What are the signs that someone has false teeth?

A few things: Loose teeth, lost of the fullness in the face, taking the teeth out to clean, unable to speak, chew and laugh with confidence.

False teeth : Can nowadays be difficult to detect given the brilliant new materials we have and some very talented ceramists / lab technicians. Undoubtedly premium work utilizing premium materials and labs doesn't come cheap. Dentures of today don't need to look artificial. Often people in dentures today want white, perfect teeth, so that is often a tell tale sign when an 80 year old has perfect pearly white.

Many: Signs of false teeth may include difficulty in chewing foods, noticiing movement of the denture during function, teeth in an elderly patient that look too perfect - straight and pearly white.

Many indications: Although dentists think of "false teeth" only in terms of removable dentures, patients often include crowns or bridges as being "false". Some indications are uniformity in color, texture, and position; lack of delineation between teeth; collapse of bite or facial contours; bulkiness or protrusion; metal clasps; abnormally small or large teeth; and unusual staining patterns.

Hard to say...: You might not be able to know. However, some signs may include all the teeth being exactly the same color, all the teeth being too perfect in alignment and shape, the person in question may resist biting into foods and may choose to cut all foods first, or the teeth may look too fat.

Many factors !: False teeth, or dentures, can look incredibly realistic and natural. However, you typically 'get what you pay for'. If you go to a prosthodontist (a specialist in removable, fixed, and implant prosthetics), the dentures will look natural. Poor color, shape, position, size, and bite can all lead one to conclude that a person has 'false teeth'. If made well, however, it is very hard to tell !