Class V Tooth

Preparation for

Amalgam Restorations

MARYAM ARBAB

Tooth Preparation

It is defined as the mechanical alteration of a tooth to receive a

restorative material, which will return the tooth to proper anatomical

form, function and esthetics.

The procedure of preparing the tooth by removal of defective or

friable tooth structure.

Any remaining infected or friable tooth structure may result in further

caries progression, sensitivity or pain or fracture of the tooth and/or restoration.

Classification for restoration

Class V restorations

Class V restorations ,by definition, include

the gingival one third (i.e., cervical area) of

the facial and lingual surface of the tooth

crown

Amalgam

Amalgam is an alloy in which mercury occurs as a main

component.

Dental Amalgam is an alloy of mercury with silver, tin and varying

amounts of copper, zinc and other minor components.

Advantages of amalgam

1. Ease of manipulation

2. Satisfactory marginal adaptation

3. Wider range of application

4. Physical characteristics are comparable to enamel and dentin

5. Less technique sensitive

6. Self sealing

7. Biocompatible

8. good wear resistance

9. Low cost

10. Can be completed in 1 dental visit

Disadvantages of Amalgam

1. Less aesthetic

2. Extensive preparation to hold an amalgam filling

3. Amalgam filling can corrode or tarnish over time, causing

discoloration

4. Does not bond to tooth

5. No-insulating

6. Does not support weakened tooth structure

7. Poor tensile strength, thus brittle

8. Results in galvanic current with gold restorations or even same

restoration with non-uniform condensation

Contraindications of Amalgam

When aesthetics is the prime concern

Small to moderate class I and II preparations

Class V Tooth

Preparation for

Amalgam Restorations

Principles of tooth preparation

There are 2 steps

Initial tooth preparation

Outline form

Primary resistance form

Primary retention form

Convenience form

Final tooth preparation

Management of remaining caries

Secondary resistance and retention form

Pulp protection, if required

Finishing of enamel margins

Final inspection of preparation

Initial Tooth Preparation

The same general principles for tooth

preparation apply for all other tooth

locations .

Using an inverted cone bur of suitable size,

enter the carious lesion (or existing

restoration) to a limited initial axial depth of

0.5 mm inside the DEJ .

The depth is usually (1-1.25mm) total axial depth, depending on the

incisogingival/occlusogingival location.

The enamel is considerably thicker occlusally and incisally than

cervically.

Extend the preparation incisally,gingivally,

mesially and distally until the cavosurface

margins are positioned in sound tooth

structure to establish an initial axial depth of 0.5 mm inside the DEJ( if on the root

surface, the axial depth is 0.75mm) .

The axial wall should be in sound dentin,

unless there is remaining infected caries or

old restorative material .

Preparation of the axial wall depth 0.5 mm inside the DEJ results in a

uniform depth for the entire preparation .

A depth of 0.5 mm inside the DEJ will permit placement of necessary

retention grooves without undermining the enamel .

Final Tooth Preparation

Final tooth preparation involves removal of any remaining infected

dentin, pulp protection, retention form, finishing external walls, and

final procedures of cleaning, inspecting, and desensitizing.

Remove any remaining infected axial wall dentin with a No. 2 or

No. 4 bur.

As the mesial, distal, gingival, and incisal walls of the tooth

preparation are perpendicular to the external tooth surface, they usually diverge facially.

Consequently, this form provides no inherent retention, and retention

form must be provided .

Use a No.1/4 bur to prepare two retention grooves, one along the

incisoaxial line angle and the other along the gingivoaxial line angle.

The depth of the grooves should be approximately 0.25 mm, which is

half the diameter of the bur.

Finally, clean the preparation using air-water spray and evacuation.

use the air syringe to remove visible moisture

(do not desiccate tooth structure), and

inspect the preparation for completeness.

If the preparation is complete, either apply :

desensitizer (for a non-bonded

restoration)

or

begin the bonding procedures (for a

bonded restoration).

Condensation and Carving

Using the amalgam carrier, insert the mixed amalgam into the

preparation in small increments and condense it into the retention

areas first with an appropriately sized condenser.

Next, condense the amalgam against the mesial and distal walls of

the preparation

Finally, provide sufficient bulk in the central portion to allow for

carving the correct contour .

Carving may begin immediately after insertion of the amalgam

the side of the carving instrument should always rest on unprepared

tooth surface adjacent to the prepared cavosurface margin. This

prevents overcarving.

Begin the carving procedure by removing excess amalgam to

expose the incisal (or occlusal) margin.

Continue removing excess to expose the mesial and distal margins.

Finally, carve away excess at the gingival margin

Finishing and Polishing

If carving procedures were performed correctly, no finishing of the

restoration should be required.

However ,additional finishing and polishing of amalgam restorations

may be necessary to correct a marginal discrepancy or improve

the contour.

Care is required when using stones or any rotating cutting instruments

on margins positioned below the cementoenamel junction (CEJ).

This is because of the possibility of removing cementum or notching the

tooth structure gingival to the margin or both

References

• Art and Science of

Operative dentistry

• Textbook of Operative

Dentistry

• Internet

Questions

Thank You!