The application of the strips couldn't be simpler. Apply the shorter strip first to the lower teeth, press on the front for 2-3 seconds, fold over the remainder of the strip behind the teeth for 2-3 seconds, and repeat for the top teeth. Sensitivity wise, I only had discomfort during the last five minutes of the application on day 1. Other than that I did have very slight sensitivity for about 5 days after using the pack, but I was expecting that to happen.
I noticed a visible difference after using the strips for 10 days, and so did my mum and my partner - success! Below is a before and after photo, just look at the change for yourself.
These photos haven't been edited in any way and are shown without me wearing makeup. They have also been taken in similar lighting, as to not give a bias view of my teeth. So yes, those are horrible close ups of my mouth, complete with peach fuzz and a scar from when I was younger, deal with it. It happened when I fell off a chair and bit my skin, ouch. Clever Frankie!
So anyway back on topic, you can clearly see just how much of a change the Crest whitening strips have made, and I couldn't be happier. I don't have the smallest teeth in the world, but at least now it means I can continue smiling without worrying about how they look.
I purchased the Crest 3D Professional Effects whitening strips on eBay from this seller for £27.30.