I want to see what you think about this, Aldbigbang. I am going to change your 'OF'S' to "in" as in added into... I am also shortening the sentence a great deal, because repeating long phrases unnecessarily, can make people think there is more being said than there is (when you repeat long phrases unnecessarily.) :)
The results indicated that ________ can be an effective active component IN whitening toothpaste and varying THE amount of _________ showed a significant difference on its effectiveness.