Hello, I'm a 25-year-old from Canada, currently working in a marketing firm. I'm getting married to my best friend next month. My beautician told that my teeth need to be cleaned as they are dark yellowish in color, and it may appear weird in photographs. I'm planning to do a teeth whitening at Appleton Dental Clinic in Whitby. How long does this last? Do they cause sensitivity to teeth? I'm eager to know, and any advice on this topic is highly appreciated.