A 9-year-old boy was referred to the Department of Pediatric Dentistry, Mashhad University of Medical Sciences, Mashhad, Iran. The patient needed comprehensive dental treatment due to amelogenesis imperfecta. At the same time his parents requested to treat his gingival pigmentation. His oral examination revealed that his gingiva is deeply pigmented from the right second primary molar to the left second primary molar (). He had been checked by a physician previously and there were no pathologic disorders (e.g. Albright syndrome, trauma, hemachromatosis and racial pigmentation) in this case. Therefore, we started depigmentation therapy by cryosurgery technique.\nLiquid nitrogen was provided in the morning of treatment day by a consumer gas factory and was transferred to the dental facility. In order to transfer the liquid nitrogen, it had been saved in a two-layer flask (metallic inner layer and glassy outer layer).\nIn the first step isolation was instated by suction and cotton rolls; then hyperpigmentation areas were dried byair spray and 10% topical lidocaine gel was used to achieve anesthesia. During treatment, liquid nitrogen was poured into the glass mug and was rolled on the pigmentation area by cotton swabs (). After the gingiva blanched, the operation was started in another area; after 20 seconds this process was repeated. It is possible repeat this process three or four times for each area. The total time needed for this operation was 30 minutes. In order to record and analyze the results, five standard photos were taken in different positions. Standard high-quality images were taken at baseline and after one, three, six and twelve months (). All the photos were taken by a Canon digital camera (Ixus 800IS, Japan) in the same position, while the patient was sitting upright, and the distance between patient and camera was fixed to about 30 centimeters.\nMinimal reddish erythema was observed after cryosurgery. After one month the gingival color was ideal. No complications were observed during the follow-up. No recurrent lesions were observed in 12-month follow-up ().
A 32-year-old female who requested cosmetic therapy for "black gum" in the anterior part of the mandibular gingiva visited the Department of Periodontology, School of Dentistry, Kyung Hee University. There were no contributory medical problems. Melanin hyperpigmentation was found on the labial surface of the mandibular arches and maxillary lateral incisor. Compared with case 1, pigmentation showed more focal pigmented lesions ().\nThe same depigmentation techniques were applied: the Er:YAG laser on the right side and mechanical depigmentation of rotary round bur on the left side. Since the patient had focal pigmentation, depigmentation was conducted on both the maxilla and mandible area simultaneously. Due to the patient's thin gingival biotype and careless laser application, case 2 showed exposure of underlying bone around the incisal area on the right side of the mandible ().\nAt 1 week, the gingiva showed gradual epithelization, but was in an immature state. The laser surgery area showed redness and unfavorable healing with an appearance of necrosis. On the other hand, on the left side where the high speed rotary was applied, almost complete re-epithelization was observed (). After 2 weeks, epithelization was completed except in the right mandibular area (). A linear cleft was observed in the right mandibular area until 3 weeks. The wound healing was almost completed, but slight redness still remained at 4 weeks after surgery. However, the patient was satisfied with the significant improvement in color. Gingival recession and loss of papilla were not observed at 4 weeks after surgery ().