Theoretical model for bone graft success.

Theoretical assumptions must correlate with clinical efficacy and good surgical outcomes to be of value to clinicians and patients. This article examines several common assumptions regarding the use of bone marrow aspirate to enhance bone grafting procedures. Contrary to these assumptions, evidence-based research suggests the following: (1) No more than 4 mL of bone marrow should be aspirated from a single donor site. Aspiration of more than that amount does not substantially increase the number of progenitor cells harvested but instead dilutes the concentration of progenitor cells with other nucleated cells from peripheral blood. (2) Bone marrow aspirate should not be concentrated using centrifuge technology. Rather than isolating desired cells, centrifuging concentrates all nucleated cells, increasing the overall metabolic activity to the detriment of the desired cells. (3) Increasing the volume of graft material brought to a graft site has the unwanted effect of increasing the diffusion distance for oxygen and nutrients and may lead to graft necrosis. (4) Histomorphometric analysis is the most effective method of evaluating bone graft outcomes because only such analysis allows for quantification of the percentage of bone and viable cells within a bone core biopsy.

Antral membrane elevation using a post graft: a crestal approach.

The crestal approach to elevating the antral membrane by a resorbable StemVie post is a modification of the sinus lift technique. This technique can add 4-10 mm of bone height for severely atrophic ridges in areas that are difficult to access through a lateral window. The procedure is minimally invasive, simple, and predictable, and has less postoperative morbidity due to smaller flap design and minimal osteotomy. If sufficient alveolar bone is present for stabilization, an implant can be placed simultaneously with an antral elevation and graft. The StemVie post resorbs completely and is replaced by the patient's own bone. Healing is enhanced with the addition of bone marrow aspirate and/or peripheral venous blood to the StemVie post graft. The graft will absorb the blood or the marrow, allowing them to infiltrate through the porosity present in the graft. Bone marrow aspirate aids in healing with the addition of precursor osteoblastic stem cells, cytokines, and growth factors, while peripheral blood supplies mostly cytokines and growth factors.

Monocytes: super cells for bone regeneration.

Monocytes are progenitor cells that lead the inflammatory cascade reaction responsible for guiding revascularization and regeneration of tissue at injury sites. They do this by secreting inductive cytokines responsible for endothelial cell migration. When released into the peripheral blood, monocytes enter tissues and become macrophages. Monocytes also trigger the body's defense mechanism against microbial invasion by lysing and removing cell debris and dead tissue. The aim of this article is to explain the role of monocytes in the processes of bone healing and regeneration and describe their interaction with stem cells and other entities. Results of a pilot histomorphometric study in which concentrated monocytes were combined with demineralized allograft material to augment implant-placement sites in 2 patients also are presented.

The crestal approach: antral membrane elevation via a post graft.

The crestal approach to elevating the antral membrane by a resorbable StemVie Post is a modification of the sinus lift technique. This technique can add 4 to 10 mm bone height for severely atrophic ridges in areas that are difficult to access through a lateral window. The procedure is minimally invasive, simple, predictable, and has less postoperative morbidity because of smaller flap design and minimal osteotomy. If sufficient alveolar bone is present for stabilization, an implant can be placed simultaneous with antral elevation and graft. The StemVie Post completely resorbs and is replaced by the patient's own bone.

Bone grafting by means of a tunnel dissection: predictable results using stem cells and matrix.

Bone marrow aspirate has been shown to add stem cells, growth factors, and cytokines to bone graft matrices used in bone augmentation sites. The combination of bone marrow aspirate and resorbable scaffold material has a significant osteogenic capability that exceeds that of autogenous bone grafts. This article describes a subperiosteal tunneling technique for applying such grafts to defective sites. Treatment of 2 patients for whom the technique was used to graft 6 deficient sites is described. Histological results and histomorphometric analysis of bone core samples taken from 4 of the 6 grafting sites are also reported. Analysis of the 4 bone cores taken between 4 and 6 months showed a range of 34% to 45% of new bone.

Growth factors and gene expression of stem cells: bone marrow compared with peripheral blood.

PURPOSE: To evaluate and compare the presence of cytokines and growth factors in both bone marrow (BM) and peripheral blood. MATERIAL: Samples of autogenous BM aspirate and peripheral blood (PB) from 7 patients ranging in age from 49 to 80 years were analyzed with real-time polymerase chain reaction technology to identify and compare selected gene expression for specific cytokines and growth factors. The genes selected for analysis included those involved in osteogenesis, hematogenesis, angiogenesis, extracellular matrix molecules, and cell-adhesion molecules. A maximum of 4 cc';s BM aspirate was taken from the anterior iliac crest and 0.5 mL of venous blood was drawn from each of 7 patients. RESULTS: The results of the analysis indicate that both circulating blood and BM aspirate contain large quantities of a host of growth factors and cytokines. More platelet-derived growth factor is expressed in patient blood (PB) than in BM. Vascular endothelial growth factor alpha is expressed slightly greater in BM and vascular endothelial growth factor beta is slightly more prominent in PB. Transforming growth factors (TGFs) TGFA, TGFB1, and TGFB3 were equally expressed in BM and PB, and TGFB2 had a greater expression in PB. Bone morphogenetic proteins (BMPs) 1, 3, 7, 8B, R1A, and PR2 were almost equally expressed in BM and PB. BMPs 4 and 6 were expressed greater in PB. BMP2 was expressed more in BM. Extracellular matrix factors were equally expressed in PB and BM. Mesenchymal stem cell lineage markers varied in PB and BMA, and hematopoietic stem cell lineage markers were expressed more in PB than BM. Gene expression for angiogenic factors were equally expressed in PB and BM. CONCLUSION: In this investigation, specific cytokines and growth factors in BM are compared with those in peripheral blood. Each has similar biologic effects and most expressed equally in BM and PB. However, BMP2 and vascular endothelial growth factor alpha had greater expression in BM.

Bone marrow: orchestrated cells, cytokines, and growth factors for bone regeneration.

Bone regeneration requires an orchestrated interaction between various cells and other biological components. The synthesis of bone matrix with the release of cellular cytokines and growth factors facilitates and regulates cell growth. This leads to the maturation of bone that can support functional implants. Bone-marrow aspirate is a rich source of cells, cytokines, and growth factors needed for bone formation. Harvesting the marrow from the anterior iliac crest is a simple, safe, and cost-effective procedure. Mixing it with a resorbable scaffold and transplanting it to a site can predictably enhance bone regeneration. This article explores the anatomy of the bone marrow and describes the necessary elements for successful bone grafts, such as cells, bone matrix, and cellular regulators (both soluble and insoluble).

The inverted periosteal flap: a source of stem cells enhancing bone regeneration.

The periosteum is a necessary component for bone growth, healing, and remodeling. It provides vascularity, osteoblasts, and osteoclasts. It is a regenerative source for stem cells similar to those obtained from bone marrow aspiration. This article describes the inverted periosteal flap technique at an oral bone graft site as a means of enhancing bone regeneration. The technique is recommended when augmenting sites with 3- or 4-wall defects, in conjunction with implant placement or in combination with bone graft surgery.

Toward the identification of mesenchymal stem cells in bone marrow and peripheral blood for bone regeneration.

BACKGROUND: The advent of monoclonal antibody stem cell marker technology has made it possible to identify a variety of human stem cells and their progeny. Specific markers exist for cells related to bone healing and bone regeneration. These include but are not limited to hematopoietic, mesenchymal, endothelial, angiogenic, and vasculargenic precursor cells. PURPOSE: The purpose of this investigation was to (1) to identify, by means of cell markers, the presence of stem cells needed for bone formation within peripheral blood and bone-marrow aspirate, and (2) to ascertain whether more of those stem cells were present in the bone-marrow aspirate than the peripheral blood. MATERIALS: Samples of autogenous bone-marrow aspirate and peripheral blood from 6 patients ranging in age from 23 to 73 were analyzed with 6-column flow cytometry using cell markers for stem cells relating to bone growth and bone healing. Six monoclonal antibody cell markers were utilized: CD14, CD34, CD36, CD105, CD106, and CD309 (also known as vascular endothelial growth factor receptor or KDR). Subgroups reacting to these markers or combinations of markers were then further tested with other marker combinations. RESULTS: : The expression of specific monoclonal antibody cell markers revealed that bone marrow contained more osteogenic stem cells than peripheral blood. Bone marrow contained a higher percentage of cells that reacted with the CD34 and CD14 markers. This suggests that bone marrow contains more hematopoietic stem cells that proliferate to become myeloid progenitor cells, megakaryocytes, monocyte/macrophages, and osteoclast progenitors. When the fractions of bone marrow and peripheral blood samples that reacted with both CD34 and CD14 were further tested for CD105, more of the fraction from bone marrow reacted to CD105 than that from peripheral blood, suggesting more osteogenic potential in the bone marrow than the peripheral blood. When the fraction of bone marrow and peripheral blood samples that reacted with CD34 and CD14 were tested for the combination of CD105, CD106, and CD36, a smaller percentage of cells from the bone marrow reacted with CD36 than those from peripheral blood, suggesting that CD36 does not express for mesenchymal stem cells (MSCs). CONCLUSION: Bone-marrow aspirate seems to contain a significantly greater percentage of hematopoietic, endothelial, and MSCs than peripheral blood. Of particular significance is the higher percentage of bone-marrow cells reacting to CD105, an indication of the presence of MSCs. The ability of multipotent MSCs to form osteoblasts for bone regeneration makes transplanted bone-marrow aspirate a promising tool for enhancing bone regeneration.

Bone block allograft impregnated with bone marrow aspirate.

PURPOSE: To evaluate the influence of bone marrow aspirate when added to bone block allograft to repair osseous defects. BACKGROUND: Bone-marrow aspirate has been combined with xenograft and allograft particulate material and has produced a significant quantity of new bone growth. However, the use of allograft bone blocks has advantages in some clinical situations. This article discusses cell-based therapies by means of in vivo transplantation of stem cells derived from bone-marrow aspirate and incorporated into allograft corticocancellous bone block for bone regeneration. MATERIALS: A technique for combining bone-marrow aspirate with block allografts was developed. To evaluate its influence in repairing osseous defects, a maximum of 3 to 4 mL of bone marrow was aspirated from the anterior iliac crest of 5 patients who had severely atrophic maxillary and mandibular ridges. Five sites were grafted with allograft bone blocks saturated with bone-marrow aspirate and secured with bone screws (ACE Surgical Supply Company, Inc. Brockton, MA). At one of the sites a core specimen was taken 4 months after implant placement and submitted for standard histologic and histomorphometric analysis. RESULTS: After 4 to 8 months of healing, all the grafts had integrated into the recipient bone. Implants were placed at all 5 sites and osseointegrated successfully. Examination of the bone core showed the graft to be well-integrated, with 54% of the core consisting of bone and 46% of marrow. Eighty-nine percent of the bone was vital. CONCLUSION: Impregnation of bone-marrow aspirate into allograft bone block activates the body's ability to form new bone. The bone-marrow aspiration technique is less invasive than harvesting autogenous bone from a second surgical site, offers predictable results, and is cost effective.

A histomorphogenic analysis of bone grafts augmented with adult stem cells.

PURPOSE: To evaluate the influence of bone marrow aspirate added to xenograft or alloplast graft matrix scaffold to produce bone. MATERIALS: A maximum of 4 cc bone marrow was aspirated from the anterior iliac crest of 5 patients to saturate the matrix scaffold prior to bone graft. Seven graft sites evaluated included sinus lift augmentation, particulate onlay graft of the maxilla via a tunneling procedure, and particulate onlay graft of the maxilla stabilized with titanium mesh. The xenograft scaffold was either PepGen Putty (DENTSPLY Friadent CeraMed, Lakewood, CO) or C-Graft resorbable algae material (Clinician's Preference, Golden, CO). The alloplast scaffold was beta-tricalcium phosphate (either Curasan AG, Kleinostheim, Germany, or Vitoss; Malvern, PA). RESULTS: Graft sites healed for 4-7 months. Core specimens of graft sites were taken with trephine drills, and submitted for standard histologic and histomorphogenic analysis. The percentage of graft material converted into bone, percentage of vital graft matrix, percentage of unresorbed matrix, and percentage of remaining interstitial tissue were measured. After a 4-month healing of sinus-lift augmentation with C-Graft, the biopsy showed 31% bone that was 100% vital. Unresorbed graft material was 26%, and remaining interstitial material constituted 43%. Using pure phase beta-tricalcium phosphate, a 4-month core biopsy showed 40% bone that was 100% vital. Residual graft was 3% and interstitial material 57%. A sinus grafted with PepGen P-15 (DENTSPLY Friadent CeraMed) was found to be 14% bone, with 100% of that bone vital. The non-bone within the core was 36%. After a 4 1/2-month healing of bilateral sinus grafts using a nonpure phase beta-tricalcium phosphate, the percentage of the biopsy that was bone was 23% on the right side and 16% on the left side. Vital bone was 89% (right side) and 86% (left side). The core taken after 4 months of healing from the anterior maxilla particulate onlay graft with PepGen P-15 showed 32% bone, with 100% found to be vital. Non-bone within the core was 15%, and 53% was interstitial material. After 7 months of healing, a biopsy core from the maxillary ridge augmented with C-Graft was 45% newly formed bone, with 100% of the bone vital. There was no residual graft material present. DISCUSSION: Bone regeneration by cell-based strategies depends upon an understanding of the biology and potential of adult stem cells as a method of regenerating bone. CONCLUSIONS: Bone marrow aspirate containing adult stem cells when mixed with bioengineered graft materials provide a scaffold to support the proliferation, differentiation, and maturation of the stem cells, as well as facilitating angiogenesis. This article presents histological evidence that stem cells aspirated from bone marrow and transplanted onto biocompatible scaffolds can successfully regenerate bone. This new standard for bone grafting may emerge as an alternative to autogenous bone grafts.

Bone marrow aspiration: technique, grafts, and reports.

This article describes a technique for obtaining adult stem cells from bone marrow aspirate. Case reports show how this procedure might replace the gold standard for bone grafts with the platinum standard of obtaining stem cells. The bone marrow aspirate and transplantation of adult stem cells within the resorbable) matrix and under the influence of soluble regulators have the potential for introducing the platinum standard for bone grafts. There are several advantages to using bone marrow aspirate. The technique is simple, a second surgical site is not needed, there is minimal postoperative morbidity, and adult stem cells populate the graft site with osteoblasts.

The bone-grafting decision tree: a systematic methodology for achieving new bone.

Successful bone grafting requires that the clinician select the optimal bone grafting material and surgical technique from among a number of alternatives. This article reviews the biology of bone growth and repair, and presents a decision-making protocol in which the clinician first evaluates the bone quality at the surgical site to determine which graft material should be used. Bone quantity is then evaluated to determine the optimal surgical technique. Choices among graft stabilization techniques are also reviewed, and cases are presented to illustrate the use of this decision tree.

A new "platinum" standard for bone grafting: autogenous stem cells.

Autogenous bone has long been considered the gold standard of all bone grafting materials. However, complications have been associated with autogenous bone-harvesting procedures. This article suggests that an alternative approach, grafting with autogenous bone marrow aspirate, may become a new platinum standard. Bone marrow can be extracted from the large flat bones of the body with relative ease and safety, and it provides a rich source of adult stem cells as well as growth factors that facilitate osteogenesis. Mixed with a resorbable matrix or scaffold, bone marrow aspirate has the potential to reconstitute various bony defects in the mouth to reconstruct the severely atrophic maxilla and mandible. The potentiality and plasticity of stem cells have been well documented.

Antral membrane balloon elevation.

Many edentulous posterior maxilla are found to be encumbered by alveolar resorption and increased pneumatization of the sinus. These factors limit the quantity and quality of bone necessary for successful implant placement in these areas. One solution is to use shorter implants, but this often results in an unfavorable crown-root ratio. To create an improved environment in such regions, the classic sinus floor elevation with bone augmentation is a well-accepted technique. However, when the edentulous area is limited to a zone between 1 and 2 teeth, lifting the membrane becomes difficult and may subject it to iatrogenic injury. The antral membrane balloon elevation technique, which is introduced in this preliminary report, is a modification of the currently used sinus lift. It elevates the membrane easily and makes the antral floor accessible for augmentation with grafting materials.

Trephine bone core sinus elevation graft.

The sinus cavity often limits the amount of available bone for the placement of implants in the posterior maxilla. The sinus lift operation and graft is a technique that can add grafted bone in excess of 10 to 16 mm through a lateral wall quadrilateral osteotomy. However, when moderate alveolar atrophy is present, an osteotome technique can provide an average bone height in crease of 3.5 mm. This article presents the trephine bone core sinus elevation graft, which is intended to increase bone height 4 to 8 mm. This procedure is especially indicated when adjacent teeth are present and there is only moderate atrophy of the alveolus.