Reports supporting the shortened dental arch concepts showed that the SDAs were stable in occlusion and TMJ for several years, and that effects of partial dentures on distal extension edentulous patients were unclear. However some studies are difficult to understand their conclusions after careful reviewing. Our data of 921 subjects demonstrated the prevalence of SDA, percentage of denture wearers in distal extension missing patients, and comparisons of occlusal force and masticatory performance between denture wearers and non-wearers (SDAs). To clarify the effect of prostheses, longitudinal studies or randomized controlled trials on oral function must be needed in further investigation.