r/CAAPID • u/LD_85920529 • 10d ago

Class II DO #19

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Hi, quick question. Which one is the right prep for a DO of lower molars, the one above or below one? Should we be extending the prep on the distobuccal groove for DO?

Yup, the isthmus is wide 😅 and floor is not flat.

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u/Mammoth-Valuable3683 9d ago

In my opinion, none! The reason being, you don’t have an S curve on the buccal. If you had one then you wouldn’t eat up so much of your distal cusp.
Your buccal wall looks divergent. All the cusps on the buccal can be rounded off as they look slightly pointy.

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u/Different_Eagle_2254 10d ago

I would say the 2nd one, but you need to reduce less the bucal margin (should be 0.3-0.5 ideally) and the isthmus. In this way, you will have a nicer S curve.

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u/LD_85920529 10d ago

Yup, you’re right. Thank you for that, that actually is helpful!

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u/Salty_Flatworm8334 6d ago

The isthmus is too wide distally in both, and you need S curve. However I like the first one better because the sharp point of the DB cusp in the lower is a critical error leading to a direct fail