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ePaper created 2018-02-16, 10:54:19 | version 1.38.0
laser dentistry case report | Procedure Depigmentation technique is the same as de- scribed with the 810 nm wavelength (above). Under local anaesthesia, a non-initiated 320 μm fiber delivers the energy at a distance of 2 mm to the pigmented area with constant movement. Immediate change to pink colour without surface ablation of the pigmented mucosa was observed. The procedure took approximately 40 seconds to complete between lower left and right canine region. Results In this case, the mucosa turns pink without any signs of surface mucosal ablation except one spot between teeth 31, 32 (Fig. 9). Sub-surface coagula- tion of blood vessels gave a pink coloured appear- ance. There was very mild post-op discomfort for about one hour after loss of the anaesthetic effect. No analgesics were required as the discomfort feeling disappeared fast. Laser peeling of mucosa between 31 and 41 was noted during photograph taking at one day post-op review (Figs. 10 and 11). The three day post-op photo taken by the patient showed that the laser peel disappeared with new gingival mucosa for- mation (Fig. 12). Two weeks post-op showed com- plete recovery of the gingival mucosa without melanin pigmentation (Fig. 13). Discussion There has not been much information on this new wavelength. From Fig. 7, the absorption coefficient for haemoglobin is estimated at 7 x 10²/cm–1 and 10³/cm-1 for melanin. Penetration depth for hae- moglobin is calculated at 140 μm and 10 μm for melanin. The penetration depth of haemoglobin and melanin with 810 nm are 2 mm and 0.1 mm re- spectively. Furthermore, scattering curve showed Fig. 14 Fig. 15 higher tissue scattering effect with 445 nm than 810 nm. Fig. 14: Diagram 3. Fig. 15: Diagram 4. In comparison with the NIR diode lasers, the ab- sorption of collagen and scattering increases in the blue light spectrum. In view of the above together with high absorption of haemoglobin and melanin to 445 nm, 1 W cw was used. Power density of 88 W/cm² (Fig. 14) delivering at 88 J/cm² fluence at 2 mm distance was calculated. Although the power density of 1,697 W/cm² (Fig. 15) delivering 543 J/cm² fluence used by 810 nm is higher than 445 nm delivered, the eight years post-op showed stable gingival contour with no recession (Fig. 6). The understanding of the optical properties of the wavelength, power parameters and laser tissue interaction are important information for the cli- nician to achieve the desired treatment outcome. Conclusion The use of 1 W cw 445 nm blue diode laser is effective in non-ablative depigmentation of oral mucosa. This non-ablative technique provide im- mediate aesthetic result with very short procedure time. To the author’s knowledge, this is the first case presented using 445 nm for melanin depig- mentation._ Editorial note: A list of references is available from the publisher. Dr Luk reports no potential conflicts of interest. contact Dr Kenneth Luk 502, Winway Building, No. 50 Wellington Street Central Hong Kong Tel.: +852 2530 2837 laserdontic@me.com cosmetic dentistry 1 2017 39