I nearly ordered the 20% based on all the reviews complaining about the 35% being "too strong," until I checked with a friend who works at a dental practice. She assured me that the 35% is the way to go, and she was right on.

I experienced no undue sensitivity in my teeth or gums using the 35% and am really pleased with the results! My teeth immediately looked noticeably whiter and brighter.

To all the folks complaining that the gel hurts their gums, there's an easy solution. Do not get it on your gums. If you do get it on your gums, wipe it off. lol

A tiny, tiny amount of the gel is all that is needed in your trays: if you are getting it all over your gums, you have put too much in the trays. If you can't figure out the proper amount to put in the trays, you can at least protect your gum line by coating it with a little bit of vaseline before starting the whitening process.

But, please, get real: overloading the trays -- and not having the common sense to wipe off excess gel that oozes out as a result -- is not legitimate grounds to bash a product that performs as advertised. It is user error, pure and simple.

Five stars, all the way, especially given the reasonable price (as compared to what a dentist charges in-office)!

I purchased 8 tubes (2x 4 Packs) and I am noticing that there are some differences in packaging from what I typically get from the dentist. After trying the gel, it does not seem to have the same consistency or "bubbling on teeth" characteristic of the gel provided by the dentist. --- I do not believe that this is an authentic product. --- I have attached photos... The first photo is the expiration date + Batch number of the syringe in question - The expiration date on the paper that came with the tubes differs from what is actually on the tube. In all subsequent photos, the bottom syringe is what I received from my dentist and the top is what I received - You will also notice the difference of the gel in the actual tube itself.

the packaging plus the syringe both had expiration dates. My 2nd picture was only 30 mins of bleaching. Be sure to use just a little bit so it doesn't rise to your gums. Your gums could turn white but they will go back to pink within 20 mins. I used this product when I got my teeth professionally whitened 14 years ago from the dentist and it still works great!

I have been a Hygienist for over 20 years.. When I got out of school, my instructor turned me on to this Whitener. I used it one time and did not have to whiten my teeth for years. I have tried other products and none of them work for more than two weeks and the the press ons did not last but two days. This whitener does the job. I just happened on it one day on Amazon and have it on my shelf ready to go when needed, Tell everyone not to use an product that is not 22-35% strong. It will not give you the whitener you are looking for. If you have sensitive teeth use the new Colgate Tooth Paste for Sensitive teeth after you clean off the whitener. Just put some on your finger and rub it on the teeth and keep the tube handy. It will immediately stop the sensitivity and is better than other pastes for sensitive teeth. I promise you will be happy with the results and they don't pay me to tell you this.- Pam Oldershaw, RDH

My teeth are tetracycline stained a very dark yellowish brown. I have had Invisalign for almost 2 years in preparation for dental veneers. I never show my teeth in pictures and cover my mouth when I laugh. My dentist recommended Opalescence but warned me there was a slim chance of it working. I am delighted to say it has lightened my teeth! I have gone from a dark yellow to a not quite white! I do not expect my teeth to ever be really white, but what a difference this product has made! For the first time I posted a picture with a real smile! I am amazed. Now, I have found I have to do this often, but it is worth it to have a brighter smile. And it has saved me the cost of the veneers.