qi 27 8 zuckerman 13
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Prosthodontics
Abstract
fVhen the abtttment
teeth
of a fixed partial
denture are severely
mlmligned
insertion
ofthe pmsthesis
becotnes tnoredifficult
Some ofthe tnethods
traditionally recomtnended to overcome the probletns associated with this situation
are examitied Otiedes ign that simplifiestreatmentandimproves the prosthesis is
suggested (Quintessence hit
1996:27:527-532.
Clinical relevance
A segmented fixed partial denture design with an
extracoronal interlocking attachment made from
prefabricated plastic patterns is tnore esthetic and
requires less tooth reduction than do traditional
designs recommended for ftxed partial dentures on
severely misaligned abutments.
to
be
replaced after the second and third molars have
).
raditional procedures
11731.
commit the time and funds necessary for this extended
and extensive treatment, requiring the coordinated
services of an orthodontist and a restorative dentist.
A Itered patho finsertion
It is possible to prepare the m olar abutment with a path
of insertion that is compatible with the premolar prep-
aration, but this approach has several disadvantages.
The retention and resistance of the molar prepared
under these conditions are severely compromised,-"'*
and the risk of creating a mechanical exposure ofthe
mesial pulp horn ofthe molar is increased. Further-
more, the mesial marginai ridge ofthe third molar, if
present, would interfere with insertion ofthe prosthe-
sis (Fig 2).
Mesial
half-crown retainer
Rosenstiel et a and Shillingburg et a i- have recom-
mended the use ofthe mesial half crown as a retainer
for tilted molars (Fig 3). A mesial half-crown retainer
has several disadvantages:
1.
The mesial half crown cannot be used if the molar
has previously been restored on the distal surface.
2.
Preparation ofthe molar could resuit in exposure of
the mesial pulp horn.
3.
The patient may object to the use of a cast-metal
restoration.
4.
Caries occurring on the unrestorcd distai surface of
the second molar abutment after insertion ofthe
prosthesis jeopardizes the restoration.
Shillingburg et al- have suggested use of a complete
coping with retentive grooves and a teiescopic mesial
halfcrown for the molar retainer {Fig 4 ). A retainer of
this design requires more tooth reduction and could
ce International Volume 27 Number 8 /t 99 6
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Fig 1 The missing mandibular first molar has allowed
second and third molars to tilt mesially. Note the severe
misalignment between the long axes of the second pre-
molar A) and the second molar B),
Fig 2 Three-unit FPD with rigid connecto rs. The prosttie-
sis will not seat because the distal margin of the molar
retainer engages the mesial marginal ridge of the third
molar during insertion. Note the proxim ityof the mesial pulp
horn to the mesial axial wall of the molar preparation.
Fig 3 Three-unit FPD with rigid connectors. The second
molar abutment has been prepared for a mesial half-crown
retainer with facial and lingual grooves for added retention.
Note the proximity of the mesial pulp horn to the mesial axial
wall of the molar preparation.
Fig 4 fr/gh Three-unitFP with full coping and telescopic
mesial half crown on the molar abutment.
result in pulpal exposure or an overcontoured retainer.
Preparation of the tooth for the complete-coverage
coping would be excessively tapered. Even if retention
between the mesial half crown and the coping were
ideal, retention ofthe coping to the abutment tooth
might fail because of the excessively tapered tooth
preparation,^-^
Segmented FP
The use of a segmented F PD , in which each section of
the prosthesis has its own path of insertion and there is
a mechanical interlock between segments, has been
advocated. The literature contains a variety of seg-
mented prosthetic designs recommended to overcome
the problems associated with insertion of an FPD
when the abutments are divergent,
Shillingburg et a|- have suggested th e use of a
segmented FPD with a nonrigid attachment between
the second premolar retainer and pontic. This design
requires tooth prep aration o fth e premolar with a box
on the distal surface to accommodate the female
com ponen t of a nonrigid con nec tor Fig 5), Tooth
preparation of the premolar to accomrnodate this
connector could jeopardize the pulp and the retentive
528
Quintessence International Volume 27, Numb er 8/1996
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g 5 Segmented FPD witb nonrigid connector between Fig 6 Segmented FPD with an interlock between the
second molar retainer and the ponfic. Excessive tooth
reduction is required on the mesial surface of fhe second
molar abutment to accommodate the female portion of fhe
interlock.
rface o fthe anterior retainer and can be cosmetically
O'Co nnor et a have proposed a segmented FP D
nonrigid conn ecto r is oriented parallel to the path
insertion of the molar retainer. The gingival half of
d cormector. The occlusal half of the p ontic
attached to the m olar retainer and houses the female
th e nonrigid connector (Fig 7). This
Moulding et al^ have advocated the use of a
Fig 7 Segmented FPD with a split pontic containing a
nonrigid connector.
lternative procedure
A segmented FPD with a nonrigid connector between
the pontic and the molar retainer can be designed
without the disadvantages of the previously described
prostheses. The male portion of
tbe
nonrigid connec-
tor can be placed on the mesial surface of the molar
retainer and oriented parallel to the path of insertion of
the premolar retainer (Fig
),
The female section ofthe
International Volume 27 Number 8/1996
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Fig 8 Segmented FPD with a nonrigid connector. The
premolar has the maie portion of the inleriock on its distal
surface. Note the iarge gingival embrasure between the
premolar and the pontic.
Size 1mm)
Smail
i_arge
A
70
ao
B
2.8
3.5
C
2.0
2.5
6.7
7.0
E
2.4
3.0
F
2 3
3 3
Fig 9 Segmented FPD with the maie portion of tiie
interiook on the mesial surface of the second molar retainer
The tooth preparation of the second molar is retentive hut
withoutr siioi pulpal exposure.
Fig 10
left)
Design and dimensions of PDC components.
Fig
below)
ivtale portion of the PDC on tfie mesiai axiai
wail of the moiar retainer. 1) Guiding piane; 2| crest of
ridge;
3] gingival end of male PDC contoured to ridge.
nonrigid connector is located under the pontic in the
anterior segment ofthe prosthesis.
This design is ideal for metal-ceramic restorations.
Both abutments are prepared for metal-ceramic com-
plete yeneer crowns with a path of insertion parallel to
their long axes. This allows the dentist to prepare the
teeth with maximum retention and minimal risk of
pulpa exposure.
The male and female components of this nonrigid
connecto r are manufactured in two sizes and are listed
in the catalogs of denial supply dealers as Plastic
Dovetail Connector (PDC} attachments (Fig 10). The
PDC attachments are designed so that the mating
surfaces of male and female components restrict the
movements of the two segments of the FPD to ore
plane. If the vertical height for the con nec tor is limited,
the PDC components may be reduced in height about
40% and still remain effective.
is dv nt ges
Use of
t is
design for FPDs with long spans should be
ayoided, particularly when the connector has beeti
530
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Zuckerman
g 12 Molar preparation with palh ot insertion along ts
Fig 13 Molar retainer with male porlion of the PDC on Ihe
mesial surface. The nonrJgid conneotor is aligned parallel to
Ihe path ol insertion of the premolar preparation.
g 14 Anterior section ot FPD placed over the PDC and
the premolar abutment.
Fig 15 Completed prosthesis atter insertior.
inheight. Slight movement of the abutmentto
the
pontics
are
rigidly connected
can
produce
the components ofthe
Another disadvantage of this design is that the
for asegmentedFPD arehigher than
of a rigidly assembled FPD. Furthermore,
are
unfamiliar with this
ofa nonrigid connectorandwill
to he instructed accordingly.
echnical procedure
Thediesandcastsarefabricatedandarticulatedas
for any FPD.
Waxpatternsaremadeforboth retainers.
The
male pattern
of
th e
PDC is
recessed into
the
mesial surfaceofth patternfor the molar retainer.
The male attachment is positioned parallelto the
path
of
insertion
of
the premolar retainer.
4. The guiding p lane of the connector is locatedin the
contact area between the molar retainer and the
pontic. The gingiva end of the connector is
conto ured to establish even contact with the crestof
the ridge Fig 11).
5.
The
female pattern
of
the
PDC is
piaced over
the
male pattern.Awax patternforthe ponticismade
over ihc female pattern. The gingival facing
end of
the assembled connector should present a smooth, un-
interrupted continuation of the ridgelapsurfaceof
the pon tic when the prosthesis has been com pleted.
6. The patterns of the pontic and the premolar
retainerareconnectedandcastas onepiece.
7.
The
sections
ofth
FPD framework
are
assembled
andthegingival embrasure betweenthemoiar and
ponticiscontoured with an abrasive separating disk.
Figures 12to 5illustrate the clinical applicationof
th e PDC,which is completely concealed withinthe
FPD,
International Volume27 Number 8 1996
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Zuckerman
Summary
Segmented FPDs are a well-established methodre-
comm ended to overcotne the problems associated with
the insertion ofFPDswhen the abutments are severely
misaligned. Traditional designs used
to
create
seg-
mented FPDs were examined, and their disadvantages
were discussed.
A new design was suggested that does not have most
ofthe disadvantages associated with segmented pros-
theses . Manufactured plastic patterns that can be used
to create this segmented FPDdesign are available.
These economical, prefabricated, burnout patterns
simplify laboratory fabrication and produce uniform,
consistent,
and
reliable nonrigid connectors.
The
extracoronal application of an interiocking attachment
for segmented FPDs provides
a
practical solution
to a
difficult probiem.
References
1. Lubow
RM
Cootey
RL
Kaiser
D.
Periodontat
and
restorative
aspects
of
molar uprighting.
J
Prosthet Dent I982;47:37.1.
Shillingburg HT Hobo S. Whitsett LD. Fundamentals of Fixed
Prosthudonties,ed 2.Chicago: Quintessence, i9Bi.
1 Zuckerm an GR . Faetors that influence
the
meciianicai retention
the complete erown. Int JPros lhod ont 19SB;i; 36-20O.
4. Zuckerman GR. Resistance form for the complte veneer crown:
Principles ofdesign and anaiiis. Int JProsthodont t9S;l:302-: 07.
5. Rosenstiel SF. LandMEFujimotoJ Contemporary Fked Prostho-
dontics.
ed I. St
Louis: M osby.
19S8
6. O'Connor
RP.
Caughman
WF.
Bemis
C. Use of the
split pontic
nonrigid connector with
the
tilted molar abutment.
J
Prosthet Dent
1986;56:249-2;i.
7. Moulding MB, Holiand GA . Sulik WD.
An
alternative orientation
of
nondgid connectors
in
fixed partial dentures.
J
Prosthet Dent
8
532
Aesthetic Design
for Ceramic Restoratioi is
T
he most
natrural,
esthetic results
in dental
ceramics can
be achieved
with contem-
porary' techniques and this hook descrihes
how. Investigated are thecharacteristicsof
natural dentition, tissue tnanagement, impres-
sions, occlusal records, waxing techniques,
color,andlahorato r)' technique s, including
methodsfor anaesthetic ceramic m argin,
opalescence,anddevelopment ofth e dentine
mamelon. Filled with practical tips, this hook
is idealfordentistsandtechnicians.
59 pages; 292 color illus; ISBN -85097-034-3
ontents
1 StudiesofNatural Dentition
2 Dentist-Technician-Paticnt Communication
3 Tissue Management
for
Aesdietic
and Biological Ha rmo ny
4 Impressions artti Occlusai Records
5 Aesthetic Wax Diagnostic Control
6 Accurate Registration and Communication
of Colour Characteristics
7 Advanced Laboratory Techniques
8 Case Studies
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