Home kits from the stores are totaly useless, there are two types of whitening from your dentist, one costs £400 and the other £200.
The £400 takes approx an hour and lasts about a year
The £200 you take home and apply top and bottom shields for 1 1/2 hrs every day for approx 4 weeks or until your teeth are as white as you want them and again lasts about a year.
The Shields have to be made but only take about a week..
I went for the £200 one and I'd set my alarm 2hrs before I had to get up, put in the shields which takes minutes to do and go back to sleep. My alarm clock has two settings so I could set it to wake up to put the shield in and do the other setting to wake me up when I had to get up..
Did it work.. yep brilliantly and I love the results, I thought i'd get fed up having teh shields in my mouth but by doign it early morning it never bothered me.
Well worth the money..
Also rather than wait a year and possibkly need to do a full course again you can buy a Syringe which lasts about 5 days and do a top up maybe every three or 4 months or longer, these cost £25.
I am so pleased I did mine but yeah definately avoid the shop ones, total waste of money