A common mistake is to shift the location of the Oblique Ridge. The problem behind this is that they place the depth groove directly on top of the oblique ridge. The result is that they will make the distolingual cusp bigger and will shift the oblique ridge more to the mesial. The correct way of placements is rather a little distal from the groove of the oblique ridge. The rationale behind this is that the groove belongs to the distolingual cusp alone and the entire bulk of the oblique ridge belongs to the mesiolingual cusp. It is not the same as any normal groove wherein two cusps meet at the same groove.

When everything is done correctly, there must be an immediate step from the oblique ridge to the distolingual cusp.

ERRORS

Placing the bur directly on top of groove as if the bur fits snugly within it is NOT a good placement. You will definitely take a part of the mesiolingual cusp and incorporate it to the distolingual cusp making it a whole lot bigger.

PREVENTION

When placing the depth groove, it should be located distal to the groove with only the mesial side of the bur touching the groove.

The highest point of the oblique ridge must be also placed with a depth groove to mark its location.