FINISH LINES.pptx

Finish lines in FPD

1. FINISH LINES DR.MEENAKSHI AKSHAYALINGAM,MDS, PROFESSOR AND HEAD OF THE DEPT, PROSTHODONTICS.

2. Closely adapted margins to finish lines of survival of restoration in the oral environment Configuration of finish line- dictates the shape and bulk of metal at the margins affects the marginal adaptation affects degree of seating

3. Margin Placement Whenever possible, the margin of the preparation should be supragingival Subgingival margins often lead to the periodontal disease

4. Supragingival Margin : coronal to the gingival crest. Equi gingival margin at the gingival crest Subgingival Margin apical to the free gingival margin. JPD 1990; 64: 636-42.

5. Advantages of supragingival margins They can be easily finished. They are more easily kept clean. Impressions are more easily made . Less potential to soft tissue damage. Restorations can be easily evaluated at recall appointments.

6. INDICATION OF SUBGINGIVAL MARGIN Caries, erosion, restoration extending subgingivally Additional retention is desired Short clinical crowns Esthetics Root sensitivity Modification of axial contour is indicated

7. Chamfer Heavy chamfer Shoulder Sloped shoulder Radial shoulder Shoulder with a bevel Knife edge

8. Indications- Cast metal crowns Metal-only portion of PFM crowns Distinct, easily identified Least stress Round end tapered diamond Half the tip of the diamond

9. Indicated for all-ceramic crowns 90 degree cavosurface angle with a large radius rounded internal angle Round end tapered diamond Better than conventional chamfer but not shoulder Bevel added - to use with metal restoration

10. All-ceramic crowns Facial margin of PFM crowns Wide ledge- resistance to occlusal forces minimizes stresses which leads to fracture of porcelain Flat-end tapered bur Healthy contours Maximum esthetics

11. Destruction of more tooth structure Sharp 90° internal line angle concentrates stress on tooth Coronal fracture Not used for cast metal restorations

12. 120° sloped shoulder margin Facial margin of a metal-ceramic crown No unsupported enamel, yet sufficient bulk to allow thinning of the metal framework to a knife-edge for acceptable esthetics

13. Modified shoulder Cavosurface 90° Shoulder width lessened with rounded internal angles Lesser stress concentration Good support for porcelain

14. Indications: Proximal box of inlays, onlays Occlusal shoulder of onlays and mandibular ¾ crowns Facial finish line of metal-ceramic restorations (gingival esthetics not critical) Situations where a shoulder is already present (destruction by caries, previous restorations)

15. Bevel: allows the cast metal margin to be bent or burnished against the prepared tooth structure minimizes the marginal discrepancy removes unsupported enamel

16. Permit acute margin of metal Axial reduction may fade out Thin margin - difficult to wax and cast Susceptible to distortion Indications: Mandibular posterior teeth with very convex axial surfaces Lingually tilted lower molars

17. Chisel Edge Advantage: Conservation of tooth structure. Disadvantage: Location of margin is difficult thus produces overcontouring Indication: Occasionally on the tilted tooth, Not acceptable

18. All metal crowns – Chamfer depth: 0.3-0.5 mm Axial surface reduction: 0.5 -0.8 mm Occlusal reduction: 1- 1.5 mm Metal ceramic crowns – Finish line depth: 1-1.5 mm Occlusal reduction: 2mm All ceramic crowns– Finish line and facial reduction depth: 1mm Incisal/occlusal reduction: 2mm Goodacre C J. Designing tooth preparations for optimal success. Dent Clin N Am 2004; 48: 359-85.

19. Uniformly reduced : normal crown form improved aesthetic Makes easier for laboratory technician to create esthetic restorations Best achieved by placing depth grooves Goodacre C J. Designing tooth preparations for optimal success. Dent Clin N Am 2004; 48: 359-85.

20. Should be rounded (increases crown strength) Sharp line angles – stress concentration Facilitates laboratory fabrication and fit Ease to pour impressions Goodacre C J. Designing tooth preparations for optimal success. Dent Clin N Am 2004; 48: 359-85.

21. Recent methods of Tooth preparation? Ultrasonic Laser Robotic

22. Thank you!!!