This study will compare clinical and radiographic outcomes of three different treatment modalities for atrophied distal extension maxillary ridges these modalities include

1. Implant retained distal extension RPD
2. Sinus lift and long implant and screw-retained prosthesis
3. Short implant and screw-retained prosthesis

Patient selection:

For this study, 60 patients were selected from the clinic of Prosthodontic Department, Faculty of Dentistry, Mansoura University.

Inclusion criteria:

The patients will be selected according to the following:

• They have distal extension maxillary ridge with sinus pneumatization and remaining alveolar bone height 6- 8mm as verified by preoperative CBCT, have no previous denture experience. They are healthy, free from any systemic diseases relating to the bone resorption (diabetes - hyperparathyroidism). This can be achieved through medical history and clinical examination by a physician and laboratory investigations.
• Posterior maxillary alveolar ridge deficient in height, width and covered with healthy firm mucosa.
• Patients are less satisfied with conventional RPD.
• Absence of maxillary sinus diseases. Exclusion criteria

Patients were not eligible for this work if any of the following criteria were met:

• Acute or chronic sinus pathology
• History of a sinus augmentation in the past in the relevant sinus
• Poor dental hygiene. Smoker.
• Compromised general health (uncontrolled diabetes, bleeding disorder….). All patient were informed about all procedures that will be done and they sign the written consent form of ethical committee in faculty of dentistry Mansoura university.

Three treatment groups will be classified randomly, as follow:

• Group A: patients received two implant in premolar area mesial to maxillary sinus and used to retain partial overdenture
• Group B: patient underwent sinus lift and receive screw retained prosthesis on long implant
• Group C: patients received short implants in premolar area mesial to maxillary sinus and received screw retained prothesis All implants were inserted using computer guided implant surgery and conventional loading protocol was used.

Evaluation methods Clinical and radiographic evaluation

1. Modified Plaque index. Assessment of plaque accumulation with a modified plaque index (mPI): Score 0: No detection of plaque, Score 1: Plaque only recognized by running a probe across the smooth marginal surface of the implant, Score 2 Plaque can be seen by a naked eye, Score 3 Abundance of soft matter.

2. Gingival index. Assessment of bleeding tendency with a modified sulcus bleeding index (mBI): Score 0 No bleeding when a periodontal probe is passed along the gingival margin adjacent to the implant. Score 1 Isolated bleeding spot visible, Score 2 Blood forms a confluent red line on margin, Score 3 Heavy or profuse bleeding.

3. Attachment level. Distance from the junction implant/crown to the most apically probeable portion, in millimeters.

4. Pocket depth. Distance between the gingival margin and the most apically probable portion, in millimeters Assessed by insertion of a standard periodontal probe with a point diameter of 0.5 mm using a probing force of 0.5 N.

5. Implant stability quotient. Using resonance frequency analysis

   b- Radiographic evaluation will be performed in terms of:

   Vertical bone loss (VBL) will be evaluated as follows:

   The distance between implant plate form and first bone to implant contact (DIM) will be evaluated at T0, T6 and T12. VBL will be calculated by subtracting DIM at T6 and T12 from DIM at T0.

Inclusion Criteria:

The patients will be selected according to the following:

• They have distal extension maxillary ridge with sinus pneumatization and remaining alveolar bone height 6- 8mm as verified by preoperative CBCT, have no previous denture experience. They are healthy, free from any systemic diseases relating to the bone resorption (diabetes - hyperparathyroidism). This can be achieved through medical history and clinical examination by a physician and laboratory investigations.
• Posterior maxillary alveolar ridge deficient in height, width and covered with healthy firm mucosa.
• Patients are less satisfied with conventional RPD.
• Absence of maxillary sinus diseases.

Exclusion Criteria:

• Acute or chronic sinus pathology
• History of a sinus augmentation in the past in the relevant sinus
• Poor dental hygiene. Smoker.
• Compromised general health (uncontrolled diabetes, bleeding disorder