tooth preparation principals and steps involved for making crown and bridge for fixed arch tooth replacement

2. 1. INTRODUCTION
2. DEFINITION
3. INDICATIONS AND CONTRAINDICATIONS
4. ADVANTAGES AND DISADVANTAGES
5. SPECIAL FEATURES
6. ARMAMENTARIUM
7. PREPARATION
8. METAL CERAMIC CROWN
9. ALL CERAMIC CROWN
10. REVIEW OF LITERATURE
11. REFERENCES
CONTENTS

3. TERMINOLOGIES
Tooth preparation: is defined as the mechanical treatment of
dental disease or injury to hard tissues that restores a tooth to
original form. (Tylman)
Crown / artificial crown: a metal, plastic, or ceramic restoration
that covers three or more axial surfaces and the occlusal surface or
incisal edge of a tooth (GPT-7; 1999)
Full veneer crown / Complete crown: A restoration that covers all
the coronal tooth surfaces ( mesial, distal, facial, lingual and
occlusal ) (GPT-7; 1999)
Chamfer Finish line: A finish line design for tooth preparation in
which the gingival aspect meets the external axial surface at an
obtuse angle (GPT-7; 1999)
Shoulder finish line : A finish line design for tooth preparation in
which the gingival floor meets the external axial surfaces at
approximately a right angle(GPT-7; 1999)

4. Retention form : The feature of a tooth preparation
that resists dislodgement of crown in a vertical
direction or along the path of placement (GPT-7; 1999)
Resistance form : The features of a tooth preparation
that enhance the stability of a restoration and resist
dislodgement along an axis other than the path of
placement (GPT-7; 1999)
Bevel : The process of slanting the finish line and
curve of a tooth preparation (GPT-7; 1999)

5. FULL VENEER
CROWNS
COMPLETE CAST
CROWN
ALL CERAMIC
CROWN
METAL CERAMIC

6. Clinicians have long
considered full veneer crowns
to be the most retentive of
veneer preparations
when compared with partial
veneer designs, the full veneer
crown exhibits superior
retention and resistance
It does not mean that it must
be used in every case
FULL CAST METAL CROWN

8. • teeth that exhibit extensive coronal destruction
by caries or trauma
• the restoration of choice whenever maximum
retention and resistance are needed
• short clinical crowns or when high displacement
forces are anticipated, such as for the retainer
of a long-span FPD
• used to support a removable partial denture,
• indicated on endodontically treated teeth.
• Correction of occlusal plane.
INDICATION;

9. Extensive decayed Long span fpd

10. Short clinical crowns

11. Crown to support rpd Endodontically treated
teeth

12. • should not be used in mouths with uncontrolled
caries.
• Less than maximum retention necessary.
• Esthetics.
• Wherever an intact buccal or lingual wall exists.
• if less than maximum retention and resistance
are needed (e.g., on a short-span fixed partial
denture.
CONTRAINDICATION;

13. • greater retention.
• Also has greater resistance form
• strength of a complete cast crown is superior
• this restoration is less easily deformed than its
counterparts,
• allows the operator to modify axial tooth
contour.
• easy- modification ^the occlusion
ADVANTAGES;

14. Removal of large amount of tooth
structure.
Adverse effects on tissue.
Vitality testing not readily feasible.
Display of metal.
DISADVANTAGES;

15. ROTARY INSTRUMENTS USED FOR
FULL VENEER PREPARATIONS
Shape Use
Round end tapered
diamond
1.Depth orientation grooves
2.Occlusal reduction
3.Functional cusp
Torpedo diamond 1.Axial reduction
2.Chamfer finish line
Short needle 1.Initial interproximal axial
reduction in posterior teeth
Long needle 1.Initial proximal axial
reduction in anterior teeth

16. Small wheel diamond 1. Lingual reduction in anterior
teeth
Tapered fissure bur
(171L)
1.Seating groove
2.Proximal groove (posterior
teeth
3.Smoothing and finishing
4.Occlusal and incisal bevels

17. Occlusal guiding grooves
Occlusal reduction
Axial alignment grooves
Axial reduction
Finishing and evaluation Armamentarium
PREPARATION;

18. • with occlusal reduction, -1.5mm of clearance on the
functional cusps and 1.0mm on the non functional
cusps.
• occlusal reduction should follow normal anatomic
contours
• Axial reduction should parallel the long axis of the
tooth -6 degree taper
• The margins -chamfer -supragingivally
• The chamfer should be smooth and distinct and allow
for 0.5mm of metal thickness at the margins
CRITERIA;

19. • Functional (Centric) Cusp Bevel- give 1.5 mm of
occlusal clearance),bevel must be angled flatter than
the external surface
• placed at about_45 degrees to the long axis.
• Nonfunctional (Noncentric) Cusp Bevel -A minimum of
0.6 mm clearance
• Chamfer Width -(minimum 0.5 mm) is important for
• developing optimum axial contour.
SPECIAL CONSIDERATIONS;

20. Use round-end tapered diamond to make
depth orientation grooves on the triangular ridges
and in the primary developmental grooves
Occlusal Reduction

21. Guiding groove for occlusal reduction;
1.place depth holes approximately 1 mm deep in the central, mesial,
and distal fossae and connect them
2.place guiding grooves in the buccal and lingual developmental
grooves and in each triangular ridge extending from cusp tip to
center of its base.
3.because the centric or functional cusp is to be protected by an
adequate thickness of metal ,place a functional cusp bevel.
4.use the guiding grooves to ensure that occlusal reduction follows
anatomic configuration.
A groove should be placed in the low point and high point of each
cusp.low point are the central and development grooves,high point
are the cusp tips and triangular ridges.

22. ROUND END TAPERED diamond is used.
Complete the occlusal reduction in 2 steps. Half the
occlusal surface is reduced first so that the other half can
be maintained as reference.
The clearance must be checked in all excursive
movements .
The patient should close into several layers of dark
colored utility wax in maximum intercuspation.
OCCLUSAL REDUCTION;

23. 1.5mm deep on functional cusp and
1.0mm deep on the nonfunctional cusps
Occlusal Reduction

24. Enamel chisel used to precisely judge
the depth of grooves
Occlusal Reduction

25. Removal of tooth structure between the grooves
in an inclined manner
Occlusal Reduction

26. Planar occlusal reduction :
round-end tapered diamond and no.171 bur
Occlusal Reduction

27. Functional cusp bevel :
round-end tapered diamond and no.171 bur
Occlusal Reduction

28. Checking the occlusal clearance with utility wax
Occlusal Reduction

29. Examining the imprint of the occlusal surface
Occlusal Reduction

30. Placement of depth orientation groove for
Axial Reduction

31. Axial reduction;
Grooves- One in center and one in each mesial and distal
line angle.
1.when these guiding grooves are placed be sure the
shank of the diamond is parallel to proposed path of
withdrawal of the restoration.
2.do not let the diamond cut into the tooth beyond its
midpoint.

32. Axial Reduction

33. Facial and lingual axial reduction :
torpedo diamond
Axial Reduction

34. Buccal surface reduced with a torpedo diamond
the chamfer finish line is created at the same line
Axial Reduction

35. The facial axial reduction is carried as far as
possible into interproximal embrasures without
nicking the adjacent teeth
Axial Reduction

36. Lingual axial reduction with the same diamond
Axial Reduction

37. The lingual axial reduction also extends as far
interproximally as can be easily accomplished
Axial Reduction

38. An occlusal view of the tooth preparation at this
stage reveals isolated areas of intact tooth
structure surrounding each proximal contact
Occlusal view

39. Short thin needle diamond is placed against the
remaining island of tooth structure and moved in
a up and down motion
Proximal Reduction

40. In tight areas sometimes the tip may be used
Proximal Reduction

41. Gaining access by sweeping the
short thin diamond
Proximal Reduction

42. Repeating the process on the opposite
proximal surface
Proximal Reduction

43. Increasing the depth of reduction and producing
a finish line with torpedo
Proximal Reduction

44. Critical area of preparation
Proximal Reduction

45. More reduction achieved in this area
Proximal Reduction

46. Chamfer finishing : torpedo bur
Axial Reduction

47. Placement of seating groove
0.5mm above chamfer
Axial Reduction

48. The completed full veneer crown preparation

49. The features of a full veneer crown preparation
and the function served by each
Completed Preparation

51. Maxillary premolar,maxillary first molars,
mandibular first premolar,are - appearance
zone.
SAME AS FULL METAL EXCEPT PLACES
WHERE CERAMICVENEER.
PREPARATION;

52. Facial Index prepared in putty silicone.
Facial Index

53. Cutting it Facio - lingually
Facial Index

54. Facial half of Index
Facial Index

55. Planar occlusal reduction : round-end tapered
diamond and no.171 bur.
Occlusal Reduction

56. Placement of depth orientation grooves
1.5MM TO 2MM
Occlusal Reduction

57. Removal of tooth material between grooves
Occlusal Reduction

58. Functional cusp bevel : round-end tapered
diamond and no.171 bur
Occlusal Reduction

59. Orientation grooves for functional cusp bevel
FUNCTIONAL CUSP BEVEL-2MM WHERE
CERAMIC IS VENEERED.
Occlusal Reduction

60. Removal between grooves
Occlusal Reduction

61. Depth – orientation grooves :
flat-end tapered diamond 1.2mm for base
metal and 1.4mm for the noble metal ceramic
Facial Reduction

62. Aligning the bur parallel to the occlusal
segment of facial surface.
Facial Reduction

63. Cutting grooves in the occlusal portion
Facial Reduction

64. Aligning the bur in the gingival portion
Facial Reduction

65. Cutting grooves in the gingival portion
Facial Reduction

66. Facial reduction, occlusal half :
flat-end tapered diamond
Facial Reduction

67. Occlusal segment reduced between grooves
1.2MM FOR BASE METAL AND 1.4 FOR NOBLE
METAL
Facial Reduction

68. Facial reduction, gingival half :
flat-end tapered diamond
Facial Reduction

69. Extending reduction interproximally.
Facial Reduction

70. Proximal axial reduction :
short-needle diamond.
Proximal Reduction

71. Initial reduction with short needle diamond
Proximal Reduction

72. Achieving Proximal Separation.
At lingual most extension of facial
reduction,lingual to proximal contact-wing
preparation
Proximal Reduction

73. Needle diamond to plane the axial wall
Proximal Reduction

74. Lingual axial reduction :
torpedo diamond.
Lingual Reduction

75. Lingual reduction with torpedo diamond
Lingual Reduction

76. Axial finishing :
Torpedo finishing bur and no.171 bur
Lingual Reduction

77. Finishing the axial surface
Lingual Reduction

78. Smoothening occlusal reduction
Finishing

79. Rounding the line angles and point angles
Finishing

80. Shoulder finishing : no.957 bur.
Finishing

81. Using end-cutting bur
Finishing

82. Smoothing the Shoulder
1MM WIDE SHOULDER FINISHED WITH RS-
1MODIFIED BIN ANGLE CHIESEL
Finishing

83. Gingival bevel :
Flame diamond and finishing bur
Beveling the finish line

84. Flame shaped diamond to place
bevel 0.3mm deep
Beveling the finish line

85. Finishing the bevel
Finishing

86. Completed Preparation

87. Viewing facial reduction
Verification of the preparation

88. Viewing Overall reduction
Verification of the preparation

89. The features of a preparation for PFM crown on a
posterior tooth and the function served by each
Completed Preparation

90. REVIEW OF LITERATURE;
1. David A. Felton et al (1987) found that teeth prepared
for full crowns by using diamond burs will have 31%
greater retention than preparations made with carbide
bur. Alternative retentive features should be
considered in preparation design if carbide burs are
used.

91. 2. Shillingburg HT et al (1987) - stated that
theoretically, the most retentive preparation
would be with parallel walls. However in order to
avoid undercuts and allow complete seating of
the restorations during cementation, the walls
must have some taper. One which lies within the
range of 2 to 6.5 degrees has been considered to
be optimal.

92. 3. Jeffrey Nordlander et al (1988) studied the
convergence angles of full coverage preparations
performed in a clinical environment and concluded that
the ideal convergence of 4 to 10 degrees is seldom
achieved.The mean convergence angle of mandibular
preparations were greater than mean maxillary
convergence angle and premolar convergence angle
tended to be smaller than anterior convergence angles.

93. 5. Mohammed F. Ayad et al (1997) studied the
relationship between surface characteristics of teeth
prepared for complete cast crowns and retention of
restorative cemented restorations. Greatest retention
value was for tooth preparations refined with carbide burs
and cemented with Panavia-EX, an adhesive resin
cement. Least retention values was for teeth preparations
completed with finishing bur and luted with zinc
phosphate cement.

94. 1.FUNDAMENTALS OF FIXED PROSTHODONTICS-THIRD
EDITION SHILLINGBURG.
2.CONTEMPORARY FIXED PROSTHODONTICS-
ROSENTIEL.
3. Felton DA, Ed Kanoy B and White JT. The effect of
surface roughness of crown preparations on retention of
cemented castings. J Prosthet Dent. 1987; 58: 292-296.
4. Nordlander J Weir D, Stoffer W and Ochi S. The taper of
clinical preparations for fixed prosthodontics. J Prosthet
Dent. 1988; 60: 148-151.
REFERENCES;

95. 5. El-Mowafy O.M., Fenton A.H.,Forester N., Milenkovice
M.-Retention of metal ceramic crowns cemented with
resin cement :effects of preparation taper ,,and height –
J.Prosthet.Dent 1996;76:524-29.
6. Ayad MF, Rosenteil SF and Salama M. Influence of
tooth surface roughness and type of cement on retention
of complete cast crowns. J Prosthet Dent. 1997; 77: 116-
121.

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