The Inverted Periosteal Graft
RESEARCH: THE INVERTED PERIOSTEAL GRAFT
Compendium • March 2007
The Inverted Periosteal Graft
ABSTRACT
The adult human periosteum is known to contain fibroblasts and their progenitor cells, osteoblasts and their progenitor cells, and stem cells. In all age groups, the cells of the periosteum retain the ability to differentiate into fibroblasts, osteoblasts, chondrocytes, adipocytes, and skeletal myocytes. The tissues produced by these cells include cementum with periodontal ligament fibers and bone. The inverted periosteal graft is designed to place multipotent cells in the periodontal lesion with the ability to regenerate cementum, periodontal ligament, and bone.
Periodontal therapy has made significant strides in developing methods and materials for regenerating lost tissue. The inverted periosteal graft (IPG)a places cells in the periodontal defect with the potential to produce cementum,1 periodontal ligament,1 and bone.2-5 Bone repair in the skeleton occurs as a result of a significant contribution from the periosteum. This method of healing found in the skeleton can be applied to the diseased periosteum.
Tissue regeneration of any type has certain requirements to be successful. Initially, a space is necessary for regeneration to take place. In addition, the correct cells with the potential to create the desired tissue must be present in the regenerative site. The raw materials needed to produce the tissue must be available, and the cells with the potential to produce the tissue must be stimulated. Last, the correct physiologic environment must be present to optimize the regenerative potential. Given these factors, the body possesses the potential to re-create lost tissue.
The maxilla and mandible are created by intra-membranous bone formation. Embryonic cells arrange in sheets in the facial tissue and produce the facial bones. After the facial bones are formed, these sheets of cells condense into the periosteum. The cells of the periosteum retain much of their embryonic multipotent properties.6
Adult human periosteum is known to possess fibroblasts and osteoblasts as well as their progenitor cells. The adult human periosteum also has been found to contain a significant number of multipotent stem cells.6 Regardless of age, periosteal cells have been found to be clonogenic, display long telomeres, and express markers of stem cells.6 Both parental and single-cell–derived clonal cell populations originating from adult periosteum have been found to differentiate to the chondrocyte, osteoblast, adipocyte, and skeletal myocyte lineages in vitro and in vivo.6 The adult human periosteum contains cells that are multipotent stem cells at the single-cell level.6
The outer layer of the periosteum, which is adjacent to soft connective tissue, is comprised of dense collagen fibers, fibroblasts, and their progenitor cells.7 Research shows that these cells can produce cementum with integrated collagen fibers when placed over dentin.1 In the IPG, cells on the outer layer of the periosteum (those with the ability to produce cementum and periodontal ligament) are inverted and cover the coronal portion of the periodontal defect. In this manner, the first cells to populate the periodontal defect are cells of the outer periosteal layer.
The most critical phase of regenerative periodontal therapy is reattachment of collagen fibers to the root surface. However, regeneration of bone needs to follow reattachment of collagen to the root surface. The normal anatomy of the periosteum includes an outer layer of fibroblasts, fibroblast progenitor cells, and stem cells adjacent to soft connective tissue and an inner layer of osteoblasts, osteoblast progenitor cells, and stem cells adjacent to bone.7 In the IPG, osteoblasts and their progenitor cells cover the layer of fibroblasts and are immediately available for osteogenesis. During healing, the cells with the potential to regenerate cementum and periodontal ligament are the first cells presented to the root surface. Osteoblasts and their progenitor cells are immediately behind the fibroblasts and populate the osseous defect. The IPG places the proper cells in the proper location for regeneration of the diseased periosteum.
In the adult, the inner osteoblastic layer is inactive and very thin. However, surgical release of the periosteum stimulates cells in both layers of the periosteum and active cell multiplication occurs.8 Fibroblasts of the outer layer and osteoblasts of the inner layer and their progenitor cells respond to surgical release by a thickening of the periosteum and an increase in cellular activity.8
Training in the use of inert barriers has instilled in this surgical technique the need to suture the barrier tightly against the root surface. Any area without firm barrier-to-tooth apposition is likely to have invasion of gingival cells, resulting in surgical failure. When using the IPG, firm apposition of the periosteum to the root surface is not required. While close apposition of the periosteum to the root surface may be good surgical technique, merely placing cells with the potential to regenerate lost tissue in the area of the defect appears to be adequate for success. When the root surface is populated with fibroblasts and collagen, epithelial invasion would be contrary to normal wound healing. When the body has the proper cells available to regenerate itself, it is programmed to produce normal tissue.
The periosteum covers most of the bones in the body. If the periosteum is grafted into soft connective tissue, it will grow bone in areas where bone is not found.5 The periosteum is a very dense, tough layer of fibrous tissue intended to act as a covering for bone and provide progenitor cells for bone growth and repair. In the mouth, the periosteum can be found in most areas where bone is covered with mucosa but not in areas of attached gingiva. The hard palate is covered with periosteum, as it is covered with keratinized gingiva but not attached gingiva. Bone covered by periosteum is always cortical bone.
In the mouth, the periosteum begins at the mucogingival junction and covers the maxilla and mandible. As a result, an entire arch or entire mouth can be treated at one appointment because of the availability of periosteum adjacent to the graft site.
The IPG retains its attachment to either the gingival flap or alveolar bone. The periosteum thereby retains its blood supply and will survive even if exposed after surgery. Because the IPG is attached to either the gingival flap or bone it can be sutured securely over the graft site to hold the bone graft material and maintain space for regeneration.
The IPG can be used with any graft material. However, the ideal graft material should not require resorption before the initiation of regeneration; it should stimulate osteoblasts to produce bone and inhibit osteoclasts to prevent collapse of the graft site. The graft material should supply the raw materials used in bone formation and be simply and efficiently converted by osteoblasts into bone. Another significant factor in regenerating bone is that, by themselves, local osteoblasts in alveolar bone have limited regenerative potential.
An entire arch or entire mouth can be treated at one appointment because of the availability of periosteum adjacent to the graft site.
The IPG, in combination with the proper graft material, stimulates regenerative cells, inhibits resorptive cells, and supplies the raw material for regeneration. The IPG is designed to place progenitor cells that have the potential to regenerate cementum, periodontal ligament, and bone in the proper position to immediately begin the regenerative process.
DESCRIPTION AND ILLUSTRATION
The IPG is intended to acquire the periosteum and place it in the periodontal lesion. Two different methods can be used to achieve the same result. It is up to the operator to determine which technique is appropriate. One method is to raise a split-thickness flap, leaving the periosteum covering the bone. The flap is extended apically to a point where the periosteum can be incised and lifted off the bone. With this method, the periosteum remains attached to the bone near the mucogingival junction. Once the periodontal lesions are treated and grafted, the buccal and lingual periosteal membranes are sutured interproximally with resorbable sutures. After suturing the periosteum over the bone grafts, the buccal and lingual gingival flaps are closed over the inverted periosteum.
Another method is to raise a full-thickness flap, incise the periosteum at the apical extent of the flap, and dissect the periosteum off the flap. Again, after the lesions are treated and bone grafts are placed, the periosteal flaps are sutured interproximally. After the inverted periosteal flaps are closed over the bone grafts, the buccal and lingual gingival flaps are sutured. 
Figure 1A—The patient presented with chronic adult periodontitis. Significant horizontal bone loss with vertical defects were present upon examination. Approximately 2 mm of exposed cementum was found as a result of gingival recession with loss of papilla. The periodontal tissue was cyanotic and bled when probed. Probings of 7 mm to 8 mm are found mesial to tooth No. 12 and distal to teeth Nos. 13 and 14. Recession, vasodilatation, and cyanosis are evident.
[clearboth]
Figure 1B—The preoperative radiograph shows vertical defects mesial to tooth No. 12 and distal to teeth Nos. 13 and 14.
[clearboth]
Figure 1C—Buccal view of horizontal bone loss.
[clearboth]
Figure 1D—The granulation tissue is removed, showing vertical defects mesial to tooth No. 12, distal to teeth Nos. 13 and 14.
[clearboth]
Figure 1E—Palatal alveolar bone loss.
[clearboth]
Figure 1F—The periosteum is incised at the base of the flap and dissected off the buccal flap. The periosteum is rolled up at the mucogingival junction and is being grasped with the pickups buccal to the bicuspids.
[clearboth]
Figure 1G—The periosteum is incised at the base of the palatal flap and dis-sected coronally. In this photo, the periosteum is grasped by the tissue pickups.
[clearboth]
Figure 1H—The buccal periosteum is sutured to the lingual periosteum. The periosteum is reflected back between the bicuspids to show the site grafted with Regen Biocement.
[clearboth]
Figure 1I—The lingual periosteum is sutured to the buccal periosteum and the buccal flap is reflected with a periosteal elevator.
[clearboth]
Figure 1J—At 1 month after surgery, this radiograph shows reossification of the periodontal lesions.
[clearboth]
Figure 1K—At 1 month after surgery, the gingival margins are maintained at preoperative levels with loss of interproximal tissue around the bicuspids. Tissue health is excellent with no probing defects or bleeding upon probing.
[clearboth]
The decision regarding whether to use a split-thick-ness or full-thickness flap approach will depend on many factors such as the nature of the lesion, the amount of attached gingiva, the location of the periosteum, and the position of the teeth. Every patient presents with a unique set of circumstances, and as a result, the IPG requires fore-thought before initiating the surgery.
The first case presented in the illustrations is a step-by-step series of photographs that describes the significant aspects of the IPG (Figures 1A-1K). Following this is a series of cases that show how the IPG can be used to treat different types of periodontal lesions (Figures 2-7).
[clearboth]
Figure 2A—Teeth Nos. 30 and 31 were planned for surgery using the IPG and Regen Biocement. Probing on tooth No. 30 was to the apex of the mesial root with a deep class 2 lingual furcation.
[clearboth]
Figure 2B—Buccal view of the lesions on teeth Nos. 30 and 31 at the time of surgery. The mesial of tooth No. 30 presents with a 1-wall defect that wraps around the lingual into a class 2 lingual furcation.
[clearboth]
Figure 2C—The 2-month postoperative radiograph shows immature bone fill-ing the vertical defects with all probings 3 mm or less. The bone regenerat-ed on the mesial aspect of the mesial root was scheduled for biopsy, histological evaluation, and regrafting.
[clearboth]
Figure 2D—The bone biopsy was taken from only regenerated bone. The left of the photomicrograph was adjacent to the root surface. The tissue of the attachment apparatus is stained dark green. The blue arrows point to remain-ing graft particles.
[clearboth]
Figure 3A—This preoperative radiograph shows a 3-wall mesial lesion on tooth No. 19 with a severe interproximal 2-wall lesion to near the apex between teeth Nos. 18 and 19. A class 2 buccal furcation defect is pres-ent on tooth No. 18 with distal horizontal bone loss.
[clearboth]
Figure 3B—At 7 months after surgery, the vertical defects and the furcation defect are fully regenerated. The gingival tissues are healthy with no probing defects.
[clearboth]
Figure 4A—This preoperative radiograph shows a class 2 mesial furcation on tooth No. 14.
[clearboth]
Figure 4B—The postoperative radiograph shows new bone formation in the mesial defect with no probing defects. The regenerated bone shows greater density than the surrounding bone.
[clearboth]
Figure 5A—Tooth No. 14 exhibits severe class 3 furcation bone loss with endodontic disease. Clinically the gingiva on the distal buccal root exhibited recession to the apex.
[clearboth]
Figure 5B—After a distal buccal root amputation and an IPG with Regen Biocement, 80% of the furcation bone is regenerated. Ectopic bone formation has occurred distal to this molar above the alveolar ridge. (Endodontics and restorative dentistry courtesy of Dr Ron Ask.)
[clearboth]
[clearboth]
Figure 6—This patient presented with generalized periodontitis case type IV. Teeth Nos. 6 to 11 had 6-mm to 7-mm probing with purulent exudate. The post-operative radiographs show fill of all angular defects and approximately 2-mm to 3-mm horizontal bone regeneration.
[clearboth]
[clearboth]
Figure 7A—This figure presents the preoperative findings of a complete case with generalized chronic periodontitis. The goal was to maintain papilla in the esthetic zone while regenerating lost periodonteum throughout the dentition.
[clearboth]
[clearboth]
Figure 7B—Six weeks after full mouth surgery using the IPG and Regen Biocement the photographs show minor differences between pre- and postoperative gingival margins. Rapid bone growth in the early stages of healing produces bone that is high in percent of mineralized tissue but low in mineral content. As the regenerated bone matures, the mineralized content of the bone increases and trabecula are formed.
[clearboth]
DISCUSSION
Periodontists have a keen understanding of the healing process that occurs after periodontal surgery. If the surgical flaps are closely apposed, the epithelium quickly covers the surgical site as fibroblasts of the attached gingiva seek to reestablish their connection to bone and teeth. Regeneration of the periodontal ligament and bone occurs from the apex of the lesion and progresses in a coronal direction until met by the gingival epithelium.
Postoperative healing after regeneration using the IPG is unique. For the first 2 weeks there appears to be no growth of the epithelium or attached gingiva. The papilla and gingival margins are often slightly retracted from the crowns of the teeth. At this stage, the periosteum forms a covering of tissue that extends from under the flap surrounding the roots of the involved teeth and is in immediate contact with the roots. There is no probing past this tissue layer. Between weeks 2 and 6, the clinical appearance of the gingiva gradually reverts to a normal clinical picture of attached gingiva.
The radiographic image of healing after the IPG is also different from that seen with guided tissue regeneration (GTR). During the healing process using GTR, the regeneration of periodontal ligament and bone is produced by tissues at the apex of the lesion. However, healing after the IPG appears to occur not only from the apex of the lesion but also from the coronal aspect of the lesion. The early radiographic appearance of healing with the IPG also may be a result of the bone graft material used in these studies.
Regen Biocementa has very little radiodensity, so initially radiographs appear radiolucent. As the regeneration process occurs, radiodensity increases but is homogeneous in appearance as the grafted site is filled with rapidly growing bone lacking trabecula. Over a period of months, this bone is remodeled with an increase in radiodensity and the development of trabecula. While regenerated sites radiographically give the appearance of a normal periodontal ligament, no histology is currently available to elucidate the method of attachment.
During the 3 years of development of the IPG, all defects were grafted with Regen Biocement. Because both the surgery and graft material are unique, it is unknown what the exact effect the IPG and Regen Biocement have on the healing process independent of each other. However, after 3 years of developing this surgical technique, it appears the rapid production of bone without trabecula is the result of the osteogenic properties of the bone graft material. Reattachment to the tooth with what appears to be a new periodontal ligament seems to be the result of the presence of the periosteum.
The dimension and thickness of the periosteum varies in different areas of the mouth and between patients. Vital structures underneath the periosteum must be understood and considered during surgery. However, accessing the periosteum and acquiring the graft can be accomplished quickly and effectively with the proper training and experience. This surgical modality allows the practitioner to efficiently and effectively perform regenerative surgery on all surfaces for all teeth in a quadrant or mouth.
Bone regeneration in periodontal lesions is unlike the rest of the body, because skeletal bones are covered by periosteum and no other part of the body has attached gingiva. The IPG heals periodontal lesions by using the same healing process seen in the regeneration of bone fractures, where periosteum is a principle ingredient. By using the body’s own healing mechanism for bone regeneration, the IPG may prove to be an advancement in the regeneration of the lost periodonteum.
The periosteum is commonly found in contact with root surfaces because of malposition of the dentition or after surgical therapy. Because this situation is well tolerated by the body, no long-term postoperative complications have been noted during the 3 years of developing the surgical modality. Reentry after the use of the IPG has found normal periodontal architecture.
The graft material used for these procedures was Regen Biocement wetted with Hydrasea graft wetting agent. Regen Biocement is a powder that forms a paste when hydrated, which can be applied with a spatula or injected with a syringe. While the paste will set in vivo, it will not carry load during the early healing process. For this reason, when horizontal bone regeneration is attempted, any vertical defects, craters, or furcations are injected with Regen Biocement alone, but then a layer of hard particle graft material mixed with Regen Biocement is placed on top of the ridge.
Regen Biocement mixed with a hard granular graft material will set quickly, and the granules will maintain space during the early healing phase. The case of horizontal bone regeneration presented in Figure 6 was grafted with Regen Biocement mixed with Bio-Ossb. Regen Biocement is a calcium phosphate–based cement that has been classified by the Food and Drug Administration as a bone graft with a drug component. The calcium phosphate cement binds to gingiva and bone and is osteoconductive. The drug component has been shown to stimulate osteoblasts and inhibit osteoclasts and phagocytes. Hydrase bone graft wetting agent provides the optimum pH and ion concentration for osteogenesis.
CONCLUSION
Bone regeneration and healing in the body depends on the periosteum. Activation of the periosteum is essential to healing bone fractures. The periosteum contains undifferentiated cells with the capacity to reproduce connective tissue. Alveolar bone is unique in the body. Attached gingiva is necessary for effective mastication, but the presence of attached gingiva and the lack of periosteum sacrifices the potential for regeneration found in the rest of the body. The IPG uses the unique regenerative potential of the periosteum to regenerate lost periodonteum.
DISCLOSURE
All funding for the development of this surgical modality was provided by Steiner Laboratories. Gregory Gene Steiner and Dainon Michael Steiner are principals of Steiner Laboratories, a division of Steiner Healthcare LLC. The inverted periosteal graft is the intellectual property of Steiner Laboratories. Steiner Laboratories permits use of this surgical modality free of charge with written permission from Steiner Laboratories.
REFERENCES
- Groeneveld MC, Everts V, Beertsen W. Formation of afibrillar acellular cementum-like layers induced by alkaline phosphatase activity from periodontal ligament explants maintained in vitro. J Dent Res. 1994;73:1588-1592.
- Schantz JT, Hutmacher DW, Chim H, et al. Induction of ectopic bone formation by using human periosteal cells in combination with a novel scaffold technology. Cell Transplant. 2002;11:125-138.
- Nakahara H, Goldberg VM, Caplan AI. Culture-expanded periosteal-derived cells exhibit osteochondrogenic potential in porous calcium phosphate ceramics in vivo. Clin Orthop Relat Res. 1992;276:291-298.
- Sakata Y, Ueno T, Kagawa T, et al. Osteogenic potential of cultured human periosteum-derived cells—a pilot study of human cell transplantation into a rat calvarial defect model. J Craniomaxillofac Surg. 2006;34:461-465. Epub 2006 Dec 8.
- Fujii T, Ueno T, Kagawa T, et al. Comparison of bone formation ingrafted periosteum harvested from tibia and calvaria. Microsc Res Tech. 2006;69:580-584.
- De Bari C, Dell’Accio F, Vanlauwe J, et al. Mesenchymal multipotency of adult human periosteal cells demonstrated by single-cell lineage analysis. Arthritis Rheum. 2006;54:1209-1221.
- Youn I, Suh JK, Nauman EA. Differential phenotypic characteristics of heterogeneous cell population in the rabbit periosteum. Acta Orthop. 2005;76:442-450.
- Simon TM, Van Sickle DC, Kunishima DH, et al. Cambium cell stimulation from surgical release of the periosteum. J Orthop Res. 2003;21:470-480.