Class V Tooth Preparation for Amalgam RestorationsMARYAM 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 manipulation2. Satisfactory marginal adaptation3. Wider range of application4. Physical characteristics are comparable to enamel and dentin5. Less technique sensitive6. Self sealing7. Biocompatible8. good wear resistance9. Low cost10. Can be completed in 1 dental visit

Disadvantages of Amalgam

1. Less aesthetic2. Extensive preparation to hold an amalgam filling3. Amalgam filling can corrode or tarnish over time, causing

discoloration4. Does not bond to tooth5. No-insulating6. Does not support weakened tooth structure7. Poor tensile strength, thus brittle8. 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!