Gingival grafting using palatal donor tissue primarily to increase the zone of attached gingiva was introduced more than 40 years ago in the form of the free gingival graft.1 Successful use of this procedure for coverage of exposed roots was not reported until 20 years later.2 At about this same time, a significant modification of the donor harvesting technique was introduced.3,4 The principal feature of the new harvesting method was the excision of a subepithelial connective tissue graft, reducing the palatal donor site to an internal pouch. This allowed for a complete or near-complete surface closure and reduction of the postoperative sequellae of pain and bleeding. Along with this change to an internally harvested tissue, preparation of the recipient site evolved from the standard, exposed vascular surface to methods utilizing pedicle flaps to cover the subepithelial connective tissue graft.5-8 These advances in surgical design have been further improved with the introduction of microsurgery, with more precise incisions, closer wound apposition, reduced hemorrhage, and reduced trauma at the surgical site.9 Microsurgery uses smaller instruments and smaller sutures, providing less invasive surgery and less complicated postoperative sequellae.
In spite of these significant refinements in surgical technique, many patients remain fearful of palatal surgery and resist recommendations for treatment involving soft-tissue grafting. Additionally, in patients who seek treatment, anatomical or medical concerns may be present that rule out use of the palate as a donor source. For these reasons, an effective substitute for palatal donor tissue is necessary.
ALLODERM REGENERATIVE TISSUE MATRIX
AlloDerm (LifeCell), widely used in both medical and dental surgery over the past 10 years, is an acellular dermal matrix. It is derived from donated human skin tissue supplied by tissue banks in the United States utilizing American Association of Tissue Banks standards and FDA guidelines. Human skin consists of both epidermis and dermis. In nature, the dermis contains a framework of cells and structural components that allow it to regenerate and replace itself continually throughout life. The structural framework consists of a 3-dimensional arrangement of the following:
(1) proteins, including a structurally intact basement membrane;
(2) intact collagen fibers and bundles to support tissue in-growth, to provide the architecture and support for tissue and its vasculature, and to direct cell growth and behavior;
(3) intact elastin filaments for biomechanical integrity; and
(4) hyaluronan and proteoglycans for maintaining hydration and regulating growth factor activity.
After determining that donated skin tissue is eligible for transplantation (ie, including free of infection from HIV and hepatitis viruses), LifeCell processes the tissue. When AlloDerm is prepared, the human donor tissue undergoes a multistep, proprietary process without damaging the structural and biochemical components of the matrix. This process removes the epidermis and the cells in the dermis that can lead to a recipient response, tissue rejection, and graft failure. The resulting extracellular matrix is freeze-dried by a proprietary method to preserve the tissue without the formation of damaging ice crystals. This entire process is performed under stringent, documented, quality-controlled systems that have been demonstrated to reduce HIV-l and the surrogate for hepatitis C virus to nondetectable levels (>99.9%). Histology testing is completed on each lot of final product to verify cell removal. Cell removal ensures against viral replication and would render free particles more susceptible to detergent inactivation. In addition to viral safety, both incoming tissue and final products are screened for bacterial and fungal growth and deemed negative. The remaining fibrous matrix or framework of biological components stimulates the recipient to initiate its own tissue regeneration, integrating and replacing the graft tissue with newly formed dense, collagenous connective tissue. Thus, AlloDerm provides a viable biologic substitute for palatal donor tissue.10-12
USE OF ALLODERM IN PERIODONTICS
Randomized controlled clinical trials have demonstrated that AlloDerm is equivalent to palatal donor tissue when used in the treatment of gingival recession and covered by a coronally advanced flap.13-16
An increase in marginal tissue thickness equivalent to palatal tissue grafts has been demonstrated at 6 and 12 months postoperatively by both clinical and histometric analysis.12,15 Equivalent attachment to the root surface has been found by histologic evaluation of human block sections at 6 months postoperatively.12
|Figures 1a and 1b. Multiple teeth with gingival recession in the maxillary anterior region (1a). Three years after grafting with AlloDerm, complete root coverage and an aesthetic appearance are exhibited (1b).|
The advantages of Allo-Derm in root coverage grafting include the following:
(1) palatal donor surgery is avoided;
(2) unlimited donor tissue is available;
(3) multiple teeth can be treated in one visit;
(4) consistent quality of donor tissue;
(5) natural aesthetic appearance (Figures 1a and 1b); and
(6) improved patient acceptance of therapy.
Although root coverage outcomes with AlloDerm have been demonstrated to be equivalent to those with palatal connective tissue, AlloDerm is less forgiving than palatal connective tissue, probably due to palatal connective tissue’s unaltered physical properties and thus better early survivability. Consequently, use of Allo-Derm requires modification of the recipient site and precise surgical technique. The recommended technique, referred to as the Alternate Papilla Tunnel (APT) method, is a coronally positioned pouch without vertical releasing incisions. The author developed this method, which is described below.
|Figures 2a to 2f. Multiple teeth with recession in the mandibular anterior region (2a); initial papillary incisions in alternating papillae (2b); preparation of a recipient pouch by facial dissection and tunneling of alternating papillae (2c); AlloDerm graft placed within the pouch and secured with sling sutures (2d); pouch coronally positioned and secured with sling sutures to cover the graft completely (2e). Three years after grafting there is complete root coverage of the cuspids and lateral incisors and near-complete root coverage of the central incisors (2f).|
In the APT method (Figures 2a through 3d), an incision is made in a papilla on one side of a tooth with recession, while the papilla on the other side is tunneled. The next papilla is incised, and the following papilla is tunneled. The papilla at the anatomic midline is always tunneled to prevent retraction of the recipient pouch. At the incised papilla, a v-shaped incision (or inverted v-shaped incision in the mandibular arch) is made to form a new surgical papilla tip approximately 3 mm from the tip of the anatomic papilla. The portion of the anatomic papilla coronal to the surgical papilla is denuded to create a recipient vascular bed for the surgical papilla when coronally advanced. The initial pouch preparation is accomplished by blunt reflection performed with a microperiosteal elevator (Allen Elevator, Hu-Friedy), extending apically past the muco-gingival junction and laterally under the facial aspect of the tunneled papillae. The tunneling process is facilitated by the access provided at the incised papillae. Following blunt reflection, supraperiosteal sharp dissection is used to deepen and mobilize the recipient pouch, and the tunneled papillae are lifted from the interdental crest by blunt reflection with a curette.
Upon completing preparation of the recipient site, the length of graft needed is measured so that the graft will extend 3 mm past the last tooth with recession at each end of the prepared site. The vertical dimension of the graft should be 6 to 8 mm. The AlloDerm, following rehydration in 2 successive, normal saline washes, is measured and trimmed to fit the recipient site. The allograft is then placed into the surgical pouch with the basement membrane surface facing outward and secured coronally with 6-0 sling sutures (surgeon’s choice of material). The graft should be well adapted to the root surface extending to, but not coronal to, the cemento-enamel junction. The pouch is then coronally advanced to cover the allograft completely and secured with 6-0 or 7-0 sling sutures. A surgical microscope may be used for this procedure if the surgeon chooses.
Advantages of the APT method include the following:
(1) incised papillae allow access for dissection and graft placement and facilitate coronal positioning of the pouch; and
(2) tunneled papillae provide retraction resistance and wound stability.
Postoperative care includes the following:
(1) systemic antibiotics for 10 days;
(2) chlorhexidine mouth-rinse for 2 to 3 weeks;
(3) pain medication as needed;
(4) ice applied to face for 24 hours intermittently at 10-minute intervals;
(5) cold liquids for the first 3 meals;
(6) no mastication or toothbrushing at surgical site for 2 to 3 weeks;
(7) removal of surface sutures at 2 to 4 weeks; and
(8) removal of subgingival sutures at 2 months.
|Figures 3a to 3d. Advanced gingival recession of the mandibular posterior region (3a); AlloDerm sutured and pouch coronally positioned and sutured (3b). The papillae between the premolars and the molars have been incised, while the others were tunneled; 2 weeks after surgery healing is excellent with near complete root coverage (3c). Two months after surgery root coverage is near complete and marginal tissue is thick and stable (3d).|
Platelet-derived growth factor (PDGF) and transforming growth factor-b (TGF-b) are polypeptide growth factors known to regulate cell proliferation, chemotaxis, and differentiation.17 PDGF and TGF-b are abundant in the alpha granules of platelets.18 Surgical wound healing has been shown to accelerate by adding a concentration of autogenous platelets, called platelet rich plasma (PRP), to the surgical site.19,20 A dedicated system (Harvest Technologies) is used to collect and concentrate active platelets from 20 cc of peripheral blood at the time of surgery. Two fractions are separated: a platelet poor fraction (PPP) containing fibrin and fibrinogen and a platelet rich fraction (PRP). The AlloDerm graft is placed in the PPP fraction for at least 2 minutes and then the PRP fraction for at least 1 minute prior to placing the graft into the recipient pouch. Following suturing of the graft and the pouch, PRP is added to the site through the pouch margin. Preliminary results suggest reduced edema, reduced discomfort, and more rapid healing.
Developed more than 10 years ago, AlloDerm is a safe and effective biomaterial for use as a substitute for palatal connective tissue in root coverage grafting. There have been no reports of disease transmission as a result of AlloDerm use in medical or dental applications. AlloDerm has proven equivalence to palatal connective tissue for root coverage procedures in randomized, controlled clinical trials.12-16 The use of Allo-Derm produces a thicker marginal tissue and yields a higher percentage of root coverage than a coronally advanced flap alone.21 Also, the use of AlloDerm under a coronally advanced flap extends the application of the most aesthetic root coverage procedure and produces an aesthetic outcome superior to that achieved with a palatal connective tissue graft.16
AlloDerm provides distinct advantages over palatal connective tissue in that it does not require a second surgical site to obtain donor tissue and it provides an unlimited amount of tissue to treat multiple teeth at one appointment. Patient acceptance of recommended treatment is increased due to elimination of the fear associated with using the palate for harvesting donor tissue. As compared to the use of palatal donor tissue, the postoperative experience with AlloDerm is less complicated without the sequellae associated with palatal donor surgery.
The surgical method outlined represents an advance in the approach to surgical root coverage. The APT is a minimally invasive microsurgical technique that enhances wound stability while reducing morbidity. The postoperative period is characterized by reduced discomfort, more rapid healing, and improved patient satisfaction. AlloDerm grafting can also be used for other applications, including treatment of soft-tissue alveolar ridge defects involving loss of buccal contour and soft-tissue deficiencies associated with implants.
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2. Miller PD Jr. Root coverage using a free soft tissue autograft following citric acid application. Part I: technique. Int J Periodontics Restorative Dent. 1982;2:65-70.
3. Raetzke PB. Covering localized areas of root exposure employing the “envelope” technique. J Periodontol. 1985;56:397-402.
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5. Nelson SW. The subpedicle connective tissue graft. A bilaminar reconstructive procedure for the coverage of denuded root surfaces. J Periodontol. 1987;58:95-102.
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10. Silverman RP, Li EN, Holton LH III, et al. Ventral hernia repair using allogenic acellular dermal matrix in a swine model. Hernia. 2004;8:336-342.
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16. Tal H, Moses O, Zohar R, et al. Root coverage of advanced gingival recession: a comparative study between acellular dermal matrix allograft and subepithelial connective tissue grafts. J Periodontol. 2002;73:1405-1411.
17. Kiritsy CP, Lynch AB, Lynch SE. Role of growth factors in cutaneous wound healing: a review. Crit Rev Oral Biol Med. 1993;4:729-760.
19. Garg AK. The use of platelet-rich plasma to enhance the success of bone grafts around dental implants. Dent Implantol Update. 2000;11:17-21.
20. Krupski WC, Reilly LM, Perez S, et al. A prospective randomized trial of autologous platelet-derived wound healing factors for treatment of chronic nonhealing wounds: a preliminary report. J Vasc Surg. 1991;14:526-536.
21. Woodyard JG, Greenwell H, Hill M, et al. The clinical effect of acellular dermal matrix on gingival thickness and root coverage compared to coronally positioned flap alone. J Periodontol. 2004;75:44-56.