If the nose has a hole in it, if part of the nose is missing, or if the outside of the nose is cut, then the Bechor (firstborn animal) is disqualified. All of this refers to the outside of the nose. If the blemishes are on the inside of the nose and they are not visible, then the animal is still valid. If the outer part of the lip has a hole in it, if part of the lip is missing, or if part of the lip is cut, even though no part is missing, the Bechor is disqualified. As we said previously, in this case as well, if the blemishes were not visible from the outside, then the animal remains valid.
If pieces from the front teeth are missing, or if the front teeth are worn out, that they don't look like they don't stick out of the animal's mouth anymore, like they usually do, or if the back teeth are uprooted and completely missing, the Bechor is disqualified. In all cases of teeth, we say that they are visible. When the animal opens its mouth, they can be easily seen, so they are all considered external blemishes. They are not part of the hidden part of the body. Here, for the back teeth, we are saying that if they are uprooted, they are considered to be a Mum (blemishes), but if they are missing a piece or are worn down, the Bechor is still valid because if they are not fully out, they are not visible since they are in the back of the animal's mouth. We don't check the animal's teeth for blemishes from the back teeth inward, farther back into the mouth, toward the inside of the animal's body. We don't check the molars themselves either. Those back teeth all the way inside the mouth are considered hidden parts of the body and would not disqualify the Bechor. So even if the Bechor is missing the molars, they would still be valid according to Rabbi Chanina ben Antigonus. He argues on the opinion of Tanna Kama (first tanna).