COMPOSITE - ITS RATIONALE AS A 'BLOCK-OUT' MATERIAL IN CAST GOLD PREPARATIONS

1. The outline can be made more ideal and conservative by controlling the depth of the cavity preparation.

2. Composite used as a 'block-out' material enables the operator to control the depth of the pulpal and axial walls.

3. The draw and flare of a preparation of ideal depth will result in a preparation which conserves tooth structure.

4. Composite 'block-out' allows the operator to prepare very smooth, flat pulpal and axial walls with sharp proximal line angles and point angles.

5. The 'block-out' material enables the operator to prepare and visualize a more ideal preparation from both the intracoronal and extracoronal aspects.

6. The composite permits a smoother preparation to be cut, thus resulting in an impression of finer detail which generally allows for a smoother, sharper die.

7. A cavity preparation of uniform depth results in a wax pattern thickness that is less affected by the shrinkage of gold on cooling.

8. A smooth, uniform preparation results in a smooth uniform die that allows easier removal of the wax pattern without distortion, a common cause of poorly fitting castings.

9. Smooth internal surfaces of a casting permits any tiny bubbles or fins of gold to be more easily spotted and removed prior to cementation. This can ensure a more precise fit of the casting.

10. The removal of composite 'block-out' prior to cementation can assist in a more precise fitting casting by elimination of potential interference on the pulpal or occlusal surface. This also creates a secondary die space relief.

11. Composite as a 'block-out' material is easier to smooth with rotary and hand instruments than other commonly used 'block-out' materials.

12. The use of a 'block-out' material saves gold by permitting the operator instead of the laboratory Techniqueian to control the depth of the preparation both axially and pulpally.

13. Composite 'block-out', as a teaching aid, permits students to reprepare a cavity preparation, if it is overcut pulpally and axially.

14. A composite 'block-out', with calcium hydroxide on the axial and pulpal surfaces, appears clinically to result in less sensitive teeth during the period of temporization.