Tooth Bleaching Increases Dentinal Protease Activity

Hydrogen peroxide is an oxidative agent commonly used for dental bleaching procedures. the structural and biochemical responses of enamel, dentin, and pulp tissues to the in vivo bleaching of human (n = 20) premolars were investigated in this study. Atomic force microscopy (AFM) was used to observe enamel nanostructure. the chemical composition of enamel and dentin was analyzed by infrared spectroscopy (FTIR). the enzymatic activities of dental cathepsin B and matrix metalloproteinases (MMPs) were monitored with fluorogenic substrates. the amount of collagen in dentin was measured by emission of collagen autofluorescence with confocal fluorescence microscopy. the presence of Reactive Oxygen Species (ROS) in the pulp was evaluated with a fluorogenic 2',7'-dichlorodihydrofluorescein diacetate (DCFDA) probe. Vital bleaching of teeth significantly altered all tested parameters: AFM images revealed a corrosion of surface enamel nanostructure; FTIR analysis showed a loss of carbonate and proteins from enamel and dentin, along with an increase in the proteolytic activity of cathepsin-B and MMPs; and there was a reduction in the autofluorescence of collagen and an increase in both cathepsin-B activity and ROS in pulp tissues. Together, these results indicate that 35% hydrogen peroxide used in clinical bleaching protocols dramatically alters the structural and biochemical properties of dental hard and soft pulp tissue.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)NIDCRUniv Mogi das Cruzes, Ctr Interdisciplinar Invest Bioquim, Mogi das Cruzes, BrazilUniv Estadual Campinas, Piracicaba Dent Sch, Dept Restorat Dent, Piracicaba, BrazilGeorgia Hlth Sci Univ, Coll Dent Med, Dept Oral Biol, Augusta, GA USAUniv Oulu, Inst Dent, Oulu, FinlandUniv Western Ontario, London, ON, CanadaUniversidade Federal de São Paulo, Dept Bioquim, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Bioquim, São Paulo, BrazilNIDCR: de 015306Web of Scienc