Definition: Convenience form is defined as that form of cavity preparation that allows adequate observation, accessibility and case of operation in preparing and restoring the cavity.
Modification in tooth preparation for convenience form:
- Occlusal step in classII.
- Labial/lingual access for classIII/classIV.
- Occlusal divergence of cavity walls in cast restorations.
- Contra angling
- Addition of angles to the shank of the instrument.
SUPPORT OF ENAMEL RODS:
- All enamel walls should be supported by sound dentin.
CAVOSURFACE ANGLES FOR DIFFERENT RESTORATIVE MATERIALS
- Amalgam-90 degree cavosurface
- Inlay– beveled cavosurface (20-40 degrees)
- The margins should always should be always located on self-cleansing areas. They should be in smooth curves.
Low speed with tungsten carbide burs are preferred for finishing cavity walls and the margins, as there is lessening of tactile sense and rapid removal of tooth structure with high speed.