Cavity Preparation Design

Direct Tooth Colored

Restoration

Epita Sarah Pane

Conservative Department

2007

Direct Restorative Materials

PLASTIC =

readily deformable when first mixed,

and are placed and are placed into a prepared cavity

in a tooth while still in this condition.

General Principles

Outline Form

Retention and Resistance Form

Convenience Form

Removal of Carious Dentin Removal of Carious Dentin

Biologic Form

Finishing of Enamel Walls

Preparation Debridement

Retention and Resistance Form

Acid conditioning of surface enamelRetentive cavity preparation with internal Retentive cavity preparation with internal

detailsPhysico-chemical adhesion to some

components of the tooth structurePins and postsCombination of 1 to 4

Types of retention

Chemical = Glass Ionomer Micromechanical = composite resin Micromechanical = composite resin Macromechanical / mechanical = amalgam

GIC : Adhesion is dictated by:

Use of high powder:liquid ratio Use of high powder:liquid ratio Conditioning to remove smear layer Maintenance of the water balance during setting

MICROMECHANICAL ADHESION

BETWEEN COMPOSITE RESIN AND

ENAMEL IS

The strongest adhesion The strongest adhesion

available

Dependent upon the strength

of surrounding enamel

Guidelines No prescribed cavity form required Important:

the best and the strongest bond is obtained between composite resin andobtained between composite resin and

enamel, it is desirable to maintain anenamel margin around the full

circumferential of the lesion.

Basic requirements:

1. An internal cavity form should be rounded to avoid incorporation of stress point

2. Bevel enamel margins to enhance the

seal between C.R and enamel

3. Where esthetic is important enlarge the bevel to provide a smooth transition of C,R. to the tooth structure

4. Do not place a bevel on occlusal margins to avoid

allowing thin sections of the restoration to come

under occlusal load

5. Do not place a bevel on the gingival margin

of a proximal box if it is in dentin

6. Access to a proximal lesion on an anterior tooth should be from

the lingual to preserve the facial tooth structure and maintain

esthetic.

Bevel

Partial Bevel

Long Bevel

Hollow ground Bevel

Scalloping the margins Scalloping the margins

Skirting

Hollow ground bevel

Long bevel

Partial bevel

Skirting

bevel

Scalloping the margin

Preparation DesignClas I

Clas II

Clas IIIClas III

Clas IV

Class V

Class I and and

Class II

Differences amalgam direct tooth colored

materials

The intercuspal width of preparation of direct tooth colored materials may be as direct tooth colored materials may be as small as 1/5 the intercuspal distance

In preparations for direct tooth colored materials, internal line and point angles may are extremely rounded, especially if they are in enamel

If anatomically, cariogenically, and mechanically possible, surrounding walls and/or pulpal and gingival floors could all be in enamel in preparations for dtcm.be in enamel in preparations for dtcm.

Surrounding walls of floors having dentinal components may accommodate dentinal grooves as reciprocating and auxiliary means of retention.

In dtcm, undermined enamel may be retained.

Unlike preparation of amalgam, these preparations do not require a reverse preparations do not require a reverse curve at the occluso-proximal juncture.

For thinned cuspal elements circumferential skirting is indicated.

Dentinal preparation for dtcm should always be mortise shaped

Peripheral portions of enamel walls to be etched should be beveled.

Soucer-shaped Class II preparations for dtcm could be used if the lesion is continued to could be used if the lesion is continued to enamel with minimal, forward dentinal involvement at its center.

When restoring with dtcm, the preparations should allow for contact area to remain totally or partially in tooth structure.

Class III Design 1 (conventional labial

approach)

Indications: Proximal surface lesion in anterior teeth, except the distal of

cuspid, where decay is extending more labially than lingually, and involving part of the labial embrasure.

Class III in labio-verted rotated teeth. Direct loading of the restorations cannot be avoided. Distal part of the cuspid, if part of the contact area remains in

tooth structure

General shaped: triangular with

rounded corners

Location of margin:

Design 2

(conventional

lingual

approach)

Indications: Indications: Preferred for all

Class III lesions General shaped

Design 3 ( without labial & lingual

approach)

Indications: The entire labial or lingual wall is lost during

access or for cariogenic reasonsaccess or for cariogenic reasons The incisal angle is approached too closely by the

incisal margin Distal of cuspids The remaining labial or lingual wall should be bulky

enough to accommodate a retentive groove

General shaped & internal anatomy

Design 4 ( both labial & lingual

approach)

Indications: Decay extend labially and lingually brings the Decay extend labially and lingually brings the

margins to corresponding embrasures There has been partial and complete loss of labial

an d/or lingual walls There are pronounced labial and/or lingual

embrasures facilitating two-way access There is a diastema or spacing between teeth

Design 5 ( saucer shaped)

Indications: Conditioned enamel and sometimes treated dentin

will be the principle means of retentionwill be the principle means of retention Caries control measure, preparatory to permanent

restorative treatment Deciduous or young permanent teeth Rampant lesion with extensive surface

decalcification

General shaped and internal anatomy

Class IV Design 1 (conventional design)

Indications: After the removal of diseased tooth structure, bulky

labial and lingual walls should connect with a labial and lingual walls should connect with a gingival floor

Incisal angle involvement in the preparation is very limited, almost to the corner only

Teeth have normal occlusal contact during centric and excursive relation of the mandible

Thick labio-lingually

General shaped and internal anatomy

Design 2 (labial and/or lingual approach

conventional design)

Indications: Incisal angle loss is substantial Incisal angle loss is substantial The entire labial and/or lingual walls are lost The labial and/or lingual walls are formed

completely of unsupported enamel The restoration will be directly loaded Not to be used in the distal of cuspids

General shaped and internal anatomy

Design 3 (unilateral angle involvement)

Indications: The defect involves more of the incisal ridge than

the proximal surfacethe proximal surface Young teeth with large pulp chambers Not indicated for distal of cuspids if contact in tooth

structure is lost

General shaped and internal anatomy

Design 4 ( bilateral angle involvement)

Indications: All indications for design 3 The incisal defect is larger than the proximal defect The incisal defect is larger than the proximal defect

General shape and location of margin (A, B, C)

General shaped and internal anatomy

Class VDESIGN 1 (MORTISE SHAPED

PREPARATION)

Indication This is a conventional indicated design This is a conventional indicated design

General shape

DESIGN 2 (NON-MORTISE SAUCER

SHAPED)

Indications: It is used for erosion and abrasion lesions where

the teeth are very sensitive and cavity preparation may increase that sensitivity

General shaped and location of margin

Instrumentation

1. Gross removal2. Removal of irreparable carious dentin3. Preliminary shaping3. Preliminary shaping4. Retention grooves formulation5. Final shaping6. Cavity finishing