Effect of PEEK and Titanium Framework Reinforcement on Marginal Bone Loss Around Implants Supporting a Fixed All-on-four Prosthesis in Completely Edentulous Mandibles

Inclusion Criteria: 1. Completely edentulous patients requesting a fixed, implant supported restoration. 2. Patients aged from 45 to 60, able to sign an informed consent will be considered eligible for this trial. 3. Implant sites must allow the placement of four implants. 4. Non- heavy Smokers will be included (smoking up to 10 cigarettes/day) 5. In case of post-extraction sites, they must have been healed for at least 3 months before being treated in the study. 6. Patients with no systemic condition that may interfere with implant placement (e.g., Immunosuppressed or immunocompromised patients, patients under treatment of intravenous amino-bisphosphonates) \- Exclusion Criteria: 1. Patients with poor oral hygiene and motivation. 2. Female patients taking any medical treatment for management of osteoporosis. 3. Drug abusers. 4. Psychiatric problems or unrealistic expectations. 5. Patients with active infection or inflammation in the planned implant area at the time of implant placement. 6. Immuno-compromised patients (Diabetic with HBA1C \> 7 or patients undergoing chemo or radiotherapy or bisphosphonates)