The lower molar has 5 major cusps. The smallest among them is the distal cusp. A good way of dealing with the lower molar occlusal reduction is to disregard the distal cusp.

ERRORS

The operator tried to preserve the distal cusp. The resulting problem would be two things: (1) the distobuccal cusp will be compromised because the operator will try to recreate the distal cusp, eating the distobuccal cusp along the process and (2) eventually, there will be two high cusps in the area that will create an inadequate interocclusal clearance.

PREVENTION

It’s okay if it will be totally obliterated along the way. What you will be left with is that the remaining 4 major cusps are maintained.

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Imagine placing a depth groove here and with the tapering of the distal axial wall, the distal cusp will surely be gone afterwards. This problem is very common to see to some who are starting their practice its because they have this mindset to “save” every structure that the tooth has had. But actually, you really have to weigh some important features at hand: it’s either maintaining the structures or establishing a good interocclusal clearance. Well, the answer to that is interocclusal clearance!

In the first place, the reason why we are preparing for crowns is to create space and clearance, right? So we could sacrifice the distal cusp to make way for other more important features.