PRECLINICAL students : Class II cavity preparation

Here are some tips that help succeed in your cavity preparation

      Know what you want to achieve before you start. 

 

    Draw the outline form with a sharp pencil.

 

       Adopt the ideal position. 

 

     Place matrix band and wedge(s).

 

        Start with small size burs.

 

         Work slowly.

 

        Accomplish the cavity preparation in an orderly sequence .

 

         Use instruments properly (respect the orientation).

 

 Steps of clII cavity preparation

 

 

The Class II cavity preparation is done in two stages: 

1.Occlusal portion.

2.Proximal portion.

Step 1. Begin occlusal segment .

Step 2. Establish outline form.

Step 3. Check occlusal segment .

Step 4. Prepare the proximal box.

Step 5. Define proximal box.

Step 6. Check proximal segment.

( for more details see lectures)

Now let’s look what we will have at the end

 

 A proximal box with the following walls:

• axial wall: parallel to the long axis of the tooth.
 
• gingival seat : perpendicular to the long axis of the tooth.
 
• buccal wall.

• lingual (palatal wall).
 

Retention form

1. In addition to the convergence of the buccal and lingual walls of the occlusal portion, and the dovetail.   The parallelism of Buccal and lingual walls of the box  (proximal portion)  to the corresponding surfaces.
 

2. Flat gingival wall (seat) to prevent dislodgement of the restoration.
 

3. Retentive grooves: using a small fissure bur to make a retentive grooves on axiobuccal and axiolingual line angles( they should be placed in dentine because its resiliency.)
 

Resistance form
 
1. width of the cavity 1/4 of intercuspal distance. 
 
2. cavosurface line angle (90° – 110°).
 
3. Axiopulpal line angle is beveled. To eliminate stress concentration on the restoration.
 
4. Gingival cavosurface line angle is beveled. To remove the unsupported enamel.
 
5. rounded internal line angles.
 
6. Removal of the unsupported enamel.

Evaluate yourself (cl II cavity prep on molars)

Feature	Outline form of the occlusal portion		B L Extension
Proper status	Smooth sweeping curves	Includes pits and fissures	- 1/4 the inter-cuspal distance & centeralized - Extended within 1 mm from the inter-cuspal distance

  

Proximal box	Gingival seat	Direction of walls                 Buccal and lingual walls
- Free of contact and 90º with imaginary tangent.	- Extended 0.5 to 1 mm above the inter-proximal gingiva (supra-gingival).	Occlusal portion - Parallel to the corresponding external surfaces	Isthmus portion -Parallel to the corresponding external surfaces	Proximal portion - Parallel to the corresponding external surfaces

  

Pulpal floor	Gingival Floor And axial wall	Cavity refinement And adjacent  tooth preservation
- Pulpal floor  depth :1.5 – 2mm   - Smooth                     -Flat.	Gingival wall depth  is  2- 2.5mm. - Smooth                      -Parallel to the gingival margin.	- Defined line angles and  walls - Rounded Axio-pulpal line angle. - Adjacent tooth preserved intact. - Adjacent soft tissues remained intact.

Transcript for class II cavity preparation ,Columbia university.
Class II cavity preparation ,characterestics of an ideal class II