Effect of casein phosphopeptide-amorphous calcium phosphate on the flexural strength of enamel-dentin complex following extracoronal bleaching

Abstract

Background: Bleaching can affect the mechanical properties of enamel-dentin complex, such as flexural strength. Casein\rphosphopeptide-amorphus calcium phosphate (CPP-ACP) is often used following bleaching treatment to reduce hypersensitivity and\rto increase demineralization of tooth. Purpose: The purpose of the study was to investigate the effect of CPP-ACP on the flexural\rstrength of enamel-dentin complex following extracoronal bleaching. Methods: Forty-eight enamel-dentin plates (size 8 x 2 x 3 mm)\rwere randomly assigned into 6 groups, each consisted of 8 samples. Group 1, no bleaching and immersed in artificial saliva. Group\r2, no bleaching, CPP-ACP application only. Group 3, bleaching using 15% carbamide peroxide. Group 4, similar to group 3, except\rapplication of CPP-ACP for the times between bleaching. Group 5, bleaching with 40% hydrogen peroxide. Group 6, similar to group\r5, except application of CPP-ACP for the times between bleaching. Flexural strength of each enamel-dentin plate was tested by threepoint\rbending test using universal testing machine. Results: The results showed that 15% carbamide peroxide and 40% hydrogen\rperoxide significantly reduced flexuralstrength of enamel-dentin (216.25±26.44 MPa and 206.67±32.07 MPa respectively). Conversely,\rapplication ofCPP-ACP following both bleachingsincreased flexuralstrength (266.75±28.27MPa and 254.58±36.59 MPa respectively).\rA two-way Anova revealed that extracoronal bleaching agents significantly reduced flexural strength (p<0.05), while application of\rCPP-ACP significantly increased flexuralstrength of bleached enamel-dentin complex (p<0.05). Conclusion: Extracoronal bleaching\ragents reduce flexural strength, whereas application of CPP-ACP following bleaching either with 15% carbamide peroxide or 40%\rhydrogen peroxide can increase the flexural strength of enamel-dentin complex.