Teeth can only take so much abuse -- as I've learned. Spend your whole life mistreating them and eventually, all the "Crest" in the world isn't going to put them back the way they belong.
And it's not just smoking (like I used to) or drinking coffee (like I do continuously) or soda (ditto) or eating foods that stain them (any food that turns your mouth purple is high on my list of comestibles) that can wreck teeth. You could have been born with a crooked tooth, or taken a punch to the face while trying to rescue some adorable kittens from a rogue gang of scooter enthusiasts (you maybe live an exciting life?) or perhaps you wrecked up your mouth trying to teach yourself to bungee jump via a mail order course (who am I to judge?)
However your mouth got messed up, it can be fixed up, too. All you have to do is go see a dentist. They're the professionals, after all. They can clean your teeth, fill your cavities, bridge your...whatever it is dentists bridge... and maybe even adopt one of those kittens. At the very least, they can tell you "Mail Order is no way to learn to bungee jump. You should use Youtube for that."
Finding the right dentist is easy, too. Say you want a to find a Dentist Katy Texas; all you have to do is click that link and you're there -- the Welch Dental Group, which promises you a beautiful smile regardless of your insurance coverage. They can handle cosmetic dentistry, tooth whitening, and more, and they have the right attitude: You DESERVE proper dental care.