Explain bone grafting please. Where are you getting this bone?

Bone grafts are when
additional bone is added to a portion of your mouth in order to save, restore,
or place new teeth when existing bone levels are poor. There are different
types of sources that can be used: from your own body (through surgical
methods), donor bone, or bovine bone.

Great question.  This topic has textbooks on it.  I'll try to be brief in this summary.   Bone grafting is a procedure used to increase the volume of bone in a horizontal and/or vertical dimension.   Bone used may come from autogenic ( own bone), allogenic ( others bone), xenogenic ( animal sources) or artificial/ chemical sources.  If it's autograft then the most common sources are jawbone or chin bone, hip bone, tibial bone or more rarely calvarium(skull) bone.  Allograft usually comes from pre screened cadaver bone that has been irradiated.  Xenografts are most commonly bovine(cow) or porcine(pig) and more recently equine(horse).  These are usually only matrix or mineral and do not contain live cells.  The artificial stuff may be ceramic or calcium sulfate like materials.  Whatever material is being used it's resorbed by the body and replaced with your own bone.  Depending on the material some may be left behind and some materials are 100% resorbed.  Often we use growth factors to help in healing these may be your own that are obtained from drawn blood like PRGF or PRP and some come prepared from donors and contain BMPsAll the materials work and it's the surgeon that decides what material best works in his/her hands.  Hope this was not overly confusing and somewhat helpful.  

Without going into much detail it's really simple, 4 main categories:1. Autograft - comes from the patient.2. Allograft - same species (donor bone)3. Xenograft - different species (animal bone)4. Alloplast -  chemical bone substitutes (not exactly bone, but work well) Each material has it's pros and cons. What's being used depends on surgeon, procedure and sometimes on patient's preference.