It isn't unusual to have an A/F sensor go bad at 80k. Sometimes it is the heater circuit which is unrepairable. Cleaning the sensor will do no good. I suggest you chuck the old ones. Your new sensors will likely outlast your car. Even if they don't, do you really want to go to the trouble of replacing a sensor with a used one which may or may not work OR may or may not last more than a few thousand miles?
You can do a continuity check on your old sensors to determine if the heater circuits are fried.
PS I hope you didn't pay $185 for your denso sensors. You can get them at Amazon for $125.