PRINCIPLES OFjjjbbbbbhnJj TOOTH PREPRATION.pptx

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2. BASIC PRICIPLES FOR TOOTH PREPRATION IN CROWN AND BRIDGE RESTORATIONS Lecture by DR.MUHAMMAD FAROOQ KAMRAN BDS, FCPS (PROSTHODONTICS) Professor & Head Department of Prosthodontics RIHS

3. Why we prepare natural teeth? Create Space for the Restoration Ensure Proper Fit and Stability Remove Damaged or Decayed Tissue Improve Aesthetics and Function Enhance Retention and Bonding Support Bridge Framework

4. 1.CONSERVATION OF TOOTH STRUCTURE 1 . PARTIAL-COVERAGE RESTORATIONS

5. 1.CONSERVATION OF TOOTH STRUCTURE 2 . MINIMUM PRACTICAL CONVERGENCE ANGLE (TAPER) 8

6. 1.CONSERVATION OF TOOTH STRUCTURE 3. anatomical occlusal reduction 9

7. 1.CONSERVATION OF TOOTH STRUCTURE 4. Orthodontic uprighting /repositioning 10

8. 1.CONSERVATION OF TOOTH STRUCTURE 5. Conservative margins 11

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10. 1.CONSERVATION OF TOOTH STRUCTURE 6. AVOIDANCE OF UNNECESSARY APICAL EXTENSION 13

11. Biological principles Prevention of damage during tooth preparation to: a) The adjacent tooth. b) Soft tissue. c) The pulp.

12. Causes of pulpal damage: Extreme temperature:  Excessive pressure  Higher rotational speed Type and condition of cutting instrument. Chemical irritation. Bacteria irritation.

13. 2. Retention form 16 Retention form : R esistance to dislodgement of crown in a vertical direction or along the path of placement

14. RETEnTION AND TAPER RELATIONSHIP 17

15. RETENTION AND SURFACE AREA 18

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17. 3. Resistance form Resistance form : The resistance to dislodgement of a crown along an axis other than the path of placement 20

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20. Structural durability 23

21. Marginal integrity 24

22. Marginal integrity 25

23. Health of periodontium Finish line Biological width Restoration contour Hygiene access 26

24. Esthetics CONSIDERATION 8/31/2025 27

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27. CLINICAL STEPS FOR CROWN PREPRATION OF MOLAR 8/31/2025 30

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30. RECOMMENDED TOOTH REDUCTION FOR PFM

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32. CLINICAL STEPS FOR MOLAR REDUCTION The clinical procedure to prepare a tooth for a complete cast crown consists of the following steps: Occlusal guiding grooves Occlusal reduction Axial alignment grooves Axial reduction Finishing and evaluation

33. Occlusal surface reduction 1.0mm UNIFORM REDUCTION OF OCCLUSAL SURFACE following the contour of the tooth. Round- end tapered diamond bur-depth grooves A. PRIMARY DEVELOPMENTAL GROOVES B. CREST OF THE TRIANGULAR RIDGES Orient bur parallel to the inner inclines With sweeping movements, remove the tooth structure between depth grooves .

34. 4 . Follow the up and down contours of the ridges and cusp inclines Occlusal morphology is never flat Achieve occlusal planar reduction

35. Verification of uniformity and the amount of occlusal reduction. T he silicone putty index Articulating the maxillary and mandibular arch A softened piece of wax

36. Buccal and lingual surface reduction Remove the natural undercut contour of the teeth Achieve 6 degree total occlusal coverage 6. With round end tapered diamond bur, place the depth grooves in Developmental groove(s) Line angle(s)

37. 7. Orient the bur at 3 degree from long axis of the tooth 8. With the sweeping movement, remove tooth structure between depth grooves. 9.Make sure all natural undercuts on unprepared tooth are removed 10. Reorient the bur angulation to reduce the second plane of the buccal surface 11. Follow the outline of the unprepared buccal contour 12. Verify the uniformity and the amount of buccal reduction by The silicone putty index

38. 13. Repeat the same procedure on the lingual surface making sure that the orientation of bur is at 3 degrees There is, however, no second plane for the lingual surface. 14. Verify the removal of undercut and the amount of lingual reduction by the silicone putty matrix

39. Proximal surface reduction T he goal of proximal reduction are to Eliminate proximal contact with the adjacent teeth Create sufficient convergence to the occlusal surface

40. 16. Initial proximal cuts can be made in a “sawing motion” with a smaller diameter round-end tapered diamond bur. 18. Avoid contact with the adjacent teeth 19. Once sufficient space has been obtained, use the larger diameter round-end diamond bur to plane the walls and extending apically forming the chamfer margin at 0.5 mm above the margins of the gingiva

41. 20. Maintain the taper of each surface at 3 degree

42. Functional cusp bevel The goal of functional cusp bevel is to reduce further the cuspal height by 0.5mm on the functional cusp to provide adequate thickness of the restorative material on the area of significant functional loading 22-using the round-end tapered bur, depth grooves are placed at 45 degree to the long axis of the tooth at the line angle created between the second plane of the buccal surface and occlusal surface

43. Margin preparation The goal of margin preparation is to establish a visible termination of the preparation that provides a definite finish line configuration. 27. Follow the contour of the margin of the gingiva Remove any rough and uneven surface along the margin 29.Margins should be smooth, even, definite chamfer margin

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47. Preparation Guiding groves. Incisal / Occlusal reduction. Labial / buccal reduction. Axial reduction Final finishing. 8/31/2025 50 Proximal . Lingual surfaces.

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50. Buccal reduction 8/31/2025 53

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