Well, they are tender. If you got only partial damage, you could cut off the mushy leaves. If you got full out damage, I would dig them up and cut the growth off about 1 cm from the tuber. You'll have to start all over, but they should grow.

I disagree with the need to dig them up -- what would that do but set them back.

Frost isn't a big deal at all - if the top dies off, more will grow. In essence, it is the equivalent of a hard pinch or cutback at this time.

When I worked at the garden center, the first crop of Dutch dahlias would be cut completely back when too big and floppy, and would regrow and be ready to put out for sale in about 4 weeks.

Personally, I think cutting back or pinching helps them to be a little less tall and floppy. Depends on the kind, of course, some of the tall dinnerplate types won't throw many side shoots no matter what you do.

My Dahlia's made it...the frost was a heavy one, and it amazed me that no damage was done to any of the plants...thank you both for your response...I deeply appreciate it...