Prosthetic Management of All on Four Versus All on Six to Rehabilitate Completely Edentulous Maxillary Ridge Opposed by Natural Teeth

Inclusion Criteria: * 1\. All patient wearing a maxillary implant supported overdenture or implant supported fixed restoration and mandibular natural teeth or fixed restoration within natural dentition. 2\. All patients were unsatisfied by the maxillary restoration and presented clear preference for a better prosthesis. 3\. They were healthy, free from any systemic diseases relating to bone resorption such as uncontrolled diabetics or osteoporosis. This was achieved through medical history and clinical examination by physician. 4\. At least one year passed after the last restoration. 5. At least 15 mm restorative space must be available (from the mucosa covering the crest of the residual ridge to proposed occlusal plane) to permit construction of all types of tested prosthesis (class I according to Ahuja and Cagna).195 This was detected by a tentative jaw relation. Exclusion Criteria: * 1\. Patients had head and neck radiotherapy, patients with bleeding disorders or hepatic patients. 2\. Patients with metabolic disorders as diabetes mellitus, osteoporosis and hepatic disorders which might affect implant lifespan. 3\. Long term immunosuppress and corticosteroid drug therapy. 4. Patient with abnormal habits as clenching and bruxism. 5. Smoking patient. 6. Uncooperative patients. 7. Neuromuscular diseases. 8. Patient with problems in TMJ.