LASERS FOR ESTHETIC REMOVAL OF GINGIVAL HYPERPIGMENTATION: A SYSTEMATIC REVIEW OF RANDOMIZED CLINICAL TRIALS

Hanaa El-Shenawy 1 , Ali Fahd 2* , Mohamed Ellabban 3 , Mushira Dahaba 4 and Mohamed Khalifa 4 . 1. Oral Surgery and Medicine Department, National Research Centre, Egypt. 2. Oral and Maxillofacial Radiology department, Faculty of oral and dental medicine, South Valley University, Egypt. 3. Orthodontic department, Faculty of oral and dental medicine, Assiut University, Egypt. 4. Oral and Maxillofacial Radiology Department, Faculty of Oral and Dental Medicine, Cairo University, Egypt. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History

A critical concern in the management of hyperpigmented gingiva is relapse or gingival repigmentation which can be defined as the reappearance of pigmentation after a period of no clinically hyperpigmentation. Recurrence usually varies according to the used methodology and the length of follow-up (Hegde et al. 2013).
The clinical rationale for comparing laser to conventional methods can be simply based upon the need for minimally invasive techniques for achieving a patient relevant outcomes (Ribeiro et al. 2014).
Based on this background, the aim of the present systematic review is to evaluate and compare the effects of conventional techniques versus lasers for gingival depigmentation as regards to removal of pigmentation, patient preference and time taken for repigmentation.

Materials and Methods:-
The methods as well as inclusion/exclusion criteria used in the present study were determined in advance. The current systematic review was performed following the PRISMA guidelines for identification, screening, eligibility, and inclusion (Moher et al. 2010). The following focus question was developed: In patient requiring esthetic removal of gingival hyperpigmentation, is laser use recommended over conventional techniques, what is the evidence based recommendation for both patients and operators?
Information Sources:-The electronic search was performed in two databases, MEDLINE (PubMed) and Cochrane library databases for articles with no date restrictions.

Search:-
The researched keywords were: (Black OR pigment OR melanin OR pigmentation OR hyperpigmentation OR pigmented OR dark OR Pigmentary OR pigmentations OR melanin) AND (Lased OR laser OR LLLT) AND (Gingiva OR mucosa OR gingival OR mucosal OR gum).

Selection of studies:-
Titles and abstracts resulted from the search were screened by authors considering the inclusion criteria. Authors decisions about choices and their qualification for further analysis was affirmed after discussion. According to Cochrane risk of bias tools, each RCT was assigned either; low risk of bias (if it is low for all key domains), high risk of bias (if it is high for one or more of key domains) and unclear risk of bias (if it is unclear for one or more of key domains). Because it was impossible to blind participants or personnel due to nature of intervention and control (i.e. Laser VS surgery), the "BLINDING OF PARTICIPANTS, PERSONNEL" item was not considered.

Results:-
Out of the initial search that yielded 183 studies, 21 were considered potentially relevant for the present study, out of which 4 were finally selected. Figure    The trials presented in this review agreed that both techniques are successfully used for the treatment of gingival hyperpigmentation but which one is recommended over the other, an issue that needs further discussion.
Blade surgery for gingival depigmentation is a definite precise and controlled procedure beside being the most economical procedure. Any depigmented areas are appreciated immediately and there is no chance for any residual pigments. On the other hands, this technique required the use of local anesthesia, associated with pain and hemorrhage and required care not to expose the bone or create gingival recession (Grover et al. 2014).
Also, periodontal dressing for at least a week is mandatory to guard against food debris, foreign irritants, thermal stimuli and infection (Gurumoorthy Kaarthikeyan et al. , Grover et al. 2014). The denuded tissues which heal by secondary intention after conventional surgery may promote bleeding after the procedure and is associated with some discomfort and pain for the patient (Ribeiro et al. 2014) Thorough removal of pigments, pain reduction, and higher patient preference were associated with Er: YAG laser but more sites showed repigmentation. The CO2 laser was beneficial in terms of complete hemostasis intraoperatively and delaying the rate of repigmentation. Repigmentation was least after the surgical stripping procedure. Diode laser Vs Electro-surgery A statistically highly significant difference in the pain levels between the two groups 24 h post-operatively in favor of laser group. Despite of lesser mean pain level for the laser group at other times, it was a non-significant difference.

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The expected complicated postoperative period, even if mild, may interfere with patient daily activities and wellbeing (Ribeiro et al. 2014). An experience that should be avoided by the modern patient centered care strategy.
Despite that surgical stripping has been the old gold standard for gingival depigmentation, lasers start to gain prominence in that field (Coluzzi 2004).
Using of lasers for oral soft tissues provides benefits not only to dental operators but also for the patients. Patientcentered outcomes are the main target for researches in the last decade (Hujoel 2004, Ozcelik et al. 2007).
Concerning the cosmetic outcomes, some aspects of using lasers may benefit the purpose as precise cutting and control and the application of delicate contact tips during the procedure which enhances trans-operative visualization (Cobb 2006).
One of the advantages of using laser is that patients felt no pain either during or after the treatment without requiring an additional anesthetic injection. Fear of pain during dental surgeries or even the needle used for anesthesia are among the causes of avoiding dental visits. Thanks to lasers that solve a part of that problem (Matys and Dominiak 2016) .
The reduced pain in comparison with conventional surgery may be due to the protein coagulum formed on the surface of the wound that acts as a biologic dressing. Sealing of the ends of sensory nerves may be also considered which is not the case in surgical stripping where the nerve endings is left exposed Patients also appreciated the shorter operating time and minimal bleeding which is not the case in patients treated with the surgical scalpel technique (Hegde et al. 2013, Grover et al. 2014). The time taken for laser treatment was less than the surgical stripping may be attributed to better visibility due to less bleeding because of the coagulation of blood vessels (Ko et al. 2010, Ribeiro et al. 2014, Basha et al. 2015).
Several studies have compared different lasers with varying results, similar advantages includes a relatively bloodless surgical field, minimal swelling and scarring, reduction of surgical time and less postoperative pain (Giannelli et al. 2014, Kishore et al. 2014, Soliman et al. 2014, Basha et al. 2015).
It is the ablative property of laser that makes it possible to be used for gingival depigmentation by targeting the melanin in melanocytes in epithelium which absorbs and converts light energy into heat or what is known as photothermolysis (Nakamura et al.

1999, Coluzzi 2004).
A variety of laser systems can be used for gingival depigmentation, including carbon dioxide (CO 2 ) laser  Atsawasuwan et al. 2000). Neodymium-yttrium aluminum garnet (Nd:YAG) laser treatment has been considered as an alternative for gingival hyperpigmention because of rapid healing and minimal bleeding during and after the procedures (Ko et al. 2010).

Fortunately, Nd:YAG laser is selectively absorbed by hyperpigmented tissues (Cobb 2006).
It is the inherent ability of diode lasers to be absorbed within the chromophores that allows controlled cutting with a limited depth of necrosis or by other words a tissue-specific ablation. The other advantage of diode laser is that its energy is transmitted through water and fortunately it is poorly absorbed in hydroxyapatite (Convissar 2004). It was noted that repigmentation appeared in the papillary areas and marginal gingiva which may be due to difficulty in treating these areas with lasers because of lying near tooth structure and the risk of thermal damage which recommends lower energy dose with inadequate depth of penetration of the laser beam, incomplete depigmentation, and faster recurrence (Hegde et al.

2013)
To avoid recurrence, the gingival tissue should be entirely cleared of melanin to avoid recurrence by melanocytes migration (Sharon et al. 2000). Also, patient race, environmental exposure exposure and smoking may play a role in repigmentation It is important to mention that care should be taken not to injure the gingival margin and interdental papilla during ablation of pigmented gingival tissue in these delicate areas. Also, higher doses can cause like delayed wound healing promoted by severe coagulation or pain caused by uncontrolled carbonization (Ribeiro et al. 2014).
Laser requires more advanced technology and armamentarium and it causes higher financial costs than more economical scalpel technique

Conclusion:-
The found clinical studies are not only too limited in number but also exhibit small sample sizes, besides being clinically heterogeneous so that a solid conclusion cannot be reached. Researchers should pay attention to this interesting field to work upon. Each kind of laser application should pull attention of researchers in oral and maxillofacial field to close obvious, yet important, research gaps of lack of enough randomized clinical trials that can be relied upon to get a standard evidence based clinical practice.
Within the limitations of this review, it can be concluded that lasers can be used as a safer and effective treatment modality to provide optimal esthetics and enhanced comfort with lesser pain to the patients during the treatment for 1246 gingival hyperpigmentation. However, surgical stripping is a cost-effective procedure for achieving gingival depigmentation. Higher patient preference and pain reduction favor laser depigmentation, but more sites showed repigmentation. The lower cost of surgical stripping and the lower rate for repigmentation favor the old technique. Further studies with a larger study samples and a longer follow-up period would be desirable with special concern on multiple laser sessions to reach a solid evidence based conclusion regarding which technique is better keeping in mind the effect on repigmentation.