16 In human tissue, intrinsic sources of H 2O 2 are organelles (especially mitochondria), salivary cells, microorganisms and the lungs. Hydrogen peroxide is a reactive oxygen species, along with superoxide (O2-), hydroxyl (HO), peroxyl (ROO) and alkoxyl (RO). 15 Chemical reactions of hydrogen peroxide Low concentrations of H 2O 2 have been found in rain and surface water, in human and plant tissues, in foods and beverages and in bacteria. H 2O 2 is an oxidising agent with a wide number of industrial applications in for example, bleaching or deodorising textiles, wood pulp, hair, fur and foods, in the treatment of water and sewage, as a seed disinfectant and neutralising agent in wine distillation. Hydrogen peroxide (H 2O 2) is a colourless liquid with a bitter taste and is highly soluble in water to give an acidic solution. It is the purpose of this paper to review the available information on the side effects and safety of H 2O 2 in tooth whitening. The adverse effects that have been reported in cellular, animal and human studies include: cervical root resorption associated with non-vital bleaching increased tooth sensitivity associated with vital bleaching alteration in the surface topography of enamel reduction in bond strength of resin based materials and the possibility that H 2O 2 may have carcinogenic or tumour promoting capabilities. 14Ĭoncerns have been expressed over the potential adverse effects of the use of H 2O 2 tooth whitening agents. 13 The method was later modified and water replaced by 30-35% H 2O 2, to improve the whitening effect. 11, 12 The 'walking bleach' technique introduced in 1961 for the bleaching of non-vital teeth involved sealing a mixture of sodium perborate and water into the pulp chamber between patients' visits. Such agents can be applied externally to the teeth (vital bleaching) or internally within the pulp chamber (non-vital bleaching).Ĭase reports and small clinical studies have confirmed that predictable tooth whitening can be achieved using a 10% carbamide peroxide gel in a bleaching tray at night, (the nightguard vital bleaching technique), 1, 2, 3, 4, 5, 6, 7, 8, 9 H 2O 2 strips 10 and 'power bleaching' using 35% H 2O 2 with or without light and/or heat activation. These bleach the chromogens within the dentine, thereby reducing the body colour of the tooth and are often used in combination with an activating agent such as heat and/or light. For nightguard vital bleaching, minimal amounts of low dose H 2O 2 (including in the form of carbamide peroxide) are preferred, thereby avoiding prolonged and concentrated exposures.Ĭontemporary tooth whitening (tooth bleaching) systems are based primarily on hydrogen peroxide (H 2O 2) or one of its precursors, carbamide peroxide. Until further clinical research is concluded to address the question of possible carcinogenicity, it is recommended that: tooth-bleaching products using concentrated H 2O 2 should not be used without gingival protection that H 2O 2 containing products should be avoided in patients with damaged or diseased soft tissues. Several carcinogenesis studies, including the hamster cheek pouch model, indicate that hydrogen peroxide (H 2O 2) might possibly act as a promoter. Direct contact with hydrogen peroxide induces genotoxic effects in bacteria and cultured epithelial cells, but the effect is reduced or totally abolished in the presence of metabolising enzymes. However, clinical studies addressing other adverse effects are lacking. Tooth sensitivity is experienced in 15-78% of patients undergoing external tooth bleaching. Cervical root resorption is a possible consequence of internal bleaching and is more frequently observed in teeth treated with the thermo-catalytic procedure. Hydrogen peroxide in the form of carbamide peroxide is widely used for tooth whitening (bleaching), both in professionally- and in self-administered products.
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