The gingival colour differs from person to another .It varies from pale pink to dark brown . Gingival brown pigmentation , is the most common natural pigment contributing to endogenous pigmentation of the gingiva. Melanin pigmentation is a naturally occurring chemical that makes skin dark. These melanin granules are produced by melanoblasts in the basal layer in the gingival epithelium . Gingival hyperpigmentation is considered a genetic trait irrespective of age and sex ; it is termed physiological or racial gingival pigmentation. The distribution and intensity of colour are different not only among different races but also in different areas of the same oral cavity (1).
Although natural pigments do not consider a medical disease,they are unacceptably aesthetics due to dark complexion especially among those with a gummy smile . Pigmentation is more common in the gingiva of dark-skinned individuals due to the deposition of higher quantities of melanin, which may not be aesthetically suitable. These melanin patches present on the gingiva can cause adverse psychological effects. Therefore, it becomes important to apply a proper method for the removal of excessive melanin pigmentation and converting the appearance of gingiva from dark colour to pink colour (2 ).
There is another type of hyperpigmentation of the gingiva that is considered pathological hyperpigmentation. Various skin diseases can cause pathological hyperpigmentation. Pathological hyperpigmentation caused by smoking, ingestion of heavy metals, Kaposi's sarcoma, endocrine disorders and drugs induced a variety of medications including chloroquine, quinine, minocycline, zidovudine, chlorpromazine, ketocoquine, quinine, minocycline, zidovudine, chlorpromazine, HIV, etc . This pigmentation does not need to be treated . It is symptomless ,and only seeks treatment if the patient has psychogenic problems so the systemic condition of patients should be pursued or the cause should be removed to reach a desirable outcome before deciding to perform any other depigmentation methods (3) .
Dummet (1960)proposed the following explanation for gingival pigmentation. The color of the healthy gingiva varies, ranging from a pale pink to a deep bluish-purple hue. Between these limits of normalcy is a large amount of pigmentation that depends primarily upon (i) the intensity of melanogenesis, (ii)the depth of epithelial cornification, and (iii)the arrangement of gingival vascularity. Dummet proposed the Dummet Oral Pigmentation Index (DOPI) assessment: 1964 • Score 0: Pink tissue (No clinical pigmentation) • Score 1: Mild light brown color(Mild clinical pigmentation) • Score 2: Medium brown or blue -black tissue (Heavy clinical pigmentation) • Score 3: Deep brown or blue -black tissue (Heavy clinical pigmentation) (4).
Gingival depigmentation is a periodontal plastic surgical procedure whereby the hyperpigmentation is removed or reduced by various modalities techniques, which are classified into two categories: methods to remove pigments and methods that mask the pigment. Removal of pigment can be done by surgical and nonsurgical or chemical methods. Surgical methods mainly include bur abrasion, scalpel surgery, electrocautery, laser ablation, cryosurgery, radiosurgery, gingivectomy, gingivectomy with free gingival autograft, application of chemical agents , abrasion with diamond bur, Nd: YAG laser, semiconductor diode laser and CO2 laser. Nonsurgical methods mainly refer to chemical cauterization. The methods that mask gingival pigments include gingival grafting procedures and the use of acellular dermal matrix allografts. All these treatment modalities have their own advantages and disadvantages (5).
The selection of the technique should be based on clinical experiences and individual preferences. One of the first and still popular techniques to be employed is the surgical removal of undesirable pigmentation using scalpels. The procedure essentially involves surgical removal of gingival epithelium along with a layer of the underlying connective tissue and allowing the denuded connective tissue to heal by secondary intention. The new epithelium that forms is devoid of melanin pigmentation (6).
The depigmentation procedure by using the scalpel technique is simple, easy to perform, noninvasive, and cost-effective . According to Almas and Sadiq, the scalpel wound heals faster than other techniques (7)
The bur abrasion method is a technique using a diamond bur at high speed to denude the gingival epithelium layer .This method was found to have difficulty controlling the depth of de-epithelialization. Moreover,bleeding and postoperative pain are predicted (8).
Cryosurgery was performed by using the effect of low temperature on living tissues in which cells were killed by freezing. The biological effect of physical factors such as cold behaves like ionizing radiation and the maximum lethal effect is obtained when they are applied to cells undergoing mitosis. Most vital tissues freeze at approximately −2°C, and ultra low temperature (below −20°C) result in total cell death. In this technique, liquid nitrogen is circulated so as to cool the tip of the cryoprobe, which is to be applied to the lesion. Hence, freezing occurs by conduction. This technique is slower than the spray technique. The depth of penetration of the ice ball is difficult to estimate, and prolonged freezing could cause excessive tissue destruction(9)
The laser technique for gingival depigmentation is recognized as one of the most effective, comfortable, and reliable techniques. In the laser studies, repigmentation was treated by using a CO2 laser, a diode laser or –an Er : YAG laser . Laser treatment of pigmentation is based on the principle of selective photothermolysis.It was declared that laser light must be at a wavelength that is specific and well absorbed by the particular chromophore being treated. Melanin is the ideal target chromophore for the diode laser. The results declare that the diode laser has the highest clinical effect for melanin depigmentation(10).
Electrocautery is another effective method when compared to the scalpel. It has many advantages such as the absence of bleeding and patient discomfort .Electrosurgery has a strong influence in the retardation of the migration of melanin cells from locally situated cells ,reducing the chance of repigmentation .Electrocautery application for a prolonged time leads to the accumulation of heat in tissues with tissue destruction, so to overcome this disadvantage, soft tissue lasers can be used instead (11).