Margin (Finish line) placementMargin (Finish line) placement

Finish line of the preparation is the end of tooth Finish line of the preparation is the end of tooth preparation.preparation.

Finish LineFinish Line

Studies have supported the use of Studies have supported the use of supra-gingival supra-gingival or or equi-gingivalequi-gingival finish lines rather than finish lines rather than sub-gingivalsub-gingival finish finish line whenever possible to ensure periodontal healthline whenever possible to ensure periodontal health

Supra-gingival finish lineSupra-gingival finish line

v Sub-gingival finish linev Sub-gingival finish line

Hanaa I. Sallam

Advantages of supra-gingival margins:

– Easily preparedEasily prepared– No soft tissue traumaNo soft tissue trauma– Easy impressionEasy impression– Easy finishing, easy Easy finishing, easy

cleaningcleaning– Easy evaluation of the Easy evaluation of the

preparation margins preparation margins at the time of at the time of placement and at the placement and at the call appointmencall appointments ts

Apr 11, 2023Rasha Nabil Sami4

1-Cervical caries , erosion, 1-Cervical caries , erosion, abrasion or restoration.abrasion or restoration.

Apr 11, 2023 Hanaa I. Sallam

Proximal contacts extending to the Proximal contacts extending to the gingival crest.gingival crest.

Apr 11, 2023 Hanaa I. Sallam

To increase the occluso-gingival dimension for To increase the occluso-gingival dimension for better retention and resistance .better retention and resistance .

Apr 11, 2023 Hanaa I. Sallam

For esthetics in anterior regionFor esthetics in anterior region

Apr 11, 2023 Hanaa I. Sallam

Root sensitivity which cannot be controlled by Root sensitivity which cannot be controlled by more conservative procedures (such as more conservative procedures (such as application of dentin bonding agents).application of dentin bonding agents).

Apr 11, 2023 Hanaa I. Sallam

When a subgingival finish line is required, it has been When a subgingival finish line is required, it has been suggested that extension to the epithelial attachment be suggested that extension to the epithelial attachment be avoided. avoided.

The distance from the epithelial attachment to the crest of The distance from the epithelial attachment to the crest of the alveolar bone has been described as the the alveolar bone has been described as the ““Biologic Biologic WidthWidth””.. It is normally about It is normally about 2mm wide2mm wide, including the , including the epithelial attachment and the connective tissue attachment.epithelial attachment and the connective tissue attachment.

If the margin of a restoration intrudes into this biologic If the margin of a restoration intrudes into this biologic width inflammation will result and osteoclastic activity is width inflammation will result and osteoclastic activity is stimulated.stimulated.

Apr 11, 2023 Hanaa I. Sallam

3- Margin Adaptation3- Margin AdaptationThe presence of marginal discrepancies The presence of marginal discrepancies

in the restoration exposes the luting in the restoration exposes the luting agent to the oral environmentagent to the oral environment

The longevity of tooth could be The longevity of tooth could be compromised not only by caries but also compromised not only by caries but also by periodontal diseaseby periodontal disease. .

Clinically acceptable marginal gap values of Clinically acceptable marginal gap values of cast restorations have been reported in the cast restorations have been reported in the literature to be up literature to be up to 50-70μmto 50-70μm

A well-designed preparation has a smooth A well-designed preparation has a smooth and even margin. and even margin.

Rough, irregular, or "stepped" junctions Rough, irregular, or "stepped" junctions greatly increase the length of the margin and greatly increase the length of the margin and substantially reduce the adaptation of the substantially reduce the adaptation of the restorationrestoration

Apr 11, 2023 Hanaa I. Sallam

A : Poor preparation design leading A : Poor preparation design leading to increased margin length.to increased margin length.

C: rough, irregular margin will C: rough, irregular margin will make the fabrication of an make the fabrication of an accurately fitted restoration almost accurately fitted restoration almost impossible.impossible.

4-4- Margin Geometry:Margin Geometry:

.The configuration of the preparation finish line dictates the shape and bulk of restorative material in the margin of the restoration. It also affects both: marginal adaptation and degree of seating of the restoration.

Guidelines for establishing a good finish line

1. It should be easily prepared1. It should be easily prepared

2- It should be easily identified in 2- It should be easily identified in both impression and dieboth impression and die

3-It should not be overextended 3-It should not be overextended cervicallycervically

4- It should provide a definite 4- It should provide a definite edge to which the wax pattern edge to which the wax pattern could be easily adapted and could be easily adapted and finishedfinished

5- Should allow sufficient bulk of 5- Should allow sufficient bulk of material to :material to :

Enable wax pattern handling Enable wax pattern handling without distortionwithout distortion

Provide sufficient strength at the Provide sufficient strength at the restoration marginsrestoration margins

Provide enough bulk for porcelain Provide enough bulk for porcelain (in PFM) to enhance good (in PFM) to enhance good esthetic.esthetic.

6- Allow conservation of tooth 6- Allow conservation of tooth structure as possible.structure as possible.

7- Ideally whenever possible the 7- Ideally whenever possible the margins should be placed in margins should be placed in areas where the dentist can areas where the dentist can finish and inspect them and finish and inspect them and the patient can clean them.the patient can clean them.

Types of Gingival finish linesTypes of Gingival finish lines

1-Feather- edge Finish line1-Feather- edge Finish line

It is mainly indicated for It is mainly indicated for cast metal cast metal crowns .crowns .

Advantages:Advantages:

1.1. Less destruction of tooth Less destruction of tooth structure than is structure than is necessary for a shoulder necessary for a shoulder or a chamferor a chamfer

2.2. Dose not leave a fragile Dose not leave a fragile lip of unsupported enamellip of unsupported enamel

tooth

Disadvantages:Disadvantages:

1.1. It is difficult to follow on It is difficult to follow on both tooth and die (location both tooth and die (location of the margin is difficult to of the margin is difficult to control )control )

2.2. Thin margins are difficult to Thin margins are difficult to wax and cast , thus being wax and cast , thus being thickened by technicians lead thickened by technicians lead to over-contoured to over-contoured restoration .restoration .

3.3. The margin is weakThe margin is weak

tooth

2- Chisel edge margin2- Chisel edge margin

It is mainly indicated for It is mainly indicated for cast metal cast metal crowns .crowns .

It is a variation of the feather edge finish line and its is formed when there is a large angle between the axial surfaces and the unprepared tooth structure.

tooth

Unfortunately, this margin is frequently associated with an excessively tapered preparation

or one in which the axial reduction is not correctly aligned with the long axis of the tooth(tilted teeth)

3-Bevel Finish Line 3-Bevel Finish Line

This type is frequently This type is frequently indicated for indicated for cast metal cast metal restorationsrestorations, specially if a , specially if a ledge or shoulder already ledge or shoulder already exists due to caries, cervical exists due to caries, cervical erosion or a previous erosion or a previous restoration.restoration.

Its shape forms an obtuse Its shape forms an obtuse angle with the unprepared angle with the unprepared axial tooth surfaceaxial tooth surface

tooth

Objectives of beveling :Objectives of beveling :

1-Allows cast metal margin to be burnished 1-Allows cast metal margin to be burnished against prepared tooth structure.against prepared tooth structure.

2-Protect the unprepared tooth structure 2-Protect the unprepared tooth structure from chipping by removing the from chipping by removing the unsupported enamel.unsupported enamel.

N.B. If no accessibility for burnishing, there N.B. If no accessibility for burnishing, there is minimal advantage of this type of finish is minimal advantage of this type of finish lineline

4-Chamfer Finish Line 4-Chamfer Finish Line `̀ It is mainly indicated for It is mainly indicated for cast metal cast metal

crowns .crowns .

The instruments which made this FL. The instruments which made this FL. Is tapered stone with roundIs tapered stone with round

tip .tip .

The chamfer should never be prepared The chamfer should never be prepared wider than half the tip of the wider than half the tip of the diamond; otherwise, an unsupported diamond; otherwise, an unsupported lip of enamel could result.lip of enamel could result.

tooth

5- Shoulder Finish Line5- Shoulder Finish Line This type of finish line is This type of finish line is

usually recommended for the usually recommended for the all-ceramicall-ceramic crowns and the crowns and the facial part of metal-ceramic facial part of metal-ceramic crowns particularly when the crowns particularly when the porcelain margin technique is porcelain margin technique is used.used.

It is not used as a finish It is not used as a finish

line for cast metal restorations.line for cast metal restorations. tooth

Advantages :Advantages :

Provides space for proper Provides space for proper porcelain bulk thus enhancing porcelain bulk thus enhancing resistance to occlusal forces resistance to occlusal forces and minimizes stresses which and minimizes stresses which might lead to porcelain might lead to porcelain fracture.fracture.

Facilitates constructing Facilitates constructing healthy restorations of good healthy restorations of good contours and maximum contours and maximum esthetics esthetics

tooth

Disadvantages:Disadvantages:

The preparation requires The preparation requires destruction of more tooth destruction of more tooth structure than any other finish structure than any other finish line.line.

Some claimed that its sharp Some claimed that its sharp 9090ººdegree internal line angle degree internal line angle would concentrate stress in the would concentrate stress in the tooth and increases its liability tooth and increases its liability to coronal fracture.to coronal fracture.

tooth

6-Rounded ( modified) Shoulder 6-Rounded ( modified) Shoulder Finish Line Finish Line

It is a modified formIt is a modified form

of shoulder finish line of shoulder finish line

characterized by a characterized by a

rounded internal angle rounded internal angle

(gingivo-axial). (gingivo-axial).

It is indicated for It is indicated for

All- ceramicAll- ceramic crown preparation crown preparation tooth

Advantages:Advantages:

Less stress Less stress concentrationconcentration

Some claimed that its Some claimed that its preparation is lesspreparation is less

destructivedestructive

7-Sloped Shoulder Finish Line 7-Sloped Shoulder Finish Line

It is a modification of the classic It is a modification of the classic shoulder finish line being shoulder finish line being characterized by characterized by a 120a 120º º as an as an alternative to the 90alternative to the 90ºº. .

It´s advantage reduce the It´s advantage reduce the possibility of leaving possibility of leaving unsupported enamel and still unsupported enamel and still leaving sufficient metal thickness leaving sufficient metal thickness to allow for its thinning to a knife to allow for its thinning to a knife edge for good adaptationedge for good adaptation to

oth

8-Shoulder with Bevel Finish 8-Shoulder with Bevel Finish Line Line

This type is recommended for the This type is recommended for the facial surface of a metal-ceramic facial surface of a metal-ceramic restoration in those situations restoration in those situations where gingival esthetics are not where gingival esthetics are not critical and a shoulder is already critical and a shoulder is already present either because of present either because of destruction by caries or the destruction by caries or the presence of previous restorationspresence of previous restorations

The beveling removes The beveling removes

unsupported enamel and may unsupported enamel and may allow finishing of the metal.allow finishing of the metal.

tooth

4- Margin geometry4- Margin geometry

Apr 11, 2023 36 Rasha Nabil Sami