Abstract
Teeth form an important part of the body that aids chewing, speech as well as contributing to appearance and a healthy smile improves self-image, confidence and projects an aura of health to others. Robinson mentioned that the colour of the teeth is an important feature in determining the attractiveness of the face. Tooth discolouration can be defined as any change in hue,colour or translucencyof a tooth due to any cause. Tooth staining can cause an adverse psychosocial effect on a patient and can create an esthetic challenge for the clinician. The appearance of the dentition is of concern to a large number of people seeking dental treatment, and the colour of the teeth is of particular cosmetic importance. In general , “perfect smile’ have gained more and more importance. Over the past two decades tooth bleaching has become one of the most popular treatment in esthetic dentistry. It is the intial step in analysis and reproduction of smile esthetics,so it is very important that the dentist knows how to diagnose the cause of colour change and to indicate whitening before proposing the appropriate dental procedure. There are several bleaching techniques in the literature, with different types of substances such as carbamide peroxide and hydrogen peroxide and in different concentrations. In additions to the variety of the bleaching substance,light sources can be used to potentiate bleaching action. Tooth whitening has been described by the chromophore concept . The bleaching agent (hydrogen peroxide) by method of diffusion through tooth structure interacts with organic chromophores converting the latter’s molecular chains to simpler units. This changes its optical properties and yields products with lower molecular weight which can be eliminated from the tooth surface. Tooth bleaching can be performed externally i.e vital tooth bleaching or intracoronally known as non vital tooth bleaching.