Monday, April 19, 2010

Bone Grafting in Dentistry

The knowledge that we have developed in the science of dental implantology has grown tremendously in the past couple of decades, and bone grafting has developed into an integral part of it, allowing dentists to develop procedures and achieve outcomes that would not have been possible without grafting.

Bone grafting is utilized routinely in day to day procedures such as ridge preservation after tooth extraction, ridge augmentation, guided tissue regeneration in periodontal defects, ridge repair of ailing or failed implants, sinus augmentation procedures, and repair and reconstruction after surgical resection in the treatment of neoplasms.

For the average dentist, bone grafting is used most commonly in ridge preservation after extractions and associated with implant placement.
A basic understanding of the available bone grafting materials , their similarities, their differences and how they work will allow the dentist to select the best material for a particular situation, since they all have their advantages and disadvantages.

Starting with the basic classification of bone grafting materials which distinguishes them by the source or where the material comes from, we have:
Autografts: Graft material comes from the same patient (which means usually a second surgical site). Autografts are the best choice since it is the only osteogenic material.
Allografts: Graft material comes from a different patient (human, usually a cadaver) This material undergoes extensive processing to reduce or eliminate the chances of antigenicity and disease transmission. Allografts carry bone morphogenetic proteins in a limited amount and are considered osteoinductive (can produce chemotactic signals that stimulate mesenchymal cells to differentiate into osteoblasts and form bone) and osteoconductive.
Xenografts: This graft material comes from a different species, usually porcine or bovine and is also treated to reduce or eliminate the chances of antigenicity and disease transmission. Xenografts are osteoconductive and slower to resorb.
Alloplasts: This is synthetic material such as tricalcium phosphate, and has the advantage of carrying no risk of antigen or disease transmission. This material is osteoconductive (acts as a matrix which maintains graft space and gets replaced by viable bone).

The easiest and most predictable bone grafting procedure is socket preservation. Here the dentist has a five walled defect which, when treated properly by removing any soft tissue, fibrous of granulation tissue, infection*, cystic lesion, etc...and creating a bleeding bone surface, which will be the source of bone progenitor cells, growth factors and angiogenesis that will allow the replacement of the graft material placed in the socket by new bone called woven bone. *If an active infection was the cause of the extraction and there is doubt as to the complete removal of all the tissue infiltrated by the infection, it is prudent to postpone grafting for a period of four to six weeks.
The alloplast materials such as beta tricalcium phosphate are well suited for these socket preservation procedures.

The type and morphology of the bone defect is an important factor. If the graft is an onlay graft, such as a narrow posterior ridge that requires augmentation in width, it is basically a one walled defect, and the only source of cells, vaculature and bmp's come from preparing a bleeding surface on that wall. Since the morphology of the defect is not conducive to particulate materials, these are only possible when you only need a couple of millimeters of additional width and requires tenting and a membrane. A decision to split or expand the ridge may be a better choice when only a couple of millimeters of additional width is needed.

Sinus grafting procedures utilize a much larger quantity of grafting material which is usually packed to a height of about ten millimeters. It has been proposed that bone will grow in the sinus regardless of what type of material is used, but some authorities recommend allograft material that will contain bone morphogenetic proteins for bone induction, or at least a mixture of allograft, alloplast, and ideally some autograft content also.

There has been concern recently pubicized about the safety of bone allografts due to the possibility of disease transmission to the recipient. The author is not aware of literature reports of any disease transmission by bone allograft in dentistry.It is this author's opinion that the current FDA regulations and the donor tissue handling protocols in place today make the chance of antigen or disease transmission from allograft bone almost non-existent.
An interesting paper about the safety of bone allografts used in dentistry was published in the ADA journal and a link is provided below:

Bone grafting will continue to advance and help improve the outcome of modern dental procedures.
If you need a bone graft in west palm beach please call our office or visit our website.
West Palm Beach Dentist
Carlos Boudet, DDS, DICOI