title: Change in surface hardness of BisGMA/TEGDMA polymer due to enzymatic action.
abstract: The surface microhardness of specimens made of a BisGMA/TEGDMA polymer was measured before and during treatment for 60 days with phosphate buffer or phosphate-buffered esterase solution with an activity corresponding to the mean hydrolase activity of human saliva. The hardness of the buffer-treated specimens was unchanged during the incubation period, while that of the esterase-treated specimens decreased gradually. After about five days of treatment, no further change in hardness was observed for up to 60 days. Based on the difference in the calculated hardness of the specimens as a function of the applied load during measurement, it was estimated that the mean microhardness of the outermost surface layer of the esterase-treated specimens was diminished by about 15%, compared with that of the buffer-treated specimens. From these results, it was concluded that the wear resistance of a BisGMA/TEGDMA polymer is most likely diminished by hydrolases in saliva.
authors.affiliation: Department of Dental Materials, School of Dentistry, Faculty of Health Sciences, University of Copenhagen, Denmark.
authors.forename: I B
authors.initials: IB
authors.lastname: Larsen
authors.forename: M
authors.initials: M
authors.lastname: Freund
authors.forename: E C
authors.initials: EC
authors.lastname: Munksgaard
mesh_terms: D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry*; D004950:Esterases / Q000737:chemistry; D006244:Hardness; D006245:Hardness Tests; D006868:Hydrolysis; D008422:Materials Testing; D011092:Polyethylene Glycols / Q000737:chemistry*; D011109:Polymethacrylic Acids / Q000737:chemistry*
chemical_list: D011109:Polymethacrylic Acids; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; D004950:Esterases