Whitening pens are better and safer (in my opinion).
The main reason that I like Whitening Pens over Whitening Trays is that I don’t like the idea of those chemicals sitting against the gum tissue.
With trays, the harsh peroxide sits right up against your gums. I don’t like that.
With Whitening Pens you have more control and you can just target the tooth, which is the part you really want to whiten, and leave the gums alone.
For these Whitening Pens which you can see here : I suggest using coupon code a-per10 because you will get free shipping and a free tube of perio-therapy toothpaste.
You can find more coupons here.