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Margin (Finish line) placement Finish line of the preparation is the end of tooth preparation. Finish line of the preparation is the end of tooth preparation.

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Presentation on theme: "Margin (Finish line) placement Finish line of the preparation is the end of tooth preparation. Finish line of the preparation is the end of tooth preparation."— Presentation transcript:

1 Margin (Finish line) placement Finish line of the preparation is the end of tooth preparation. Finish line of the preparation is the end of tooth preparation. Finish Line Studies have supported the use of supra-gingival or equi-gingival finish lines rather than sub- gingival finish line whenever possible to ensure periodontal health Studies have supported the use of supra-gingival or equi-gingival finish lines rather than sub- gingival finish line whenever possible to ensure periodontal health

2 Supra-gingival finish line Supra-gingival finish line v Sub-gingival finish line v Sub-gingival finish line Hanaa I. Sallam

3 Advantages of supra-gingival margins: –Easily prepared –No soft tissue trauma –Easy impression –Easy finishing, easy cleaning –Easy evaluation of the preparation margins at the time of placement and at the call appointmen ts

4 13-Jun-14Rasha Nabil Sami 4

5 1-Cervical caries, erosion, abrasion or restoration. 1-Cervical caries, erosion, abrasion or restoration. 13-Jun-14 Hanaa I. Sallam

6 Proximal contacts extending to the gingival crest. Proximal contacts extending to the gingival crest. 13-Jun-14 Hanaa I. Sallam

7 To increase the occluso-gingival dimension for better retention and resistance. 13-Jun-14 Hanaa I. Sallam

8 For esthetics in anterior region For esthetics in anterior region 13-Jun-14 Hanaa I. Sallam

9 Root sensitivity which cannot be controlled by more conservative procedures (such as application of dentin bonding agents). Root sensitivity which cannot be controlled by more conservative procedures (such as application of dentin bonding agents). 13-Jun-14 Hanaa I. Sallam

10 When a subgingival finish line is required, it has been suggested that extension to the epithelial attachment be avoided. When a subgingival finish line is required, it has been suggested that extension to the epithelial attachment be avoided. The distance from the epithelial attachment to the crest of the alveolar bone has been described as the Biologic Width. It is normally about 2mm wide, including the epithelial attachment and the connective tissue attachment. The distance from the epithelial attachment to the crest of the alveolar bone has been described as the Biologic Width. It is normally about 2mm wide, including the epithelial attachment and the connective tissue attachment. If the margin of a restoration intrudes into this biologic width inflammation will result and osteoclastic activity is stimulated. If the margin of a restoration intrudes into this biologic width inflammation will result and osteoclastic activity is stimulated.

11 13-Jun-14 Hanaa I. Sallam

12 3- Margin Adaptation The presence of marginal discrepancies in the restoration exposes the luting agent to the oral environment The presence of marginal discrepancies in the restoration exposes the luting agent to the oral environment The longevity of tooth could be compromised not only by caries but also by periodontal disease. The longevity of tooth could be compromised not only by caries but also by periodontal disease.

13 Clinically acceptable marginal gap values of cast restorations have been reported in the literature to be up to 50-70μm Clinically acceptable marginal gap values of cast restorations have been reported in the literature to be up to 50-70μm A well-designed preparation has a smooth and even margin. A well-designed preparation has a smooth and even margin. Rough, irregular, or "stepped" junctions greatly increase the length of the margin and substantially reduce the adaptation of the restoration Rough, irregular, or "stepped" junctions greatly increase the length of the margin and substantially reduce the adaptation of the restoration 13-Jun-14 Hanaa I. Sallam

14 A : Poor preparation design leading to increased margin length. A : Poor preparation design leading to increased margin length. C: rough, irregular margin will make the fabrication of an accurately fitted restoration almost impossible. C: rough, irregular margin will make the fabrication of an accurately fitted restoration almost impossible.

15 4- 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.

16 Guidelines for establishing a good finish line 1. It should be easily prepared

17 2- It should be easily identified in both impression and die 3-It should not be overextended cervically

18 4- It should provide a definite edge to which the wax pattern could be easily adapted and finished 4- It should provide a definite edge to which the wax pattern could be easily adapted and finished

19 5- Should allow sufficient bulk of material to : Enable wax pattern handling without distortion Enable wax pattern handling without distortion Provide sufficient strength at the restoration margins Provide sufficient strength at the restoration margins Provide enough bulk for porcelain (in PFM) to enhance good esthetic. Provide enough bulk for porcelain (in PFM) to enhance good esthetic.

20 6- Allow conservation of tooth structure as possible. 7- Ideally whenever possible the margins should be placed in areas where the dentist can finish and inspect them and the patient can clean them.

21 Types of Gingival finish lines

22 1-Feather- edge Finish line It is mainly indicated for cast metal crowns. Advantages: 1. Less destruction of tooth structure than is necessary for a shoulder or a chamfer 2. Dose not leave a fragile lip of unsupported enamel tooth

23 Disadvantages: 1. It is difficult to follow on both tooth and die (location of the margin is difficult to control ) 2. Thin margins are difficult to wax and cast, thus being thickened by technicians lead to over-contoured restoration. 3. The margin is weak tooth

24 2- Chisel edge margin It is mainly indicated for cast metal 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

25 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)

26 3-Bevel Finish Line This type is frequently indicated for cast metal restorations, specially if a ledge or shoulder already exists due to caries, cervical erosion or a previous restoration. This type is frequently indicated for cast metal restorations, specially if a ledge or shoulder already exists due to caries, cervical erosion or a previous restoration. Its shape forms an obtuse angle with the unprepared axial tooth surface Its shape forms an obtuse angle with the unprepared axial tooth surface tooth

27 Objectives of beveling : 1-Allows cast metal margin to be burnished against prepared tooth structure. 2-Protect the unprepared tooth structure from chipping by removing the unsupported enamel. N.B. If no accessibility for burnishing, there is minimal advantage of this type of finish line

28 4-Chamfer Finish Line `It is mainly indicated for cast metal crowns. The instruments which made this FL. Is tapered stone with round The instruments which made this FL. Is tapered stone with round tip. The chamfer should never be prepared wider than half the tip of the diamond; otherwise, an unsupported lip of enamel could result. tooth

29 5- Shoulder Finish Line 5- Shoulder Finish Line This type of finish line is usually recommended for the all-ceramic crowns and the facial part of metal-ceramic crowns particularly when the porcelain margin technique is used. This type of finish line is usually recommended for the all-ceramic crowns and the facial part of metal-ceramic crowns particularly when the porcelain margin technique is used. It is not used as a finish It is not used as a finish line for cast metal restorations. tooth

30 Advantages : Advantages : Provides space for proper porcelain bulk thus enhancing resistance to occlusal forces and minimizes stresses which might lead to porcelain fracture. Provides space for proper porcelain bulk thus enhancing resistance to occlusal forces and minimizes stresses which might lead to porcelain fracture. Facilitates constructing healthy restorations of good contours and maximum esthetics Facilitates constructing healthy restorations of good contours and maximum esthetics tooth

31 Disadvantages: The preparation requires destruction of more tooth structure than any other finish line. The preparation requires destruction of more tooth structure than any other finish line. Some claimed that its sharp 90 º degree internal line angle would concentrate stress in the tooth and increases its liability to coronal fracture. Some claimed that its sharp 90 º degree internal line angle would concentrate stress in the tooth and increases its liability to coronal fracture. tooth

32 6-Rounded ( modified) Shoulder Finish Line It is a modified form It is a modified form of shoulder finish line characterized by a rounded internal angle (gingivo-axial). It is indicated for All- ceramic crown preparation tooth

33 Advantages: Less stress concentration Less stress concentration Some claimed that its preparation is less Some claimed that its preparation is less destructive destructive

34 7-Sloped Shoulder Finish Line It is a modification of the classic shoulder finish line being characterized by a 120 º as an alternative to the 90 º. It is a modification of the classic shoulder finish line being characterized by a 120 º as an alternative to the 90 º. It´s advantage reduce the possibility of leaving unsupported enamel and still leaving sufficient metal thickness to allow for its thinning to a knife edge for good adaptation It´s advantage reduce the possibility of leaving unsupported enamel and still leaving sufficient metal thickness to allow for its thinning to a knife edge for good adaptation tooth

35 8-Shoulder with Bevel Finish Line This type is recommended for the facial surface of a metal-ceramic restoration in those situations where gingival esthetics are not critical and a shoulder is already present either because of destruction by caries or the presence of previous restorations This type is recommended for the facial surface of a metal-ceramic restoration in those situations where gingival esthetics are not critical and a shoulder is already present either because of destruction by caries or the presence of previous restorations The beveling removes unsupported enamel and may allow finishing of the metal. The beveling removes unsupported enamel and may allow finishing of the metal. tooth

36 4- Margin geometry 4- Margin geometry 13-Jun-14 36Rasha Nabil Sami


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