Long Term Stability of Implants Placed With Crestal Sinus Approach Versus Osseodensification in Atrophic Posterior Maxilla. A Randomized Clinical Trial.

Rehabilitation of the edentulous posterior maxilla using osseointegrated implants is often challenging due alveolar bone resorption, low bone density and maxillary sinus pneumatization. Many protocols were suggested to overcome this phenomenon; placing short implants, 2nd premolar occlusion and finally maxillary sinus elevation.

Maxillary sinus elevation is one of the most common surgical techniques used for increasing the available bone volume to place implants and restore function and esthetics. Sinus elevation was introduced when Boyne and James presented lateral window approach as a modification of the Coldwell Luc technique; the access to lift the sinus floor is performed by a window through the lateral wall. This technique was proven to be effective and successful for sinus elevation even up to 12 mm in cases of severely atrophic ridge. It was later divided into three techniques according to the lateral wall preparation; hinge, elevated and complete.

Lateral approach for sinus lift is usually indicated when residual bone height is less than 5mm. While transcrestal approach can be successfully adopted when residual bone height is at least 5 mm. Osteotome sinus floor elevation was 1st introduced by Summers (1994) and proved to be less invasive, more conservative, less time consuming, and reduces postoperative discomfort to the patient.

Osseodensification is a new surgical technique of biomechanical bone preparation performed for dental implant placement where bone is compacted and autografted into open marrow spaces and osteotomy site walls in outwardly expanding directions. The use of densah burs for preparing implant site had many advantages including the increase of implant bone contact by compaction autografting rather than excavation of bone in conventional drill, this mainly depends on the viscoelastic nature of bone where time dependent stress produces time dependent strain, it also allows for higher insertion torque and increased stability of dental implant.

The use of densah burs for maxillary sinus lifting was first introduced by Huwais and Meyer utilizing the advantages of the osseodensification approach for elevation of the maxillary sinus floor. The idea of compaction autografting supported by the design of densah burs with specially tapered geometry and specially designed flutes to compact the bone on its walls and apex. The idea of this concept is that the special design of flutes in the densifying non cutting mood with counter clockwise motion and presence of irrigation cause a hydraulic wave at the apex of the bur, this wave cause pushing of the sinus membrane upward, also in presence of grafting material cause the same effect and subsequent elevation of the Schneiderian membranewith limited risk of perforation. So this approach is suggested to provide a safe technique for maxillary sinus lifting with limited complications as in osteotome or lateral approach, less perforation and less invasiveness.