 INTRODUCTION
Periodontal therapy has made significant strides in developing methods and materials for regenerating lost tissue. The most common method of regenerating lost periodontal tissue is guided tissue regeneration. The success of this method is dependant on the exclusion of cells from the periodontal defect. A superior approach to the exclusion of cells may be the placement of cells in the periodontal defect with the potential to produce cementum, periodontal ligament and bone. Bone repair in the skeleton occurs readily with regeneration of ligament and muscle reattachment. This method of healing found in the skeleton can be applied to the diseased periodontium.
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 to 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. Lastly, the correct physiologic environment must be present to optimize the regenerative potential. Given these factors, the body possesses the inherent genetic potential to recreate lost tissue.
Regenerative surgery using inert membranes and granular bone graft materials requires resorption of the graft materials before regeneration can occur. Cells capable of resorbing the graft material must be brought to the site and resorb the graft material prior to the initiation of regeneration. Significant loss of graft volume occurs as a result of resorption or rejection of the graft material. In addition, inert membranes used in the traditional manner have no benefit for use in horizontal bone loss. According to the American Academy of Periodontology’s position paper on regenerative therapy, inert membranes have little benefit in class three furcations but show some improvement when used to treat class two furcations. Although barrier membranes show an improvement in connective tissue attachment and bone when treating class two furcations, they cannot completely regenerate these furcation defects. Inert barrier membranes have been shown to be most effective when used to treat three wall bony defects.1
The inverted periosteal graft delivers cells to the periodontal lesion that have the potential to regenerate cementum, periodontal ligament and bone. The maxilla and mandible are formed by intramembranous bone formation. Embryonic mesenchyme cells arrange in sheets in the facial tissue and produce the facial bones. After the facial bones are formed the sheet of mesenchyme cells turns into the periosteum. The cells of the periosteum retain much of their pluripotent properties.
Adult human periosteum is known to possess fibroblasts and osteoblasts as well as their progenitor cells. However, adult human periosteum has also been found to contain a significant number of multipotent mesenchymal stem cells. Regardless of age, periosteal cells have been found to be clonogenic, display long telomeres and express markers of mesenchymal stem cells. Both parental and single-cell-derived clonal cell populations derived from adult periosteum have been found to differentiate to the chondrocyte, osteoblast, adipocyte, and skeletal myocyte lineages in vitro and in vivo. The adult human periosteum contains cells that are multipotent mesenchymal stem cells at the single-cell level.2
The inverted periosteal graft populates the defect with fibroblasts that have the ability to produce cementum and periodontal ligament and osteoblasts, which can produce bone. The outer layer of the periosteum, which is adjacent to soft connective tissue, is comprised of fibroblasts and their progenitor cells. Research shows that these cells can produce cementum with integrated collagen fibers when placed over dentin.3 In the inverted periosteal graft, 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 which have been shown to posses the ability to produce cementum and periodontal ligament.
The most critical phase of regenerative periodontal therapy is reattachment of collagen fibers to the root surface. However, regeneration of lost bone needs to follow reattachment of collagen to the root surface. The normal anatomy of the periosteum includes an outer layer of fibroblasts adjacent to the soft connective tissue and an inner layer of osteoblasts and their progenitor cells adjacent to bone. The periosteum is very thin, and its inner and outer layers are in intimate contact with each other. By design, the inversion of the periosteum places fibroblasts and their progenitor cells immediately over the periodontal defect in order to populate the defect with fibroblasts and their progenitor cells. However, osteoblasts and their progenitor cells cover the layer of fibroblasts and follow them into the defect. During healing, the cells with the potential to regenerate cementum and periodontal ligament are the first cells to populate the root surface and the osseous defect. Osteoblasts and their progenitor cells are immediately behind the fibroblasts and populate the osseous defect. The inverted periosteal graft places the proper cells in the proper location so that the correct sequence of regeneration can occur.
Training in the use of inert barriers has instilled in our 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 surgical failure. When using the inverted periosteal graft, firm apposition of the periosteum to the root surface is not required. The inverted periosteal graft is not guided tissue regeneration. 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 is adequate for success. There is no need to block the invasion of epithelial cells. With the root surface 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 the majority 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. 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 majority of the maxilla and mandible. As a result, an entire arch or entire mouth can be treated at one appointment due to the availability of periosteum adjacent to the graft site. The inverted periosteal graft reduces the cost of surgery by eliminating the need for barrier membranes. Additionally, the inverted periosteal graft eliminates many of the side effects of barrier surgery such as allergic reactions, infection, rejection and the need to remove a foreign object.
The anatomic location of the periosteum is a significant factor in the reconstruction of lost periodontium. Attached gingiva has no ability to produce cementum, periodontal ligament, or bone. In fact, attached gingiva likely plays a roll in blocking bone growth and facilitating reepithelization of the periodontal lesion. Guided tissue regeneration, using inert membranes, is widely believed to be successful because it blocks the epithelium from growing down the root surface and reforming the periodontal pocket. However, the possibility also exists that guided tissue regeneration is successful because it excludes attached gingiva which may inhibit the regeneration of bone and periodontal ligament. Irrespective of why guided tissue regeneration works, it is accepted as a predictable way to regenerate lost periodontium. However, it is also accepted that guided tissue regeneration is limited and useful only in certain types of periodontal lesions.
The inverted periosteal graft 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 inverted periosteal graft is attached to either the gingival flap or the bone it can be sutured securely over the graft site to hold the bone graft material and maintain space for regeneration.
The inverted periosteal graft can be used with any graft material. However, a there exists a wide disparity of results between the various commercially available bone graft materials. The majority of bone graft materials are osteoconductive. This term describes a graft material that is porous and has the ability to allow ingrowth of cells into the graft site. Most osteoconductive materials are considered to be resorbable; however, the rate of resorption is based largely upon the patient’s physiology. Hard granular graft material often significantly inhibits the regeneration of bone due to the difficulty and time needed to remove the graft material from the graft site. The only cells capable of removing hard granular graft material are osteoclasts. Hard graft material requires the graft site be populated with cells that remove bone rather than cells that regenerate bone.
The ideal graft material should not require removal prior to the initiation of regeneration; it should stimulate osteoblasts 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.
The inverted periosteal graft, in combination with the proper graft material, stimulates regenerative cells, inhibits resorptive cells and supplies the raw material for regeneration. The inverted periosteal graft 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 when surgery is complete.
DESCRIPTION AND ILLUSTRATION
The inverted periosteal graft is intended to acquire the periosteum and place it in the vicinity of the periodontal lesion. There are two different methods that can be utilized 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 periostium covering the bone. The flap is extended apically to a point where the periostium 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 periostium off the flap until the mucogingival junction is reached. 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.
The decision regarding whether to use a split thickness or full thickness flap approach will depend on may factors such as the nature of the lesion, the amount of attached gingiva, the location of the periostium, the position of the teeth and the operator’s skill. Every patient presents with a unique set of circumstances, and as a result, the inverted periosteal graft requires considerable forethought prior to initiating the surgery. Due to the unique characteristics of this surgery it is advised that training in this surgical technique be acquired if the best possible result is to be achieved.
The following case walks through the significant aspects of the inverted periosteal graft. This patient presented with adult periodontitis. Significant horizontal bone loss with vertical defects were present upon examination. Approximately 2 mm exposed cementum was found as a result of gingival recession. The periodontal tissue was cyanotic and bled when probed. |
Figure 1 
Figure 2 
Figure 3 
Figure 4 
Figure 5 
Figure 6 
Figure 7 
Figure 8 
Figure
9
Figure
10
Figure
11
Figure
12
Figure
13
Figure
14
Figure
15
Figure
16
Figure
17
Figure
18
Figure
19
Figure
20
Figure
21
Figure
22
Figure
23
Figure
24
Figure
25
Figure
26
Figure
27
Figure
28 
Figure
29 
Figure
30 
Figure
31
Figure
32 
Figure
33 
Figure 34 
Figure 35 
Figure 36
Figure 37