The ingredients of the whiteners you get at the dentist office are the highest concentrations of the active ingredients, which is more efficient in changing the color of the teeth. They work better and will give you a better result, but I will say that over-the-counter whitening products do work. They just take a lot longer. Crest Whitestrips for example work; however, they don’t cover all of the teeth, which is one drawback. On the other hand, some patients come in because they didn’t get the result they wanted from over-the-counter whiteners. What’s good about going to the office is that the dentist can monitor the treatment and make sure it’s done safely.