Principles of cavity preparation presented by DR.rupali

1. PRINCIPLES OF CAVITY
PREPARATION
Presented By,
Rupali Balpande
Guided By,
Dr.Sarvesha Bhondave
Dr.Vishal Mahajan

2. CONTENT
INTRODUCTION
CAVITY PREPARATION DEFINITION
HISTORY
OBJECTIVES OF CAVITY PREPARATION
FACTORS AFFECTING CAVITY
PREPARATION
CLASSIFICATION
STAGES OF CAVITY PREPARATION

3. Introduction
• Dr. G.V. Black
Chicago, Illinois
1836-1915
• "The Grand Old Man of Dentistry"
• The basic principles governing the
design of cavity and steps in their
preparation was first suggested by
American Dentist and teacher
Dr.G.V.Black in the first decade of
last century.

4. Definition of Cavity preparation
The mechanical alteration of
a defective, injured, or
diseased tooth in order to
best receive a restorative
material which will re-establish
a healthy state for
the tooth including esthetic
corrections where indicated,
along with normal form and
function.

5. HISTORY
Archaeological evidence of dental treatment
from 5000 BC
1800 early drills by hand
1955-Page Chyles handpiece-1st driven angle handpiece
9 th century –cavity prepared for inlay
19 th century Hamelton Jameson -1st emphasized the
organized cavity preparation.
Extension For Prevention- Marshall Ebb & G.V. Black
1930-G.V.Black-systemic approach to cavity preparation
Simon –sixth classification
1998 G.J.Mount classification

6. OBECTIVES OF TOOTH PREPARATION
• Remove all defects and provide
necessary protection to the pulp.
• Extend the restoration as
conservatively as possible .
• Tooth prep such that under
mastication both the tooth and
restoration will not fracture or
displace.
• Allow the functional and esthetic
placement of a restorative material.

7. Factors affecting tooth
Preparation
GENERAL
FACTORS
 Diagnosis
 Prevention
 Interception
 Preservation
 Restoration
PATIENTS
FACTOR
Economic status
Age
Choice of Material

8. Classification
G.V. Black Classification
Modification of G.V.Black
Classification
Graham J Mount
V.K. Sikri

9. G.V.Black Classification
First Classification
Universally Accepted
Based on type of treatment and area
involved
Controlled by no. of factors
I. To gain access & visibility
II. Removal of affected dentin from floor
III. Room for restorative material
IV. Extension for prevention
V. Retentive designs
VI. Cavosurface margins self cleaning areas

10. G.J.Mount classification
-design to simplify identification of lesions
According to site lesion
1.Pits &fissure
2.Contact area
3.Cervical
According to size of lesion
1.Minimum
2.Moderate
3.Enlarged
4.Extensive
Sikri classification-classify same as G.V. Black
and then gave division in each class

11. TOOTH PREPARATION
TERMINOLOGY :
• Simple tooth preparation
-Only one tooth surface
is involved.
• Compound tooth
preparation – Only two
tooth surface is involved.
• Complex tooth
preparation – Involves
three or more surfaces.

12. Terminology in Cavity
Preparation
Definition –
Cavity-Cavity is defined as
a defect in enamel or dentin
resulting from pathologic process
of dental caries(breach in the
continuity of the surface integrity
of tooth).
The term cavity was used to
describe a carious lesion in a
tooth that has progressed to the
point that part of tooth structure
had been destroyed.

13. Tooth preparation walls
INTERNAL WALL-An internal is
prepared surface that does not
extend to external tooth surface.
AXIAL WALL – An axial wall is an
internal wall parallel with the long
axis of the tooth.
PULPAL WALL- A pulpal wall is an
internal wall that is perpendicular
to the long axis tooth and occlusal
of pulp.

14. External wall – An external wall is
prepared surface that extend to the
external tooth surface
Floor / seat-A floor is a prepared
wall that is reasonably flat and
perpendicular to the occlusal forces
that are directed occlusogingivally.
Enamel wall –Enamel wall is that
portion of a prepared external wall
consisting of enamel.
Dentinal wall- The dentinal wall is
that portion of a prepared external
wall consisting of dentin ,in which
mechanical features can be located.

15. CAVITY PREPARATION ANGLES :
 Line angle : It is the junction of two planar surfaces of
different orientation along a line. internal line
angle and an external line angle.
Internal line angle : Is a line angle whose apex points into
the tooth
e.g. FP.
External line angle : Is a line angle whose apex points away
from the tooth e.g. ap.
Point angles : A point angle is junction of three planal
surfaces of different orientation.

16. Cavo surface angle :
The cavo surface angle is the angle of the tooth
structure formed by the junction of a prepared cavity
wall and the external surface of the tooth.
Line angles & point angles Cavo-surface angle

17. Classification of cavity
 Class I
 Class II
 Class III
 Class IV
 Class V
 Class VI
— G. V. Black

18.  CLASS I CAVITY
1) Pits & fissures
2) Occlusal surface of premolars & molars
3) Occlusal 2/3 rd of buccal & lingual surface
4) Lingual surface of maxillary incisors

19.  CLASS II CAVITY
1) Restoration on Proximal
surface of posterior teeth

20.  CLASS III CAVITY
1)Restoration on the proximal
surface of the anterior teeth that
do not involve incisal edge.

21.  CLASS IV CAVITY
1)Restoration on the proximal
surface of anterior teeth that do
involve the incisal edge .

22.  CLASS V CAVITY
1) Restoration on the gingival
third of the facial / lingual
surfaces of all teeth.

23.  CLASS VI CAVITY
1) Restoration on incisal edge of anterior
teeth and occlusal cusp height of posterior
teeth.
2) It is given by Simon.

24. Stages of Cavity Preparation
 INITIAL STEPS OF CAVITY PREPARATION

25.  FINAL STEPS OF PREPARATION

26. 1. Outline Form and Initial Depth
Definition:
placing the cavity margins in the
positions they will occupy in the final
preparation except for the finishing
enamel walls and margins;
preparing an initial depth of 0.2~0.8 mm
pulpally of the dentinoenamel junction.

27. Principles :
1.All friable and weakened enamel
should be removed.
2.All fault should be included
3.All margin should be placed in
a position to afford good
finishing of margins of
restoration.

28. PROCEDURE

29.  Features:
1.Preserving cuspal strength.
2.Preserving marginal ridge.
3.Minimizing facio-lingual
extension.
4.Using enameloplasty
5.Connectiong two close
faults of the tooth which are < 0.5 mm apart
6.Restricting depth of penetration into dentin
for pits and fissure-0.2
for smooth surface-0.2 to 0.8

30. 1.Preserving cuspal strength
-avoiding termination of the margin on
extreme eminence, such as cusp height
-if extension of primary groove includes
half / > of cusp incline, then CUSP
CAPPING consider.

31. 2. Preserving marginal ridge strength
• Remaining Marginal ridge should be greater
than 1.6 mm for premolar & 2mm for molar
• If Remaining Marginal ridge
will be less than 1.6 mm
there there may be the chances of
fracture due to undermining
the ridge.

32.  Direction of mesial & distal walls
• When >1.6 mm
thickness width is
remained at mesial
/distal marginal ridge ,
then mesial / distal
wall should be
parallel.
• When less than/= 1.6
mm thickness width is
remained at mesial
/distal marginal ridge ,
then mesial / distal
wall should be
divergent.

33. 3. Minimizing facio –lingual Extension
- Minimizing facio –lingual Extension ,which
prevents the weakening of cusp.
- For conservative class I CAVITY
facio-lingual width should be 1 to 1.5 mm

34. 4. Depth of preparation
Restricting depth of penetration into dentin
for pits and fissure-0.2
for smooth surface-0.2 to 0.8
Because,
1.To avoid the seating
of the restoration on
the very sensitive DEJ.
2.To give the bulk of
restoration.
3.To take advantages of
dentin elasticity during
insertion and function.

35. 5. Enameloplasty
• This is the procedure of reshaping the enamel
surface by making it rounded / Saucered ,the area
becomes cleansable and finishable.
• It is indicated when remaining fissure is not greater
than 1/3 rd of enamel thickness.

36. Outline form for class I
• The outline form varies from one tooth to another .
• Premolars-
• Upper premolars have “ Dumb- bell “ shape with
their ends triangular.
• In lower premolar –are confined to pit only
but if they involve entire occlusal surface ,then
they resemble like upper premolar.
• In tricuspid lower premolar it will assume Y-shape

37. Class I
upper premolar
Class I
lower premolar

38. Class I & II Outline form for
MOLARS
• Preparation in lower molars have an elongated
shape mesio-distally with three lateral extensions.
• In upper molars if cavity involves all the occlusal
surfaces ,the preparation elongated mesio-distally .
• If the oblique ridge is not involved the mesial
preparation will assume kidney shape & distal will
appear as heart shape .
• In class II the shape of proximal box is Inverted
Truncated Cone.

39. Mandibular Maxillary
ClassⅠoutline form
Occlusal view Proximalview
Class II outline form

40. Position of Gingival floor
• In class II cavity
preparation ,gingival
margin should be
extended apically of
proximal contact to
provide a minimum of
0.5 mm clearence
between the gingival
margin and djacent
tooth.

41. Position of Embrassure wall
Isthmus –
By G.V.Black-
Advocate that class II cavity
preparation with isthmus width
equal to 1/3rd of intercuspal distance.
By Vale & Brooner-
It should be 1/4th of intercuspal
distance.

42.  The axio-pulpal line angle should be
beveled to reduce the concentration of
stresses and provide grater bulk of
material in the isthmus area, which is
liable to fracture.

43. Final location for the facial and lingual
Walls of proximal box relative to the contact
area
REVERSE CURVE –When viewed
from occlusal outline form of class II cavity
particularly in max . teeth the proximal contact
lies towards the buccal surface whereas the
groove line occurs in the central portion of th
occlusal table. This disparity necessitates
occlusal outline with a REVERSE CURVE.
Advantages
1.It preserve the triangular ridge of cusp
2.Facilitates formation of 90°angle
between proximal wall & the tangent of
proximal surface.

44. Initial cavity preparation stage
Step 1 Outline form and initial depth
Step 2 Primary resistance form
Step 3 Primary retention form
Step 4 Convenience form

45. 2. Primary Resistance Form
Definition:
It is defined as that shape and placement of
the cavity walls that best enable both the
restoration and the tooth to withstand,
without fracture, when masticatory forces
delivered principally in the long axis of the
tooth.

46. Primary Resistance Form
Principles:
To utilize the box shape with a relatively
flat floor to resist occlusal loading by
virtue of being at right angles to
mastication force;
To restrict the extension of the external
walls (keep as small as possible) to
allow strong cusp and ridge areas to
remain with sufficient dentin support;

47. Primary Resistance Form
Principles:
To have a slight rounding of internal
line angles to reduce stress
concentration in tooth structure;
To provide enough thickness of
restorative material to prevent its
fracture under load.

48. Primary Resistance Form
Feature:
Box shape
Relatively flat floors
Inclusion of weakened tooth structure
Preservation of cusps and marginal ridges
Rounded internal line angles
Adequate thickness of restorative materials
Reduction of cusps for capping if indicated

49. Flat pulpal floor prevents rocking of the restoration which produce
wedging forces

50. Exception
Pulpal wall is flat in all cases
except in lower 1st premolar
,where the lingual cusp is very
small & buccal cusp is
pronounced with very large
pulp horn. So in this case we
have to make flat pulpal floor
which is parallel to imaginary
line joining the tips of the and
lingual cusp.

51. Rounding of line angles prevents stress concentration & provide
resistance form
&
Shows strongrst enamel margin by full length of enamel rods

52. Facio-lingual width
should be not more than
¼ th the intercuspal
distance . As minimum
tooth structure is
removed, it increases the
resistance of tooth.
¼ th intercuspal
distance

53. The type of restorative material
also dictates resistance form need
Silver amalgam needs thickness -1.5 mm
Cast metal needs thickness -1to2mm
Porcelain needs thickness - 2 mm

54. Initial cavity preparation stage
Step 1 Outline form and initial depth
Step 2 Primary resistance form
Step 3 Primary retention form
Step 4 Convenience form

55. 3. Primary Retention Form
Definition:
primary retention form is the shape
or form of conventional preparation
that resists displacement or removal
of the restoration from tipping or
lifting forces.
In many respects retention and resistance form
are accomplished in the same cutting procedure.

56. Principal means of retention
Frictional retention -
1.Greater surface area (length, width,
depth)produces greater frictional component.
2.Parallel walls / convergent wall
provide greater frictional retention
3.Proximity –bringing the restorative material
closer to tooth structure during insertion provide
greater frictional retention component.
4.Elastic deformation of dentin –during
condensation within dentin proportional limit can
add more gripping action.

57. 4.Inverted truncated cones
-In class II cavity preparation ,
proximal surface have inverted
truncated cones shape
-It prevents the occlusal displacement
of restoration in class II Cavity.

58. 6. Dovetail
In Class II Cavity
-Dovetail provide retention in class II
cavity .
-It prevents lateral displacement of
restoration in class II cavity.
In Class I Cavity
-In class I ,it is given for the purposeful
modification in outline usually for
‘EXTENSION FOR PREVENTION’

59. Primary Retention Form
Principles:
 For Amalgam restoration:
-developing external cavity walls that
converge occlusally.
-Adhesive system provide retention by
micromechanically bonding amalgam to
tooth structure.

61. Primary Retention Form
Principles:
Composite restoration:
a mechanical bond between the material
and conditioned, prepared tooth structure.

63. Initial cavity preparation stage
Step 1 Outline form and initial depth
Step 2 Primary resistance form
Step 3 Primary retention form
Step 4 Convenience form

64. 4 . Convenience Form
Conception:
The shape or form of the cavity that
provides for adequate observation,
accessibility, and ease of operation
in preparing and restoring the cavity.

65. Convenience Form
Principles:
Allow access for caries removal
Allow access for restoration placement
Allow access to margins for finishing,
evaluation and cleaning

66. Convenience Form

67. -In class II cast restoration divergence of
vertical wall
-extending proximal preparation beyond
proximal contact
-In class III cavity convenience form mainly
through lingual side.
- In class I & V , divergence of wall of cavity
in INLAY

68. Final cavity preparation stage
Step 5 Removal of any remaining infected
dentin or old restoration, if indicated
Step 6 Pulp protection
Step 7 Secondary resistance & retention form
Step 8 Procedure for finishing external walls
Step 9 Final procedures

69. 6. Removal of any remaining
infected dentin or old
restoration, if indicated
Definition:
The elimination of any infected carious
tooth structure or faulty restorative
material left in the tooth after initial
cavity preparation.

70. Removal of dentinal caries using round burs and spoon excavators

71. Removal of dentin depends on the two
condition
whether it is affected or infected?
• Affected dentin
-Does not contain micro-organisms
-can be remineralise by
restorative mean.
-it is accepted to allow
affected dentin to
remain in prepared
tooth.
• Infected dentin
-It contain micro-organisms
-can not be remineralise
by restorative mean.
-it should be removed
during cavity
preparation.

72. -Soft decay can be best removed using spoon
excavator by flaking up the caries
-Hard decay, heavily discolored should
removed using very low speed bur.
-care should have to take during removal as
pulp may infected by forcing micro-organisms
into dentinal tubules through
excessive pressure.

73. Final cavity preparation stage
Step 5 Removal of any remaining infected
dentin if indicated
Step 6 Pulp protection
Step 7 Secondary resistance & retention form
Step 8 Procedure for finishing external walls
Step 9 Final procedures

74. 6. Pulp protection
- Using liners or bases
- to protect the pulp or
- to aid pulpal recovery or both.
LINERS-liners are volitile /aquous suspension
/dispersion of zinc oxide or calcium hydroxide
that can be applied to tooth surface in relatively
thin film & are used to effect a particular pulpal
response.
BASES-Are those cements used in thicker
dimensions beneath permanent restoration to
provide for mechanical, chemical ,thermal
protection of the pulp

75. -Liners are primarily used to provide a barrier to
protect dentin from residual reactants.
-Bases are used to provide thermal protection for the
pulp and to supplement mechanical support for the
restoration by distributing local stresses from
restoration across the underlying dentin surface.
If remaining dentin overlying the pulp is 2mm
then no need of liners
But if it is less than 2mm ,pulp protection is
mandatory .

76. Schematic view of needs for pulpal
protection below metallic restoration

77. For shallow tooth
preparation
For moderate
tooth preparation
Schematic examples of liners & bases for
amalgam restoration
For very deep
tooth preparation

78. Final cavity preparation stage
Step 5 Removal of any remaining infected
dentin if indicated
Step 6 Pulp protection
Step 7 Secondary resistance & retention form
Step 8 Procedure for finishing external walls
Step 9 Final procedures

79. 7. Secondary resistance and
retention forms
Most compound and complex cavity
preparations require additional
resistance and retention form.
The exception being those preparations
that are very conservative.

80. Secondary resistance and
retention forms
Mechanical forms
Cavity wall conditioning form

81. Mechanical form:
 Retention locks, grooves, and coves
 Groove extensions
Skirts
Beveled Enamel Margins
Pins, Slots, Steps, Amalgampins

82. Proximal Grooves
for cast restoration
Retention locks
for amalgam

83. Incisal retention
coves
Incisal & Gingival
retention groove

84. Groove extensions & skirts
When lingual wall
absent or inadequate in
proximal preparation,
then retention form can
be improved by facial
skirt extension.

85. Pins slots steps & amalgampins
Dentin slots Amalgampins
Beveled Enamel margins
-The bevels for cast metal may improve retention form
-Primarily to afford a better junctional relationship
-Beveled margins increases the surface area of etchable enamel

86. Cavity wall conditioning form
Placement of etchant , Primer , Adhesive on
prepared wall
-in addition to mechanical alteration to tooth
structure certain bonding agents also provide
some extent of retention & resistance form
-such treatment require in bonded restoration
like porcelain , composite , or amalgam
materials

87. Micromechanical retention of bonding system to dental
enamel

88. Final cavity preparation stage
Step 5 Removal of any remaining infected
dentin if indicated
Step 6 Pulp protection
Step 7 Secondary resistance & retention form
Step 8 Finishing external walls
Step 9 Final procedures

89. 8. Finishing the external walls
Definition:
is the further development of a
specific cavosurface design and
degree of smoothness that produces
the maximum effectiveness of the
restorative material being used.

90. Finishing the external walls
Objectives:
 To create the best marginal seal possible
between the restorative material and tooth
structure;
 To afford a smooth marginal junction;
 To provide maximum strength of both the
tooth and the restorative material at and
near the margin.

91. The strongest enamel margin is that margin
which is composed of full-length enamel rods
that are supported on the cavity side by shorter
enamel rods, all of which extend to sound dentin.

92. Finishing the external walls
The design of the cavosurface angle
The degree of smoothness of the wall

93. The design of the cavosurface angle:
depending on the material
 amalgam: 90°(Cavosurface margin 90°-Butt joint)
Help to minimize the marginal deterioration of
restoration by locating the margins away from the
enamel eminence where occlusal forces may be
concentrated.
composite: beveling 30°~ 40°
Is indicated primarily in larger restoration
because the potential for retention increased by
increasing the surface area of enamel available
for etch.

94. Occlusal
cavosurface
margin
Proximal
cavosurface
margin

95. Vertical section of Class II Tooth preparation
-a slight bevel is given to remove unsupported
enamel rods

96. Gingival Bevel placed with an
instrument
Gingival marginal trimmer

97. Final cavity preparation stage
Step 5 Removal of any remaining infected
dentin if indicated
Step 6 Pulp protection
Step 7 Secondary resistance & retention form
Step 8 Procedure for finishing external walls
Step 9 Final procedures

98. Final procedures
 cleaning
 inspecting
Sealing

99. A .Water, air, or combinations of both
B . Dry cotton pellets are very efficient
and safer way to dry preparation .
C. Using cavity cleaner (vey low conc. Of citric
acid ,ascorbic or acetic acid),dilute sol. Of
hydrogen peroxide.
D. Scraping preparation walls with sharp
hand instrument.
E. Irrigate the cavity with saline before drying.
F. Inspecting the cavity for any remaining
debris
G. Sealing the cavity
H. Composite requires etching ,priming &
bonding before insertion of restoration.

100. Cavity preparation seen after final
procedure

101. References
1.Sturdevants- Art and Science Of Operative Dentistry
2.Marzouk – Modern Theory and Practice
3.G.V. Black –Work on operative dentistry
3.Vimal Sikri- Textbook of Operative Dentistry
4.Journal of Australia- Conservative Dentistry
5.American Dental Association Document
6.Vale –Cavity preparation
7.www.googleimages.com
8.www.dentalacademy/images/cavity preparation.com