A complete denture (also known as a full denture, false teeth or plate) is a removable appliance used when all teeth within a jaw have been lost and need to be prosthetically replaced. In contrast to a partial denture, a complete denture is constructed when there are no more teeth left in an arch; hence, it is an exclusively tissue-supported prosthesis. A complete denture can be opposed by natural dentition, a partial or complete denture, fixed appliances or, sometimes, soft tissues.

There has been a decline in both the prevalence and incidence of tooth loss within the last decades; people retain their natural dentition for longer. Nonetheless, there is still a great demand for complete dentures as more than 10% of adults aged 50–64 are completely edentulous, with age, smoking status and socioeconomic status being significant risk factors. Tooth loss can occur due to many reasons, such as:

Following the loss of teeth, there occurs a resorption (or loss) of alveolar bone, which continues throughout life. Although the rate of resorption varies, certain factors such as the magnitude of loading applied on the ridge, the technique of extraction and healing potential of the patient seem to affect this. The edentulous ridge can be classified according to the amount of bone in both the vertical and horizontal axes:

Alveolar bone resorption is an important consideration when designing complete dentures. In the absence of natural dentition, such dentures rely completely on soft tissues for their support. As a consequence, the forces exerted on the mucosa are significant and may, in turn, lead to an increased rate of bone resorption. Therefore, in order to ensure an equal distribution of forces across the mucosa, complete dentures should have maximum extensions.

Facial muscles on the cheeks and lips also lose their support as teeth are lost, contributing to an 'aged' appearance of the individual. Although complete dentures cannot prevent the loss in muscular tone (as they are not firmly attached to the skeletal system), they can nevertheless provide some artificial support to mask this loss in tone. Furthermore, perhaps the most noticeable effect of tooth loss from a patient perspective is the loss in masticatory (or chewing) efficiency. Teeth function to help with the chewing of food, breaking it down in small pieces that can be swallowed. Denture-wearing can bring some masticatory function back to normal. It cannot, however, fully compensate for the efficiency of the natural dentition because (1) dentures are not fixed in place like teeth are and so have to be actively controlled by the muscles and (2) biting forces are greatly reduced (about one-sixth of the natural dentition) as the dentures are impinging on soft tissues.^{[citation needed]}

Complete dentures are prone to a variety of displacing forces of differing magnitude as they are resting on oral mucosa and are in close proximity with tissues that are constantly changing due to the action of muscles. Consequently, for complete dentures to be retentive and stable, the retentive forces that hold the dentures in place must be greater than the ones aiming to displace it. Obtaining maximum stability and retention is one of the biggest challenges in full denture construction.

Retention in removable prosthodontics can be defined as the resistance to vertical dislodgment that can arise from either muscular forces or physical forces. It can be gained from three different surfaces of the denture:

The peri-oral muscles (muscles of the cheeks and lips) can cause displacement of the dentures. Patients can, however, learn to control and coordinate their muscles so that the forces exerted are minimised or counter-acted to prevent such displacement. With age, the ability to learn new skills and acquire some level of neuromuscular control declines. Therefore, the "training" time-frame for patients to learn how to successfully use their new complete dentures is expected to be much longer for older patients.