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. Successful use of this procedure for coverage of exposed roots was not reported until 20 years later. At about this same time, a significant modification of the donor harvesting technique was introduced. 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.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. 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.
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