Dentist is buying all assets of another dentist's practice. Seller has very small balance @ another bank, with a blanket UCC filed on A/R/, intangibles, equipment, etc. We are taking all A/R & equipment of new dentist.
Seller paid off their $100 balance with their bank, but we don't have a copy of UCC termination (likely hasn't happened yet). We are filing the new UCC on borrower today. Do we need to make sure that termination of seller's lien is filed? If we have a lien on all the stuff owned by our borrower, is that sufficient?

I would check with your legal counsel. Maybe you do have a first lien but at what legal costs might you have to pay to prove it? The only real way to be sure of your first lien is with a release of that prior lien. Too much ambiguity for me. What if they didn't pay it off? What if the UCC secures other loans?

Texas Business and Commerce Code:

9.509(d) A person may file an amendment other than an amendment that adds collateral covered by a financing statement or an amendment that adds a debtor to a financing statement only if:

(1) the secured party of record authorizes the filing;

or(2) the amendment is a termination statement for a financing statement as to which the secured party of record has failed to file or send a termination statement as required by Section 9.513(a) or (c), the debtor authorizes the filing, and the termination statement indicates that the debtor authorized it to be filed.

You need to refer to 9.513 for the specifics that would apply to your transaction. Legal counsel is always a good suggestion when it comes to perfecting security interests. It is not something you want to screw up.