Q: "If you get a cap or crown on your tooth, does it always stay the same color if your real teeth stain yellower? and does it look white in under a black light?"
A: Good question! Both porcelain crowns and natural teeth stain in your mouth at varying degrees. Natural teeth and enamel are much more porous than porcelain and will pick up stains a lot more quickly. The best way to ensure an even color long term is to talk to your dentist about whitening your teeth before your crown is placed (especially if it is in the front of your mouth). Then you have the crown matched to the new shade of your teeth. After your porcelain crown matches your natural teeth in color, you start a maintenance program where you can use a whitening pen with a low level of hydrogen peroxide similar to what ZOOM or BRITESMILE or have your dentist make you whitening trays to wear at home. This will help oxidize any extrinsic stains before they get a chance to settle in and account for any differences in the rate of staining between porcelain and enamel.