Dr. lama khaled El Banna Faculty of Oral and Dental Medicine Al – Azhar University Fixed prosthodontic

1. FIXED PROSTHODONTIC I
Department of Fixed Prosthodontics

2. Preparation
Finishing
Cementation
Impression
Cast
Wax Technique
Alloy
Main steps in the crown and bridge
technique

3. Problem zones in the restoration of a tooth
with a crown
Everywhere, where the crown comes in contact with neighboring
tissues
-Finishing line
-Approximal
-Occlusal

4. Problem zones in the
restoration of a tooth with
a crown!!

5. Problem zones I
Exact visible finishing lineGap-free seating of the crown lack of marginal seal of a crown

6. According to a study of the marginal gap is
usually mesial and distal larger than oral
and vestibular

7. Accuracy of finishing line

8. Problem zones II
Mesial contour slightly concave, distal outline
slightly convex
Concave recovery below the
proximal

9. Problem zones III
The ratio of transverse diameter to
transverse cusp spacing on average 2-1
Measurement of the cusp-fossa
depth
Fossa depth and intercuspation
depth
Incorrectly designed occlusal
surface

13. Occlusal disturbances
increase the risk of
TMJD significantly
)Ferger et al 1991 u.a.(

14. How should the finishing line be like?
a) Chamfer finish line
b) Shoulder finish line
c) Bevel finish line
d) Featheredge margin
e) Shoulder with bevel finish line

15. a b c
a) Featheredge margin
b) Chamfer finish line
c) Bevel finish line

16. Chamfer finish line Shoulder finish line Shoulder with bevel finish
line

17. Preparation
Finishing
Cementation
Impression
Cast
Wax Technique
Alloy
Main steps in the crown technique

18. Set of preparation according
to Prof. Marxkors

19. Systematic preparation
Phase 1: Depth-orientation grooves
Phase 2: Occlusal surface reduction
Phase 3: Proximal dissolve
Phase 4: Visible finishing line
Phase 5: Deepen the fissures
Phase 6: Finishing

20. Depth of cut:
1.Diamond ring = 0.6 mm
2.Diamond ring = 0.8 mm
3.Diamond ring = 1 mm
4.Diamond ring = 1.3 mm
Depth-orientation grooves:
Round diamond wheels
The depth grooves are initially of 1mm
to allow more reduction during finishing

21. Occlusal surface reduction:
with
Oblong diamonds (football) while
preserving the occlusal
configuration
Tooth structure remaining between
the grooves is removed in two
steps using oblong diamonds and
tapered diamond

22. ca. 80% adjacent teeth
)partilly damaged(
Thin tapered diamond (flame)
proximal dissolve:
A metal matrix band around the
adjacent tooth for protection
Inadequate axial reduction can cause
thin restoration walls i.e. weak casting

23. visible finishing line:
Straight cylinder diamond with a
tapered point
)Angle of preparation ca. 6 deg.(

24. deepen the fissures:
Round diamonds

25. Finishing:
Straight cylinder diamond with a
tapered point (finishing bur)
Smooth preparation surfaces will
aid all fabrication phases as
impression, wax technique…….

26. To examine a preparation for undercuts, one eye should
be closed
If both eyes are open when the preparation is viewed,
undercuts may remain undetected
Preparations in the mouth are viewed through a mouth
mirror using one eye.

27. exact visible finishing line
no undercuts

28. Clinical example

29. Phase 1: Depth-orientation grooves

30. Diamond wheels with rounding
and end stop

31. Diamond wheels with rounding and
end stop

32. Diamond wheels with rounding and end
stop

34. Diamond wheels with end stop and without
rounding

35. Phase 2: Occlusal surface resp. incisal edge reduction

36. convex diamond for
concave forms

37. Phase 3: proximal dissolve

38. Phase 3: proximal dissolve

39. Phase 4: visible finishing line

40. Phase 6: finishing

41. R= ragosity measurement
Metal Cement Tooth

42. 1.Anaesthesia
2.Impression
(Alginate / Silicone(
other clinical example
Mouth mirror protecting the soft tissues
during tooth preparation……

43. At temperatures of over 42C,
it is to damage the pulp, so...
...Cooling at
least 50 ml / min

44. Depth-orientation grooves
Surface reduction
proximal dissolve

45. finishing
finishing line
deepen the fissures

46. exact visible finishing line

47. The preparation should be parallel
to the tooth axis

48. 1.No axial alignment preparation
2.Finishing line <gutter<
3.Very broad or very narrow shoulder preparation
4.Very conical preparation → pulp!!
5.Unevenly, very littel or a lot of substance removal → pulp!!
Failure mode

49. No axial alignment
preparation

50. Axial alignment
preparation

51. <gutter<

52. <gutter<

53. Unevenly
substance removal

54. Error avoidance

55. Error avoidance

56. Error avoidance

57. Subgingival Supragingival
Preparation - +
Impression - +
Control - +
Accuracy - +
Position of finishing line

58. A subgingivalen preparation must be
-Inadequately retention
-Patients with high caries risk / activity
-Aesthetic requirement
-Caries, erosion or restoration
-Root sensitiviy!!!
One or more of these reasons make for about 75% of the patients!
)Gernet et al 1984 u.a.(

59. The minimum height of a
prepared tooth = 3-4 mm
)Angle of preparation
ca. 6 deg.(