Self teeth whitening

As I get older, even if I brush my teeth diligently and take care of them, my teeth tend to turn yellow. I haven't visited a hospital for teeth whitening to get an estimate, but I think it might be expensive, so lately I've been tempted by the self-whitening products that are heavily advertised. In fact, since we don't have professional knowledge about teeth, there are many things we don't understand even when we see advertisements. Just as dermatologists are the answer for blemishes and freckles, I wonder if teeth whitening is also best handled by a dentist. I am curious about what a dental specialist would think.