If you glance at your deed, you will notice that your name appears as "grantee", but the bank is never mentioned. That means that when you pay your mortgage in full it is not necessary to update your deed.
What does need to be done is to have a Satisfaction of Mortgage document recorded with the Register of Deeds office. Financial institutions are required to record such a document within a specified timeframe. If you receive a Satisfaction of Mortgage endorsed by a Register of Deeds with a time, date and document number, nothing further needs to be done. If you have not received the endorsed satisfaction, you should check with your lender to be certain they processed the appropriate paperwork.