Since "teething" is a normal and natural behavior,..it's something you
cannot avoit...but you can help it by redirecting the behavior towards
a toy or something he is allowed to chew.
Everytime the dog is chewing your stuff...ask him to stop...and as
soon as it leaves it...say: Good Boy! and reward with a treat or a toy
to chew.
This is called re-directing....you can see a ncie little article in my
blog: http://goodpuppy.blogspot.com/

I hope this helps!

rei.