35% with PF Gel Syringes Teeth Whitening - (8 Syringes) Refill Kit Carbamide Peroxide. Made by Ultradent, in Melon Flavor. Tooth Whitening Refill Syringes 5404-4

Bought this to try as it was a little cheaper than my Dentists of the same %strength. This worked better but was also a tiny bit irritating to my gums. Irritation was not bad at all as was gone between middle and end of next day. Irritation was only felt, gums a little deeper pink but nothing more. Will buy again when I run out. Note: I don’t bleach often, just every couple of months.

Very easy to apply with pre-fabricated dental trays from my dentist office. Same product my dentist provided but cheaper. The product works as advertised whitening my teeth. Use once a month.

Couldn’t really tell a difference. I didn’t really stick with it. But my younger sister tried it and her teeth look stunningly white. And she’s a smoker. I was shocked. They really do look stunning. We’re both in our 50’s.

Been using this Opalescence 35% gel twice a week overnight in my Invisalign trays and—wow—this stuff works. As a card-carrying coffee addict, my teeth were starting to look a little too espresso-forward, but now they’re gleaming like I’ve never touched a latte. That said, 35% is no joke. Leaving it on for 10–12 hours definitely brings the brightness, but also brings the zing—hello sensitive teeth and slightly angry gums for a couple days. It’s like my mouth goes through a bit of a whitening boot camp, but hey, no pain, no pearly gain? Melon flavor is... interesting. Not bad, just kind of a weird moment when your mouth tastes like fruit salad while your teeth are turning snow-white. Would I do it again? Yep. Already did. Just maybe not right before a big bowl of ice cream.

Love this for my trays. Easy to use and is the same that my dentist had for twice the price.I usually whiten after a dental cleaning, really whitens well. It is pretty strong so if you leave it on too long, your gums will start to tingle and can burn some.Highly recommend for real results

I love this whitening gel! I've been using it for some time, and I frequently get compliments about my white teeth. I have fitted trays that I got from a dentist years ago, which helps greatly, but the gel is highly effective and you don't have to wear the trays very long -- I can pop in my trays, go out for a walk, and be done by the time I return. (Personally, I never liked the overnight gels -- I prefer stronger whitening products that you wear briefly during the day.) In addition to being effective, the gel does not cause the gum sensitivity that I have experienced with other products (unless you leave your trays in WAY too long, of course). I will definitely continue to purchase this product!

I literally never write Amazon reviews but I was so impressed that I just had to! This product works! I only used it two times and it was so much whiter. I’ve tried crest white strips, and so many other products for whitening, spent so much money on it and this is the first thing that really works and works so fast! I love the 35 percent. I just put a dot in each tooth in my Invisalign retainer tray and leave it on for an hour, and it’s instantly whiter and I haven’t had sensitivity issues with it. I am also using their sensitivity toothpaste so that may help too but yeah it’s amazing!!!!

It does work somewhat as far as whitening but as soon as I put it on with my Invisalign there was a foaming crackling sound and it was super uncomfortable and I wanted to take off the retainer straight away but I barreled through. Taking it off 25 min later I see my gums are white, swollen, and irritated. Probably won't get this strength again !