It seems Toothpaste is a decent disk cleaning abrasive for removing minor scratches that may be preventing dvd/cd rom drives from reading it correctly.
I had two DVD disks about 4 years old that were scratched enough that I could only copy half of the 4.7GB off for both of them. About to throw them both out in frustration, I had the sudden idea of cleaning the disks with toothpaste as I have heard before, but had never tried it myself. Using a small cotton bud and a small dab of toothpaste (normal, no extra strength or special versions) I cleaned the disk in a inside to outside motion. After cleaning and the removal of the toothpaste (using just a small cotton bud with water), I dried it, stuck it in my machine and it read. No errors :-)
I definitely won’t be using this disk again but i was able to extract the data and put it onto a new disk. All fixed.