The surface of a bioactive (45S) and a bioinactive (65S) glass composition has been modeled using shell-model classical molecular dynamics simulations. Direct comparison of the two structures allowed Lis to identify the potential role of specific surface features in the processes leading to integration of a bioglass implant with the host tissues, focusing in particular oil the initial dissolution of file glass network. The Simulations highlight file critical role of network fragmentation and sodium enrichment of the surface in determining the rapid hydrolysis and release of silica fragments in solution, characteristic of highly bioactive compositions. Oil file other hand, no correlation hits been found between the surface density of small (two- and three-membered) rings and bioactivity, thus suggesting that additional factors need to be taken into account to fully understand the role of these sites in the mechanism leading to calcium phosphate deposition oil the glass surface.