The future right now, and will be for several years to come, is gel + laser technology. It has revolutionised the world of teeth whitening because it gets things done much faster, i.e. a session takes only 20 minutes without any side effects. That is why top centres like The Smile Bar offer it because it is a lot more efficient and safe. You can check all about it on their website. They get it done that fast because they only have to apply the gel on your teeth and then boost it with the unique LED laser light.