marginal configurations in fpd

7/25/2019 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@?==

marginal configurations in fpd

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