Meanwhile, the gerbil cannot gnaw and the remaining teeth may grow too long and require trimming. This is not as difficult as it sounds. The first time it happens, you may need a vet to show you what to do, but after that you should be able to trim the teeth yourself. An excellent test for teeth problems is to offer your gerbil a piece of paper. It will immediately try to chew it.
All gerbils do.
If the teeth are able to cut the paper, they are fine. However, if they can't, then there is a problem. The odd scab, especially around the base of the tail, probably indicates fighting has broken out. This may have been a trivial argument over an extra-large sunflower seed. But it may also be a warning of worse to come.