Erythropoietin Gel as an Adjunct to Split-Thickness Apically Positioned Flap in Augmentation of Attached Gingiva

The gingiva is divided into three parts anatomically: marginal, attached, and interdental. Attached gingiva, as defined by Orban, is the part of the gingiva that is firmly attached to the underlying tooth and bone and is stippled on the surface.

From the base of the gingival crevice to the mucogingival junction, lays the attached gingiva which is the firm resilient component of the gingiva. Through connective tissue, it is closely adhered to the underlying periosteal tissues of alveolar bone. To stabilize the marginal gingiva and resist external harm, an adequate zone of attached gingiva is required.

Lang proposed in 1972 that periodontal tissues require at least 2 mm of attached gingiva to maintain their health and survive the functional pressures of mastication and tooth cleaning. Gingival recession can be exacerbated by insufficient width or thickness of attached gingiva.

Many surgical procedures, such as apically positioned flaps, connective tissue grafts, and free gingival grafts, have been described to enhance the width of attached gingiva.

The apically positioned flap was one of the strategies that allowed surgeons to preserve and extend the width of attached gingiva. Two vertical incisions are made to release a complete full-thickness flap of gingiva and alveolar mucosa. The gingiva, alveolar mucosa, periosteum, and all structures within this flap are all shifted apically and sutured into place so that the flap's margin just covers the alveolar crests. With this surgical procedure, there was a risk of crestal bone resorption and additional attachment loss.

Carnio introduced a modified approach in 1999 to decrease the possibility of recession and attachment loss associated with the traditional apically positioned flap. The split-thickness flap used in this technique differs from the original in that the coronal aspect of the keratinized tissue is not separated from the tooth.

It is a useful method for increasing the width of attached gingiva by exposing the periosteum in the area where gingival augmentation is needed. Because there is no palatal donor tissue, this partial thickness flap elevation reduces the danger of recession and crestal bone loss, has low morbidity, and has a predictable tissue color match. The surgical site is completely encompassed by keratinized tissue, which acts as a source of keratinized tissue cells.

Secondary intention healing takes place by passing through four stages: Blood Clot formation, Inflammation, Granulation tissue formation and, Epithelialization. The blood clot formed contains large numbers of microorganisms that are phagocytized by polymorph nuclear leukocytes which migrates to the area in large numbers. Macrophages multiply, engulfing RBCs and dissolving PMNs. During healing, the source of granulation tissue is the retained periosteal connective tissue, the periodontal ligament, and the surrounding gingival tissues and lining mucosa. Epithelial cells start to migrate from the surrounding tissues. These cells move along a fibrin network. It can take up to 14 days for surface epithelialization to occur.

The split-thickness apically positioned flap has several advantages over other procedures, including low morbidity due to the lack of a second surgical site, less tissue handling, quicker operative time, good color match, good aesthetics, and no risk of postoperative recession. A key drawback of this procedure is that at least 0.5 mm of attached gingiva must be present clinically in order for the wound to be completely encompassed by keratinized tissue, which aids in the production of keratinized tissue in the surgical site.

Erythropoietin (EPO) is a glycoprotein hormone produced predominantly by the kidney that regulates the synthesis of red blood cells. The mature protein is made up of a 165-amino-acid polypeptide chain that is highly glycosylated at three N-linked and one O-linked glycosylation sites, resulting in a molecular mass of 30-34 kDa.

EPO is a pleiotropic factor with anti-apoptotic and cytoprotective properties in a variety of tissues. EPO receptors have been found on a variety of cells, including fibroblasts, macrophages, mast cells, and melanocytes. EPO boosts the production of vascular endothelial growth factor (VEGF) and speeds up the angiogenesis, granulation tissue creation, and collagen formation processes in the dermis.

In both acute and chronic tissue injury, erythropoietin has shown to have restorative effects. EPO promotes healing and function restoration by inhibiting pro-inflammatory cytokines such as TNF-α, IL-1 β, IL-6, IL-12, and IL-23 at the local level. The US Food and Drug Administration (FDA) approved recombinant human erythropoietin (EPO) for the treatment of anemia in patients with chronic renal disease and chemotherapy-associated anemia. It not only decreases the formation of reactive oxygen species and membrane lipid peroxidase, but also inhibits the synthesis of pro-inflammatory cytokines.

In 2017, Hosseinjani et al. investigated the effects of EPO mouthwash (50 IU/ml, 15 ml four times a day) on the healing of oral mucositis in a randomized controlled clinical trial. The mouthwash decreased the severity and duration of the oral mucositis lesions.

In 2018, Yaghobee showed that applying EPO to surgical palatal wounds had a healing effect. Because the oral mucosa's basal cells also express erythropoietin receptors, topical erythropoietin treatment was thought to be useful in treating oral lesions. 4,000 IU EPO was mixed with 1 mL of 3 percent hydroxyl ethyl cellulose to make EPO-containing gels.

Although mouthwash local therapy improved the healing of oral mucositis lesions, the anatomical features of the mouth and the washing effect of saliva in the oral cavity result in a short retention time for mouthwashes and other conventional liquid dosage forms, resulting in a short-lasting effect and low therapeutic efficacy of active medications.

For their unique characteristic of sol-gel transition in response to environmental stimuli such as temperature, pH, or ionic strength, environmentally responsive hydrogels have piqued interest in drug delivery and other biological sectors. As a result, these hydrogels can be easily supplied as a solution that swells and gels very quickly after administration. Due to the reduced frequency of medication administration, the so-formed gel will have the advantage of longer drug release in the surrounding medium, which will increase patient compliance.

A randomized controlled trial was conducted to determine the safety and efficacy of a topical EPO-containing gel as an additional therapy to standard-of-care (SOC) in the treatment of diabetic foot ulcers. Following daily treatment of DFUs with the EPO-containing gel, no side effects were observed. For the treatment of DFUs, topical EPO can be a safe and effective option.

The combination of erythropoietin gel on the split-thickness apically positioned flap in an attempt to benefit from its regenerative and healing capacity is a good point of research. To measure the gel's effect on tissue keratinization, attached gingival gain and controlling post-operative pain is our point of concern.