The aim of the present study will be clinical and radio graphical comparison of four basal and compressive implant designs will be installed in the interforamina area of atrophied edentulous mandible and immediately loaded by screw retained mandibular overdenture .

Implant design comparison will be done clinically and radiographically after one and two years of implant loading

Patients will be divided randomly in to 2 equal groups:

• Group1: this group will receive immediate loaded screw retained complete overdenture supported by 4 basal implants design .
• Group2 :this group will receive immediate loaded screw retained complete overdenture supported by 4 compressive implants design
• After final implant placements, they will be immediately scanned by intraoral scanner to construct milled in titanium bar which will be immediately screwed into the implants
• Mandibular screw retained complete overdenture will be constructed.

Evaluation will be for:

• Peri implant tissue health that will be measured according to mombelli(12) at the time of insertion(T0), 6months(T1) and 12months (T2).
• Marginal bone height changes will be measured using standardized digital panoramic x-ray(13) after 6months (T0), 12month(T1) and 24months(T2) after prosthesis insertion.
• Periotest will evaluate the stability of the implants during implantation (T0) , 3months(T1) and 6months(T3) following surgery(14) .

Inclusion Criteria:

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mandibular and maxillary alveolar ridges are completely edentulous (2) There is not sufficient bone in the mandibular posterior molar area to place implants and there is a thin ridge anteriorly (3) skeletal class I maxilla-mandibular relationship (4) Devoid o f any systemic disorders related to bone resorptio

Exclusion Criteria:

• present of systematic disease Chem therapy Bone diseases

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