This is very popular these days—it seems everyone wants a brighter smile. One way to get there is porcelain veneers, but if your teeth are merely stained, at-home tooth whitening, or “bleaching,” is an excellent option. It works well for brown and yellow stains; gray discolorations usually aren’t stains, but are the intrinsic color of the tooth. Teeth with lots of fillings don’t bleach well—the fillings stay dark as the teeth get light. A few people get sensitive teeth or gums from the bleach, but this resolves when they quit using it. Teeth will stain again over time, but they can be touched up as needed. All whitening products can cause increased tooth sensitivity to hot and cold. If you have generally sensitive teeth, you probably won’t be able to bleach.
Whitening involves taking impressions of the teeth, and making custom bleaching trays to fit snugly over the teeth. A small amount of bleaching gel is placed in each tray and the trays are snapped over the teeth. The trays may be worn overnight, or an hour at a time (20 or so hours total contact time). Overnight use is the most popular, but not everyone can tolerate this. Frequently you can see results within several contact hours, and the cost is reasonable, currently under $200 for routine cases.
Bleaching can also be done in the office, using more concentrated solutions and dentist supervision. The cost is somewhat higher, but you do get instant gratification. There are over-the-counter whitening systems available in stores, but the bleach is much less concentrated and results are usually disappointing. One exception to this is Crest Whitestrips: these will whiten an amazing amount if you use them long enough. They’re a bit difficult to use, and if you need several boxes to get whitened, you won’t save much money. You’ll need to persevere with a lot of strips to get results. There used to be a product called Rembrandt Whitening Strips, which were much easier to use than Whitestrips, but they’re not currently being sold. You conspiracy theorists may conclude they were forced out of the market by a cabal of greedy cosmetic dentists because they worked too well. Do a web search for them, they may come back one of these days