, screw-
retained restoration
The nonsegmenfed restoration
connects direotiy
to the
implant fixfure. This technique,
introduced
by
Lewis
et
al,
is
populariy referred
ta
as the
UCLA abutment. Far single-unit
UCLA abutment implant
restorations,
it
is criticai to utilize
implant fixtures that cantain
hexagcns
on
their coronal
aspect. Because the restoration
is begun directly at the impiant
fixture, it
is possible
to
incorpo-
rate
a
hexagon within the base
of the restoration
to
engage
the hexagon
at
the implant
(Fig
1 ). With
this connection, the
restoration shouid exhibit the
antirotation neoessary for a sfa-
bie single-tooth restoration.
Also,
with proper implant coun-
tersinking,
beginning
the
restoration
at
this level shouid
allow adequate vertical space
to develop
a
natural and grad-
ual emergenoe prafiie, provid-
ing exceilenf esfhetios and
easy aooess
for
aral hygiene
measures.
With
the
nonsegmented
technique, only screw-retained
restorations are recommen-
ded.
Cementing directly
to
the
implant makes retrievabiiity
and access to the implant itself
quite difficuif,
To tabricate fhe nonseg-
mented screw-retained resto-
ration
to fit
directiy
to the
implant fixture, an impression
coping that fits directiy
to
the
implant fixture must be used.
It
is important that the impression
coping contain
a
hexagonai
base that matches the hexa-
gon
of
fhe implanf. This is crifi-
cai, because fhe tinal restora-
tion must engage the impiant
hexagan;
theretore, the rota-
tional aiignment
of
the hexa-
gon
in
the wori<ing oast must
match that
of fhe
actuai
impianf. When fhe impression
coping is seated intraoraliy
to
the impiant,
a
radiograph
is
necessary
to
ensure that the
hexagons are matched and
compiete seating is achieved.
After fhe impression is made,
a
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labo rato ry im plon t rep l ica is
connected to the impression
coping and a cost is poured
Fig 2), The lab ora tory replica
must a lso conta in o hexagon
identicol to the implant fixture.
Because the implont fixture
snould ideally be positioned 3
to 4 mm beneath the gingival
margin to create an esthet ic
anterior restoration with a grad-
ual emergence profile, the finai
cast should contain a tiexible
materiai that duplicotes the sul-
cular tissue around the implant
Fig 3). This soft t issue ca st
a l lows the laboratory techni -
c i a n t o f a b r i c a t e t h e t i n a i
res tora t ion w i thout acc iden-
taily altering the soft tissue con-
tours.
Mony technicians prefer
that this materiai be separable
from th e master cast. Thus, as
the restoration is being waxed
and contoured, the soft t issue
mate r i o l may ac tuo i l y be
removed f rom the cast , ideai
emergence prot i les can then
be aftained without being dic-
t a ted by the des ign o f t he
heal ing abutment or subgingi-
val port ion of the impression
coping.
The UCLA abutment inifioiiy
was a piastic burn-out pattern
that connected direcf iy to fhe
imp lanf t ix tu re . One pa t te r n
con ta ined o round base fo r
muit iple implant restorat ions,
wh i ie the o ther conta ined a
hexagonal base for the antiro-
ta t io n necessary in s ing le -
imp lan t res toro t ions . Today
these plastic pafterns may still
Fig 2 An imptanf fixfure onalog is con-
nected to the impression cop ing
before the cast is poured
be uti l ized, or m ach ine d goid
al loy cyl inders may be used.
These fit to the impiant fixtures
as do the p iast ic pat terns.
Fabrication of a restoration w ith
the p last ic pot tern invoives
secur ing fhe pa t te rn to the
implant f ixture repl ioo of the
moster oast and incorporating
it withih the substructure pot-
tern Fig 4). The wox an d p lastic
burn out otter being invested,
resulting in a tramework with o
cast base. The m achin ed cylin-
der would also bec om e part of
the wax substructure, but after
investing,
it does not burn out.
After the wox burn out, o frome-
work is made by casting to the
machined oyi inder. Thus, the
bose of the metal substructure
contains o mochined cyl inder
w i th a mach ined hexogona l
paftern. he adva nta ge of this is
thot the quality of the fit of the
restoration to the impiont fixture
Fig 3 The master oasf contains fhe
implanf tixfure replica wifft the fofation
ol alignmen t of the hexago n identical
to thot of fhe acfuai implant.
The
soft
tissue maferial wiil preserve the soft fis
sue contours during fobricafion of fhe
tinai restoration.
Fig d The UCL abutment burn-ouf
pattern
ñts
direcfly to the implanf fix-
ture and has a hexagonai paftern at
the base that
ñfs
over
f i ie
implant
hexagon. Once secured fo fhe tixture
anaiog the burn ouf potfern will
become parf of the substructure wax
pottern.
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Fig Tile com pieteú porcelain-fuse d-to-metal restoration
fits directly to fhe top of fhe implont ñxfure matcfiing the hex
of the fixture and is refaihed wifh a titanium alloy screw
fighfened fo 20 Ncm
Fig 6 The nonsegmenfed impiant resforotion replaces the
max iiiary left central incisor with a natural appeara nce.
is always pre de term ined with
the machined cylinder. In con-
trast, the quality of the fit with
the castable plastic pattern is
more technique sensit ive and
di f fers f rom restorat ion to
restoration. In any case, no ma t-
ter w hich tech nique is utilized, it
is always best to check the fit of
the res tora t ion to an ac tua i
implant tixture microscopically.
Discrepancies may be over-
come with a milling instrument
when necessary.
Use of alioys with at least
50
go ld hos be en rec om -
mended with the UCLA abut-
ment technique, ' This should
minimize the potential for gai-
vanism or corros ion at the
implant - res toro t ion junc t ion .
However, the long-term ramifi-
cations of placing two dissimilar
metals at this level are st i l l
unknown.
Porceloin is ap plie d to the
casting and the restoration is
co m pi e te d (Fig 5) . This f ina l
restorat ion is reta ine d to the
implant fixture with the use ot a
titanium alloy screw tightened
to a force of 20 Ncm (Fig ó).
Rad iographs ore abso lu te ly
c r i t i ca l t o assu re adequa te
seating.
Unless the hexagon ot
the res tora t ion i s per tec t l y
o l igned wi th the hexagon ot
the implant tixture, the restora-
tion vi/ill not be seo ted .
The screw-access channel
is uitimately sealed with gutta-
percha and either amaigam or
resin. If the restorative materia
surrounding the surface ot the
screw-access o pen ing is m etal,
amalgom is p re ter red . I t the
screw -acce ss o pe nin g is sur-
rounded by porcelain, resin is
used. In either case , the restora
tive ma teriai is easily rem ove d
when access to the retent ion
sorew is desired. The gutta-per-
cha protects the heod ot the
sc rew t rom be ing damaged
when access is being gained,
because this material may be
removed w i th an excava to r
rather than a hondpiece.
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Fig 7 The titanium EsfhetiCane is secure d to the top of the
impiant fixture w ith a pure titanium abutment screw The
external walls of the abutm ent may b e used for antirotatian.
FigB The ¡ mm collar EsfhetiCone abutment wil iallow the
restoration to begin 2 fo 3 mm beneath Ihe gingival margin.
he
restoration has a natural ond gradual eme rgence profile
Segm ented, screw-retained
restoration
Segmented restorat ions may
be cons idered those tha t f i t
over t i tanium abutment cy l in-
d e rs r a t h e r t h a n c o n n e c t
directly tc the implant fixtures.
Thus, the re are var ious seg -
ments to th e restaration.
Advantages of having the
t i tanium abutment include the
ta ct th at the re is now a t i ta-
nium-t i tanium interface at the
leve l o f the imp lan t f i x tu re .
Ga l van i sm and co r ros ion
shou ld no longer be o con-
cern. The interface at this level
is now betw een tw o mach ined
c o m p a n e n t s a n d t h u s t h e
technique sensitivity of a cast-
ing is e l iminated. Also, there
now exists a titanium -soft tissue
i n t e r f a c e . A l t h o u g h s o m e
researchers oons ider the
p o t e n t i a l h e m i d e s m o s o m a l
attachment betvyeen the t i ta-
nium and soft tissue to be an
important factor for long-term
success,^'^ others feel that this
sa-cal led b io logic seal may
minimize pocket depth but will
in no way inhib i t epi thel io l
downgrow th . shou ld t he
implant become mobi le, St i l l
o thers moin ta in tha t o
hemidesmosomal ottachment
to sott tissue is not unique to
t i t on ium and con oc tuo l l y
occur with ceramics or a vori-
ety c t m etal alloys.^ Thus, the
true significance of this inter-
face is somewha t unclear
Ta achieve an acc ep tab le
esthetic result, it is critical that
the restoration beg in 2 to 3 mm
beneoth the mucosa. With the
nonsegmented technique, the
restorot ion begins direct ly at
the im plo nt f ix ture. Wi th the
placement ot a ti tanium abut
me nt, however, the restoratio
must begin closer to the ging
val morgin. Titanium abutment
such as the Esthet iCon
(Nobelpharma) are designe
for subgingival restorations (Fi
7), These abutm ents con ta i
either
1 -,
2-, or 3-mm collars a
the bas e. The restora tion fit
over the abutment down t
the top ot the collar. Thus, wit
the 1-mm titonium collar, th
restorot ion may beg in 1 mm
from the implont fixture. s lon
OS the implant f ixture is pos
t ioned 3 to 4 mm beneath th
mu cosa , the restorat ion ha
adequate room (2 to 3 mm) t
develop o natural and gradu
em ergenc e profile (Fig 8). Wit
a properly positioned implan
the result is the a pp ea ran ce o
a to oth at the gingival margin
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i 9 The gold alioy cylinder contains an
internal hexagon that engages the
iater
al walls af the Estheti one abutment
Fig 1 a The ¡mpressian coping con
tains an internal hexagan ta prope riy
align the laboratory repiica
Fig IQb The laboratory replica IS
similar to the EsthetiCane abutment
replica use d for muitipie implant
restorations (left) excep t that it con
tains an externai hexagonal pattern
(right) that is necess ary far single tooth
restorations.
Whi ie the Es the t iGone
abutment was or ig inai iy cre-
a ted fo r mu i t i p i e imp ian t
restorations oniy, ^ modifications
have been made to al low i ts
use as a singie-tooth impiant
restoratian. To provide stabiiity,
an ant i rotat ionai des ign was
necessary. The goid aiioy cyiin-
ders that become part of the
wax pattern and then part of
the meta i subs t ruc ture now
conta in an in te rna i hexagon
t h a t m a t c h e s t h e e x t e r n a i
hexagon o f the Es the t iCone
ab ut m en t (Fig 9). The impres-
s ion cop ings and labora tory
repl icas aiso contain hexago-
n a i p a t t e r n s m a t c h i n g t h e
hexagon of the abutment so
that the rotationai ai ignment of
the abutment hexagon is trans-
ferred to the master cast (Figs
10a and 10b).
The technique of fabricat ing
a singie-impiant restorat ion is
fa ir iy s imp ie . i h e ab u t m en t
cy i inde r is ca nn ec te d to t he
imp lant f i x tu re , an d a rad i -
ogra ph is taken to ensure th at
the hexagon of the abutment
base is a i ig ne d prop er iy wi th
the he xag on o f t he imp ian t
f ix tu re , a l i ow ing co m p ie fe
seating.
The titanium abu tme nt
screw is the n t ig hte ne d to 20
Ncm.
The
impression coping fits
over the abutm ent cyiinder a nd
is reta ined vy i th a guide p in.
Because the internai aspect of
this impression c op ing contains
a hexag on matching th at of the
abutment, care must be taken
to ensure proper
seating.
radi-
ograph is often useful to con firm
this,
and the same radiograph
that evaluates abutment seat-
ing may aiso be used to evaiu-
a te t he impress ion cop ing
seating.
The impression coping is
retrieved with the impression,
and t f ie iaboratory abutment
rep i i ca w i th the hexagon is
connected (Fig 11). As with the
UCLA a butm ent an d aii subgin-
gival impiant restorations, a soft
tissue cast is fab rica te d (Fig 12).
The goid ai ioy cyl inder is
s e c u r e d t o t h e i a b o r a t o r y
repi ica and becomes incorpo-
rated wi th in the wax pat tern.
The buccai inci inat ion of thé
imp ian t f ixture is cr i t ic ai with
th is tec hn iqu e, bec aus e th e
restoration wiii co nta in a screw-
access opening on the surface.
An imp ian t ang ied too fa r
faciaiiy wiii resuit in an unac-
cep tab ie faciai screw chan nel.
This is tr ue of th e no ns eg -
mented or UGi-A abutment as
weil. The screw-ohannei open-
ing with the segmented tech -
nique wiii be smaiiet, however,
because the retention screw is
a smaii goid aiioy screw that fits
wi th in the t i tanium abutment
screw. The s eg m en ted t e c h -
nique ut i i izes a iarger screw
th a t is th e sam e size as an
abu tme nt screw.
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F/g í î (lefr) The
impresión ooping
Is
retrieved with the impression and fhe
at:>utment repiica is connected.
Fig 12 (right) The master oast contains
the hexed abutment replica.
The
soft tis
sue m aterial wiii preserve the satt tissue
contours during laboratory procedu res.
Fig 13 ( left) The compieted porcelain
tused to metai restoration contains the
gold aiiay cylinder with the internal
hexagon.
Fig 14 ( r igM) The tinal restoration is
secured in piace by tightening the
gold aiioy screw to 1 Nom.
A variety of alloys may be
cast to the gaid alloy cyiinder.
as iong as a nonpreciaus aiioy
is av oid ed . The g old aiioy cylin-
de r wou ld be des t royed a t
temperatures h igh enough to
cast th e non precious aiioys.
An infraora l fry-in is not neo -
essary tor the metal substruc-
t u re , because the f i t o f th is
res tora t ion i s p redetermined
by fhe f i t be tween fhe
mach ined go ld cy i inder and
the mach ined t i tan ium abut -
me nt . Porcela in is ap pl ie d to
the metal substructure and fhe
restoration is readied for a clini-
ca l try-in (Fig 13). A t this time ,
the interpraximal contacts are
adjusted,
the occlusion is eva lu-
ated, an d the final esthetics are
deveioped.
The restoration is secured
in p lace wi th a gold a l loy
re tent ion screw (Fig 14). This is
the same screw used to retoin
multiple implant restorations on
the EsthetiCone abutment sys-
t e m . These screws are t ight-
ened to 10 Ncm. Radiographs
are usefu l to evaluate com-
plete seating. As with fhe non-
s e g m e n t e d t e c h n i q u e , t h e
screw channeis are then obtu-
rated wi th gut ta-peroha and
either resin ar am alga m .
The advantage of this seg-
m en te d teohn ique is t ha t a
so rew- re ta i ned , re t r i evab le
impiant restoration that can be
both esthetic and funotionaiiy
sfabie is fabricated. Al though
this is s imi iar to the advan-
tages o f t he nonsegm en ted
restorat ion, the t i tanium-t i ta
nium implant-abutment junc
tion and the titanium-soft tissue
inter face are b iomeohanioa
considerations that are more
similar to the time-tested and
wel l -dooumented oy l indr ioa
titanium abutments used in 15
year olinioai trials. The long
te rm rami f i ca f ions o f fhe
changes infroduoed wifh fhe
nonsegmented technique are
stiii unknown.
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Segmented, cement-
retained restoration
The CeraOne abutm ent (Nobel-
ph arm a) is a pure t i tan ium
obu tmen f cy i i nde r t ha t p ro -
vides a cem en t retained singie-
to o th restoration^ (Fig 15), The
obutment conta ins coi iars at
the bose just i ike the
Es the t iCone abu tmen t a i -
though 4- and 5-mm collars are
available as well. Thus, the tita -
n iu m C e r a O n e o b u t m e h t
adheres to the b io iogic and
mechanicol pr inc ip les of the
EsthetiCone abutment by pro-
v id ing o moch ined t i tan ium-
titanium interface at the ievei
ot the implan t fixture and a tita-
n ium-sof t t i ssue in te r face
between the t i tan ium co l ia r
an d suicuiarep itheiium (Fig 16).
The f inai restorat ion is
designed to cement over the
CeroOne abutment . Becouse
there is no need for a restora-
tive retention screw, there is no
need fo r on ex terna l sc rew
channe l . The porallel waiis of
the abutment cyiinder provide
exceilent retention. However, if
the abutment sc rew were to
l oosen ,
acce5S to this screw
would be di f f icul t and i t moy
be necessary to sect ion the
final restoration, it is for this rea-
son tha t the a bu tm en t sorew
joint was designed to be tight-
ened to a torce of 32 Ncm. The
retentive strength of this screw
jo in t is ap p ro x im a te l y t h ree
t imes that ot the EsthetiCone
go ld sc rew . This a bu tm en t
screw itself is also m ad e out o f
a differeht materioi than other
a b u t m e n t s c r e w s m a n u t a c -
tu red by Nobe lpha rma . The
CeraOne abutment sc rew is
m ad e ot a g oid aiioy.
The abutment screw must
be t ightened with an electr ic
torque controiier, whioh can be
p r o g r a m m e d t o 3 2 N c m . A
cou nter to rque dev ice is o lso
utiiized to prevent the possibiiity
damaging the bone-impiant
intertace during tightening.
The segmented, cemeht -
retained restorations described
in the fo l iow ing pora grap hs
(both al i -ceramic ond porce-
iain-fused-to-metai) were fobri-
ca fed to rep iace the same
tooth used to iiiustrate the non-
s e g m e n t e d , s c r e w - r e t o i n e d
technique.
The impression coping fits
over the various sized abut-
ments and remains in p iace
through t r ic t ional res is tohce.
Because plastic provides better
frictionai resistance than does
meta l , the impression coping
and the laboratory repiico are
made of plastic. The impression
co p i ng is p ic ke d up in the
impression, and the laboratory
repiioa is inserted into it (Fig 17).
A soft tissue cast is then poured
(Fig 18).
The CeraOne system allows
several prosthetic designs. An
ail-ceramic restoration may be
t a b r i c o t e d b y i n c o r p o r a t i n g
the a luminous ox ide cap: a
p o r c e i a i n - f u s e d - t o - m e t a i o r
even ali-metal restoration moy
be made by Inoorporoting the
gold a l loy cy l inder. Both the
ceromic c o p a nd gold cylinder
are designed to f i t prec lseiy
over the abutment. Thus, when
either one becomes incorpo-
rated in the final restoration, the
restorat ion is ce m en ted onto
fhe abutment cyiinder, seating
to the ievei ot the collar.
The ce ram ic c a p is ava i i -
ab le in tw o sizes, short and toll
(Fig 19), These aiuminous ox ide
caps moy be ground down as
iong as they remain at leost 0,5
m m t h ic k . A d d i t i o n a l c o r e
m a t e r i a l m a y b e a d d e d t o
increase the size of the core
and to prevent excess unsup-
po rte d porc ela in in the t inai
res to ra t i on . The po r ce lo i n
added to the cop to develop
the restorotion must be an alu-
minous oxide porcelain rather
than felspathic porcelain (Fig
20).
The ma te r i a i rec om
m en de d is Vitddur Alpha (Vita
Zahnfabr ik ) , The f ina i a i l -
ce ram ic restoration is the n per-
manently cemented into posi
tion (Fig
21).
Temporary cemen
is not recommended with this
restoration, because fracfure af
t he oe ramic ma te r i a l cou ld
ocour dur ing any a t tempt to
remove the c rown f rom the
paraliel-sided abu tme nt.
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39
Fig
5
left)
The
CeraOne abutment
is
o pure titanium abutme nt held to the
impiant fixture with a gold a lloy a but-
ment screw.
Fig
IÓ
right)
The
CeraOne abutment
siiouid allow the testorotion to begin
approximately 2 to 3 mm beneath the
gingival margin.
The
finai restoration wili
be cemented over the obutment.
i
7
left)
The
impression coping
comes out with the impression.
The
plas-
tic laboratory abutm ent replica
is
then
inserted into the impresión coping.
Fig IS right) Tiie mas ter cast contains
the plastic laboratory ob utmen t replica
with soft
tissue
material surrounding it.
Fig 19 The tall ceramic cap
is
placed
ah the master cast
This
ceramic cap
has been mod ified by slight grinding.
Fig 20 The
Una
ati-ceramic restoration
is
fabricated by adding porceiain to
the ceramic cap.
i 2 The
ali-ceramic restoration
is
permanentiy cemented aver the
CeraOne abutment.
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40
Fig 22 (ieft)
he
gold alloy cylinder fíts
over the laboratory replico as does th,-
ceramic cap.
his
cylinder allows the
fabrication of a porceiain-fused-to-
metal restoration.
Fig 23 (rigtit) Th e inal estcraflon con-
tains
tfie gold
cylinder
which provides the
fit
of the restorafian onto the abutm ent
The gold al loy cyl inder is
designed to o i low porcelo in-
tused-to-metal restorations (Fig
22),
Similar to the pro pe rt ies
of the EsthetiCone gold cylin-
der , the go ld a l loy cy l inder
bec om es pa r t o f t he wax
pat tern and then part of the
metal substructure. Ultimately
the porce la in - fused- to -meta l
restorat ion contoins this gold
cyl inder as i ts core, al lowing
i t to fi t over the ab ut m en t
(Fig
23).
While a va rief/ of olloys
may be used to c rea te the
subs t ruc tu re , nonp reo ious
al loys are not recommended,
because the gold alloy cylinder
would be destroyed under the
high-temperature condi t ions.
Conventional felspathic porce-
lains may then be appl ied ta
the m eta l subs t ruc ture . The
advantages of the porcela in-
fused - to -me ta l res to ra t i on
inc lude the possib i l i ty of
improved structural integrity as
wel l as the obi l i ty to ut i l ize
tem po ra ry ce men t. It is less risky
to affempt to remove a porce-
lain-fused-to-metal restoration
than ah all-ceramic restoration.
The metal lingual surface also
provides the obility to place o
ce m en t es cop e c han ne l. This
allows the restoration to seat
more easily during the cemen-
tation process and minimizes
the amount ot excess cement
at the subgingival restorative
marg ih . This ce m eh t eso ap e
channe l cou ld u l t imate ly be
restored with resin or amalgam.
Another poss ib le advan-
tage of the porcelain-fused-to-
metal technique
s
the ability to
create G screw-access op en-
ing in the restoration. Thus, the
CeraOne res to ro t i on cou ld
actually be considered screw-
r e t a i n e d a n d r e t r i e v a b l e .
Without the obility to ploce the
countericrque device ever the
cemen ted res to ra t i on , how-
ever, the gold al loy abutment
screw should probably not be
t ightened more than 20 Ncm,
This would still provide consider-
qbly more retent ive s t rength
than the Es the t iCone go ld
retehtive screw, which is much
smaller and tightened to only
10 Ncm, Retrieval would actu-
ally involve retrieving the crown
o n d a b u t m e n t o s o n e s eg
men t , beca use the c row h
v^ou ld be cemen ted to t he
abutment . Even i f permonen
oement were used, this cemen
cou ld bu rn ou t a t opp rox i
mately 1,OOOF if it were nece
sary to separa te the c rown
from the abutment. The screw
access open ing wou ld a l so
p r o v i d e a c e m e n t e s c a p e
channel dur ing the cementa
tion procedure, although Vi/ith
this technique the crown could
be oemented to the abutmen
either intraorally or extraorally.
If size of the screw-access
opening is o concern, it should
be no ted tha t t he CeraOne
a n d t h e U C L A a b u t m e n
screws are similar a nd consider
ab l y l a rge r i n d i ame te
(app rox im a te l y 35 l a rge r
than the EsthetiCone gald alloy
screw. W i th a Vi /e l l -p laced
implant, hov^ever. the screw
channels are en the lingual sur
face and once obturated with
res in or omalgam prov ide a
very normal lingual contour.
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41
For impiants that are posi-
tioned with a siightiy buocai
inci inat ion, the cement-
retained CeraOne restoration is
the technique of choice.
Screw-retained restorations in
this situation would contain a
screw channei through the
incisai edge or faciai surface,
seriousiy compromising the
restoratian. A cement-retained
restoration contains no externai
screw channei and so the
externai surface wouid not be
compromised trom the buccai
inciination.
Summary
Singie anterior implant restora-
tions are categorized as either
nonsegmented or segmented.
Nonsegmented restorations
connect direotiy to the impiant
fixture and are screw-retained.
These restorations are fabri-
cated with either piastic burn
out patterns resuiting in a cast
base or the use of prefabri-
cated goid aiioy cylinders that
are cast-to, becoming part of
the metai substructure. Screw-
retained and cement-retained
segmented restorations are
thase that fit aver titanium
abutm ent cyiinders. This may
be advantageaus. because
the bioiogic considerations of
piacing t i tanium abutments
subgingivaiiy inciuding a tita-
nium-titanium interface at the
levei of the impiant fixture as
well as a titanium-soft tissue
intertace, have been weii doc-
umented over extended peri-
ods of time.
Utilization of a goid alloy
cylinder with an internal hexa-
gon allows the fabrication of
singie-impiant restorations on
the EsthetiCone abutment. The
OeraOne abutment is primariiy
designed for cemenf-retoined
singie impiant restorations.
Geromic cops aiiow the tabri-
cation of aii-ceramic restora-
tions and goid alioy cyiinders
aiiow the fabrication ot porce-
lain-fused-to-metal restorations.
Although not originally in-
tended tor this modification,
the use of the gold cylinder
does give the opportunity for
screw retention on the
GeraOne abutment.
With these components, a
variety ot techniques exist
today for the fabrication of
esthetic singie-tooth impiant
restorations. iHowever, despite
the evoiution in components
and techniques, paramount to
the finai prosthetic success are
proper impiant placement and
soff tissue management.
Restorative components can-
not overcome deficiencies in
either of these two criticoi
aspects.
References
1
Lewis S, Beurre r J, Per i G, Hom burg
W. Sing le-tooth im plan t -su ppo r ted
restora t ions. In t J Ora l Moxi l lo tac
Implonis 1988:3:25-30.
2. Gou ld TRL Brunette DM , Westbury L.
The a t t a c h m e n t m e c h o n i s m o f
epith elial cells to fitan ium in vitro. J
PeriodonI Res 1981:16:61 l-óló.
3. Honsson HA, Albrektsson T Branemark
P-l. Structural a spe cts of the inter-
face be tween t i ssue and t i t an ium
imp lon ts . J P ros the t D en f 1983
50:108-113.
4.
ten Co te AR. The gingival junc tion. In
Brân em atk P-l, Zarb G , Albrektsson T
(eds). t issue-Integrated Proslheses
Osseointegration in Clinical Dentistry
C h i c a g o Q u i n t e s s e n c e , 1 98 5
145-153.
5. Jansen JA. Epittielial oeil adh esion to
den ta l imp lan t ma te r i o l s [ t hes i s ]
Nijmegen, The Netherlands, Caitiolic
University. 1984.
6. Lewis, S. An esthet ic t i taniu m ab ut
ment : Report a f o techn ique. In t J
Ora l Max i l l o foc Imp lan ts 1991
6:195-201.
7. Ad el l R, Lek ho lm U, Rookler B
Bran ema rk P-l . A 15-year study o
o sse o i n t e g r o t e d i mp l o n t s i n t t i e
treotment ot the edentulous jow. In
J O ral Surg 1981:0:387-416.
8 . Andersson 6 , O dm an R Car lsson L
Branemark P-l. A new Branemark sin
g le - toa th abu tmen t : Hond l i ng an
early clinical experiences. Int J Oro
Maxillotac Implonts 1992:7:105-111
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