These are the ones that you would get an impression taken at your dental office, usually alginate impressions, but it can vary the type of impression regardless they are custom fabricated. So they look like clear aligners and they fit perfectly to your teeth to your dentition. They are usually moderately priced, but they can last for a very long time, maybe even forever. If you take care of them and then, whenever you want to whiten, you purchase the whitening product to go into them. This whitening product is available to purchase at your dental office. 

Pros:

• They are known to be the least reported in causing sensitivity generally because they fit your teeth perfectly, and it's less likely that the whitening product will touch your gums

• lots of custom whitening materials contain the ingredients that help reduce tooth sensitivity

• you can make your own routine at home and take them on and off as needed

Cons:

• They can be more expensive than strips and less convenient because you can't just go to the store to buy them. You need to have your dental trays fitted and fabricated by a dental professional

Pros:

• this will be the quickest and you will be in and out in one dental appointment, sometimes two depending on the treatment but you'll be in and out with the whitening results you want.

Cons:

• this is generally the most expensive option and it commonly has the most sensitivity upon use in office whitening solutions are much stronger than the at-home products because they work fast.