Some of the roots of your upper teeth extend into your sinuses, which leaves only a thin wall of bone between sinuses and the mouth when these teeth are removed. This thin sinus wall makes it difficult to place dental implants in this bone. In some cases sinus augmentation bone grafting is necessary to build a sound foundation for implants placed in the posterior areas of the upper jaw.
All told, the process can take several months. Years ago, dentures would have been the only solution but today, the sinus graft makes it possible for many patients to have dental implants.