The important here is to preserve the location of the structures here. The cingulum and the lingual should still be evident.

Step by Step

Step 1: Lingual Fossa Reduction

With the use of a football or egg-shaped bur, mark the lingual ridge with a depth groove. Then reduce the mesial and distal fossa. To check whether you made the right amount of reduction, reduce the mesial (or distal) half first then measure. If it is right, replicate the reduction on the other half.

Step 2: Lingual Wall Reduction

This area takes a lot of bur angulation to keep in mind of, and on top of that to maintain the angulation, always keep a firm finger rest. The angulation of the lingual wall should be in match with the gingival portion of the labial surface. So when you look it up from the mesial point of view, both of these walls should have an equal taper and have no undercuts.

To do this nicely, align your bur to the gingival portion of the labial surface and then bring it over to the lingual side. After that, tilt it a little bit towards the labial. When you are happy with the angulation, you may now start reducing this area. Extend as far as you can near the proximal area.