Dr. Manjiri Honap
Department of Conservative Dentistry
and Endodontics
FUNDAMENTALS OF TOOTH
PREPARATION

FLOWCHART
• Recap of initial stage of tooth
preparation
• Final stage of tooth
preparation
• Modifications of cavity
preparation for amalgam

INITIAL TOOTH PREPARATION STAGE
• STEP 1: Outline Form and Initial depth
• STEP 2: Primary Resistance Form
• STEP 3: Primary Retention Form
• STEP 4: Convenience Form

OUTLINE FORM AND INITIAL DEPTH
• To determine and develop the outline form/ design while establishing the initial
depth.
• Extend the preparation to maintain sound tooth structure.
• Initial depth should be 0.2 -0.8 mm from dentinoenamel junction.
• Cuspal strength and marginal ridge strength should be preserved.
• Distance between two defects in tooth preparation is less than 0.5mm then
both the preparation of the tooth should be connected.
• Enemeloplasty : It involves removal of shallow enamel developmental fissure
or pit to create smooth ,saucer shaped surface that is self cleansing or easily
cleaned.

PRIMARY RESISTANCE FORM
• It is that form/shape of tooth preparation that enables the restoration to
withstand the masticatory forces without fracture.
• The pulpal floors should be relatively flat.
• Box like shape preparation
• Rounded internal line angles so that no dislodgement or fracture of
restoration.
• Adequate thickness of restorative material.
• Preserving the cuspal and marginal strength
• Consideration for cusp capping

PRIMARY RETENTION FORM
• tooth walls that converge occlusally
• The cavosurface angle - 90 degrees
• Dove tail preparation

CONVENIENCE FORM
• Shape or form of the preparation that provides for adequate observation,
accessibility, and ease of operation in preparing and restoring the tooth.

STAGES OF TOOTH PREPARATION
• FINAL STAGE OF TOOTH PREPARATION :
Step 5: Removal of any remaining infected dentin and/or old restorative
material, 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 procedures: cleaning, inspecting, sealing

STEP 5: REMOVAL OF ANY REMAINING
INFECTED DENTIN
• Elimination of any infected carious tooth structure or faulty restorative
material left in tooth after initial preparation
• Spoon excavators/carbide burs

STEP 6: PULP PROTECTION
Pulp irritation etiology
• Heat generated by rotary instruments
• Some ingredients in various materials
• Thermal changes conducted through restorative materials
• Forces transmitted through materials, to dentin
• Galvanic shock

SECONDARY RESISTANCE AND RETENTION
FORM
Mechanical features
• Retention grooves,
• Pin retained amalgam
• Internal boxes, Skirts

AMALGA PINS
• Vertical posts of amalgam anchored in dentin
• Increase resistance and retention form

STEP 8: PROCEDURES FOR FINISHING THE
EXTERNAL WALLS
• Further development of degree of surface smoothness or roughness
that produces them max effects of a restorative material
FEATURES:
Design of the cavosurface angle
• 90° cavosurface angle for amalgam.

STEP 9: CLEANING , INSPECTING,
DESENSITIZING
• To free the prep of visible debris with water from the Syringe & then to
remove the visible moisture with a light burst of air from the Syringe
• Desensitizers:
• ◦ 5% Glutaraldehyde
• ◦ 35% 2-hydroxymethylmethacrylate

MODIFICATIONS OF AMALGAM PREPARATION
• Pre-requisites:
• ◦ 90º junction b/n amalgam & tooth
• ◦ Mech. Retention form [occlusally convergent prepartion]
• ◦ Adequate thickness of Amalgam

BOX ONLY
◦ For posterior tooth where proximal
surface require restoration but occlusal
surface is normal.
◦ No occlusal steps
◦ More conservative

TUNNEL PREPARATION
• Joins an occlusal lesion with proximal lesion by
means of prepared tunnel under the involved
marginal ridge.
• Marginal ridge intact.

THANK YOU