Crowns are typically used to restore a tooth's function and appearance following a restorative procedure such as a root canal.

People choose esthetic dental procedures/surgery for various reasons—to repair a defect such as a malformed bite or crooked teeth, treat an injury, or just improve their overall appearance. 

A denture is a removable replacement for missing teeth and adjacent tissues. It is made of acrylic resin, sometimes in combination with various metals.

Before development of dental implants, dentures were the only alternative to replacing a missing tooth or teeth.