Gingival depigmentation by Er,Cr:YSGG laser and diode laser: a split mouth, clinical trial study

Abstract

Background and aims

The Aim of this study was to evaluate the effectiveness of Diode laser and Er,Cr:YSGG laser ablation on the treatment of physiologic gingival melanin hyperpigmentation.

Materials and methods

This research design was split mouth, double blind, and clinical trial. The power of the diode laser was set at 1 W, fiber 320 µ, irradiation mode: continuous-wave with treatment mode of contact tip and Er,Cr:YSGG laser (2780 nm) was set at 100 MJ, frequency of 15 Hz, total power of 1.75 W, 10% water and 20% air. Bleeding, pain, healing, Dummett oral pigmentation index (DOPI) and Hedin melanin score changes and repigmentation were assessed. Patients were followed for 6 months.

Results

A total number of 14 patients were involved in this study. There were statistically significant differences in reduction of DOPI and Hedin melanin score in each treatment groups separately while diode laser group had better results (P < 0.0001). There was no statistically significant difference between groups in terms of repigmentation. There was more pain in diode laser group (P < 0.0001) and there was more bleeding in Er,Cr:YSGG laser group (P = 0.0156). Gingival healing was more in Er,Cr:YSGG laser group (P < 0.0001).

Conclusion

Diode laser had more efficiency for reduction of DOPI and Hedin melanin index scores.

Introduction

Among orofacial components, fitness and harmony play essential role in building attractive face, personal satisfaction from face and affects confidence. The most common components of the mouth that appear and are seen while a person smile or speaks are, lips, teeth, and gingival tissue. Therefore, gingiva affect the beauty of smile. ^{1, 2)}

The most common cause of gingival pigmentation is physiologic due to the over production of melanin granules from melanocytes. ^{3, 4)}

The oldest documented text about unpleasant dark gingival color is related to the study of Ginwalla et al (1966), they suggested the removal of these pigmented area ⁵⁾. Gingival depigmentation is periodontal plastic surgery whereby gingival hyperpigmentation is eliminated or reduced ⁶⁾. Gingival depigmentation should be carried out with caution and adjacent structures should be protected because improper treatment can cause gingival recession, damage to underlying bone and periost, delayed gingival healing and loss of enamel ⁶⁾.

Currently, different methods, including: gingivectomy, gingival graft ^{7, 8)}, chemical treatment with 90% phenol and 95% alcohol ⁹⁾, electrosurgery ¹⁰⁾, abrasion with diamond tools ¹¹⁾ and cryosurgery ^{12, 13)} are used in gingival depigmentation. Each of these methods have limitations such as; pain, scar, bleeding, recession, periosteal and bone damage and patient fear ¹⁴⁾. The latest gingival melanin depigmentation methods are cryosurgery and lasers ^{15, 16)}. YI Hung Lin et al stated laser therapy, electro surgery and cryotherapy as more promising methods with minimal recurrence of pigmentation ¹⁵⁾.

Presently, gingival depigmentation with lasers are been mentioned as the most effective, compatible, valid methods and choice of treatment among clinicians ^{1, 17)}.

Gingival epithelial structure is basically similar to epithelium of hard palate. Average thickness of hard palate epithelium is 0.31 ± 0.05 mm and thickness of vestibular gingival is approximately 0.30 ± 0.07 mm ¹⁸⁾. Theoretically, we need a cutting depth of more than 0.31 mm, therefore chemical agents for cauterization, bur abrasion or use of scalpel may not be able to completely eliminate basal cell layer that contains melanin ¹⁵⁾. Diode laser wavelength are between 800 to 980 nm ¹⁶⁾. This laser absorb in the chromophores of tissues (such as melanin and oxyhemoglobin). Diode laser is nonionizing and nonmutagenic. Photo thermal effect occurred after absorption of Diode laser photons and temperature of soft tissues increased. Diode laser can properly affect in darker pigmented tissues ¹⁹⁾.

Wave length of Erbium family lasers are accord with coefficient absorption of water and hydroxyapatite and don't have concordance by coefficient absorption of melanin. The mechanism of laser-tissue interaction by Er,Cr:YSGG laser demonstrate to raise the temperature of water molecules. Then water vaporized and thermomechanical micro-explosion occurred in the cells. Erbium lasers induce low thermal damage, consequently ablation occurred without carbonization and minimal heating ^{20, 21)}.

Erbium lasers have ability to eliminate melanin containing cells to exist in basal and supra basal epithelial layer ¹⁶⁾.

The objective of this study was to evaluate the treatment outcomes of Er,Cr:YSGG laser and Diode laser ablation in gingival depigmentation.

Methods

This split mouth, double blind, clinical trial study was designed to compare the effectiveness of diode laser and Er,Cr:YSGG laser for the treatment of Physiologic Gingival Melanin Hyperpigmentation. This study was approved by the ethical committee of the School of Dentistry.

The patients were aware of the procedure and the objective of the study and signed a written informed consent. Study was recorded in Iranian Registry of Clinical Trials (www.irct.ir) code: IRCT2015121925610N1.

The study population comprised 14 patients (5 males and 9 females, between the ages of 15–39 years) who requested cosmetic therapy for dark gingival color. The patients were selected from people who presented in Oral Medicine Department between November 2014 and December 2015.

Inclusion criteria for the study include having physiologic gingival melanin pigmentation, coordination of gingival pigmentation pattern in left and right side, and voluntary participation in study. Exclusion criteria include history of diabetes or autoimmune disease, use of drugs that influences gingival color, pregnant or breast-feeding women, evidence about the relation of pigmentation with malignancies, history of previous treatment of gingival pigmentation, smoking and periodontitis.

Treatment site was gingival tissue from midline to distal of right canine and midline to distal of left canine. One of the lasers was then selected on each side, to be used randomly. Before commencing the first treatment session, the doctor asked patient to select right or left side for commencement of treatment, patient was blind about the type and properties of lasers.

In this study, the following parameters were compared together:

-Intensity of Pigmentation (DOPI) (assessment time: before (Baseline), 1 month after the last session of treatment, 3 months after, 6 months after)

Intensity of pigmentation were assessed with Dummett Oral Pigmentation Index (DOPI 1971) ²²⁾. DOPI was scored as:

• Score 1:

  No clinical pigmentation (pink gingival)

• Score 2:

  Mild clinical pigmentation (mild light brown color)

• Score 3:

  Moderate clinical pigmentation (medium brown or mixed pink and brown)

• Score 4:

  Heavy clinical pigmentation (deep brown or bluish black).

The method of measurement was observation of photographs.

-Extension of pigmentation (Hedin Melanin Index) (before (Baseline), 1 month after the last session of treatment, 3 months after, 6 months after)

Extension of pigmented area were assessed by, Hedin Melanin Index ²³⁾. It was scored as:

• Score 0:

  No pigmentation

• Score 1:

  One or two solitary units of pigmentation in the papillary gingival

• Score 2:

  > 3 units of pigmentation in the papillary gingival without the formation of a continuous ribbon

• Score3:

  ≥ 1 short continuous ribbons of pigmentation

• Score4:

  One continuous ribbon including the entire area between the canines

The method of measurement was observation of photographs.

-Repigmentation

Its method of measurement was comparison of changes of DOPI and Hedin melanin index scores in 3^rd and 6^th months of follow up rather than first month of follow up. Any increase in scores of DOPI or Hedin melanin index was recorded. Changes were recorded in form of; with repigmentation or without repigmentation.

-Gingival Bleeding (during first operation session)

Its method of measurement was observation of bleeding occurrence during operation. It was recorded as: with bleeding and without bleeding.

-Gingival healing (1 week after first operation session) Its method of measurement was observation of gingival healing with a blind observer. It was recorded as: with healing and without healing. The criteria about healing were absence of erythema and ulceration in operation site.

-Pain perception (during 24 hours after first operation session)

Quantity of pain was assessed with Visual analogue scale. It was scored as:

• Score 0:

  0 mm: no pain

• Score 1:

  1 to 30 mm: slight pain

• Score 2:

  31 to 60 mm: moderate pain

• Score 3:

  61 to 100 mm: severe pain.

It's method of measurement was question from patient about the amount of pain felt and discomfort during the period of 24 hours after first operation session.

Before starting laser ablation, topical anesthesia with spray lidocaine 10% applied on all laser treated sites and in the following if patients had discomfort, then we used local anesthesia with lidocaine HCl 2%/Epinephrine 1/80.000 in all laser treated sites for creation of equal condition.

Photographs were obtained preoperatively (baseline), immediately after operation, and on each postoperative visits (1 week, 1 month, 3 months and 6 months after the last session). ‘Figure 1a, 1b, 1c and 1d’ Photographs obtained in equal distance and head position and mouth were opened with Kerr (Switzerland) mouth opener. Samsung camera -16 mega pixels –Resolution CMOS was used in taking photographs.

Fig. 1a:

Pre-operation

Fig. 1b:

1 month post operation

Fig. 1c:

3 months post operation

Fig. 1d:

6 months post operation

The decision for proper irradiation condition was made based on previous studies ^{1, 3)}. Also after a pilot study on three patients the most effective setting was determined. The Er,Cr:YSGG laser (2780 nm) Waterlase- Biolase technology (Germany) was set at 100 MJ, frequency of 15 Hz, total power of 1.75 W, 10% water and 20% air. Hand piece was used in a non-contact mode by sweeping motion, it was held 1 mm away from the tissue in defocused mode. Tip MZ8 (0.8 mm) was used for de-epithelialization procedure. Spot size was 0.8mm. The tip movement was apico-cervical, laser ablated attached gingival from mucogingival junction to 1 mm distance to free gingival margin, then tip moved toward mesial or distal direction.

Periodontal Coe-Pack was utilized to avoid damage to tooth structures adjacent to the free gingival margin in Er:Cr:YSGG laser side ‘Figure 1e’. During preoperation, labial surface of teeth were covered, which was removed on completion of the procedure. The major biological/absorbers in Er,Cr:YSGG laser is hydroxyapatite and water, while the highest absorption coefficient in diode laser is melanin and hemoglobin. The tooth structure is hydroxyapatite and water ¹⁾. For this reason, to prevent accidental and unwanted irradiation of the Er,Cr:YSGG laser to dental structures, the surface of teeth were covered.

Fig. 1e:

Sample of Coe-Pack coverage of teeth

Diode laser (808 nm) Dr-smile (ITALY) set at a power of 1 W, fiber 320 µ, irradiation mode: continuous-wave with treatment mode of contact tip was used. Tip was moved using forward and backward to prevent damage to the tissue. Tip movement was apico-cervically, papilary edges and free gingival margins were left intact in order to avoid unwanted destruction of these sites. Operation field were wet and cleaned with moist gauze soaked with normal saline. Ventilation with suction was done during the procedure.

Patients were advised not to eat acidic, salty, hot and spicy foods for the first few days after operation.

After two weeks, treatment was evaluated on residual pigmentations. Additional lasing was utilized for all Patients. All diode laser sites were treated in two sessions and all Er,Cr:YSGG laser sites were treated in three sessions. Third session was performed 2 weeks after second session. Number of treatment sessions in all patients was the same.

An oral medicine specialist with 6 years clinical work was trained on how to evaluate the changes in intensity and extension of pigmentation. She was tested about the stability of her comments. With using Kapa test, intra-rater agreement reliability was 1 and her scores was 100% same. This individual was not aware of the laser type and location of lasers that was used.

Photographs were analyzed on Asus Note Book with Display 13.3A 16:9 HD with EWV (1366 × 768).

Also, 1 week after first session treatment, this person who was blind about treatment procedure, commented about healing status of gingival tissue.

Statistical analysis

The sample size was chosen based on clinical considerations.

Data analyses were carried out using SPSS version 21 statistical software. Statistical significance was set at P < 0.05.

The frequencies of scores in studied groups were recorded with Wilcoxon, Friedman, Mc nemar, GEE regression model (ordinal, binary, logistic) statistical tests.

Results

In this study, treatment was performed in both jaws of 12 patients and in 2 other patients, only one jaw was treated (one patient maxilla and other one mandible).Total treated sites in each laser group were 26 areas. In this study, one of the patients with both jaws treated, was absent in the first month of post operation. During this recall time, 2 loss of data occurred in both laser group as a result of the analysis of parameters relating to the first month of follow up which was calculated without the presence of this patient.

Evaluation and comparison of both groups is titled inter group changes while evaluation of changes in each group is titled Intra group change.

Changes in intensity of pigmentation (DOPI index)

Inter group changes

Table 1 shows the comparison of changes in distribution of DOPI scores in base line in the first, third and sixth month of recall.

Table 1: comparison of DOPI index scores in Er,Cr:YSGG laser and Diode laser groups at baseline and follow ups.

Parameter	Score	Diode laser group		Er,Cr:YSGG laser group		Wilcoxon P-Value
		Frequency Percent)	Median (Q1–Q3)*	Frequency (Percent)	Median (Q1–Q3)*
Intensity of pigmentation (before)	Score 1	0 (0%)	4 (3–4)	0 (0%)	4 (3–4)	0.083
	Score 2	2 (7.7%)		4 (15.4%)
	Score 3	8 (30.8%)		7 (26.9%)
	Score 4	16 (61.5%)		15 (57.7%)
Intensity of pigmentation (1 months after)	Score 1	20 (76.9%)	1 (1-1)	1 (3.8%)	3 (2–3)	< 0.0001
	Score 2	3 (11.5%)		9 (34.6%)
	Score 3	1 (3.8%)		11 (42.3%)
	Score 4	0 (0%)		3 (11.5%)
	Missing	2(7.7%)		2(7.7%)
Intensity of pigmentation (3 months after)	Score 1	19 (73.1%)	1 (1–2)	1 (3.8%)	3 (2–3)	< 0.0001
	Score 2	6 (23.1%)		10 (38.5%)
	Score 3	1 (3.8%)		10 (38.5%)
	Score 4	0 (0%)		5 (19.2%)
Intensity of pigmentation (6 months after)	Score 1	16 (61.5%)	1 (1–2)	1(3.8%)	3 (2–3)	< 0.0001
	Score 2	9 (34.6%)		10 (38.5%)
	Score 3	1 (3.8%)		10 (38.5%)
	Score 4	0 (0%)		5 (19.2%)

^*Q₁: First Quartile - Q₃: Third Quartile

The inter group comparison with Mc Nemar statistic test result revealed no statistical difference at the base line (P < 0.83). But at the first, third and sixth month of recalls, diode laser was better than Er,Cr:YSGG laser which was statistically highly significant (P < 0.0001).

Intra group changes

Er,Cr:YSGG laser group

Reduction in DOPI scores obtained in Er,Cr:YSGG laser group was statistically significant. Comparison of DOPI scores in baseline with 1st, 3rd and 6th month post operation was statistically significant (P < 0.001, P < 0.005 and P < 0.005 respectively).

Diode laser group

Changes in DOPI scores were statistically highly significant. Score changes between baseline and 1st, 3rd and 6th month of post operation revealed significant differences (P < 0.0001). P values were obtained by Friedman test.

Use of GEE regression model (binary logistic) revealed, with control, the effect of time of recall, age, gender, primary scores of Hedin melanin index and DOPI index. Er,Cr:YSGG laser versus diode laser obtained more Hedin melanin index and DOPI index scores and this difference was statistically significant. Details are presented in Table 2.

Table 2: The results of GEE regression modelling for extension and intensity of pigmentation.

Variable			B*	SE**	95% CI		P - Value
					Lower	Upper
Extension of pigmentation	Intercept		2.671	1.1162	0.483	4.858	0.017
	Treatment	Diode	−2.637	0.2911	−3.207	−2.066	< 0.0001
		Er,Cr:YSGG	---
	Gender	Male	0.399	0.2350	−0.062	0.859	0.090
		Female	---
	Time	1 month	−0.267	0.0742	−0.413	−0.122	< 0.0001
		3 months	−0.154	0.0527	−0.257	−0.051	< 0.003
		6 months	---
	Age		−0.057	0.0240	−0.104	−0.009	0.019
	Extension of pigmentation before intervention		0.480	0.1637	0.160	0.801	0.003
	Scale		0.905
Intensity of pigmentation	Intercept		1.131	0.3228	0.499	1.764	< 0.0001
	Treatment	Diode	−1.448	0.1459	−1.734	−1.162	< 0.0001
		Er,Cr:YSGG	---
	Gender	Male	0.276	0.1444	−0.007	0.558	0.056
		Female	---
	Time	1 month	−0.162	0.0523	−0.265	−0.60	0.002
		3 months	−0.058	0.0290	−0.115	−0.001	0.047
		6 months	---
	Age		0.000	0.0131	−0.026	−0.25	0.979
	Intensity of pigmentation before intervention		0.451	0.0942	0.267	0.636	< 0.0001
	Scale		0.362

^*B Coefficient

^**Standard Error

Samples of typical photographs were shown in figure 2 and 3.

Fig. 2:

Pre-operation scores according to Hedin melanin index and Dummett oral pigmentation index in a 18-years-old girl

Fig. 3:

Six months post operation scores according to Hedin melanin index and Dummett oral pigmentation index in a 18-years-old girl. Gingival tissue in right upper and lower quadrant was treated with Er,Cr:YSGG laser and left side was treated with Diode laser

Changes in Extension of pigmentation (Hedin melanin index)

Inter group changes

The inter group comparison with Mc Nemar statistic test revealed no statistical differences at the base line (P < 0.157). But at the first, third and sixth month of recalls, scores was lower and better in diode laser group, which was statistically highly significant (P < 0.0001) (Table 3).

Table 3: comparison of Hedin melanin index scores in Er,Cr:YSGG laser and Diode laser groups at baseline and follow ups: The results of GEE regression modelling for extension and intensity of pigmentation.

Parameter	Score	Diode laser group		Er,Cr:YSGG laser group		Wilcoxon P-Value
		Frequency (Percent)	Median (Q1–Q3)*	Frequency (Percent)	Median (Q1–Q3)
Extension of pigmentation (before)	Score 0	0 (0%)	4 (4-4)	0 (0%)	4 (4-4)	0.157
	Score 1	0 (0%)		1 (3.8%)
	Score 2	1 (3.8%)		0 (0%)
	Score 3	3 (11.5%)		4 (15.4%)
	Score 4	22 (84.6%)		21 (80.8%)
Extension of pigmentation (1 months after)	Score 0	17 (65.4%)	0 (0–1)	0 (0%)	4 (2.2–4)	< 0.0001
	Score 1	5 (19.2%)		5 (19.2%)
	Score 2	0 (0%)		1 (3.8%)
	Score 3	1 (3.8%)		3 (11.5%)
	Score 4	1 (3.8%)		15 (57.7%)
	Missing	2 (7.7%)		2 (7.7%)
Extension of pigmentation (3 months after)	Score 0	16 (61.5%)	0 (0–1)	0 (0%)	4 (2–4)	< 0.0001
	Score 1	8 (30.8%)		4 (15.4%)
	Score 2	0 (0%)		3 (11.5%)
	Score 3	1 (3.8%)		2 (7.7%)
	Score 4	1 (3.8%)		17 (65.4%)
Extension of pigmentation (6 months after)	Score 0	11 (42.3%)	1 (0–1)	0 (0%)	4 (2.75–4)	< 0.0001
	Score 1	13 (50.8%)		4 (15.4%)
	Score 2	0 (0%)		2 (7.7%)
	Score 3	0 (0%)		2 (7.7%)
	Score 4	2 (7.7%)		18 (69.2%)

^*Q₁: First Quartile - Q₃: Third Quartile

Intra group changes

Er,Cr:YSGG laser group

Changes in scores of Hedin melanin index between base line and first month of post operation, base line and third month of post operation, and base line and sixth month of post operation was statistically significant, with p values of P = 0.001, P = 0.005 and P = 0.005 respectively:.

Diode laser group

Similar to Er,Cr:YSGG laser group, changes of scores from base line to 1st, 3rd, and 6th months of follow ups was statistically significant (P < 0.0001). P values were obtained by Friedman test.

The possibility of obtaining higher scores in Hedin melanin index in Diode laser group was lesser than in Er,Cr:YSGG laser group, with the use of ordinal logistic regression modelling statistic test.

Also, the possibility of obtaining a higher Hedin melanin index scores in comparison to the 6th month versus 1st month of post operation was more.

Samples of typical photographs were shown in figure 2 and 3.

Repigmentation

The inter group comparison for gingival repigmentation (increase in DOPI or Hedin melanin indices scores) was analysed by using Mc Nemar statistical test. The p value of recurrence between two laser group in 3rd month and 1^st month after operation

And in 6th and 1^st months after operation was < 0.625 and < 0.344 respectively, which were not statistically significant. Inter group comparison of repigmentation is shown in Table 4.

Table 4: Repigmentation status in different follow up times.

Time	Repigmentation status	Er,Cr:YSGG -* Diode −	Er,Cr:YSGG +** Diode +	Er,Cr:YSGG − Diode +	Er,Cr:YSGG + Diode −	P- Value
From first month post operation to 3rd month	Frequency	18	2	1	3	0.625
	percent	75%	8.3%	4.2%	12.5%
From first month post operation to 6rd month	Frequency	11	3	7	31	0.344
	percent	45.8%	12.5%	29.2%	12.5%

^*−without repigmentation

^**+with repigmentation

It should be noted that the density of repigmentation was slight and mild.

Use of GEE regression model (binary logistic) revealed that by controlling the effect of age, gender and first month post operation scores of Hedin melanin index and DOPI index, there was no significant difference for the chance of repigmentation between two laser groups (OR = 1.01) CI 95% = (0.15 , 6.79). Details are presented in Table 5.

Table 5: The results of Gee regression analysis to determine the effect of laser type on repigmentation in terms of age, gender, intensity and extension of pigmentation. And the results of Gee regression analysis to determine the effect of laser type on no-healing in terms of age and gender.

Variable			OR	95% CI		P - Value
				Lower	Upper
Repigmentation	Intercept		.961	.006	144.908	.987
	Treatment	Diode	1.013	.151	6.796	.990
		Er,Cr:YSGG	1
	Gender	Male	1.536	.358	6.589	.563
		Female	1
	Age		.963	.833	1.113	.608
	Extension of pigmentation 1 month after intervention		.791	.397	1.575	.505
	Intensity of pigmentation 1 month after intervention		2.762	.944	8.082	.064
No-Healing	Intercept		.026	.000	2.040	.101
	Treatment	Diode	27.992	5.176	151.374	< 0.0001
		Er,Cr:YSGG	1
	Gender	Male	5.478	.474	63.315	.173
		Female	1
	Age		1.014	.875	1.175	.857

Gingival bleeding during operation

There was no evidence of bleeding in any diode laser treated sites, but there was slight bleeding in 7 (26.9%) of the 26 areas ablated with Er,Cr:YSGG laser, which was statistically significant. P value obtained by MC Nemar test was = 0.0156.

Gingival healing

Details are presented in Table 6. After a week, more number of Er,Cr:YSGG laser treated sites were healed, which was statistically significant. P value obtained by MC Nemar test was < 0.0001. It was revealed through the use of GEE regression model (binary logistic) showed that the chance of no healing in Diode laser treated sites were 27.99 times higher than Er,Cr:YSGG laser treated sites (OR = 27.99) , CI 95% = (5.18 , 151.37). Details are presented in Table 5.

Table 6: Gingival healing status in two laser treatment groups.

		Gingival healing in Diode laser group after 1 week		Total
		With Healing	Without Healing
Gingival healing in Er,Cr:YSGG laser group after 1 week	With Healing
	Frequency	10	14	24
	Percent	38.5%	53.8%	92.3%
	Without Healing
	Frequency	0	2	2
	Percent	0%	7.7%	7.7%
Total		10	16	26
		38.5%	61.5%	100%

Pain-VAS score

A day after first operation session, the average scores for VAS in diode laser group was 35 ± 20.24 while[WU1] it was 4.62 ± 9.47 in Er,Cr:YSGG laser group. The amount of pain in Er,Cr:YSGG laser treated sites versus diode laser treated sites was less. Inter group comparison by Wilcoxon test revealed p < 0.0001 which was statistically significant. The use of GEE regression model (linear logistic) revealed that, the amount of pain in Er,Cr:YSGG laser group was 30 times lesser than that in diode laser group CI 95% = (−27.08, 40.94). Details are presented in Table 7.

Table 7: The results of GEE regression analysis to determine the effect of laser type on pain in terms of age & gender.

Pain	Variable		B*	SE**	95% CI		P - Value
					Lower	Upper
	Intercept		−2.428	7.9845	−18.078	13.221	0.761
	Treatment	Diode	30.385	4.7490	21.077	39.692	< 0.0001
		Er,Cr:YSGG	---
	Gender	Male	−5.222	6.2971	−17.564	7.120	0.407
		Female	---
	Age		0.407	0.4059	−0.388	1.203	0.316
	Scale		245.400

^*B Coefficient

^**Standard Error

Discussion

The objective of this study was to compare the treatment outcomes of diode 808 nm laser and Er,Cr:YSGG 2780 nm laser ablation on physiologic gingival pigmentation.

Intensity (DOPI) and extension (Hedin melanin index) changes and repigmentation

In this study, diode laser had better effects for the reduction of DOPI and Hedin melanin index scores. But comparison of number of repigmentation revealed that there was not statistically significant difference between two lasers. It seems the cause of less decrease of Hedin melanin index scores and DOPI scores in Er,Cr:YSGG laser is less depth of penetration and remain of melanocytes and melanin containing keratinocytes in basal layer.

Berk et al ²⁴⁾ treated gingival pigmentation of two patient with Er,Cr:YSGG laser and there was no clinical repigmentation during 6 months follow up. In a study carried out by Suthprasertporn ²⁵⁾, among two patients who were treated with Er,Cr:YSGG, a slight repigmentation was seen in one patient, this patient sometimes smoked, follow up period was 11 months.

Rose et al ²⁶⁾ treated gingival pigmentation of 5 patients with Er:YAG laser. They used clinical scoring and classification of recurrency based on Ishii and Kawashima. They reported slight repigmentation in one of the patients who was a smoker. Doshi et al ²⁷⁾ treated one patient with diode laser. They stated that after 6 months, mild patchy pigmentation occurred and the size of pigmented area increased during one year follow up. They scored changes of pigmentation with clinical observation and with use of melanin pigmentation index (Takashi et al) measuring tool. Hegde et al ²⁸⁾ reported more sites of repigmentation in Er:YAG laser group versus CO₂ laser group in 6th month of follow up. Moreover, they noted a reduction in DOPI score index which was highly significant in these lasers.

In some studies, DOPI and Hedin indices were used for evaluation of clinical changes of pigmentation ²⁸⁾ and in other studies, clinicians expressed their opinion about changes of pigmentation of qualitative and descriptive method by commenting on clinical observation ^{3, 24, 27–29)} or viewing of photographs ^{17, 24, 28, 29)}. They didn't use special indices; therefore, we were not able to do exact comparative evaluation with their study. Histological evaluation ^{28, 30)}, image analysis software ²⁸⁾, questionnaire ^{17, 29)} and classification based on Ishii and Kawashima ^{26, 31)}, were other methods through which researchers evaluated their treatment outcomes. Giannelli et al ³⁰⁾ assessed histological changes of gingival pigmentation. After 180 days, there was no evidence of hyperpigmentation left on gingival tissues treated with diode and Er:YAG laser.

The following factors are responsible for the difference in repigmentation in treatment: methods of treatment, number of follow up period, difference in evaluation criteria for pigmentation, genetic and ethnic factors and hormonal factors ²⁸⁾.

Mechanism of repigmentation was not clearly stated. But according to migration theory, active melanocytes of peripheral pigmented tissue migrates to treated sites and this result to repigmentation ³⁾.

Bleeding

In this study, none of the treated sites with diode laser had bleeding but in Er,Cr:YSGG laser group, slight clinically controllable bleeding was observed. Moreover, Suthprasertporn ²⁵⁾ observed bleeding during operation with Er,Cr:YSGG laser and noted that this bleeding stopped with laser coagulation mode. Azzeh ³⁾ observed slight bleeding with Er:YAG laser. He stated that bleeding occurs when pigmentation is in deeper areas, for example under basal layer ^{25, 29)}.

According to Giannelli ³⁰⁾, the cause of obvious bleeding during treatment with Er:YAG laser is dilation of small vessels as a result of laser ablation in histological view. Measurable changes in small vessel components of lamina properia were not seen, in diode laser treated sites.

Bhanu ³²⁾ noted that one of the advantages of diode laser is sealing of blood vessels up to 0.5 diameter in surrounding tissue, one advantage of it , is homeostasis and consequently dry treatment sites.

Gingival Healing

According to this study, gingival healing in Er,Cr:YSGG laser was better than Diode laser. Suthprasertporn ²⁵⁾ states that Er,Cr:YSGG laser provided minimal trauma and faster wound healing compared with other non-erbium family lasers and after one week, gingival was completely healed.

Atsawasuwan ³³⁾ stated that the time needed for gingival healing after ablation of CO₂, diode and Nd:YAG laser is up to two weeks.

Azzeh ³⁾ stated that 4 days after treatment with Er:YAG laser, gingival healing was almost complete without scar, infection or swelling.

Giannelli et al ³⁰⁾ obtained different results with present study. They reported delayed healing of gingival tissue in Er:YAG laser compared with diode laser. They also stated that injury score in Er:YAG laser was more. Power of diode laser in this study was 0.6 W while it was 1 W in Er:YAG. However, in present study, power setting of diode laser was 1 W while Er,Cr:YSGG was 1.75 W. Nevertheless, with increase in the power of diode laser, thermal damage was more and time needed for complete healing was increased.

In a research carried out by Doshi ²⁷⁾ and Bhanu's ³²⁾, diode laser treated sites were healed after 1 week.

It should be stated that, diode laser had bactericidal effect and creates sterile inflammatory reaction in site of treatment ³²⁾. Lasers rather than other treatment modalities have rapid wound healing. Its cause may be Photo Bio modulation (PBM) effect ^{3, 34)}.

Pain

In this study, the average amount of pain in diode laser group and Er,Cr:YSGG laser was 35 ± 20.24 and 4.62 ± 9.47 respectively. In Tal's study ²⁹⁾, patients felt slight pain during first week after operation of Er:YAG laser. Hegde ²⁸⁾ stated that Er:YAG laser had less amount of pain among three techniques (Er:YAG-Surgical stripping-CO₂ laser).

In Simsek's study ¹⁷⁾, of the mode of operation was slight. There was no statistically significant difference between diode and Er:YAG laser groups. Suthprasertporn ²⁵⁾ stated that Er,Cr:YSGG laser induces less amount of pain when compared to other non-Erbium family lasers. In addition, lasers have the property of sealing sensory nerve endings. The cause of less pain in Er:YAG laser is due to minimal thermal damage or tissue penetration (1 µm) ²⁸⁾. As a result, creation of thermal necrosis is less and pain is reduced ³⁾.

Conclusion

Results of this study revealed that, treatment of gingival melanin hyperpigmentation with diode laser had more efficacy in the reduction of pigmentation than Er,Cr:YSGG laser.