FUNDAMENTALS IN TOOTH
By- Priyesh Kharat
DEFINITION OF TOOTH PREPARATION
Tooth preparation is the mechanical alteration of a
defective, injured, or diseased tooth to receive a
restorative material that re-establishes a healthy
state for the tooth, including esthetic corrections
where indicated and normal form and function.
OBJECTIVES OF TOOTH PREPARATION
Remove all defects and provide necessary
protection to the pulp
(2) extend the restoration as conservatively as
(3) form the tooth preparation so that under the
force of mastication the tooth or the restoration or
both will not fracture and the restoration will not
fracture & the restoration will not displaced, and
(4) allow for the esthetic and functional placement
of a restorative material.
TOOTH PREPARATION TERMINOLOGY
Tooth preparation walls
Internal wall –An internal wall 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 of the tooth and
occlusal of the pulp.
External Wall- An external wall is a prepared (cut) surface
that extends to the external tooth surface. Such a wall
takes the name of the tooth surface (or aspect) that the
wall is toward
Floor (or Seat)- A floor (or seat) is a prepared wall that is
reasonably flat and perpendicular to the occlusal forces
that are directed occlusogingivally (generally parallel to
the long axis of the tooth Examples are the pulpal and
Enamel Wall- The 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 retention features may be located.
TOOTH PREPARATION ANGLES
Line angle. A line angle is the junction of two planal
surfaces of different orientation along a line
An internal line angle is a line angle whose apex
points into the tooth
An external line angle is a line angle whose apex
points away from the tooth
Point angle – a point angle is the junction of three
planal surface of different orietation
CLASSIFICATION OF TOOTH PREPARATION
Class I Restoration
All pit rand-fissure restoration are class I and they are
assigned to three groups.
Restoration on Occlusal Surface of Premolars &
Restorations on Occlusal Two Thirds of the Facial and
lingual surfaces of Molars.
Restoration on lingual Surface of Maxillary Incisor
class II Restorations.
Restorations on Proximal surface of posterior teeth
are Class II
Class III Restorations
Restorations on the proximal surface of anterior teeth
that do not involve the incisal angle are Class III.
Class IV Restoration Restorations on the proximal surfaces of anterior teeth
that do involve the incisal edge are class IV
Class V Restorations
Restoration on the gingival third of the Facial or lingual
surface of all teeth( except pit-and-fissure lesions) are
Class VI Restorations Restorations on the incisal edge of anterior teeth or the
occlusal cusp height of posterior teeth are class VI
INITIAL AND FINAL STAGES OF TOOTH
Initial tooth preparation stage
Step 1: Outline form and initial depth
Step2 Primary resistance form
Step3 Primary retention form
Step4 Convenience form
Final tooth preparation stage
Step 5 Removal of any remaining infected dentin or old
restorative material (or both), if indicated
Step 6: Pulp protection, if indicated
Step 7: Secondary resistance and retention forms
Step 8: Procedures for finishing external walls
Step 9: Final procedure--cleaning, inspecting sealing
INITIAL TOOTH PREPARATION STAGE
Initial tooth preparation is the extension and initial
design of external walls of preparation at a specified
limited depth so as to provide access to the caries or
defect, reach sound tooth Structure, resist fracture of
the tooth restorative material from masticatory forces
principally directed with the long axis of the tooth,and
retain the restorativc material in the tooth .
STEP 1: OUTLINE FORM AND INITIAL DEPTH
Def Establishing the outline form means(1) placing the
preparation margins in the positions they will
occupy in the final preparation except for Finishing
enamel walls and margins and (2) preparing an
initial depth of 0.2 to 0.8 mm pulpally of the DEJ
Postion or root-surface position
PRINCIPLES:(1) all friable or weakened enamel should be
(2) all faults should be included and
(3) all margins should be in a position to afford
good finishing of the margin of the restoration.
1) Preserving cuspal strength
2) preserving marginal ridge strength
3) Minimizing faciolingual extension
4) using enamelopasty
5) Connecting two close faults or tooth preparation
6) Restricting the depth of the preparation into
dentin to a maximum of 0.2mm for pit & fissure
caries and 0.2 to 0.8 mm for axial wall of smooth
STEP 2. PRIMARY RESISTANCE FORM
Def: Primary Resistance form may be defined as the
shape and placement of preparation walls that best
enable the restoration and the tooth to withstand,
without Fracture, masticatory forces delivered
principally in the long axis of the tooth.
1) to use the box shape with a relativity flat 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 the
2) to restrict the extension of the external walls to
allow strong cusp and ridge areas to remain with
sufficient dentin support
3) to have a slight rounding of internal line angles
to reduces stress concentration in tooth structure
4) to cap weak cusps and envelope
5) to provide enough thickness of restorative
material to prevent its Fracture under load and
6) to bond the material to tooth structure when
1) Relatively flat floors
2) Box shape
3) Inclusion of weakened tooth structure
4) Preservation of cusps & marginal ridges
5) Rounded internal line angles
6) Adequate thickness of restorative material
7) Reduction of cusps for capping when indicated
STEP3: PRIMARY RETENTION FORM
Primary Retention form is the shape or form of the
conventional preparation that resists displacement
or removal of restoration by tipping or lifting forces.
STEP4: CONVENIENCE FORM.
Convenience form is the shape or form of
preparation that provide for adequate observation,
accessibility and ease of operation in preparing &
restorating the tooth.
STEP 5: REMOVAL OF ANY REMAINING ENAMEL PIT
OR FISSURE, INFECTED DENTIN, OR OLD
RESTORATIVE, IF INDICATED.
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 .
ANY REMAINING OLD RESTORATIVE MATERIAL SHOULD
BE REMOVED IF ANY OF THE FOLLOWING CONDITIONS
ARE PRESENT_- _
1) The old material may affect negatively the esthetic
result of the new restoration.
2) the old material may compromise the amount of
anticipated needed retention.
3) Radiographic evidence indicates caries is Under the
4) The tooth pulp was symptomatic preoperatively or
5) The periphery of the remaining old restorative
material is not intact.
STEP 6: PULP PROTECTION, IF INDICATED
The reason for using traditional liner or bases is to
protect the pulp or to aid pulpal recovery or both.
Other pulpal irritants that affect operative procedure
are: 1) Some ingredients of various materials
2) thermal changes conducted through restorative
3) force transmitted through materiel to the dentin
a) Galvanic shock and most importantly
5) The ingress of noxious products & bacteria through
Liners also may provide
1) A barrier that protects the dentin from noxious
agents from restorative material oral fluids
2) Initial electrical insulation
3) Some thermal protection
Ex- of bases include zinc phosphate, zinc oxide
eugenol calcium hydroxide, polycarboxylate &
STEP 7… SECONDARY RESISTANCE &
The secondary retention and resistance form are of
1) Mechanical preparation feature
Retention locks, Grooves & Coves.
Groove Extensions, Skirts
Beveled Enamel Margins.
Pins, Slots, Steps, Amalgampins..
2) treatments of preparation walls with etching,
priming &adhesive materials.
Enamel Wall Etching
Dentin Treatment .
STEP 8: PROCEDURE FOR FINISHING THE
Finishing the preparation wall is the further
development, when indicated, of a specific Cavo
surface design & degree of smoothness or
roughness that produces the maximum
effectiveness of he restorative material being used.
Objectives: 1) create the best marginal seal possible between
the restorative material and the tooth strcture.
2)afford a smooth marginal junction and
3) provide maximal strength of the tooth & the
restorative material at & near the margin
FEATURES1) the design of the cavosurface angle &
2) The degree of smoothness or roughness of wall.
. Cavosurface angle of 90° produces maximal.
Strength for the amalgam & the tooth. No bevels an
placed at the cavosurface margin.
Beveling can serve useful purpose in tooth
1) It produces a strong enamel margin
2) If permits a marginal seal in slightly undersized.
STEP. 9: FINAL PROCEDURE: CLEANING,
INSPECTING. & SEALING
The usual procedure in cleaning is to free the.
Preparation of visible debris with warm water from
the syringe & then to remove the visible moisture
with a few light surges of air from the air syringe .