A while ago I used the crest whitestrips. Worked great as there was a noticeable change in colour. Teeth were sensitive while on it, but I toughed it out no biggie. My teeth now are still white (more off white I'd say) but the "brightness" is fading. I'd go with a professional treatment (laser, etc) because the whitestrips, although they work, don't last long and are relatively expensive. You gotta constantly do it every 6 months or so and that'll add up. Plus it's a real pain in the ass the 2 weeks or so you are using the whitestrips because the sensitive is quite uncomfortable.