Cosmetic Tribune Asia Pacific Edition

22 TRENDS & APPLICATIONS Cosmetic Tribune Asia Paciﬁc Edition | 10/2017 Fig. 7: Absorption spectra of biological materials. (Courtesy of J. Meister) Figs. 8–11: Depigmentation of lower arch: pre)op (Fig. 8), immediate post)op (Fig. 9), one day post)op (Fig. 10), one day post)op laser peeling between teeth #31 and 41 (Fig. 11). Fig. 12: Three days post)op (photo) graph taken by the patient on holiday). Fig. 13: Two weeks post)op. Fig. 14: Diagram and calculations re) garding the area of effect of the 445 nm wavelength. Fig. 15: Diagram and calculations re) garding the area of effect of the 810 nm wavelength. 7 8 10 12 9 11 13 14 15 tion of blood vessels imparted a pink appearance. There was very mild postoperative discomfort for about 1 h after loss of the anaes- thetic effect. No analgesics were required, as the feeling of discom- fort disappeared rapidly. Laser peeling of the mucosa between teeth #31 and 41 was noted during photograph taking at the one-day postoperative review (Figs. 10 & 11). The three-day postoperative pho- tograph taken by the patient showed that the peeling had dis- appeared, with new gingival mu- cosa formation (Fig. 12). The two- week postoperative appointment showed complete recovery of the gingival mucosa and no melanin pigmentation (Fig. 13). Discussion There is little information available on this new wavelength. From Figure 7, the absorption co- eficient is estimated at 7 × 10²/ cm–1 for haemoglobin and 10³/ cm–1 for melanin. Penetration depth is calculated at 140 μm for haemoglobin and 10 μm for mela- nin. The penetration depth of hae- moglobin and melanin with an 810 nm wavelength is 2 mm and 0.1 mm, respectively. Further- more, the scattering curve showed a higher tissue scattering effect with 445 nm than with 810 nm. In comparison with near-infrared diode lasers, the absorption of col- lagen and scattering increases in the blue light spectrum. In view of this, together with the high ab- sorption of 445 nm by haemoglo- bin and melanin, 1 W in cw was used. A power density of 88 W/cm² (Fig. 14) delivered at 88 J/cm² lu- ence at a 2 mm distance was calcu- lated. Although the power density of 1,697 W/cm² (Fig. 15) delivered at 543 J/cm² luence of the 810 nm was higher than the 445 nm deliv- ered, the eight-year postoperative review showed a stable gingival contour with no recession (Fig. 6). An understanding of the optical properties of the wavelength, its power parameters and the laser– tissue interaction is important for the clinician to achieve the de- sired treatment outcome. Conclusion The use of a 445 nm blue diode laser at 1 W in cw is effective in non-ablative depigmentation of oral mucosa. This non-ablative technique provides immediate aes- thetic results in a very short proce- dure time. To the author’s knowl- edge, this is the irst case presented using the 445 nm wavelength for melanin depigmentation. Editorial note: This article was irst published in cosmetic dentistry No. 1/17. A list of references is available from the publisher. Dr Luk reported no potential conlicts of interest. Dr Kenneth Luk completed a Master of Science in Lasers in Dentistry at RWTH Aachen Universi) ty in Germany and runs his own clinic, Laserdontic, in Hong Kong. He can be contacted at laserdontic@me.com.

Cosmetic Tribune Asia Pacific Edition

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