Over time, our bodies change, including our mouths. When dentures are made, a mold is taken of your mouth and the denture is made to fit that mold. As your mouth changes throughout life, that denture fits your mouth less and less. If the change is minimal and the denture moves slightly or has lost its retention, a reline can be done. A reline adds more pink denture material and fills in the areas where your bone and gums have shrunk. If a dramatic change has occurred in your mouth or your bite has changed, a new denture is most likely needed.
The teeth that are placed in a denture will wear down as you chew, especially if the opposite arch has existing teeth. For example, if you wear an upper plate and have natural teeth in your lower jaw, your upper denture teeth will wear more. As a result, you can expect to have a new upper denture replaced more often than someone who has both upper and lower dentures.
Most people that have upper dentures do not have problems keeping their plate in because the palate allows for suction to be created. However, many people that wear lower dentures have poor retention because no suction can be created. In these situations, dental implants are the best solution. Implants can used to anchor the denture or support an entire set of teeth.