I tend to write long reviews, so here's a quick list of positives and negatives of the whitening pen. This may also answer some questions you have about using the whitening pen:

Positives:
-Actually whitened my teeth!
-No bad taste
-No irritation/pain
-Easy to apply
-Nice packaging

Negatives:
-Did not last as long as the box said it would (lasted 1.5 weeks instead of the 30 usages the box promised)
-You have completely to dry off your teeth and then paint on the solution on each individual tooth (I personally didn't mind this. It just took a little while to do)
-If you paint over wet teeth, it will ruin the brush
-The solution easily clumps up in areas on teeth after it dries (this didn't bother me much, but thought it was worth mentioning)

Okay so here's my more in depth review:

I've tried just about every whitening toothpaste on the market, charcoal, baking soda, and more, with no results. I heard about this pen and thought I'd give it a try. I was a bit nervous because I can have sensitive gums, but I felt no irritation whatsoever! The pen lasted exactly a week and a half before I used it all up (so it did not last the 30x stated on the box!). In that time, I can honestly say my teeth look whiter! I was pleasantly surprised. Believe me, the yellow on my teeth was stubborn! I may purchase the pen again to whiten my teeth even more.

However, I noticed a few things about the pen that might be considered negatives to some people. First of all, you have to COMPLETELY dry your teeth before "painting" on the whitening solution with the pen. Otherwise, the solution gets all clumpy and dries up on the brush, which will ruin it. Also, be aware that the pen paints this solution on your teeth and sort of leaves a thin film/coating over your teeth overnight. The solution doesn't have a taste or anything, but you will definitely want to brush your teeth in the morning to get it all off. Also, be aware that the solution will clump up in places on your teeth when it dries.

I was not aware that that was how the pen works when I bought it, but looking back, I noticed that most of the negative reviews focused around the white clumpyness of the solution on your teeth. This honestly didn't bother me much, though it was a little bit of a hassle to dry off my teeth and get an even coating on each tooth.

Additionally, you will only be able to whiten your front teeth, as it is to hard to dry off and paint the teeth at the back of the mouth.

Overall, I am pleasantly surprised and impressed by this whitening tool. I've tried so many different things and this is the first that has worked! If you are okay with the few "negatives" than definitely purchase this product! I would purchase this again!

As a note, I tried to take before and after pictures but because of bad lighting, they didn't turn out. But I did see a huge improvement in my teeth's whitening!

This product was so easy to use and doesn't leave my teeth feeling sensitive. I've been using it for a couple weeks now and I'm already seeing differences in my smile! This is a great product that makes your teeth whiter over time. Though I wouldn't say it makes as big of a difference as whitening gels, it is a great alternative if you're like me and don't want to sleep with trays in overnight. Absolutely recommend!

Like the whitening of the gel, but the applicator and application of the product leaves a bit to be desired. Someone needs to fix the design of it...in my opinion.

After about a week of daily use I can confidently say that it made my teeth noticeably whiter. I applied it every night before bed after throughly drying my teeth with a tissue. It would take several clicks for the liquid to come out of the pen and the whole pen lasted for maybe 10 solid applications, which I'm happy with. Would recommend this over strips any day. The liquid can be applied to all the nooks and crannies and stays on all night, which is why I think it works better than strips.

Getting the fluid to paint onto the teeth evenly is very tough. It does come out and coats the teeth. In the morning you have to brush your teeth pretty well to get it all off your teeth. I have only used it for just over a week and . . . maybe . . . my teeth are a bit whiter. Hard to tell at this point.