Not many people have suction with lower dentures, unlike the upper where the palate is covered in which creates a seal with the saliva and the tissue on top of the mouth. Lower dentures are held in by the muscles in the cheeks, lips and tongue the bone structure on the lower is important for those muscles to work against giving a patient their denture control.
As we get older and the bone structure disappears and the muscles get weaker the denture control is limited. It is very important at this stage that the dentures are fitting well, the occlusion is correct and the denture is the right size and shape. Relining and replacing dentures regularly is very important.