quick DA question

[Lopyswine]

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During an endodontic procedure on #21, clinical symptoms lead the dentist to suspect the presence of a second pulp canal. Which direction is MOST likely the location for the suspected canal?
a. Facial
b. Distal
c. Lingual
d. Mesial

Ok the answer is LINGUAL. But I don't know why. Can someone explain this to me?

We don't start endo until the fall, however we are supposed to take boards in August.

thanks.


ok,
I have another question about mandibular 1st premolars. Does the mesiolingual developmental groove extend on a proximal surface?

Apparently yes, according to the released papers. However, we never learned this to be the case. We were taught it was lingual. Is the location of the groove considered on the mesial surface of the crown because it is past a line angle? It doesn't appear so to me.

 

[mrswinidm]

Hello,
yes, the first question is lingual. There might be more scientific explanation embryologically but it is a rule for DA. Whenever there are two canals in a single root, it is always on the facial lingual direction and most likely the lingual is the extra one. It is also true for other teeth which means they may change the tooth #.
The second question is a tricky one. I think the answer totally depending on the wording of the question and the given answer choices. That's my two cents.