Q‐switched ruby laser is safe and effective in treating primary gingival hyperpigmentation

Physiologic gingival hyperpigmentation (PGH) is a benign condition that results from increased melanin production and is prevalent among darker skin individuals. Although the use of lasers for PGH has gained popularity in recent years, the lasers being used are mostly ablative, and act through a non‐selective tissue damage mechanism.

is far more prevalent in darker skin individuals, has no gender predilection, and most commonly affects the gingiva. 3 Physiologic gingival hyperpigmentation (PGH) is characterized by a diffuse symmetric homogenous hyperpigmented patch that involves the free and attached gingiva and demarcates at the mucogingival junction. 4 It is diagnosed clinically based on its location, symmetry, and bilateral distribution. 5 Owing to the important role of the pink to coral-pink color of the gingiva in the overall appearance of an esthetic smile, PGH is a cause for distress among patients, 6 and a search for an optimal, safe, and effective depigmentation method is still constantly pursued.
The different techniques currently available for this purpose include chemical abrasion, diamond bur abrasion, scalpel surgery, cryosurgery, electrosurgery, and laser therapy with four commonly used lasers-1064-nm neodymium-doped yttrium aluminum garnet (Nd:YAG), erbium-doped yttrium aluminum garnet (Er:YAG), carbon dioxide (CO 2 ), and diode lasers. 7,8 The 694-nm Q-switched ruby laser (QSRL) is being successfully used for the treatment of cutaneous pigmentary lesions and dark tattoos, 9,10 and although it carries the benefit of a non-ablative technology it has not been previously used for the treatment of intraoral pigmentary lesions. As the Ruby laser has the highest melanin absorption (highest absorption coefficient) compared to other available lasers (Alexendrite, diode lasers, Nd:YAG) its use for this purpose appears especially attractive. 11 We report our experience using a 694-nm Q-switched ruby laser for the depigmentation of four patients with PGH.

| Setting
This is a retrospective case series of patients with PGH treated with a QSRL between March 2019 and November 2020.

| Patients and treatment protocol
All Patients demonstrated gingival hyperpigmentation in a dental examination and were referred to the laser clinic where they were clinically diagnosed with PGH by a team of both a dermatologist and a dentist.
Treatment preparation included the administration of an injectable local anesthetic agent (adrenalin and lidocaine) and the coverage of patient's eyes with protective goggles.
Lasing was performed in a horizontal direction, using the noncontact laser tip directed at the pigmented part of the gingiva and parallel to the root surfaces with resultant frosting being immediately apparent.
Following the treatment, no antimicrobials were prescribed and no periodontal dressing was applied. To minimize post-procedural discomfort patients were instructed to avoid smoking and consumption of hot, acidic, or spicy foods and beverages for 3 days.
As for all patients undergoing laser treatment in our clinic, patient satisfaction was assessed at the final follow-up visit (graded on a score of 1-5; 1 being not satisfied and 5 being very satisfied).

| RE SULTS
Four patients, three females and one male, are included in this report.
Patients and treatment characteristics are summarized in Table 1  The average follow-up succeeding the last treatment was 11 months (7-18 months) with no patient exhibiting re-pigmentation.

| DISCUSS ION
We report for the first time the satisfactory response of four patients with PGH treated with QSRL.
Chemical, surgical, mechanical, thermal, and radiation-based methods have been used for gingival depigmentation through a nonselective tissue damage to the superficial and deep epithelial layer and to the residing melanocytes. 12 In an attempt to reduce peripheral tissue damage, chemical depigmentation, a method used since the 1950s for PGH, 13 has cleared the path for surgical and mechanical methods, 14 which in turn, are being challenged nowadays by laser therapy. 15 Ablative laser therapy has shown many advantages over the surgical techniques-pain reduction, bloodless surgical field, avoiding gingival bandages, and a shorter recovery time. 12,16 In spite of the aforementioned benefits, ablative lasers can cause undesired tissue damage due to their nonselective mechanism.
While non-ablative lasers have been integrated as an important tool for the treatment of cutaneous pigmentation, only few studies examined their use in treating intra-oral pigmentation mainly focusing on the 755-nm alexandrite Q-switched and Pico laser. [17][18][19][20] Another laser examined for this purpose is the Q-switched Nd:YAG 532-nm laser with a recent study demonstrating favorable results in 10 patients with gingival hyperpigmentation after 1-4 treatment sessions. 21 The use of Q-switched ruby laser, although having the highest affinity to melanin, has only been published in few case reports describing successful treatment of pigmented fungiform papillae of the tongue. 22,23 The QSRL used in this study works in accord with the principle of selective photothermolysis-the 694-nm wavelength enables penetration of the outer mucosa with a selective absorption by melanin, while the Q-switched pulse-width of 20 nanoseconds minimizes the thermal conduction into the surrounding tissues. 24 Aside from the obvious inherent value of diminishing tissue damage, operating on a bleeding-free intact mucosal surface enables an immediate intra-operative assessment and optimizes the outcome.
Q-switched ruby laser is a well-studied safe modality for the treatment of cutaneous pigmentary lesions, 25 and as evident in our report, is extremely beneficial in treating PGH with no repigmentation and minimal adverse events.
The use of QSRL also carries some disadvantages, the major ones being the high cost and the need for an experienced physician to administer the treatment, thus low availability of this technique is expected.
The study is limited by the relatively small number of patients and by its retrospective nature; nevertheless, this is the first published case series of QSRL used for the treatment of PGH. Additional large-scale prospective studies are warranted to further validate our findings.
Based on the results of our study, we conclude that the 694-nm QSRL is a novel, safe, and promising method for treating PGH.

ACK N OWLED G M ENTS
None.

FU N D I N G I N FO R M ATI O N
The authors did not receive support from any organization for the submitted work.

CO N FLI C T O F I NTE R E S T S TATE M E NT
The authors have no relevant financial or non-financial interests to disclose.

DATA AVA I L A B I L I T Y S TAT E M E N T
The data that support the findings of this study are available from the corresponding author [YN] upon reasonable request.

E TH I C A L A PPROVA L
The study was approved by the ethics committee of Rabin Medical Center (RMC-0610-19).

PH OTO CO N S E NT
A written permission was obtained for publishing clinical pictures by the patients.

R E FE R E N C E S
1. Ozbayrak S, Dumlu A, Ercalik-Yalcinkaya S. Treatment of melaninpigmented gingiva and oral mucosa by CO 2 laser. Oral Surg Oral