Bone resorption and atrophy in maxillary posterior region is due to severe periodontal disease and is consequent tooth extractions. Sinus pneumatisation can occur after tooth extraction and alveolar bone loss. Consequently, bone-reducing volume at that region is a great challenge to implantodontists. Sinus lifting surgery have been practiced since 80's and many biomaterials have been used to solve filling issues to maintain the sinus floor lifted in a position that can allow dental implants installation. Bone grafts have shown to be the best choice of filling grafts. Despite autologous bone are the gold standard filling biomaterial it is associates with great mortality and morbidity. So, bone allografts from tissue bank had been shown to be an advantageous alternative. Lyophilized or freeze tissue bone are the most common allografts but literature is poor in randomized controlled parallel clinical trials regarding those filling grafts for sinus lifting. The aim of this study is to perform a randomized controlled clinical trial comparing two bone allografts: lyophilized and freeze bone allografts from human bone tissue bank. The investigators want to verify which one can develop greater osteogenesis, if is there any difference between them regarding the architectural trabeculae formation, if there are different patterns of reabsorption and finally if is there any differences between them regarding primary and lately dental implants stability. To answer those questions the investigators propose firstly, to carry out microtomographic and histological analysis from trephine bone samples after six months of sinus lifting and grafting in healthy participants undergoing osseointegrated dental implants. Secondly, the primary and lately implant stability is going to be achieved employing Resonance Frequency Analysis (RFA).

Inclusion Criteria:

• healthy
• totally or partially edentulous patients, bilaterally, in upper premolar or molar region; presenting maxillary sinus lifting necessity with bilateral alveolar bone height lower than 5mm and indication for at least one osseointegrated dental implant in premolar or molar region.

Exclusion Criteria:

• recent sinusitis history
• hypersensibility for sinus allergens, tabagism, ethylism
• severe periodontal disease, diabetes, hypertension.
• Cases that occur schneiderian membrane perforation will be excluded from the final sample.