Patients in need for implant-supported restoration in maxillary posterior sites with bone deficiencies will be randomly allocated to two different arms.~Full-mouth periodontal chart and standardized radiographs will be evaluated at the time of inclusion.~Crestal sinus lift with simultaneous implant placement will be performed in both groups.~Control group: crestal sinus lift with no adjunctive biomaterial; the healing abutment in this group is made up of PEEK (poly-ether-ether-ketone).~Test group: crestal sinus lift associated with xenogenic bone graft and collagen membrane; the healing abutment in this group is made up of titanium;~Resonance frequency analysis will be performed at the time of implant placement and at 1, 3, 6 months of follow-up.~Both healing abutment will be undersized: this characteristic will allow to harvest a 1mm-wide biopsy of the transmucosal tract at the end of the healing phase (6 months).~Six months after implant placement, impression will be taken and implants loaded with definitive screw-retained prostheses.~Six months later, patients will be recalled for clinical and radiographic assessment.
Patients in need for implant-supported restoration in maxillary posterior sites with insufficient residual bone height will be randomly allocated to two different arms. Crestal sinus lift with simultaneous implant placement will be performed in both groups.~Control group: crestal sinus lift with no adjunctive biomaterial; Test group: crestal sinus lift associated with xenogenic bone graft and collagen membrane; Six months after implant placement, implants will be loaded with definitive screw-retained prostheses.~Six months later, patients will be recalled for clinical and radiographic assessment.