I currently have my custom trays and am looking for refill gel. I leaned about Opalescence Boost. Can this be purchased by the home consumer or is it just used and applied at a dentist? If it can be used by a home consumer, is it safe (and not overly powerful to apply at home) as with all the other Opalescense products 10, 20, 35% etc.? What is the difference between this and the 10, 20, 35% products they also make? Thank you!