Marginal Configurations in Fpd
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Transcript of Marginal Configurations in Fpd
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MARGINAL
CONFIGURATIONS
IN FIXED PARTIALDENTURES
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INTRODUCTIONOne of the essentials for success with tooth
preparation includes proper selection and
preparation of the cervical margin of the
preparation.
Margins are one of the most important and weakest
links in the success of the cast restorations.
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SHAPE AND PLACEMENT OFTHE MARGIN INFLUENCES
1.Marginal integrity and structural
durability of the restoration
2. Health of the periodontium
3. Esthetics
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wo ma!or decisions must be made regarding the "nish
line of every tooth to be prepared for a crown#
$osition of margin
%esign or
geometry
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M&'()*&+ ,O*-)('&)O*/
/upragingival margins
E0uigingival margins
/ubgingival margins
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-&,O'/ )*O+E% )* ,HO),E O-+O,&)O* O- ()*()&+ M&'()*/
1. $E')O%O*&+ ,O*/)%E'&)O*
oral hygiene predisposition to periodontitis
2. E/HE),/
3. 'EE*)O*
. -)*)/H)*( O* HE /O*% OOH /','E
&$),&+ O ,&')E/ O' E4)/)*( 'E/O'&)O*
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SUBGINGIVAL FINISHLINES
Esthetics
E5tensive restorations 6
fractures
,aries
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FINISH LINEShe point at which a preparationterminates on the tooth is called
the "nish line.
$eripheral e5tension of a toothpreparation. 7($8
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FUNCTIONS
isual evaluation of the teeth preparation
Measure of the amount of tooth structure
removed
,orrect marginal adaptation of the wa5 pattern
depends on an obvious "nish line.
Evaluation of the restoration
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IDEAL CHARACTERISTICS OF FINISH LINES
/hallow bevels nearly parallel to the cavo
surface should be avoided
/hould not produce very acute margin
ooth should not be reduced more than half of
the width of the diamond.
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/hould be as smooth as possible.
-ully e5posed to the cleansing action.
/hould be reproduced in the impression
/hould be in enamel when ever possible
23mm away from the alveolar crest
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GUIDELINES FOREVALUATING
FINISH LINES
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,+&//)-),&)O* 9&/E% O* HE9&/)/ O- M&'()* &*(+E7:;&&8
Margin angleangle formed between vertical pro!ection from
the e5ternal surface of the tooth and its prepared surface
=> to 3=> beveled margins
31> to ?=> chamfer
?1> to @=> shoulder
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H*E'/
,+&//)-),&)O*
Margin widths below =.3mm
Margin widths greater than =.3mm
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M&'()* +E// H&* =.3mm
&llows intraoral "nishing9urnishing of crown
margin
,onservative
)mproves marginal seal
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%)/&%&*&(E%iAcult to prepare
Margins indistinct on impression and die
Over contoured restorations
)ntraoral "nishing procedure BdiAcult and impractical
nsupported wa5distortion during investing'esistance to distortion of coping during porcelain
"ring
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M&'()* ('E&E' H&* =.3 MM
&. C. Hunter classi"es margin widths greater
than =.3mm as /houlders and bevelled
shoulders allowed incorporation of physiological
contours in temporary and "nal crowns
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&%&*&(E/ery well de"ned
,learest "nish line
$ermits guide plane for removal prosthesis
-lattening contours to facilitate pla0ue control
hickness of restorative material Brigidity
during function
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%)/&%&*&(E/+ess conservative
9ulky
hickened wa5 pattern leads to increased
casting shrinkage
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DIFFERENT TYPES OF FINISH LINE
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-E&HE' E%(E ,onservative of tooth
structureD they fail to
provide ade0uate bulk at the
margins.
Over contoured restorations
ariation chisel edge or
knifeedge margin
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:*)-E E%(E+ong slanted edgeD typically
used in a periodontally
involved tooth or where tooth
wall reduction is limited.
,onservative
+imiting with the crown
design
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,H&M-E',ast metal restoration
+ingual margins of metal
ceramic
,are needed to avoid
unsupported enamel
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%EE$ ,H&M-E'sed for all types of
facing crownsD $-M
and all ceramic crowns
hick round ended
tapered bur is used
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/HO+%E'(ingival oor meets the
e5ternal a5ial surfaces at
appro5imately a right angle
&ll ceramic
-acial margin of metalceramic
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/HO+%E' ;)H 9EE+(ingival oor meets the e5ternal
a5ial surfaces at appro5imately a
right angle with a slanted edge.Metal collar is plannedD to lower
stress concentrations on the
porcelain at the margins.
-acial margins of metal Bceramic
crowns with supragingival margins
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9evel preparation is made at 13F degree
angle from the vertical a5ial wall
/houlder is @= degree from vertical and the
bevel is an additional F degree
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O 9EE+ O' *OG9evelling reduces the closing angle at the
marginD to compensate for the incomplete
seating of the crown
'osner71@?38 bevelled "nish lines e5hibited
compensatory capable of reducing the
marginal discrepancies of cast restorations
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reduction of inherent defects in casting andcementation
burnishing after cementation
development of circumferential retention
protection of enamel rods at the margins
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Gravelis et al - eliminate casting error measuremarginal opening due to marginal con"gurationduring cementation
Least Mari!al O"e!i! #$%-&& '( -eatheredgeD shoulders and chamfers with parallel bevels
M)*erate Mari!al O"e!i! #+, '(B @=>shoulders
Mai./. Mari!al O"e!i!s #01-%21 '( B F>shoulders and chamfers with 3=> or F> bevels.
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BIOLOGIC 3IDTH
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;H& H&$$E*/ )- 9)O+O(),
;)%H (E/ )O+&E%G
9one loss of an unpredictable nature and gingival
tissue recession as the body attempts to recreate
room between alveolar bone and the margin to allow
space for reattachment
rauma from restorative proceduresgingival
recession7when gingiva is thin and friable8
(ingival inammation
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)f the margin intrudes into this biologic widthD the
inammation. he bone will recede until once again it is at least 4 ..away from
the margin
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,O*,+/)O*hey must "t as close as possible against the "nish
line of the preparation to minimiIe the width of the
e5posed cement
hey must have suAcient strength to withstand
mastication forces.
hey should be located in areas where the dentist
can "nish and inspect them and the patient can
clean them
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'E-E'E*,E/-undamentals of "5ed prosthodontics B
/hillingburg
,ontemporary prosthodontics B 'osenstiel
,urrent theories of crown contourD margin
placementD and pontic design C $rosthet %ent
2==FJ1=K11
(ingival crown margin con"gurations
$rosthet %ent 1@@= ?#FL
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he eect of crown marginal depth upon
gingival tissue. C $rosthet %ent 1K#K@LKD 1@?K
,ervical margin design with contemporary
esthetic restorations %,*& 2=='elationship of crown margin placement to
gingival inammation. C $rosthet %ent 1@K3J
3=#1F?1?1
Margins of the complete crowns B +iterature
review. C $rosthet %ent 1@L2J L#3@?==