A Randomized Comparative Clinical Study to Evaluate the Longevity of Esthetic Results of Gingival Melanin Depigmentation Treatment Using Different Laser Wavelengths (Diode, CO2, and Er:YAG)

Background: Gingival melanin hyperpigmentation is due to excessive deposition of melanin granules. The duration of pigmentation reappearance after treatment using different laser wavelengths remains controversial. Objective: The study aims to assess the longevity of gingival depigmentation (GD) and the consistency in esthetic results as three laser wavelengths (Er:YAG laser, CO₂ laser, and diode laser, 980 nm) were used in two different groups (smokers and nonsmokers). This is attained by comparing the periods of time in each group before pigmentation reappearance. Methods: Seventy-two subjects were divided into daily smokers (S) and nonsmokers. Subjects underwent a randomized GD with: Erbium laser (Er), CO₂ laser (CO₂), and Diode laser (Diode). The subjects were divided into six groups: S and nonsmokers were treated with three different wavelengths. Irradiation was performed until there was no visible pigmentation. For qualitative measurement, Hedin Melanin Index (HMI) was used, before treatment, after 2 weeks, and until 60 months. Pigmentation reappearance of degree 1 or above of the HMI was noted. Descriptive statistics were also calculated. Results: HMI showed a 0 in all groups after 14 days of treatment. The time before pigmentation rebound was: Diode > CO₂ > S-Diode > S-CO₂ > Er > S-Er. The first signs of relapse shown among all groups were seen in the group S-Er group. The longest time before rebound was observed with the Diode group for the nonsmoker. Conclusions: Diode laser provides the longest-term stability in treatment. Smoking negatively affects the longevity of GD. Er laser gives the shortest time before the reappearance of gingival pigmentation.

Effect of Er:YAG laser energy densities on thermally affected dentin layer: Morphological study

BACKGROUND AND AIMS

Physical and chemical composition of dentin is subject to modification when irradiated with Er:YAG laser. Temperature rise causes water evaporation and micro-mechanical ablation of dentin. The misuse of laser parameters could affect negatively dentin collagen fibers leading to failure in bonded composite restorations. The aim of this in vitro study was to evaluate the effect of Er:YAG laser radiation at different levels of energy on the morphology of thermally affected dentin layer.

MATERIALS AND METHODS

Forty-eight freshly extracted human third molars were randomly divided into six groups (n = 8). In all groups, except for the control groups, dentin was subject to irradiation with H02 handpiece Er:YAG laser in non-contact mode (SSP mode = 50 µs; 10 Hz; speed of 1 mm/second; air 6 mL/min; and water 4 mL/min) with the following levels of energy (40, 60, 80, 100, and 120 mJ) respectively. Teeth were sliced longitudinally. Photo-ablated cavities were observed. The cavity depth and dentin fiber collagen deterioration were measured.

RESULTS

Laser irradiation increased the depth of dentinal crater from 46.57 µm to 178.2 µm, when energy level increased from 40 mJ to 120 mJ. A superficial black layer, representing dentinal affected collagen fibers, was present in all groups except for control group. When comparing the thickness of the black layer, there was no significant difference between groups. It increased at 40 mJ to 28.17 µm then decreased to 15.19 µm at 60 mJ and then increased again for 80 mJ to 19.93 µm, 100 mJ to 22.87 µm and 120 mJ to 28.53 µm. Only one group (60 mJ) showed low values and significant difference as compared to the other irradiated groups, when multiple comparisons tests (ANOVA) were made using Newman-Keuls test.

CONCLUSION

Dentin organic matrix presented the minimum alteration when Er:YAG laser is used specifically at an appropriate level of energy (60 mJ).