There are many reasons for the use of this procedure:

When people who have lost teeth in their upper jaw (particularly the back teeth, or molars) do not have enough bone for an implant.
A Bone may have been a victim of periodontal disease.
The maxillary sinus is too close to the upper jaw for implants to be placed.

These procedures have been divided into 4 types.

These divisions of treatment include SA1, SA2, SA3 & SA4.

SA-1
There is enough bone left to place the implants in a normal fashion. Addition of any extra bone is no longer required.

SA-2
There is enough bone to secure the implant of the proper length and width. In this case, the necessary bone for the implant is created by expanding the bone in width and height from within the implant site, creating a new sinus floor.

SA-3
There is just barely enough bone to secure the implant and a total lack of bone for the proper placement of a implant of necessary length and width. The necessary bone is added in the form of a graft which creates a new sinus floor.

SA-4
There is so little bone left that initial stabilization of the implants is impossible.

The same procedure that is covered in the SA-3 is performed with the difference being that the implants are not placed at this time.

A four month period that allows the bone graft to mature is followed by the conventional placement of the implants.

A variety of graft materials can be used in these procedures.

The restoration of SA-1,2,3 and 4 is done by conventional crown and bridge techniques after a maturation period of 6 to 10 months.

It is important that the initial loads placed on these implants be light and then gradually increased over time.

Potential Risks
Main risks ocurr on rare occasions. This happens when the membrane is torn during the procedure.

For this, the surgeon will place a patch over it.

Other potential risks are infections during the cirgury procedure or when the existing bone does not integrate with the bony graft material.

For all the cases the whole procedure must be repeated.