Internal vs. External Connection in Screw-retained Multi-units Bridges With Cad/Cam Milled Co/Cr Framework (ISUS-Atlantis)

Inclusion Criteria: * Age \> 18 years. * Willingness to comply with all study requirements and to sign the IC. * Systemic health. * Compliance with good oral hygiene. * Patients with at least 2 teeth to replace in any side of the jaws. Exclusion Criteria: * Patients treated with implant with bone defects associated with severe knife-edge ridges. * Patients treated with bone defects resulting from tumor resection. * Tobacco abuse (\> 10 cigarettes/day). * Severe renal and liver disease. * History of radiotherapy in the head and neck region. * Chemotherapy for treatment of malignant tumors at the time of the surgical procedure. * Uncontrolled diabetes. * Active periodontal disease involving the residual opposite dentition. * Mucosal disease, such as lichen planus, in the areas to be treated. * Poor oral hygiene. * Non-compliant patients. * Situations judged inconvenient(by the investigator) for the surgical treatment.