We all have a hollow space in our cheekbone called Maxillary Sinus. This space is located above our upper back teeth (behind the eye tooth).
When you lose single or multiple back upper teeth, sinus space expands downwards.
Now there is not enough height of bone available to place the implant in this region. Bone grafting is done to grow bone in this sinus space to gain lost bone height so that proper length implant can be placed in this region. Please see our video under the bone grafting title which explains this procedure in detail.