Although I have been using this product for awhile and it has proven to be effective I am a little annoyed that I cannot buy the pen on it's own. I have looked in several drugstores and pharmacies to only find that you have to purchase the set. The only reason it bothers me is because the toothbrush sold with the set is one of the cheaper toothbrushes that can sometimes go on sale for a dollar. The set itself is not cheap and I feel like I rather just pay for the pen and buy my own toothbrush. Despite this flaw, I had been struggling with super sensitive teeth and nothing seemed to help until my dentist recommended this. It has been helping thus far and I do rotate using it with my other toothpastes.