It is assumed that the minimally invasive lateral approach and the traditional lateral sinus lift procedure will result in better outcomes in terms of height of augmented bone.

It is also assumed that the minimally invasive lateral approach will reduce surgical complications and patient's discomfort in comparison with a traditional lateral sinus lift procedure.

16 patients edentulous in maxillary posterior area will be treated with a bilateral sinus lift procedure.

Once a patient will be enrolled in the study impressions will be taken. After the wax-up, a radiographic stent will be prepared. Special attention will be given to position radio-opaque references in the positions where the implants will be inserted according to a prosthodontic guided insertion. Pre-surgical CT scan will be executed after placing the stent in its proper position in patient's mouth. After that, if no surgical contra-indications will be detected at CT evaluation, patients will be enrolled for surgical interventions.

Inclusion Criteria:

• - patient edentulous in the maxillary posterior area on both left and right side( not completely edentulous).
• - residual bone height in the maxillary premolar and molar region less than 4mm.

Exclusion Criteria:

• - history of systemic diseases that would contraindicate surgical treatment

15 patients edentulous in maxillary posterior area have been treated with a bilateral sinus lift procedure.