Journal of Indian Society of Periodontology
Journal of Indian Society of Periodontology
Home | About JISP | Search | Accepted articles | Online Early | Current Issue | Archives | Instructions | SubmissionSubscribeLogin 
Users Online: 4603  Home Print this page Email this page Small font size Default font size Increase font sizeWide layoutNarrow layoutFull screen layout


 
   Table of Contents    
ORIGINAL ARTICLE
Year : 2020  |  Volume : 24  |  Issue : 1  |  Page : 47-53  

Evaluation of surgical scalpel versus semiconductor diode laser techniques in the management of gingival melanin hyperpigmentation: A split-mouth randomized clinical comparative study


1 Department of Periodontics, Panineeya Mahavidyalaya Institute of Dental Sciences and Research Centre, Hyderabad, Telangana, India
2 Department of Periodontics, College of Dental Sciences, Davangere, Karnataka, India
3 Private Dental Practitioner, Hyderabad, Telangana, India

Date of Submission20-Mar-2019
Date of Decision19-Aug-2019
Date of Acceptance28-Oct-2019
Date of Web Publication02-Jan-2020

Correspondence Address:
Dr Ganachari Bharath Chandra
Room Number 101, Department of Periodontics, Panineeya Maha Vidyalaya Institute of Dental Sciences and Research, Kamala Nagar Colony, Hyderabad - 500 060, Telangana
India
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jisp.jisp_186_19

Rights and Permissions
   Abstract 


Background: “Black gums” due to melanin pigmentation of the gingiva is one reason for the demand of cosmetic therapy. Clinicians are often faced with challenge to achieve gingival esthetics in such cases because of its recurrence. Although many procedures were described in literature for gingival depigmentation, only few are mentioning about the intensity of repigmentation. Hence, this study was designed to compare two different techniques for treatment of gingival melanin pigmentation. Materials and Methods: Twenty patients who were not esthetically pleased with the color of gingiva were selected. A randomized, split-mouth, depigmentation procedure was performed using surgical scalpel and diode laser techniques. Clinical parameters such as plaque and gingival index, bleeding, pain perception, wound healing, recurrence, and intensity of repigmentation were evaluated. Paired t-test and Chi-square test were used for analysis of data. Results: No bleeding was reported in patients treated with diode laser. Moderate pain was reported by patients treated with surgical scalpel, whereas none was reported in diode laser group. No statistically significant difference was observed for both treatment techniques in terms of wound healing, reappearance of gingival pigmentation, and intensity of the same at the end of 6 and 9 months postsurgically. Conclusion: Similar outcomes were observed for both the techniques. Few patients who resulted in no recurrence at 9 months were followed even up to 3 years. Hence, further studies should be done to know the underlying mechanisms. Keeping in mind of armamentarium and cost, surgical scalpel technique remained as the “gold standard” procedure for treatment of gingival melanin pigmentation.

Keywords: Black gums, diode laser, repigmentation, surgical scalpel technique, wound healing


How to cite this article:
Chandra GB, Kumar MB, Walavalkar NN, Vandana KL, Vardhan PK. Evaluation of surgical scalpel versus semiconductor diode laser techniques in the management of gingival melanin hyperpigmentation: A split-mouth randomized clinical comparative study. J Indian Soc Periodontol 2020;24:47-53

How to cite this URL:
Chandra GB, Kumar MB, Walavalkar NN, Vandana KL, Vardhan PK. Evaluation of surgical scalpel versus semiconductor diode laser techniques in the management of gingival melanin hyperpigmentation: A split-mouth randomized clinical comparative study. J Indian Soc Periodontol [serial online] 2020 [cited 2020 Feb 26];24:47-53. Available from: http://www.jisponline.com/text.asp?2020/24/1/47/274558




   Introduction Top


Gingival architecture has been a mainstay in cosmetic dentistry, the concept of its health and appearance considered vital in facial esthetics and smile.[1] The gingival complex plays a vital role in the overall esthetics of the smile. It is often the clinical practitioners perform procedures to achieve gingival esthetics along with functional problems, making them a significant aspect.[2] Gingival pigmentation is a major concern for a large number of patients in dental practice. The presence of such pigmentation is considered to be the normal clinical characteristic of oral tissues in most of the human beings. Among pigments melanin, carotene, reduced hemoglobin, and oxyhemoglobin are mainly contributing to the normal color of oral mucosa and gingiva.[3],[4]

Melanin, a nonhemoglobin-derived brown pigment, is one of the most common natural and endogenous pigments contributing to the color of the gums.[5] Oral melanin pigmentation is considered to be multifactorial. It is seen across all the races, age groups, and is without gender predilection.[6],[7] Such melanin pigmentation of gingiva became the cause of embarrassment in smile conscious individuals, thereby increasing the demand for cosmetic therapies for the treatment of the same.

Different techniques have been proposed for the treatment of gingival depigmentation that was classified into methods to remove and methods to mask gingival pigmentation.[8] Scalpel surgical technique is a time-tested technique and considered as the gold standard technique. Lasers have been used in dentistry since the beginning of the 1980s. Recently, they have been used to ablate cells containing and producing melanin pigment.[9] They also become the treatment of choice as they improve homeostasis and causes less postoperative discomfort over scalpel surgery. Diode laser has energy and wavelength characteristics that specifically target the soft tissues has gained increasing importance and interest.[10]

Selective photothermolysis involves the use of laser beam with a wavelength that specifically absorbed in melanin and destroys the pigmented cells without affecting any nonpigmented cells. Despite advantages, lasers are relatively expensive, delayed wound healing, thermal damage, deep penetration, and have limited indications in other specialties of dentistry.[11] Among types of lasers available, diode laser uses a combination of elements to change electrical energy into light energy, which is then absorbed by pigmentation in soft tissues. This makes the diode laser an excellent homeostatic agent.[12]

In the present study, we intended to evaluate the effectiveness of two depigmentation techniques, i.e., conventional surgical scalpel scraping technique and semiconductor diode laser technique. And also, we verified repigmentation from two techniques at different time intervals.


   Materials and Methods Top


The present study is a split-mouth, randomized, comparative, clinical trial and was carried out in patients visiting the Outpatient Department of Periodontics. Ethical clearance from the Institutional Review Board was obtained prior to the start of the study.

Patient selection

Twenty patients who were complaining about bilateral physiologic melanin hyperpigmentation of gingiva (dark gums) in the anterior segment with age ranging from 20 to 35 years were included in this study. The procedure of gingival depigmentation was planned in anterior labial gingiva of the maxilla on both sides, i.e., midline to distal of the right canine and midline to distal of the left canine. The depigmentation procedure was randomly allotted to either of the areas by the flip of a coin. All the participants were informed regarding the procedure and prior informed consent was obtained. The authors made sure that participants were aware of the nature of ethnic or physiologic hyperpigmentation and understood that it has no influence on the systemic health of the patient.

Periodontally healthy individuals with bilateral melanin pigmentation in the anterior segment were included in this study. And also, individuals who were categorized as moderate or heavy clinical pigmentation as per the Dummett Oral Pigmentation Index (DOPI)[13] were included. Patients with thin gingival biotype, pregnant and lactating women, medically compromised patients, patients using drugs or chemicals that got potential to cause oral pigmentation and also patients who were under medication or condition that will interfere with bleeding or wound healing, and smokers were excluded from the study.

Depigmentation procedure

One week prior to the depigmentation procedure, all the enrolled participants underwent initial phase therapy, i.e., oral prophylaxis, scaling, and root planing. Since both depigmentation procedures were performed in the same patient on different quadrants, the author made sure sufficient time, i.e., the 1-week interval was kept in order to assess pain and healing patterns from two procedures.

Scalpel scraping technique

After achieving adequate anesthesia (using 2% lignocaine hydrochloride) to the surgical area, entire epithelium and a layer of connective tissue were scraped using surgical scalpel blade No. 15, till all the visible pigmentation was removed from margin to mucogingival junction. Bleeding from the surgical area was controlled through direct application of pressure pack and the periodontal dressing was done [Figure 1]a and [Figure 1]b.
Figure 1: (a) Preoperative; (b) Scalpel scraping; (c) Laser application; (d) Immediate postoperative; (e) 6 months postoperative; (f) 9 months postoperative; (g) 3 years postoperative

Click here to view


Laser technique

Local anesthesia with 2% lignocaine hydrochloride was administered at the surgical area. The diode laser used in the study has a wavelength of 810 nm at 1.5–2.0-watt power in a continuous wave mode with the flexible fiberoptic delivery system, in a continuous contact mode. Melanin pigmented gingiva was ablated using this laser device. Before applying the laser, proper care was taken, i.e., protective eye gear was worn by both operator as well as assistant. And also, highly reflective instruments or instruments with mirrored surfaces were avoided, as there could be a reflection of the laser beam. Precautionary measures were taken to avoid using the laser in the presence of explosive gases.

The tip of the laser was held in light contact with the tissue, and light sweeping brush strokes were performed. It was directed to the target tissue until blister formation occurred. Blistered gingiva was then scraped off with wet, saline-moistened gauze to remove the epithelium containing melanin pigmentation. The overall procedure was performed in cervicoapical direction in all pigmented areas [14],[15] [Figure 1]c and [Figure 1]d. The depigmented area was then covered with a periodontal dressing. Following the depigmentation procedure, the patient was instructed to maintain good oral hygiene and to avoid eating of any hot, spicy foods following 24 h of surgery. Moreover, they were also instructed to avoid any trauma during the healing period (4–7 days following treatment) and advised to use 0.2% chlorhexidine digluconate to rinse twice daily for 2 weeks.

Parameters measured

A single calibrated operator recorded clinical parameters such as bleeding, pain, wound healing, recurrence of pigmentation, and intensity of repigmentation. Parameters such as pain, wound healing, and bleeding were recorded according to the criteria of Ishii et al. and Kawashima et al.[16],[17] Plaque and gingival indices were also measured at all visits. Assessment of clinical repigmentation and intensity was done using Dummett Oral Pigmentation Index (DOPI) at 3rd, 6th, and 9th months postoperatively [Figure 1]e and [Figure 1]f.

Statistical analysis

Collected data were subjected to statistical analysis. SPSS version 20.0 for Windows (SPSS Inc., Chicago, IL, USA) was used. Paired t-test performed for continuous variables for comparison between treatment groups. Categorical data were analyzed using Chi-square test. Results were represented as mean ± standard deviation; with P < 0.05 was considered statistically significant.


   Results Top


[Table 1] shows the output of paired t-test between the treatment groups at different time intervals. The mean of plaque and gingival indices scores were low at 9 months postoperatively compared to baseline. Moreover, there was a statistically significant difference was seen between the treatment groups for both indices (P > 0.05). [Table 2] shows the association between treatment groups and bleeding during procedure. Slight (55%)-to-moderate (45%) bleeding observed in quadrant which was operated surgical scraping and none of the surgical sites showed bleeding seen when operated with diode laser. Chi-square test revealed statistically significant association between bleeding and treatment groups (P < 0.05).
Table 1: Comparison of plaque and gingival indices between groups at different time intervals

Click here to view
Table 2: Association between bleeding during the procedure among treatment groups

Click here to view


[Table 3] shows the association between pain evaluated at two different time intervals among the quadrants operated with different techniques. At 1-day postoperatively, sites treated with scalpel scraping had shown mild pain in 70% and moderate pain in 30% of patients. In quadrants operated using diode laser, most of the patients (60%) experienced mild pain and remaining all (40%) reported no pain. Statistical analysis revealed that there is a significant association (P = 0.001) between pain and treatment techniques at day 1, with diode laser showing significant reduction of pain. On week 1 postoperatively, all patients reported similarly in terms of pain for two treatment techniques (P > 0.05).
Table 3: Association between pain using Visual Analog Scale on 1st-day and 1st-week postoperatively in quadrants treated with scalpel scraping and diode laser

Click here to view


At 1-week postoperatively in scalpel scraping group, 65% of sites showed complete epithelization and only 33.4% showed incomplete epithelization. In the laser-treated group, 60% showed complete epithelization and 40% showed incomplete epithelization. At 1 month, all the sites in both groups were healed. Scalpel scraping group has shown better healing compared to laser group but was not statistically significant (P > 0.05) [Table 4].
Table 4: Association between healing and 1st-day and 1-month postoperatively in quadrants treated with scalpel scraping and diode laser

Click here to view


Details of occurrence of repigmentation and its intensity were presented in [Table 5] and [Table 6]. At end of 6 months, 13 (65%) patients operated with surgical scraping exhibited repigmentation. Among them, ten were presented with mild pigmentation and three with moderate. In group with laser-operated patients, 12 (60%) showed repigmentation, in ten patients exhibited mild and two exhibited moderate pigmentation. At the end of 9 months, 17 out of 20 patients (85%) operated with surgical scraping technique showed repigmentation. Ten (50%) among them are mild, five are moderate (25%), and two (10%) showed heavy repigmentation. In laser-treated group, 16 out of 20 patients (80%) showed repigmentation. Among them, 13 (65%) were mild, 2 (10%) are moderate, and 1 (5%) is heavily pigmented. Even though laser has shown a smaller number of sites in intensity of repigmentation than scalpel scraping group, there was no statistically significant difference was observed (P > 0.05). Four patients out of twenty who showed no signs of repigmentation at end of 9 months, when they were followed up after 3 years have exhibited mild repigmentation [Figure 1]g.
Table 5: Association between recurrence of pigmentation and different time intervals in quadrants treated with scalpel scraping and diode laser

Click here to view
Table 6: Association between intensity of repigmentation and different time intervals in quadrants treated with scalpel scraping and diode laser

Click here to view



   Discussion Top


A smile is dictated not just by shape, position, and color of the tooth, but also by the health of gingival tissues.[18] The appearance of gingiva plays a crucial role and has tremendous impact on smile esthetics. Owing to the problem of “black gums,” there have been growing esthetic concerns that require the removal of the same using depigmentation procedures. Scalpel surgical technique is considered most economic with no equipment constraints. Moreover, the healing period for surgical wounds is relatively faster than any other technique.[19],[20] Other procedure that considered as effective, pleasant, and reliable is laser ablation technique. Reduced pain and discomfort, clean and dry operating field, and seal of free nerve endings are few of many advantages using lasers.[21] Therefore, the present study was designed for comparative evaluation of conventional surgical scalpel procedure and diode laser application in terms of bleeding during procedure, pain, wound healing, and recurrence and intensity of repigmentation.

It was observed that both surgical scalpel and diode laser procedures provided similar results in terms of effective removal of gingival pigmentation and repigmentation when assessed at regular intervals of 3, 6, and 9 months, respectively. When bleeding was assessed between two techniques, surgical scraping showed slight-to-moderate bleeding, while laser-treated areas exhibited none, which is consistent with previous studies.[10],[22],[23] Minimal to no bleeding using laser attributed to formation of protein coagulum, which in turn seals the ends of the capillaries and venules.

Regarding pain perception, slightly mild-to-moderate pain reported by patients underwent surgical scalpel procedure, while only mild pain was reported by those (60%) treated with diode laser at the end of day 1. On day 7, there was no statistically significant difference between two techniques in terms of pain perception, with mild pain in surgical scalpel group and none in diode laser. These findings were similar to that of study conducted by Suragimath et al.[23] In terms of wound healing, no statistically significant difference was seen between two procedures and all patients had no hemorrhaging, morphological abnormalities, scarring, or infection at the surgical site. At week 1 appointment, 65% of patients treated with surgical scalpel and 55% treated with diode laser showed significantly faster wound healing. All cases (both surgical scraping and diode laser) had shown complete epithelization at month 1 appointment. The findings of faster healing in scalpel-treated areas compared to laser treated at week 1 may be because of delayed epithelial regeneration and lack of wound contraction as compared to conventional surgery [15] and is consistent with the findings of Kasagani et al.[24]

In the present study, the results from both treatment modalities were stable to some extent, i.e., up to 3 months postoperatively. Later, slight recurrence of solitary units of pigments were seen by month 6. At month 6, nearly 62.5% of cases showed postsurgical repigmentation of gingiva in both techniques. At month 9, approximately 82.5% of patients showed postsurgical repigmentation. When the intensity of repigmentation was measured by Dummet Oral Repigmentation Index, 50% of cases in either of treatment modalities exhibited mild pigmentation at the end of month 6. Moderate repigmentation was seen in three cases (15%) of surgical scalpel and two cases (10%) of diode laser technique, respectively (P = 0.375). The reappearance of pigmentation following surgical procedures reported to be varying in time, i.e., 15, 24, 30, and 33 days, respectively.[11],[25] It is believed that this difference in time of repigmentation is mainly related to the technique applied as well as the race of the patient.[25] In a study by Alhabashneh et al., the authors compared 6-month clinical efficacy of laser and scalpel technique in patients of Jordan nationality. They observed the recurrence of pigmentation in both sites at around 3 and 6 months, respectively.[26]

Even though the exact mechanism for clinical repigmentation is unclear, it is believed to occur due to the migration of active melanocytes from adjacent pigmented tissues to surgically treated areas, leading to repigmentation.[27] On the other hand, according to Ginwalla et al., repigmentation was attributed to left out melanocytes.[28]

In case series by Perlmutter and Tal, repigmentation in few cases had not occurred up to 431 days postsurgically, and in one case, it did not occur over the first 2 years. They speculated that such delay in occurrence either due to nonmigration of melanocytes or due to inactive melanocytes that were migrated.[27] Similarly, when follow-up was done at a period of 3 years for 4 patients who were scored as “no repigmentation” at the end of 9 months, it revealed mild intensity of gingival repigmentation in both groups.[Figure 1]g. Moreover, those who were scored to be mild, pigmentation appeared as small spots, bands, or streaks. All the reexamined patients are very satisfied as the intensity of repigmentation is mild when compared to preoperative pigmentation.


   Conclusion Top


Based on the findings, we conclude that both surgical scalpel and diode laser techniques were found to be clinically effective in treatment of melanin pigmentation of gingiva. Future studies must focus on melanocytic activity rather than the techniques to be used, owing to their contribution in repigmentation and also to reduce the rate of recurrence of pigmentation.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Verma SG, Rathwa V. Gingival Depigmentation. Indian J Clin Pract 2013;23:801-3.  Back to cited text no. 1
    
2.
Gupta G. Management of gingival hyperpigmentation by semiconductor diode laser. J Cutan Aesthet Surg 2011;4:208-10.  Back to cited text no. 2
[PUBMED]  [Full text]  
3.
Mokeem SA. Management of gingival hyperpigmentationby surgical abrasion. Saudi Dent J 2006;18:162-6.  Back to cited text no. 3
    
4.
Nagati RR, Al-Qahtani N, Ravi K, Tikare S, Pasupuleti M. Clinical effectiveness of gingival depigmentation using conventional surgical scrapping and diode laser technique: A quasi experimental study. Glob J Health Sci 2017;9:296-303.  Back to cited text no. 4
    
5.
Ciçek Y, Ertaş U. The normal and pathological pigmentation of oral mucous membrane: A review. J Contemp Dent Pract 2003;4:76-86.  Back to cited text no. 5
    
6.
Page LR, Corio RL, Crawford BE, Giansanti JS, Weathers DR. The oral melanotic macule. Oral Surg Oral Med Oral Pathol 1977;44:219-26.  Back to cited text no. 6
    
7.
Trelles MA, Verkruysse W, Seguí JM, Udaeta A. Treatment of melanotic spots in the gingiva by argon laser. J Oral Maxillofac Surg 1993;51:759-61.  Back to cited text no. 7
    
8.
Malhotra SS, Basavaraj P. Gingival esthetics by depigmentation. J Periodontal Med Clin Pract 2014;1:79-84.  Back to cited text no. 8
    
9.
Yeh CJ. Cryosurgical treatment of melanin-pigmented gingiva. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1998;86:660-3.  Back to cited text no. 9
    
10.
Lagdive S, Doshi Y, Marawar PP. Management of gingival hyperpigmentation using surgical blade and diode laser therapy: A comparative study. J Oral Laser Appl 2009;9:41-7.  Back to cited text no. 10
    
11.
Kumar S, Bhat GS, Bhat KM. Comparative evaluation of gingival depigmentation using tetrafluoroethane cryosurgery and gingival abrasion technique: Two years follow up. J Clin Diagn Res 2013;7:389-94.  Back to cited text no. 11
    
12.
Prabhuji ML, Madhupreetha SS, Archana V. Treatment of gingival hyperpigmentation for aesthetic purposes using the diode laser. Int Mag Laser Dent 2011;3:30-2.  Back to cited text no. 12
    
13.
Dummett CO, Gupta OP. Estimating the epidemiology of oral pigmentation. J Natl Med Assoc 1964;56:419-20.  Back to cited text no. 13
    
14.
Bhardwaj A, Grover S, Harpreet SL. Gingival depigmentation with scalpel and diode laser. World J Dent 2012;3:359-62.  Back to cited text no. 14
    
15.
Kathariya R, Pradeep AR. Split mouth de-epithelization techniques for gingival depigmentation: A case series and review of literature. J Indian Soc Periodontol 2011;15:161-8.  Back to cited text no. 15
[PUBMED]  [Full text]  
16.
Ishii SA, Kawashima Y, Watanabe H, Ishikawa I. Application of an Er:YAG laser to remove gingival melanin hyperpigmentation: Treatment procedure and clinical evaluation. J Jpn Soc Laser Dent 2002;13:89-96.  Back to cited text no. 16
    
17.
Kawashima Y, Aoki A, Ishii S, Watanabe H, Ishikawa I. Er:YAG laser treatment of gingival melanin pigmentation. Int Congr Series 2003;1248:245-8.  Back to cited text no. 17
    
18.
Parwani S, Parwani R. Achieving better esthetics by gingival de-pigmentation: Report of three cases with a review of the literature. J Mich Dent Assoc 2013;95:52-8, 78.  Back to cited text no. 18
    
19.
Moneim RA, El Deeb M, Rabea AA. Gingival pigmentation cause, treatment and histological preview. Future Dent J 2017;3:1-7.  Back to cited text no. 19
    
20.
Javali R, Deshmukh J. Esthetic management of gingival hyperpigmentation: Report of two cases. Int J Dent Clin 2011;3:115-6.  Back to cited text no. 20
    
21.
Simşek Kaya G, Yapici Yavuz G, Sümbüllü MA, Dayi E. A comparison of diode laser and er:YAG lasers in the treatment of gingival melanin pigmentation. Oral Surg Oral Med Oral Pathol Oral Radiol 2012;113:293-9.  Back to cited text no. 21
    
22.
Lee KM, Lee DY, Shin SI, Kwon YH, Chung JH, Herr Y, et al. A comparison of different gingival depigmentation techniques: Ablation by erbium: yttrium-aluminum-garnet laser and abrasion by rotary instruments. J Periodontal Implant Sci 2011;41:201-7.  Back to cited text no. 22
    
23.
Suragimath G, Lohana MH, Varma S. A split mouth randomized clinical comparative study to evaluate the efficacy of gingival depigmentation procedure using conventional scalpel technique or diode laser. J Lasers Med Sci 2016;7:227-32.  Back to cited text no. 23
    
24.
Kasagani SK, Nutalapati R, Mutthineni RB. Esthetic depigmentation of anterior gingiva. A case series. N Y State Dent J 2012;78:26-31.  Back to cited text no. 24
    
25.
Kaur H, Jain S, Sharma RL. Duration of reappearance of gingival melanin pigmentation after surgical removal - A clinical study. J Indian Soc Periodontol 2010;14:101-5.  Back to cited text no. 25
[PUBMED]  [Full text]  
26.
Alhabashneh R, Darawi O, Khader YS, Ashour L. Gingival depigmentation using er:YAG laser and scalpel technique: A six-month prospective clinical study. Quintessence Int 2018;49:113-22.  Back to cited text no. 26
    
27.
Perlmutter S, Tal H. Repigmentation of the gingiva following surgical injury. J Periodontol 1986;57:48-50.  Back to cited text no. 27
    
28.
Ginwalla TM, Gomes BC, Varma BR. Surgical removal of gingival pigmentation. (A preliminary study). J Indian Dent Assoc 1966;38:147-50 passim.  Back to cited text no. 28
    


    Figures

  [Figure 1]
 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]



 

Top
   
 
  Search
 
  
    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
    Access Statistics
    Email Alert *
    Add to My List *
* Registration required (free)  

 
  In this article
    Abstract
   Introduction
    Materials and Me...
   Results
   Discussion
   Conclusion
    References
    Article Figures
    Article Tables

 Article Access Statistics
    Viewed251    
    Printed4    
    Emailed0    
    PDF Downloaded87    
    Comments [Add]    

Recommend this journal