The aim of the present study is to compare the rate of new bone formation after sinus floor elevation with or without perforation of the cortical sinus floor prior to insertion of augmentation material. Twelve patients requiring bilateral sinus floor elevation will be recruited for a pilot study in split-mouth design. On both sides a lateral window will be prepared and the sinus mucosa will be elevated. After this step, the sides are assigned as test or control side. While the control side is just filled with augmentation material, an additional step is performed for the test side, i.e., prior to inserting the augmentation material, the cortical bone layer of the sinus floor is perforated several times into the trabecular bone layer to improve the blood supply to the grafting material. Thereafter, both sides are left to healing for 4-6 months until implant installation. At timepoint of implant installation, a bone biopsy will be collected to allow histological assessment of the grafted area.

Inclusion Criteria:

• in need of bilateral sinus floor elevation
• residual alveolar ridge height 2-6mm
• residual alveolar ridge width > 4mm

Exclusion Criteria:

• uncontrolled periodontal disease
• acute or chronic sinusitis