Pumice stones are good for gnawing on, as are coconut shells and safe wood types.
Degus need lots of wooden ledges/platforms in their cage, make sure there are no high gaps that they could fall through (eg if you're using a Liberta Explorer or similar cage make sure to use the mid section floor so that there's no potential fall from top to bottom)
Give them lots of wooden ledges
Photo from Chinchilla Scientia
They love hammocks too!