An FTIR study of the effects of artificial saliva on the physical characteristics of the glass ionomer cements used for art

To investigate the physical and chemical changes of five esthetic restorative materials in an artificial saliva using Fourier transform infrared spectroscopy (FTIR). The materials included two glass polyalkenoate (ionomer) cements, one polyacid-modified resin composite, and two resin composites. Five fresh and 20 aged specimens for each material were immersed in 2 ml of artificial saliva at 37 ^oC for 1 week, 2 weeks, 1 month, and 2 months. They were examined by laser surface profilometer and FTIR. Surface roughness average (R_a) value showed significant differences among the physical properties of glass ionomers, polyacid-modified resin composite, and resin composites. FTIR spectra showed that a major chemical changes in Fuji IX GP Fast glass ionomer cement in P-NH₂ group bonding (900-1000 cm ^-1) that may explain the previously reported increase in microhardness after immersion. There was no direct correlation between surface roughness and spectral changes of the materials tested.