specialtySpecialty of “esthetic dentistry.” Treatment of tooth discoloration is one of the most important fields of esthetic dentistry. In ancient cultures and their artworks, white teeth symbolized beauty and good health. Past dental surveys revealed that 28 to 34% of surveyed subjects are dissatisfied with the color of their teeth and seek bleaching treatment. Bleaching techniques have been markedly improved, from using pure chemical peroxides, until reaching the recent light/laser-assisted bleaching systems. In 1876, the first original work reporting the professional bleaching of stained teeth was written by M’Quillen, who stated, “It is a somewhat remarkable and inexplicable fact that none of the textbooks which have been presented to the profession, so far as my observation goes, pay even the compliment of a passing notice to the means whereby discolored teeth may be improved in appearance.” Furthermore, M’Quillen had reported that the most common cause of tooth discoloration was intrusion of hemoglobin into dentinal tubules, which turns the tooth color to pink “rosy tooth.” M’Quillen used Labarraque’s solution (liquor soda chlorinate), chloride of lime (calcium chlorinate powder), and chlorate of potash (potassium chlorate) as bleaching agents to improve the color of stained teeth. heThe first attempt to accelerate the bleaching process was introduced in 1918 by Abbot,7 who used a high-intensity light source to raise the temperature of a peroxide-based bleaching agent. Another accelerating method was introduced in 1937 by Ames and Smithfield,8 who used an external heat source. They also invented a specially designed hand instrument that was pre-warmed on a Bunsen burner and applied on the bleaching agent (the scientific name of the used bleaching agent was not clearly mentioned in their publication, however; they referred to it only as “liquid” or “solution”) to accelerate the bleaching process.