How to remove urine smell from concrete?

Please HELP!!! Due to dogs, the urine smell in the concrete in out basement will knock you over. It is so bad you can smell it all through out our house. What is the best way to get the urine smell out of concrete? I saw a remodeling show years ago, where they put something on the concrete, covered the whole floor with plastic for something like 24-48 hours, before they sealed it. It was suppose to be the best way to get the smell out, but of course I don't remember.
When you do seal it, does it really keep out any further urine smells or should we do more than just sealing it?
Any and all advice is very welcome. Thank you in advance.
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