Introduction

“Gingiva” is an umbrella term that refers to the tissues that support the tooth¹. It includes the protective gingiva (gum) and the attached gingiva (periodontal ligament, root cement, and the actual alveolar bone). Its main function is to attach the tooth to the bone tissue of the jaws, apart from maintaining the integrity of the surface of the occlusal mucosa².

One of the macroanatomical features of the gingiva is that healthy gum is usually coral-pink, color which varies depending on the degree of keratinization, the thickness of the gingiva, the degree of vascularization and the presence of melanocytic cells. The color may vary between light chestnut and dark brown.

The gingiva may be pigmented (making it darker) either physiologically or pathologically. The most common pigmentations affecting the protective gingiva are lesions of melanocytic origin, or melanocytic pigmentation (gingival melanosis), occurring due to an excessive deposition of melanin in the basal and suprabasal layers of the epithelium³.

Clinical pigmentation caused by excess melanin is normal, but it is usually a cosmetic problem for some people, mainly those with short lips and high smile lines. On some occasions, gum color conditions impact the end result of an oral rehabilitation treatment, and it is here that the principles of mucogingival surgery can be applied to remove those melanocytic pigmentations and obtain better aesthetic outcomes. However, the clinician must carefully examine the features for the diagnosis and treatment of gingival melanosis. Thus, this review aims to analyze the main diagnostic and treatment considerations necessary to treat melanocytic pigmentations in the mouth; emphasis has been placed on the current and updated concepts obtained from the multiple sources of information consulted.

Method

The author searched for papers from the PubMed, EMBASE and SciELO databases from 2005 (January) to present (December 2018). The research was supplemented with a manual search of the lists of references of each paper selected. Additionally, we obtained papers published in the 1990s and 2000s, and we studied the most relevant ones along those twenty years. The following search words (key words) were selected: ((“Pigmentation disorders” .MeSH. or (“Disorders” and “pigmentation” .all fields.) or (“Melanin precursor” .MeSH. or (“Precursor” and “melanin” .all fields.) or (“surgery” .all fields.) or (“surgical procedures” .MeSH.) or (“oral mucosa”.MeSH.) or (“mucosa” and “oral” .all fields.) or (“Oral pigmentation ” .all fields.) or (“hyperpigmentation” .all fields.) or (“gum” .MeSH.) or (“gingival disease” .MeSH.) or (“disease” and “gingiva” .all fields.) or (“procedures” .all fields.) or (“surgical operating procedures” .all fields.) o (“melanosis” .all fields.) or (“gingival melanosis” .all fields.)). A second search was conducted using health science descriptors (MeSH NLM): ((pigmentation disorders) or (pigmentation) or (skin pigmentation) or (melanosis)). These papers were selected to keep only those which best described the elements of this review. From an initial search of 150 papers, we analyzed 45 papers related to diagnostic and therapy criteria for gingival melanosis.

Development

Discussion

Many treatments have been proposed to remove melanocytic pigmentations, such as chemical agents (phenol 90% plus alcohol 95%), free grafts, abrasion with rotating or manual tools, cryosurgery with liquid nitrogen, gingivectomies, electrosurgery, and laser⁽¹⁵. Many techniques have become obsolete given their many drawbacks, and others are used less and less. Chemical agents cause major thermal damage³¹, free grafts are usually not aesthetic⁽³², rotating tools do not allow the clinician to control the depth of the de-epithelization, gingivectomy is usually linked to bone loss, and the depigmentation it creates is not permanent³³.

The term “melanocytic depigmentation” refers to a group of periodontal plastic surgery techniques used to reduce and remove pigmented gingiva⁽⁶. One of the first techniques proposed is surgical depigmentation with scalpels, which removes the epithelial tissue leaving the connective tissue to heal by second intention.

The technique known as “mucoabrasion” was proposed by Pérez Fernández in 1977³⁴, and consists in making an abrasion with a diamond bur until the melanocytic pigmentation has been removed or is no longer visible. It is a simple, quick technique, with low morbidity for the patient. It is advised to drill past the first bleeding to make sure that the basal layer of the epithelium has been reached³⁵. This technique requires copious irrigation, and it has the disadvantage that it is not possible to control the depth of the de-epithelization³⁶.

Another technique consists in applying laser (an acronym for “Light Amplification by Stimulated Emission of Radiation”), which allows for a high concentration of energy in the area, and it allows for the removal of soft tissue by ablation, but it is not indicated on hard tissue due to its thermal effects³⁷. Laser treatment is a very powerful tool to remove melanocytic stains, it only requires a topical anesthetic, it leaves no scars, it is a fast and simple technique with good results. It usually takes several sessions, and it requires great skill on the part of the operator⁶.

Laser treatment causes less bleeding and it reduces postoperative pain⁽⁶. It has the disadvantage that it causes thermal damage to the bone, for it can penetrate between 2 and 4 millimeters from the surface⁽³⁸. Er:YAG's laser has been proven to cause less thermal damage; its use must be based on maintaining homeostasis and reducing postoperative pain⁶. There is not enough evidence to indicate that using laser is better than using a scalpel for depigmentation procedures. The Nd:YAG laser has also had good results, showing a high affinity for melanine or dark pigments³⁹. This laser does not require an anesthetic either, but it is recommended to assess each patient’s pain threshold to decide whether to use an anesthetic or not⁽³.

Furthermore, cryosurgery uses liquid nitrogen (-196°C) which is applied with soaked cotton wads, or directly on the tissue and left for 20-30 seconds to freeze the epithelium. The epithelium then thaws spontaneously in one minute, necrotizes, and the area re-epithelializes in 3-4 weeks ⁽⁴⁰.

Most human tissues freeze at -2°C and there is cellular death below -20°C. Cryosurgery uses cryogens to cause cellular death in the epithelium⁴¹. Tetrafluoroethane (TFE) and liquid nitrogen are the most widely used cryogens. Shirazi et al.⁴²⁾ evaluated the use of cryosurgery in 15 patients; they found good depigmentation results with a slight degree of recurrence, which was not significant at the end of a 24-month period post surgery. Signh et al.⁴¹ compared cryosurgery with TFE versus laser diodes to remove melanocytic pigments, and they found a similar level of satisfaction among the 20 patients under study; after 18 months of control, the TFE showed less postoperative pain (p<0.001) and there was repigmentation in one case in each group.

In one case, Ahmed et al.⁴³ found good results without recurrence 30 months after the treatment with cryosurgery. They added that this technique leads to full regeneration and a sterile inflammatory reaction. Together with laser, it has been recognized for its high aesthetic effectiveness, as well as for the high level of patient satisfaction ⁽⁴¹.

A combined technique has also been proposed, which is the combination of the de-epithelization of the basal layer of the attached gingiva with a Nº15 scalpel and the abrasion of the stains in the interdental papilla with fine-grain diamond burs⁴⁴.

Grados et al.⁴⁴ state the advantages of this technique: it is a relatively simple operative technique, it is performed in a relatively short operative time, it causes little bleeding, it provides comfort to the patients during and after the intervention, it does not require costly instruments or devices, and its results are satisfactory. In a clinical case series, Castro and Grados⁴⁵ found good aesthetic results two years after the application of this technique; they add that the repigmentation index is low at the end of the period assessed.

Conclusions

Gingival melanosis is not a pathological problem for most patients; it is a cosmetic problem for people with high smile lines and gingiva exposure. It appears in the form of pigmented lesions which range from light chestnut to dark brown, they are more prevalent in dark-skinned people, but they can be present in every social group. The main gingival depigmentation techniques include gingivectomy, mucoabrasion, laser, and cryosurgery. All of these techniques are effective to remove melanocytic stains, and the differences between them include the degree of postoperative pain, discomfort, cost, and postoperative complications