Mechanism of Teeth Bleaching: The main reaction that occurs during the teeth bleaching procedure is the oxidation reduction reaction called redox reaction. Here the peroxides convert to the free radicals (which are unstable). Then these free radicals oxidize or reduce other molecules. The bleaching agent acts on the organic structures of the tooth and degrades it to carbon dioxides. These by-products are the ones that are lighter in color.
1. Effect on Enamel Carbamide peroxide decreases hardness of the tooth enamel.
2. Effect on Dentine it can cause uniform color change.
3. Effect on Pulp the bleaching agent penetrates from enamel and dentine into the pulp. Thus will cause slow decrease in blood flow ( pulpal ), and pulpal blood vessels occlusion.
4. Effects on Cementum – home bleaching materials or agents do not affect cementum. But there are patients where due to intracoronal teeth bleaching by 30 – 35% hydrogen peroxide causes cervical resorption and external root resorption.
5. Effect on Restorative Materials
6. On composites: surface roughness & gives etched appearance, decrease in tensile strength, increase in surface hardness, and increase in micro leakage.
7. On other materials: no effect on gold restoration, in case of amalgam it causes changes in micro structure , in glass ionomers there is alteration of the matrix, in interim restorative material due to hydrogen peroxide there is cracking of the restoration, the crowns made from methyl methacrylate undergo color change and turn orange.
8. Effect on Mucosa – hydrogen peroxide (30 – 35 %) causes mucosal irritation & burning sensation.
9. Causes gentotoxicity & carcinogenicity.
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