Implants

The Status of Bone Grafting for Implant Dentistry

Dr. Lee H. Silverstein December 1, 201710 Mins read3k Views

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What is your material of choice for sinus grafting?
Dr. Silverstein: Bone grafting and/or bone augmentation is a surgical procedure that tries to replace and/or regenerate the missing or lost alveolar bone in a patient. This procedure utilizes material from the patient’s own body, a synthetic/artificial substitute, or natural bone substitute. Provided that there is adequate space for the needed bone growth, the body’s bone tissue has the capacity to regenerate the lost alveolar bone. The process is possible, because while nascent bone grows, it will generally replace the grafted material, with the net result being a new region of established bone, whether the clinician is trying to regenerate lost alveolar bone as a result of odontogenic infection or trauma or attempting to correct an insufficient quantity of available bone as a result of tooth loss, which, in the case of maxillary posterior teeth, can result in pneumatization of the sinus. In the former scenario, when a tooth is lost, the primary goal of replacing the bone is to enhance the appearance of the soft-tissue topography. I remember the day that one of my mentors in dental implantology, Dr. Carl Misch, told me that almost 100% of his implant cases required bone grafting because bone is lost so rapidly after a tooth extraction that it is a very common requirement to return the ridge for something ideal for either an aesthetic or a functional implant position.

For sinus grafting, specifically for grafting the lateral window, I use a blend of allograft material. First, an alloplast demineralized bone matrix (DBM) putty-type material is utilized; then tricalcium phosphate; and then a mix of mineralized cortical bone and larger particle sizes mixed with cortico-cancellous bone. Since some of the bone is denser, it should take longer to turn over, and some of the bone is cancellous, which should turn over faster. Lastly, more of the alloplast DBM putty is placed at the most lateral aspect of the graft so it is the rafting material that becomes contiguous with the bony walls of the osteotomy, which is the lateral window. It’s more convenient to use the DBM putty than the granules at the junction of the barrier and sinus membrane, and the outer lateral window and the covering barrier. I have done thousands without any complications. I often put a resorbable cross-linked bovine collagen membrane, lasting at least several weeks, on the lateral access wall.

For a sinus bump/implosion, I prefer to use a blend of materials. First, I use an alloplast demineralized bone matrix (DBM) putty material; then tricalcium phosphate; then a mix of large and small particle sizes of cortico-cancellous allograft bone; and, lastly, more of the alloplast DBM putty so that there is no particulate graft material, which could be sharp, against the sinus membrane and wedged between the dental implant and osteotomy wall and possibly cause a macro phage/foreign body-type response. It’s more convenient to use the putty than the granules at the junction of the barrier and sinus membrane and the outer lateral window and the covering barrier. Again, I have performed thousands of sinus implosion cases without any complications.


Figure 1: Vacutainers of separated blood prior to removing the platelet-rich plasma (PRP).	Figure 2: Two monocortical block grafts after being soaked with PRP. The left is autogenous and the right is an allograft.

Figure 3: An autogenous monocortical block graft fixated to the recipient site.	Figure 4: A socket graft made up of cortico-cancellous bone and larger, demineralized, freeze-dried bone particles.

What is your current choice of bone for grafting periodontal defects?
Dr. Silverstein: The clinical objective when grafting periodontal infra-bony defects is to replace and/or regenerate the lost alveolar bone. This is typically accomplished by utilizing bone grafting material with an allograft or a synthetic bone substitute product. I believe that the success of any bone grafting around natural teeth to regenerate lost alveolar bone and periodontal attachment depends on the proper preparation of the affected tooth for root scaling and root planing; detoxification with agents such as tetracycline; root treatments such as Emdogain (Straumann USA); and bony defect preparation, such as decorticating the mesial and distal bony defect walls. My first choice of grafting material would be an allograft, specifically a cortico-cancellous allograft-type product. My rationale for this choice stems from the orthopedic literature that strongly suggests that cortical bone contributes mostly to the structural strength and support of the affected site being augmented and/or manipulated, whereas the cancellous bone contributes mostly to the process of new bone formation, termed osteogenesis. Thus, the use of a cortico-cancellous allogeneic bone grafting material can provide structural support and osteogenesis to the site being treated.

The second choice would be the use of a ceramic-based bone graft substitute, such as a tricalcium phosphate material, as one of my mentors, Dr. Hilt Tatum, would advocate. In my observation over the past several decades of clinical experience, grafting substitutes, even with many developments in technologies for bone tissue engineering that are commercially available, have natural elements along with synthetic, xenograft, or allograft (cadaver) materials.

What’s your current choice of bone for performing socket grafting?
Dr. Silverstein: Socket grafting is a procedure that will maintain the 3-D volume of a tooth socket by placing a bone substitute into a bleeding recipient site (the socket) and allowing this bone tissue to regenerate completely, provided the space to grow new bone is maintained. In essence, the bone allograft, which usually contains a very small amount of bone morphogenetic protein (BMP), is saturated with osseous blood, which contains the ability to cause the release of growth factors for bone and tissue growth. Then, as the body produces new bone, it will replace the bone substitute that was placed into the socket to maintain the necessary space.
Presently, my bone substitute of choice for socket grafting is DBM, which is resorbable, osteoinductive, and osteoconductive and is combined with a cortico-cancellous bone grafting material or a ceramic bone grafting material, such as tricalcium phosphate.

What is your opinion about using DBM putty?
Dr. Silverstein: I earnestly believe that DBM bone grafting material is clinically the most user-friendly bone substitute product available. It is the most popular product in hospitals and is frequently used in reconstructive and trauma medicine according to the FDA, the American Academy of Orthopedic Surgeons, and dental industry publications. The DBM bone grafting substitute has 3 desirable qualities: It is biodegradable, osteoinductive, and osteoconductive. DBM is currently available in user- and cost-friendly quantities in the following forms: a putty, a cube, a gel, a compressed sheet called Flex, and an injectable paste. DBM is often conjugated with carriers such as Type I collagen, gelatin, glycerol, or calcium phosphate. What is clinically important and relevant for handling characteristics is that some of the carriers are hydrophilic and stay where the graft is placed, while others are hydrophobic and tend to float away from bodily fluids (such as blood), making its handling characteristics less than desirable. More recently, DBM has been combined with rhBMP-2 and -7 proteins on an absorbable sponge.

What are your thoughts related to monocortical bone block grafting?
Dr. Silverstein: In many cases where dental implants are to be utilized to replace missing teeth, a bony ridge defect in either alveolar ridge width or height complicates the proper placement of a dental implant. These alveolar ridge defects are commonly found in the maxillary and mandibular anterior and posterior regions. These sites are treated with monocortical bone grafts to regenerate the lost and/or missing bone so a dental implant can be placed into its proper, prosthetically dictated, 3-D position. The gold standard when placing a monocortical bone graft is to use an autologous graft harvested from the mandibular symphysis and ramus regions. The autografts have highly porous bone scaffolds, with pore sizes in the donor that are suitable for optimal formation of a new bone matrix and subsequent bone regeneration. The autologous monocortical bone donor graft will contain necessary growth factors (such as fibroblastic growth factor and agents such as glycosaminoglycans (GAGs) and hyaluronic acid), which are modulatory in bone healing. Growth factors such as vascular endothelial growth factor (VEGF), fibrin growth factor (FGF), and platelet derived growth factor (PDGF) can stimulate angiogenesis in the healing scaffolds and donor graft. Thus, platelet-rich plasma (PRP) is commonly added to both the recipient and donor grafts to add a high concentration of stem cells and healing promotive factors (such as growth factors) that could provide the necessary level of healing cells for bone repair and regeneration.


Figure 5: An acellular dermal matrix soft-tissue graft being placed under a facial flap and over the facial bony alveolus housing a dental implant to create a better soft-tissue topography.	Figure 6: Dental implants placed into an area grafted with a monocortical block graft.

Figure 7: A fixated block graft being covered with PRP-soaked demineralized bone matrix (DBM) graft material.	Figure 8: Tricalcium phosphate graft material being added to the facial of a dental implant.

Figure 9: A maxillary anterior region with hopeless teeth removed.	Figure 10: A maxillary anterior bony ridge, grafted with cortico-cancellous bone on the left and tricalcium phosphate graft material on the right.

Figure 11: A maxillary anterior ridge after allowing graft maturation for 8 months.

In many instances, the morbidity associated with the harvesting of an autologous monocortical bone graft has led to the use of allogenic bone blocks for the correction of alveolar ridge bony defects in preparation for the future placement of a prosthetically driven dental implant. However, monocortical autografts currently remain the gold standard because monocortical allogeneic block grafts have several shortcomings when compared to a monocortical autograft. The literature suggests that the combined use of healing promoting factors, stem cells (obtained from PRP), and gene therapy, when combined with either autologous or allogeneic block grafts, will enhance their rate of successful integration with the bony recipient site.

In summary, I believe that since most of the reports in the current literature that have documented the use of allogeneic monocortical block bone grafts for the correction of alveolar ridge deformities to form the bony support for the proper placement of prosthetically driven dental implants, they are just case reports and, therefore, need further university-conducted prospective clinical studies to determine the effectiveness and predictability of this grafting material and technique. This author is inclined to believe that there is insufficient scientific evidence available to provide conclusive documentation and biologic rationale for the use of allogeneic block grafts relative to alveolar ridge augmentation, biologic graft incorporation, and the long-term survival of dental implants placed into a recipient site augmented with an allogeneic monocortical block graft.

Based upon your clinical experience, how often is bone augmentation used in conjunction with soft tissue grafting and vice versa?
Dr. Silverstein: In my experience, tissue grafting to increase the zone of keratinized gingiva in lieu of abolishing the vestibular depth is the therapy of choice. For this treatment, in the majority of bone augmentation cases, which should be performed to facilitate the prosthetically driven placement of dental implants, the clinical goal should be to increase the available alveolar ridge width or height. Many clinical cases that exhibit a Seibert Class III alveolar ridge deficiency (meaning a loss of buccal width and occlusal-apical height), in my experience, have required the use of a monocortical block graft (autologous or allogeneic) along with soft-tissue augmentation using an acellular dermal matrix material and placed as a sub-epithelial connective tissue (SECT), soft-tissue, autologous graft. This allows the clinician to obtain tension-free primary closure and a mode to create a very wide zone of attached keraintized gingival tissue. There are also many clinical scenarios where there is a Siebert Class I defect (buccal palatal deficiency) and a SECT graft needs to be placed to thicken the thin, friable gingival tissue type, or there is a discoloration from the underlying structures (gray from a dental implant or brown from a nonvital tooth) that needs to be masked.


Figure 12: A maxillary anterior grafted ridge 8 months post graft placement.	Figure 13: Sockets grafted with a DBM material.

Figure 14: A DBM graft material mixed with tricalcium phosphate particles to act as a radiographic marker.

What is your choice of guided bone regenerative (GBR) membrane?
Dr. Silverstein: Based upon the published literature on GBR membranes/barriers, a material should be intact for a minimum of 6 weeks to allow for the body to grow new bone into a maintained space as well as to isolate it to keep out the soft-tissue-forming cells. I believe that a GBR barrier should be occlusive to unwanted soft-tissue cells for a period of 6 to 16 weeks. Furthermore, I only advocate the use of resorbable GBR barriers. In addition, the choice of a GBR barrier depends on whether primary surgical closure is obtainable; if it is, then any bovine cross-linked barrier with a resorption time of 16 weeks is an acceptable choice. However, if the case does not lend itself to obtaining primary closure, then Acellular Dermal Matrix Allogeneic would be my product of choice. As reported in the literature, this material has been used successfully and with a predictable outcome. Currently, this material is marketing with the trade name AlloDerm (BioHorizons). Since the Dermal matrix material is indicated for soft-tissue grafting, a GBR barrier can also be used when the surgical flap tissues are thin and have little keratinized gingival tissue. Lastly, if a clinical situation exists where primary closure can be obtained but the surrounding surgical flap has little or no existing keratinized gingival tissues, then, in my opinion, the GBR barrier of choice would be an acellular dermal matrix. With this choice, the outcome would include both bone growth and the creation of a large zone of attached keratinized gingival tissue.

Dr. Silverstein is an associate clinical professor at the Dental College of Georgia at Augusta University in the Department of Periodontics and also has a private practice in Marietta, Ga, at Kennestone Periodontics. He holds Fellowships in the Pierre Fauchard Academy, both the American and the International College of Dentists, and the American Academy of Implant Dentistry. Dr. Silverstein is privileged to be on the contributing editorial boards of Dentistry Today, Compendium, Inside Dentistry, Practical Periodontics and Aesthetic Dentistry, Journal of Oral Implantology, Collaborative Dental Techniques, Functional Esthetics and Restorative Dentistry, and the Academy of General Dentistry Scientific Magazine. Having published more than 140 scientific articles in referred journals, he has also been a contributing editor for numerous textbooks, authoring 14 textbook chapters. Dr. Silverstein is the author of 4 peer-reviewed books (Principles of Dental Suturing: A Complete Guide to Surgical Closure, Principles of Soft Tissue Surgery: A Complete Step-by-Step Procedural Guide, Principles of Hard Tissue Regeneration and Implant Therapy: A Complete Step -By-Step Guide, and The Suture Book: The Definitive Guide to Dental Suturing and Surgical Flap Closure). All 4 textbooks have been peer-reviewed and have ADA-CERP certification. He lectures both nationally and internationally on the topics of periodontal plastic surgery, dental implantology, hard- and soft-tissue regenerative surgical techniques, and oral medicine. He can be reached via email at either lsilverstein@augusta.edu or info@kennestoneperiodontics.com.