Ari-Pekka Forsback

Mineralization of dentin induced by treatment with bioactive glass S53P4 in vitro.

Dentin hypersensitivity can be managed to occlude dentin tubules, but none of the agents used are components of natural dentin. Using a calcium phosphate precipitation (CPP) method, dentin tubules can be occluded with a calcium phosphate (CaP) layer similar to the major inorganic component of dentin. The CPP method utilizes acidic pH conditions, such as etching of dentin, over the course of several dental treatments. A gentler method can be used to produce a CaP layer on the surface of dentin. By treating with bioactive glass S53P4 (BAG), or regular commercial glass (CG), mineralization occurs in physiologically neutral solutions such as simulated body fluid (SBF) and remineralization solution (RMS). After a short period of immersion, silica is dissolved from both types of glass, but the amount of silica released is much greater from BAG than from CG. The dissolved silica is adsorbed on the surface of dentin during the pretreatment procedure and enhances the mineralization of dentin in SBF. After 14 days mineralization the dentin is fully covered by the CaP layer, but after 14 days immersion in RMS decalcification of the dentin occurs. Pretreatment with BAG decreases the degree of decalcification of dentin during the mineralization process. These findings suggest that bioactive glass S53P4 can be used as a therapeutic material for mineralization of dentin and its tubules in a physiological environment.

Release of silica, calcium, phosphorus, and fluoride from glass ionomer cement containing bioactive glass

The aim of this study was to examine the release of silica (Si), calcium (Ca), phosphorous (P), and fluoride (F) from conventional glass ionomer cement (GI) and resin-modified glass ionomer cement (LCGI), containing different quantities of bioactive glass (BAG). Further aim was to evaluate in vitro biomineralization of dentine. The release of Si increased with the increasing immersion time from the specimens containing BAG, whereas the amount of Ca and P decreased indicating in vitro bioactivity of the materials. LCGI with 30wt% of BAG showed highest bioactivity. It also showed CaP-like precipitation on both the surface of the test specimens and on the dentin discs immersed with the material. Within the limitations of this study, it can be concluded that a dental restorative material consisting of glass ionomer cements and BAG is bioactive and initiates biomineralization on dentin surface in vitro.

Biomineralization of Glass Fibre Reinforced Porous Acrylic Bone Cement

Acrylic bone cements are used to fix joint replacements to bone. The main substance in acrylic bone cement is biologically inert poly(methylmethacrylate), PMMA. The dense PMMA polymer structure of cement does not allow bone ingrowth into cement. Therefore, the main focus of our studies is to modify acrylic bone cement in order to improve its biological properties e.g., by creating porosity in the cement matrix. The porous structure is in situ created using pore-generating filler (i.e., 20 wt% of an experimental biodegradable polyamide) that is incorporated in acrylic bone cement. The aim of this in vitro study was to investigate the biomineralization of acrylic bone cement modified using an experimental biodegradable polyamide.

Effect of Ionic Variables (SiO2, Ca2+, PO43-) on Biomimetic Mineralization

Cellulose sponges were exposed for 24 h to bioactive glass S53P4, sol-g el derived SiO2 or CaO – P2O5 – SiO2 and then immersed for 14 days in simulated body fluid (1.5 x and 1 x SBF) to produce a layer of CaP on the substrate. The release of Si, Ca 2+ and PO4 3from the different bioactive materials in SBF was monitored for the first 24 h and the subsequent formation of CaP on the cellulose was correlated to the composition of the ion source. The results indicate that a high initial calcium (and phosphate) concentration supports biomimetic CaP f ormation on cellulose sponges in 1 x SBF. The finding suggests that implant materials pr epared by biomimetic mineralization that exhibit a high number of CaP growth centres on their surface have the best potential to promote bone bonding in vivo. Introduction Bioactive materials, such as bioactive glass (S53P4, BAG) and sint ered hydroxyapatite are known to spontaneously form CaP that simulates the apatite of bone on their surface within the body, and bond to bone through the apatite layer formed.[1,2] The surfaces produced are osteoconductive and, perhaps, even osteopromotive.[3] As described earlier, biologically acti ve apatite layers can be preproduced in an acellular simulated body fluid (SBF) on a bioactive material.[4] By using the biomimetic method [5] the formation of biologically act ive CaP can be induced on the surface of a second polymer. The method is thought to make use of the reactions at the surface of the bioactive material. Dissolved silica has been suggested to compose oligomers that serve as heterogenic nucleation centers when adsorbed on the polymer substrates [ 6] but the role of calcium and phosphate ions is not clear. The objective of this in vitro work was to establish the relative importance of silica (SiO 2), calcium (Ca) phosphate (PO 4 ) ions on CaP formation on cellulose sponge (CS) . The CaP formation on cellulose was studied as a function of ion concentrations re leased from different compositions of the ion sources. Methods Simulated body fluid (SBF) with ion concentration of that of human plasma (1 x SBF), and 1.5 x SBF were prepared as previously described [5]. These solutions were buffered at pH 7.40 by tris (hydroxymethyl aminomethane) and 2 M HCl. The buffered solutions were f iltered through a 0.45 μm (PALL) membrane. The bioactive glass S53P4 (BAG, 23 % Na 2O, 20 % CaO, 4 % P 2O5, 53 % SiO2, Abmin Technologies Ltd., Turku, Finland) was used as one of the ion sources in the mineralization. Both the Ca and PO 4 containing (CaPSi, CaO-P 2O5-SiO2: 35-5-60 mol-%) and the plain sol-gel derived Key Engineering Materials Online: 2003-05-15 ISSN: 1662-9795, Vols. 240-242, pp 249-252 doi:10.4028/www.scientific.net/KEM.240-242.249