This within -subject study will be conducted to evaluate the proper number of unsplinted implants ;( three, four and five implants) for the edentulous maxilla opposed by mandibular two-implant overdentures.

Inclusion Criteria:

• o Healthy and free from any systemic diseases that may interfere with the osseointegration of implants.

  • Patients have completely edentulous maxilla for at least 6 months after last extraction with opposing mandibular two-implant Overdentures.
  • The patients have angle class I maxillomandibular skeletal relation and sufficient interarch space not less than (10-12 mm) as detected by tentative jaw relation.
  • Maxillary and mandibular alveolar ridges covered with healthy, firm, relatively even thickness and even compressible mucosa as detected by palpation with the blunt end of the mirror and free from any signs of inflammation or flabbiness as detected by clinical examination.
  • Good quality and quantity of maxillary residual alveolar ridge, as detected by CBCT, available for implant width (3.7mm, 5mm for anterior and posterior implants respectively) and length (12mm, 10mm for anterior and posterior implants respectively) this was ascertained by CBCT.

Exclusion Criteria:

• o Any history of metabolic or systemic diseases that may affect integration of implant or connective tissue health surrounding implant.

  • History of irradiation in head-and-neck area.
  • Heavy smokers (more than 10 cigarettes per day)
  • Parafunctional habits such as bruxism.
  • Psychiatric disorders or unrealistic expectations.
  • Positive pregnancy test up to 5 days before surgery.
  • Severe thrombocytopenia and bleeding disorders.
  • Pathologic condition of soft tissue (bacterial and viral stomatitis, hyperplasia, cyst, fibrous lesions)
  • Patients with local contraindications for implant placement due to localized bone defects and poor bone quality (D5).
  • Patients with TMJ disorders or poor neuromuscular coordination.