Dentures are often needed when teeth begin to change position due to underlying periodontal or gum disease, when teeth have decayed so much that cavities can't be filled, or when teeth fall out, according to Prevention. Some people choose to get dentures for cosmetic reasons.
Partial dentures replace one or more teeth in the mouth and help keep remaining teeth in position, states WebMD. Complete dentures replace all upper or lower teeth. Some people choose dental implants instead of dentures when they need to replace their natural teeth because the look and feel is closer to that of real teeth.