Today, smile esthetics have become a crucial aspect of dentistry, particularly in Periodontology. The colour of the gums plays an important role in the overall appearance of an individual. As such, the blackish or brownish appearance of the gums, typically when smiling, is one of the most common aesthetic complaints. Although not painful, individuals with a ‘gummy smile’ and excessive smile lines often feel less confident because of this. Therefore, treatment strategies should emphasize establishing harmony between the teeth and gingiva while also addressing the functional and biological problems. The procedure for treating gingival hyperpigmentation is referred to as gingival depigmentation. The biological pigments that mainly contribute to the normal colour of healthy gingiva are haemoglobin, hemosiderin, carotene, and melanin. Gingival hyperpigmentation is characterized by excessive synthesis of melanin and its deposition in the gingiva, resulting in its blackish-brown appearance. The Oral Pigmentation Index introduced by Dummet and Gupta in 1971 scores gingival hyperpigmentation according to the degree of pigmentation but does not mention the etiology of hyperpigmentation. Thus in 2014, Peeran et al introduced the Gingival Melanin Pigmentation and Pigmented Lesions Index which scores gingival hyperpigmentation according to etiology, extent and severity of pigmentation. There are various methods for achieving gingival depigmentation, including both surgical as well as non-surgical techniques such as- scalpel scraping, electrosurgery, bur abrasion, laser ablation, and cryotherapy.

The surgical scalpel technique is a surgical procedure that involves scraping off the hyperpigmented gingival epithelium and induces secondary healing of the exposed connective tissue. It is considered to be the gold standard for gingival depigmentation, but can result in relatively large, open wounds. Bur abrasion involves the denuding of pigmented gingival epithelium by superficial abrasion using grit football shaped or doughnut-shaped coarse diamond burs in a low-speed handpiece. It is a relatively non-invasive and cost-effective technique and does not require any specific instruments. However, it is associated with various drawbacks such as technique sensitivity, increased treatment duration, and post-treatment pain. Electrosurgery involves generating heat via transmission of high-frequency electrical energy to the tissues, leading to either cutting or coagulation of the tissues. However, pain and patient discomfort during the initial healing period is seen more frequently with this technique.

Cryotherapy is the process of inducing controlled superficial tissue destruction by applying extremely cold chemicals known as cryogens. This includes substances such as liquid nitrogen, liquid nitrous oxide, solidified carbon dioxide (dry ice), dichlorodifluoromethane, and tetrafluoroethane. The minimum temperature required for cell damage, especially that of melanocytes is around -4⁰C to -7⁰C. In connective tissue, the collagen fiber network of the dermis and fibroblasts remain undamaged at temperatures between -30⁰C to -35⁰C, while ultralow temperatures below -20⁰C causes total cell death. Therefore, the physical and chemical changes induced by such low temperatures leads to cell destruction and tissue death, and the healing occurs by complete regeneration and sterile inflammatory reaction. The procedure is simple, effective and does not require sutures or periodontal dressing. 1,1,1,2-Tetrafluoroethane is a colourless, nonflammable gas that is used for cold pulp testing in endodontics. With a temperature of -26⁰C to -40⁰C, it is also used in gingival depigmentation and in a study conducted by Kumar et al in 2013, patients treated with tetrafluoroethane for gingival depigmentation showed no instance of unaesthetic re-pigmentation even after two years.

Microneedling (MN) is also called ‘collagen induction therapy’ and is a cosmetic procedure that involves making repetitive punctures using tiny, sterilized needles. It has recently gained popularity in dermatology as it is quick, easy, affordable, and well-tolerated among patients. Microinjuries caused by MN create little superficial bleeding and prompt the cascade of wound healing by forming small holes called micro-conduits which contribute to the rapid absorption of topical medications and leads to the release of numerous growth factors including fibroblast, connective tissue, transforming, and platelet-derived growth factors. This initiates collagen synthesis to maintain tissue integrity since the tissue reacts as though it has experienced tissue damage (Aust, Reimers, & Vogt, 2009; Falabella & Falanga, 2001).

Vitamin C, also called ascorbic acid, is an essential component to the biosynthesis of collagen - the dentin’s major organic matrix component. In addition to its anti-inflammatory properties, vitamin C also scavenges free radicals, co-factors enzymes in cells and induces the development of periodontal ligament progenitor cells, making it a significant dietary oxidant for periodontal health, that helps to prevent and halt the onset of periodontal disease. Vitamin C plays a critical role in collagen synthesis (type I) due to its ability to promote fibroblast proliferation. It decreases the incidence of scarring by preventing fibrosis and collagen fiber cross-linking whilst increasing the vitality and function of endothelial cells by functioning as a cofactor in the hydroxyproline production process-creating type IV collagen. Vitamin C limits the activity of the enzyme tyrosinase by interacting with copper ions at the tyrosinase active site, thereby contributing to immunomodulation and the removal of hyperpigmented areas while reducing the formation of melanin.

In recent times, lasers have emerged as the modality of choice for gingival depigmentation. Laser ablation therapy is less invasive and requires minimal amount of local anesthesia, leading to reduced postoperative pain and discomfort, unlike invasive techniques like scalpel scraping that is often associated with pain, bleeding and significant postoperative wounds. Furthermore, lasers exhibit enhanced hemostatic activity and help create a bloodless surgical field that improves the operator’s vision, thereby enhancing aesthetic outcomes. Amongst the numerous varieties of lasers that have been used for gingival depigmentation -which includes diode lasers, CO2 lasers, Erbium lasers, and Nd:YAG lasers- diode lasers reportedly have a high affinity for chromophores such as melanin and oxyhaemoglobin which makes it the most suitable option for gingival depigmentation procedures.

Since laser depigmentation and microneedling technique with vitamin C have been proven to be effective modalities, the purpose of this study is to compare the efficacy of microneedling technique using tetrafluoroethane with the above two techniques for gingival depigmentation.

The primary outcome is the measure of gingival thickness and intensity of gingival pigmentation at baseline, 1 month, 6 months, and 12 months. The secondary outcome is the patient satisfaction and patient perception of gingival aesthetics at baseline and 12 months.