Dr Sarah Tonks provides an overview of pigmentation on the gums and details treatment options available
The health and appearance of the gingiva are essential components of an attractive smile. Dark gums may cause complaints from patients regarding their appearance, even though this may be physiological rather than pathological. Visible oral melanin pigmentation can be seen in darker-skinned individuals and the gingiva is the most frequently pigmented intraoral tissue.1 It is infrequent in lighter skinned individuals. The source of the pigmentation is variable, however the most common is melanin.2
Melanocytes are located in the epithelial basal cell layer. They convert tyrosine to melanin via the tyrosinase enzyme, which is then stored in basal cells as melanosomes.3 The degree of pigmentation depends on the activity of the melanocytes; genetics, hormonal regulation and sun exposure all play a part in this.3 There have been more than 150 genes identified which influence pigmentation and their activation relies on various epigenetic factors.4
Oral pigmentation can involve any part of the oral cavity and, aside from physiological causes, these can include iatrogenic mechanisms such as implantation of amalgam (used in dental fillings), Peutz-Jeghers Syndrome (PJS) which is an autosomal dominant condition of hamartomatous polyps in the gastrointestinal tract and hyperpigmented macules on the lips and oral mucosa, and local irritations such as smoking, benign nevi and melanoma.
The colour of the gingiva can range from light brown to blue-black depending on the source and depth of the pigment.5 The gingival pigmentation can be removed if the patient desires for aesthetic reasons and several methods have been described including; cauterisation by chemical agents,6 bur abrasion using a dental handpiece,7 by scalpel,8 cryosurgery,9 electrosurgery,10 gingival grafts11 and lasers.12
Prior to the removal of gingival hyperpigmentation the relevant pathophysiology should be established.
PJS (Intrinsic process)
This is an autosomal dominant condition characterised by the association of gastrointestinal polyposis, mucocutaneous pigmentation and cancer predisposition. Hyperpigmented macules appear in childhood as dark blue to dark brown lesions around the mouth, eyes and nostrils, in the perianal area and on the buccal mucosa. They may also occur on the fingers. These macules are rarely present at birth but become more obvious around age five but then may fade during puberty.
Melanocanthoma can mimic malignant melanomas clinically so a biopsy must be performed
Noteably, approximately 65% of individuals with PJS have melanocytic macules on the buccal mucosa. Histologically there are increased melanocytes at the epidermal-dermal junction with increased melanin in the basal cells. Those with PJS are not at risk of malignancy from the melanocytic macules but are at risk of a number of epithelial malignancies such as colorectal, gastric, pancreatic, breast and ovarian cancers.5 Melanocanthoma is a rapidly growing flat or slightly raised lesion. There is a higher incidence in people with darker skin and those infected with HIV. Melanocanthoma can mimic malignant melanomas clinically so a biopsy must be performed.13
Amalgam tattoo (extrinsic process)
An amalgam tattoo is a blue/grey/black flat macule which is soft and painless. It is demarcated from the surrounding mucosa and is usually less than 0.5cm in diameter. It may be visible on dental radiographs in the case of larger lesions. There may be a long-term inflammatory response, in which case macrophanges engulf the amalgam and attempt to move the material out of the area and the lesion appears to clinically enlarge. If there is no apparent connection with nearby amalgam-filled teeth then a biopsy is essential to exclude melanocytic neoplasia.3
Hyperplastic or neoplastic processes
Melanocytic macules may be single or multiple and can occur anywhere in the oral cavity. Nevi are uncommon in the oral cavity and appear as brown and black elevated papules. They should be excised to exclude other serious pigmented lesions. Oral melanomas are uncommon and similarly arise from melanocytes in the basal layer of the squamous mucosa. Patients are normally between 40-70 years old at presentation.
Melanoma of the oral mucosa is the most aggressive cancer of the head and neck and at the time of diagnosis, 50% of oral malignant melanomas have already spread to the lymph nodes, usually to the neck.13 Cutaneous melanomas are linked to sun exposure, however, oral melanomas have no relationship to chemical, thermal or physical events such as smoking, alcohol, irritation or poor oral hygiene. Most oral melanomas are thought to arise de novo.14
Iatrogenic oral pigmentation
Most oral pigmented lesions are benign and pigmentation is due to excessive production of melanin. These lesions are usually seen most often in young or middle-aged women. This is a focal hyperpigmentation and limited to the basal epithelium and there is some overspill of the pigment to the subepithelial connective tissue.14 It is important to distinguish these lesions from malignant melanoma.
The successful removal of gingival pigmentation has been reported by various methods, however repigmentation was reported with almost all methods.2 There are a limited number of articles available featuring each different methodology and most are case reports. In a 2014 systematic review of 61 publications by Lin et al, it was found that electrosurgery (0.74% recurrence), cryosurgery (0.32% recurrence) and laser surgery (1.16% recurrence) were more reliable for treating gingival hyperpigmentation than other methods such as bur abrasion (8.99% recurrence) and scalpel surgery (4.25% recurrence) in terms of recurrence.2 The definite mechanism of repigmentation has not yet been clarified. Migration of melanocytes from the surrounding tissues could be a possible mechanism for repigmentation.15
The required depth of epithelial dissection for treating gingival pigmentation must be more than 0.31mm deep, less than this and the basal cell layer will not be reached. It is thought that this is the reason that chemical cautery, bur abrasion or the use of a scalpel may not be able to remove the cells in the basal layer.
Cryosurgery freezes tissue to destroy it, which leads to the denaturation of proteins and cell death by freezing the cytoplasm of the pigmented cells.
The same review looked at CO2 laser, diode laser, Nd:YAG and Er:YAG which have all been used to treat gingival hyperpigmentation. Of the three, the diode laser had the lowest recurrence rate (0.19%) in the laser group, it is thought because it has a spectrum of 810 nm and melanin has an absorption spectrum of 351-1064 nm.2 In the case of amalgam tattoo, these lesions can be removed surgically or with Q switched ruby or alexandrite laser.13
Cryosurgery freezes tissue to destroy it, which leads to the denaturation of proteins and cell death by freezing the cytoplasm of the pigmented cells. Electrosurgery uses an electric current to cut, coagulate or desiccate the tissue which disintegrates melanin cells in the basal and suprabasal layers of the tissue.14 In the aesthetic clinic it is more likely that laser or cryosurgery would be used to remove pigmentation as these are the most readily available treatment modalities. Prior to removal it is essential to ensure that the lesion is benign, which may include referral to a dentist for confirmation prior to treatment.
Treatment with diode laser
The laser settings should be 810 nm, pulse frequency 20,000 Hz, pulse width of 15 microseconds or interval cycle of 50 microseconds. Practitioners should ensure 810 nm specific safety glasses are worn. At a distance of 12-15mm the laser is activated until there is a visible tissue reaction. There will be a slight immediate blanching of the tissue. This should be continued until the entire area has been covered. There should be no pain, and the tissue afterwards will feel like something warm has just been eaten.16
Treatment with cryotherapy
The treatment area can be isolated with cotton rolls and topical anaesthesia, such as lidocaine (10%), can be applied for 10 minutes before treatment. Liquid nitrogen on a nitrogen cooled swab is applied for five seconds in a rolling motion. During the procedure it is recommended that patients wear protective glasses and the vital teeth are protected with a periodontal dressing.17
Gingival pigmentation can be a cosmetically troubling naturally occurring phenomenon. For some patients, it may be appropriate to treat this pigmentation in the aesthetic clinic, potentially giving more confidence in smiling. Treatment can be straightforward and minimally painful, and many aesthetic clinics will already have the necessary equipment to carry out this procedure.