If their teeth are getting long you should get something like wood, be careful what type as some are poisonous to degus, but get some degu friendly wood for them to chew on. If the teeth are already too long for them to eat or chew take them to the vet and he/she will clip them.
Haven't had to have teeth removed yet on any of my degus – just spurs so far though my vet suggested that, if it gets too bad, tooth removal is an option. I have heard that it is very tricky to do on a degu because their jaws are so small. If no one can help you here, I suggest that you check out the "Degu and Chinchilla World" forum. There are many experienced degu owners on that forum.