the purpose of the study is to look for differences in dimensional variations of augmented maxillary sinuses with or without the placement of a collagen membrane subjacent the sinus mucosa.

Material and Methods: After the elevation of the maxillary sinus mucosa, a collagen membrane with standard dimensions will be placed at the test sites subjacent the sinus mucosa and the elevated space will be filled with a xenograft, both test and control groups. A collagen membrane will be placed to cover the antrostomy at both groups and sutures will be provided to close the wound. After six months of healing, mini-implants will be installed. After 9 months, biopsies containing the mini-implants will be harvested for histomorphometric analyses. CBCTs will be taken for all patients before surgery (T0), after 1 week from sinus floor augmentation (T1) and after 9 months of healing (T2). Osseointegration of the mini-implants and dimensional changes over time of soft and hard tissues will be evaluated on the CBCTs.

Inclusion Criteria:

• presence of an edentulous atrophic zone in the posterior segment of the maxilla
• height of the sinus floor ≤4 mm
• desiring a prosthetic restoration of the zone using a fix prosthesis supported by implants;
• ≥ 21 years of age
• good general health
• no contraindication for oral surgical procedures
• not being pregnant

Exclusion Criteria:

• present a systemic disordered
• had a chemotherapic or radiotherapeutic treatment
• are smokers >10 cigarettes per day
• have an acute or a chronic sinusitis
• had a previous bone augmentation procedures in the zone of interest.

the results will be published in a Journal

will be become available after the time required by the journal for publication and will be available all the time the journal is active.

An author not involved in the surgeries will perform the randomization process. The assignments will be sealed within opaque envelopes that will be opened after the completion of the elevation of the sinus mucosa.