Thick gingiva is usually associated with wide zones of keratinized tissue and flat gingival contour, whereas thin gingiva is associated with a narrow band of keratinized tissue, and a scalloped gingival margin. The periodontal phenotype as a definition is the combination of gingival phenotype and bone morphotype (buccal bone plate thickness). Gingival phenotype involves gingival thickness (GT) and keratinized tissue width (KTW). Thin phenotypes are more vulnerable to injury and likely to induce gingival recession than thick phenotypes because thin gingiva can have an effect on plaque-related inflammatory lesions, making it prone to tissue destruction. Numerous applications, including non-surgical periodontal therapy, mucogingival therapy, guided tissue regeneration (GTR), and implant dentistry, have shown evidence of impact of gingival thickness. Patients with gingiva less than 1.5 mm thick experienced attachment loss after non-surgical periodontal therapy, whereas no attachment loss was seen at sites with gingiva over 2 mm thick. A significant moderate correlation occurred between a critical gingival thickness threshold of >1.1 mm and weighted mean root coverage and weighted complete root coverage according to a systematic review and meta-analysis. Thin gingival thickness of less than 2 mm is associated with slightly greater initial peri-implant bone loss around implants compared with thick gingival thickness for securing the supra crestal tissue attachment of the gingiva. Thus, the presence of soft tissues with a thickness >2.0 mm around implants is crucial in preserving healthy peri-implant tissues and preventing alveolar bone loss through the biological protection. Based on these findings, surgical procedures like gingival tissue augmentation have been proposed to increase gingival thickness to maintain the biologic width and minimize alveolar bone loss. However, postoperative complications, such as uncontrolled bleeding, pain, and infection of the palatal donor site, limit its establishment as a routine procedure. To avoid these complications, new methods are being studied.

Hyaluronic acid (HA), a naturally occurring polysaccharide, is considered an important component of the extracellular matrix in connective tissues of the human body. HA participates in various physiologic and structural processes that preserve tissue integrity, such as cellular and extracellular interactions, modulation of the inflammatory process, interactions with growth factors, tissue healing, collagen synthesis, regulation of the osmotic pressure, and tissue lubrication.

Vitamin C is a proven anti-inflammatory agent and also exerts a reducing and antioxidant effect, scavenges free radicals, and acts as an enzyme cofactor in cells. This nutrient is considered to be an important dietary oxidant for periodontal health, as it plays a crucial role in preventing and slowing the progression of periodontal disease by inducing the differentiation of periodontal ligament progenitor cells. Vitamin C has a very important role in collagen biosynthesis (collagen type I), as it helps in fibroblasts proliferation. It reduces the potentiality of scarring via inhibiting cross-linking of collagen fibers and fibrosis. It acts as a cofactor in hydroxyproline synthesis to produce collagen type IV and improves endothelial cell vitality and function. Vitamin C and Hyaluronic acid promote growth of tissues and wound healing by inducing synthesis of fibroblasts, collagen, elastin and growth factors which can effect gingival thickness and width of keratinised tissue.

Microneedling (MN) is also known as “percutaneous collagen induction therapy". Microinjuries created by MN result in minimal superficial bleedings and create a wound-healing cascade from which various growth factors, such as platelet-derived growth factors, transforming growth factors, connective tissue growth factor and fibroblast growth factors are released. In MN, the tissue responds as if experiencing tissue trauma and the body’s own collagen production is induced to preserve skin integrity. Growth factors are released immediately after injury, inducing the proliferation of new cells, and fibroblasts are transformed into collagen and elastin fibers from day 5 up to week 8. Fibroblasts produce collagen and elastin fibers by migrating to the point of intrusion for wound closure. Newly formed fibers thicken the tissue during a process is known as neocollagenesis. Fibroblasts also trigger neoangiogenesis by stimulating the proliferation of endothelial cells in the vessels. However there is very limited literature on microneedling and comparing the effects of Vitamin C and Hyaluronic acid on thin gingival phenotype. So this study will be  conducted to evaluate and compare the effects  of microneedling with hyaluronic acid injection and Vitamin C injection in the management of thin gingival phenotype.