Periodontal diseases are a group of conditions affecting the supporting structures of the dentition. The periodontal tissue consists of a specialized form of oral mucosa known as gingiva, which has a keratinized epithelium and covers the alveolar bone. Tobacco smoking is the main risk factor associated with chronic destructive periodontal diseases. Tobacco smoking is very common, with cigarettes being the main product smoked. Cigarette smoke is a very complex mixture of substances with over 4000 known constituents. These include carbon monoxide, hydrogen cyanide, reactive oxidizing radicals,...