It is important to distinguish between short teeth and short-looking teeth. Often, shorter teeth are actually normal-sized, but appear shorter because of an excess of gum tissue. Your dentist will determine if this is the case, and treat your teeth accordingly.
Gum Surgery
If your dentist finds that your teeth simply appear short beside an abundance of gum tissue, he or she will perform a gum lift, also known as a gum reconstruction, to reduce your gum tissue expose more of your teeth. This effect can be achieved through either a gingivectomy or a flap surgery. Both of these procedures involve surgically excising excess gum tissue. Flap surgery, however, requires also removing some of the underlying bone. In some cases, these procedures can be performed with a laser.
Porcelain Veneers
Porcelain veneers, thin ceramic shells fitted over the front of your teeth, are used for many cosmetic purposes—whitening, sealing gaps, and fixing chipped teeth, for example. Another of their possible functions is lengthening short teeth. If your teeth are too short, and reshaping your gums is not a helpful option, consider veneers to give you the appearance of normal-length teeth. A cosmetic dentist will buff away a bit of your teeth to make room for the veneers, cast a mold based on your buffed teeth, send this mold off to a lab for veneer creation, and cement the veneers to your teeth. With veneers, you can not only improve the length of your teeth but the shade, too.
Note that typically, dentists will recommend a combination of treatments to help you achieve the smile you're after.