title: In vivo corrosion of sodium silicate glasses.
abstract: Square-shaped implants of various sodium silicate glasses were weighed and implanted intraperitoneally in rat for periods ranging from 8 to about 60 days. The implants were then removed and their aspect was compared to their aspect before exposure to physiological environment. The corrosion products were studied by x-ray diffraction and electron microprobe analysis. Weight changes were also measured to calculate a biodegradation rate. The glass 66 SO (66.6 SiO2-33.3 Na2O) was strongly corroded, as early as after the first week. The nonsoluble degradation products formed a cocoon encapsulating the now smaller specimen. The analysis of the cocoon showed that it was made of a silica-rich layer containing also calcium and phosphorus. In this layer the ratio Ca/P could correspond to that of an apatite. The biodegradation rate reached 71 x 10(-4) g . cm-2 . day-1. The glass 75 SO (75 SiO2-25 Na2O) was not so quickly corroded: Cracks appeared at the surface and progressively reached the center of the implants. There was no removable shell but a white deposit, adherent to the surface. This deposit contained silica and also calcium and phosphorus at the periphery. The biodegradation rate was only 2.6 x 10(-4) g . cm-2 . day-1.
mesh_terms: D000818:Animals; D001673:Biodegradation, Environmental; D002118:Calcium / Q000032:analysis; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004577:Electron Probe Microanalysis; D005898:Glass / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008297:Male; D010758:Phosphorus / Q000032:analysis; D019736:Prostheses and Implants; D051381:Rats; D011919:Rats, Inbred Strains; D017640:Silicates; D012824:Silicic Acid / Q000378:metabolism*; D012822:Silicon Dioxide / Q000378:metabolism*; D014961:X-Ray Diffraction
chemical_list: D017640:Silicates; D012824:Silicic Acid; D010758:Phosphorus; D012822:Silicon Dioxide; C005691:sodium silicate; D002118:Calcium