Q: Do those Crest Whitestrips work or should I go to the dentist?
A: I've tried only the Classic ones and they worked well enough. If you apply the strips on your lower and upper teeth for thirty minutes twice a day, you'll start noticing a difference in just a few days. The 56 strips per box are meant to be used over 14 days.
They've also come out with Premium, Premium Plus and Supreme versions that are supposedly more potent and can do the job in a week to ten days. Regardless of which you try, I recommend you use them only on special occasions. My gut says they weaken the teeth's enamel over time.
As for going to the dentist, if you can afford to, why not? The entire whitening can be done more quickly and you have someone to ask questions to. But the dentist may also be using the so-called Crest Professional Strength or Professional Strength Supreme versions of what you can buy for yourself.