kor has mediocre, that is average, rating on mutiple review sites it's claimed to be the best by a few on http://www.realself.com/question/the-effective-teeth-lightening-product-source-answers
What Exactly Makes KOR Whitening Better Than Other Similar Products?
Doctor Answers 3
KOR whitening is a superb product for remarkable whitening.
The KOR line of whitening products is one of the best in the industry. The whitening gel used is essentially the same as the other companies but it is temperature controlled during shipping as to make sure its efficacy does not wane during transport and storage. Also the whitening trays are produced by KOR and have a remarkable fit. The combined technique seems to yield great results especially for the hard to bleach teeth. The cost of a KOR whitening is more than the average whitening because of the above reasons.
Hope this helps.
What Makes KOR Whitening (or Deep Bleaching) Better Than Other Similar Products?
After performing teeth whitening for more than twenty years-whitening is as much art as it is science. There are many ways to whiten your teeth. The best method for you may be different than the best method for someone else.
KoR whitening is good because it has a very low sensitivity rate. It can also get whitening results in cases that typically do not respond well to other types (like Zoom Whitening).
The key is to meet with an experienced cosmetic dentist. Discuss what results you are aiming for, mention how comfortable or sensitive your teeth are, discuss what home care you are willing to do and he can help you select the right type of whitening for you.
I see MANY people less than satisfied with all sorts of whitening results from other offices. The biggest reason is that they typically have one main treatment that they try to make fit for everyone. There is no one size fits all success in teeth whitening. You need to visit with the cosmetic dentist and ask your concerns about what you have read on line.
There is no reason why you shouldn't be able to get nice whitening results in a manner that is most comfortable for you.
What makes KoR Whitening better than other products
KoR is one of the best when it comes to bleaching dark or stained teeth. It is the only product that can predictably whiten tetracycline stained teeth. It lasts much longer than other products. It has has little to no sensitivity. My office has has some great success with KoR. Find a dentist in your area who can provide KoR and see for yourself.