Microbial Adhesion and Peri-Implant Tissue Health in All-on-Four Hybrid Prostheses Supported by Zantex or Zirconia Frameworks

Inclusion Criteria: 1. Completely edentulous patients in the mandibular arch. 2. Patients with a completely edentulous maxillary arch rehabilitated with a conventional complete denture. 3. Patients with sufficient mandibular bone volume and quality to allow placement of four implants according to the All-on-Four treatment concept. 4. Patients suitable for placement of two axial anterior implants in the canine regions and two distally tilted posterior implants anterior to the mental foramina. 5. Patients with adequate restorative space to accommodate a full-arch hybrid prosthesis. 6. Patients who are willing and able to maintain adequate oral hygiene and attend all scheduled follow-up appointments. 7. Patients who are willing to participate in the study and sign the informed consent form. \- Exclusion Criteria: * 1\. Patients with systemic conditions that contraindicate implant surgery or may adversely affect osseointegration or wound healing. 2\. Patients receiving medications or undergoing treatments that significantly affect bone metabolism or healing. 3\. Patients with a history of radiotherapy involving the head and neck region that may compromise implant therapy. 4\. Patients with active or uncontrolled periodontal or oral infections. 5. Patients with inadequate mandibular bone volume or unfavorable anatomical conditions that prevent placement of four implants according to the planned All-on-Four protocol without additional augmentation procedures. 6\. Patients with severe parafunctional habits, such as uncontrolled bruxism, that may compromise the prosthetic rehabilitation. 7\. Patients unable or unwilling to maintain appropriate oral hygiene. 8. Patients unable to attend the scheduled follow-up visits. 9. Patients who decline to participate or fail to provide informed consent