If the spaces between your remaining teeth are small, then porcelain veneers (and Lumineers) can often be used to close up the spaces and fill the gaps with slightly wider veneers (that make the teeth a slight be wider). If you are missing a tooth and the existing space where the baby tooth was or existing permanent tooth should be, then placing a fixed porcelain bridge or implant may be the way to go. For some unique situations cosmetic dentists can even place a lingual bonded winged porcelain bridge (don't let the name throw you off, no "wings", just the back of the adjacent teeth will have some porcelain bonded to it to hold the replacement tooth).
By the way, Lumineers are not the only type of porcelain veneers to consider. There several excellent labs that compete seriously with Lumineers and also there are some new stronger veneering porcelain that is actually stronger (and therefore most likely longer lasting) than Lumineers. The porcelain veneering material I currently favor is EMax porcelain made by Ivoclar NA. It's stronger than Lumineer porcelain, can be made just as thin (thus less drilling or tooth preparation compared with other veneering materials).
You might be interested in looking at the link below which shows photos of several different techniques to treat missing teeth.