1. b 2

2. Conservation Presentation
Topic: Tooth preparation and maintaing pulp
vitality
By:Aqdas Niazi
Guided by : Dr.Rauf sheikh (H.O.D)

3. Defination of tooth
preparation:
• Tooth preparation is the mechanical
alteration of a defective,injured,or
diseased tooth such that placement of
restorative material re- establish
normal form and function,including
esthetic correction, where indicated.

4. Need for restorations
Prevention from Dental caries often
requires prophylactic restorative
procedures.Caries progression may
cause destruction of tooth structure
which requires repair.Another common
need is the replacement or repair of
restoration with serious defects.

5. • Restorations are also indicated to
restore proper form and funtion to
fractured teeth.
• Teeth present with minor to major
amounts of missing tooth structure or
with an incomplete farcture " greenstick
fracture"

6. Objectives of tooth
preparation:
Generally, the objective of tooth
preparation are to
1) remove all defects and provide
necessary protection to the pulp.
2) extend the restoration as
conservatively as possible
3) form the tooth preparation so that
under the forces of mastication , the
tooth or the restoration will not
fracture

7. 4) Allow for the esthetic and functional
placement of restorative material.
FACTORS AFFECTING TOOTH
PREPARATION:
i)General factors => Diagnosis
ii)Knowledge of dental Anatomy
iii) Patient factors
iv)Conservation of tooth structure
v)Restorative material factors

8. Tooth Preparation walls:
Internal wall:Is the prepared surface
that does not extend to the external
tooth surface.
Axial wall: Is the internal wall parallel to
the long axis of the tooth.
Pulpal wall(Floor):Is the internal wall that
is perpendicular to the long axis of the
tooth and occlusal of the pulp.

10. External wall:Is the prepared surface
that extends to the external tooth
surface.Such a wall takes the name of
the tooth surface(or aspect) adjacent
to that wall.
Enamel wall: Is that portion of a
prepared externl wall consisting of
enamel.
Dentinal wall: Is that portion of a
prepared external wall consisting of
dentin.

11. Tooth preparation angle:
Line angle: A line angle is the junction of
two planar surfaces of different
orientation along a line.
Point angle: The point angle is the
junction of three planar surfaces of
different orientation.
Cavosurface angle and cavosurface
margin:
The cavosurface angle is the angle of
tooth stucture formed by the junction
of a prepared wall and the external
surface of the tooth.

12. The actual junction is
referred to as a
cavosurface margin.

13. STEPS OF TOOTH
PREPARATION:
The tooth preparation procedure is divided into
two stages, each with several steps:
i)Initial tooth preparation stage:
step 1: outline form and initail depth
step 2: Primary resistance form
step 3: Primary retention form
step 4: convenience form
ii)Final tooth preparation stage:
step 5: Removal of any remaining infected dentin or
old restorative material
step 6: Pulp protection, if indicated
step 7: Secondary resistance and retention forms

14. step 8: procedure for finishing external
walls
step 9: final procedure-cleaning,
inspecting,
desensitizing.

15. STEP 1:OUTLINE FORM AND
INITIAL DEPTH
Defination: Establishing the out line form
means
1) placing the preparation margins in the
positions they will occupy in the final
preparation except for finishing enamel
walls and margins.
2) preparaing an initial depth of 0.2 to
0.5mm pulpally of the DEJ position or
0.8 mm pulpally to normal root surface
position

16. Principles :
The three general principles on which
outline form is established
1)all unsupported or weakened(friable)
enamel usually should be removed.
2)all faults should be included and
3) all margins should be placed in a
position to allow finishing of the margins
of the restoration.

17. Factors:
In determing the outline form of a
proposed tooth preparation, certain
conditions or factors must first be
assessed.These factors are extend of
caries lesion, defect, or faulty old
restoration affects the outline form of
the proposed tooth preparation because
the objective is to extend to sound
tooth structure except in a pulpal
direction.

18. Features:
Generally, the typical features of
establishing proper outline form and
initial depth are
1) preserving cuspal strength,
2)preserving marginal ridge strength
3) minimizing faciolingual extenstion
4) connecting two close (<0.5mm apart)
defects or tooth preparations.
5) restrictng the depth of the
preparation into dentin.

19. Step 2: Primary resistance
form
Defination:Primary resistance form may
be defined as the shape and placement
of the preparation walls that best
enables the remaining tooth structure
and the restoration to withstand,
without farcture,masticatory forces
delivered principally in the long axis of
the tooth.

20. Principles :
The fundamental principles involved in
obtaining primary resistance form
include:
1)using a box shape with a relatively
horizontal floor,which helps the tooth
resist occlusal loading by virtue of being
at right angles to the forces of
mastication that are directed in the
long axis of tooth.
2)restricting the extension of the
external walls to allow strong cusp and
ridge areas to remain with sufficient
dentin support.

21. 3) having a slight rounding of internal line
angles to reduce stress concentration in
tooth structure.
4)reducing and covering weak cusps and
enveloping or including enough of a
weakened tooth within the restoration
in extensive tooth preparation to
prevent or resist fracture of the
toothby forces in the long axis and
obliquely.
5) providing enough thickness of
restorative material to prevent its
fracture under load.

22. 6) bonding the material to the tooth
structure when appropriate.
Factors: foremost is the assessment of
the occlusal contact on the restoration
and the remaining tooth structure.The
amount of remianing tooth structure
also affects the need and type of
resistance form.The type of restorative
material also dictates resistant form
needs.
Features: the design features of tooth
preparation that enhance primary
resistance form are as follows:

23. 1) Relatively horizontal floors.
2) Box-like shape
3) Inclusion of weakened tooth structure
4) Preservation of cusps and marginal
ridges
5) Rounded internal line angles
6) Adequate thickness of restorative
material
7) Reduction of cusps for capping , when
indicated.

24. Step 3: Priamary retention
form
Defination: Primary retention form is the
shape or form of the conventional
preparation that prevents displacement
or removal of the restoration by tipping
or lifting forces for nonbonded
restorations.
Principles: Because retention needs are
related to the restorative material
used, the principle of primary retention
form vary, depending on the
material.For amalgam

25. restorations in most class I and class II
conventional preparations, the material
is retained in the tooth by developing
external tooth walls that converge
occlusally.
Step 4: Convenience form
Convenience form is the shape or form of
the preparation that provides for
adequate observation, accessibility, and
ease of operation in preparing and
restoring the tooth.

26. FINAL TOOTH
PREPARATION STAGE:
Step 5: Removal of any remaining
enamel pit or fissure, infected dentin,
or old restrative material, if indicated
:
Definition: Removal of any remaining
enamel pit or fissure, infected dentin,
or old restorative material is the
elimination of any infected carious
tooth structure or faulty restorative
material left in the tooth after initial
tooth preparation.

27. Techniques:
Removal of remining old restorative
material, when indicated also is
accomplished with a use of a round
carbied bur at slow speed with air and
water coolant.The water spray(along
with high-volume evacuation) is used
when removing old amalgam material to
reduce the amount of mercury vapor.

28. Step 6: Pulp protection,
if indicated
The reason for using liners or bases is to
protect the pulp recovery or
both.Effective tubular sealing may
prevent penetration of bateria into the
tubules and limit the retrogarde
diffusion of baterial toxins towards the
pulp.

29. Liners: May include suspensions or
dispersions of zinc oxide, calcium
hydroxide, or resin-modified glass
ionomer(RMGI) that can be applied to a
tooth surface in a relatively thin
form.Liners may also povide
1.a barrier that protects the dentin from
noxious agents from either the
restorative material or oral fluids.
2.initial electrical insulation,or
3.some thermal protection.

30. Bases:
Bases are material, most commonly
cements,that are used in thicker
dimentions beneath permanent
restorations to provide mechanical,
thermal, electrical protection of the
pulp. Examples of bases include zinc
phospate, zinc oxide-eugenol,
polycarboxylate and the most common ,
glass ionomer.

31. Step 7: Secondary
Resistance and retention
forms:After any remining enamel pit or fissure,
infected dentin,or old restorative
material has been removed, and pulpal
protaction has been provided by
appropriate liners and bases, additional
resistance and retention features may
be deemed necessary for the
preparation. The secondary retention
and resistance forms are of two
types:1)mechanical preparation

32. 2)treatments of the preparation walls
with etching,priming,and adhesive
materials.
Mechanical features:A variety of
mechanical alteration to the preparation
enhance retention form,and these
alteration require additional removal of
tooth structure.
Retention grooves and coves:Vertically
oriented retention grooves are used to
provide additional retention for the
proximal portion of some conventional
tooth preparation.Retention coves are
placed for the incisal retention of class
III amalgams.

33. Preparation extension:
Additional retention of the restorative
material may be obtained by arbitrarily
extending the preparation for molars
onto the facial or lingual surface to
include facial or lingual groove.
Skirts: Skirts are preparation features
used in cast gold restorations that
extend the preparation around some, if
not all,of he line angles of the
tooth.When properly prepared, skirts
provide additional,opposed vertical walls
for additional retention.

34. Beveled enamel margins:
The bevels for metal cast may improve
retention form slightly when opposing
bevels are present but are used
primarily to afford a better junctional
relationship between the metal and the
tooth.

35. Placement of etchant,primer, or
adhesive on prepared walls:
Inaddition to mechanical alteration to the
tooth peparation,certain alteration to
the preparation walls by actions of
various material cause increase
retention and resistance to fracture.
Step 8:Procedure for finishing
the external walls of the tooth
preparation:
Defination:Finishing the preparation walls
is the further development, when
indicated, the degree of smoothness or
roughness that produces the maximum
effectivness of the restorativematerial
used.

36. Objective:The objectives of finishing the
prepared walls are to
1.create an optimal marginal junction b/w
the restorative material and the tooth
structure.
2.afford a smooth marginal junction
3.provide maximal strength of the tooth
and the restorative material at and near
the margin.
The following factors must be considered
in the finishing of enamel walls and
margins:

37. 1.the direction of the enamel rods
2.the support of the enamel rods at the
DEJ and laterally.
3.the type of restorative material to be
placed in the preparation.
4.the location of the margin
5.the degree of smoothness or roughness
desired.
Features: Finishing of external walls has
two primary features:
1.The design of the cavosurface angle
2.The degree of smoothness and
roughness of the walls.

38. The restorative material used is the
primary factor dictating the desired
smoothness or roughness of an enamel
wall.
Step 9: Final procedure
:Cleaning, inspecting and
desensitizing:-
The usual procedure in cleaning is to free
the preparation of visible debris with
water from the syringe and then to
remove the visible moisture with a few
light bursts of air from the air syringe.
Occlusion of the dentinal tubules limits
the potential for tubular fluid

39. resultant sensitivity.Desensitizers are
effective disinfectants,provide
crosslinking of any exposed dentin
matrix and occlude the dentinal tubules
by crosslinking tubular proteins.

40. Factors to consider before tooth preparation
Extent of caries extent of defect
Occlusion pulpal protection
Pulpal involment contours
esthetics economics
patients age patients risk status
patient's home care bur design
gingival status radiographic assessment
anesthesia other treatment factors
bone support patient co operation
patients desire fracture lines
material limitations tooth anatomy
operator skill ability to isolate areas
enamel rod direction
extent of old restoraive material

41. Instruments and equipment for
tooth preparation/restoration
preparation:-
Categories: The hand
instruments used in
the dental operatory
may be categorized
as
1. cutting (excavator,
chisels and others)
2.non- cutting
(amalgam
condensers,mirrors,
explorers,probes)

42. Design:
Most hand instruments,regardless of use,are
composed of three parts: handle,shank,
and blade

43. Excavator:
The four subdivisions of excavator are
1)ordinary hatches 2)hoes
3)angle-formers 4)spoons.
Chisels:
Chisels are intended primary for
cutting enamel and may be grouped as:
1.straight,slightly curved,or bin-angle.
2.Enamel hatches.
3.Gingival margin trimmers.

44. Hand instruments
techniques:
Four grasps are used with hand instruments:
1.modified pen. 2.inverted pen. 3.plam and
thumb, and 4.modified palm and thumb

45. Dental burs:
The term bur is applied to all rotary cutting
instruments that have bladed cutting head.
Shapes: The term bur shape refer to the
contour of the head.The basic head shapes
are :-

46. Diamond abrasive
instruments:
The second major category of rotary
dental cutting instruments involes
abrasive cutting rather than blade
cutting.Abrasive instruments are based
on small,angular particles of a hard
substance held in a matrix of softer
material.
Terminology : consist of 3 parts 1.a metal
blanks, 2.the powdered diamonds
abrasive 3.a metallic bonding material
that holds the diamond powder onto the
blank.

47. Demerits of cutting
instruments:
1.Loss of control.
2.More pain.
3.Prolong time for operative procedures.
4.Reduce the quality and precision of
tooth perparation.
5.Heat generation if water or air coolants
are not used.