DO BLEACHING OF TEETH HARM TOOTH STRUCTURE?

layers of tooth structure

YES! YES!! Generally t eeth are bleached to remove the color and make them look whiter. As has been told, the tooth enamel contain 3-4% of water in young ones and the water reduces as the age advances. With removal of water, the transparent, translucent enamel becomes opaque.  This happens more in people who takes pan, betel and tobacco.

    Colouring of tooth is two types. 
One is formation of colour on enamel surface. This is due to factors like use of iron tonics, which form Iron stain  and stains formed by chromogenic bacteria ( bacteria present in many people which is quite harmless except for producing color). These stains can be easily removed by surface polishing with fine pumice and motor rotating brush.

The second one is internal stains. These are as a result of embedding of colour within enamel /dentine ( as in case of dead tooth)structure. This cannot be removed with surface scrubbing. Hence we have to use some chemicals which penetrate in to tooth structure and removes colour along with water from tooth (oxidation) releasing nascent oxygen or chlorine. Generally carbamide peroxides are used. Due to this removal of water from tooth structure, the tooth become brittle and surface shows more tendency to absorb colour faster immediately after bleaching.