Effect Of Glass Composition On Properties Of Glass Ionomer Cement

Glass ionic cement?GIC?is widely used in clinical stomatology,but its mechanical strength,acid resistance,wear resistance and biological activity limit its application.Therefore,it is an important research content in the field to improve the performance of GIC to meet its clinical applicability.The traditional glass ionic cement is composed of glass powder and polycarboxylic acid?polyacrylic acid,tartaric acid,etc.?aqueous solution,which reacts with acid and alkali to form a composite material with polycarboxylic calcium/aluminum as matrix.Glass powder has a decisive influence on GIC performance.Therefore,this study focused on the influence of the structure and composition of glass powder on the performance of glass ionic cement.Glass of SiO₂-0.6Al₂O₃-0.6CaF₂-0.1P₂O₅-xTiO₂/ZrO₂?TiO₂/ZrO₂:0wt%,0.5wt%,1wt%,3wt%,5wt%?system was prepared by a melting method,and the effects of TiO₂?compared with ZrO₂?on GIC properties?curing time,mechanical strength and acid resistance?were studied.And with 3%TiO₂ glass as the studying object,we researched the effect of heat treatment temperature?400?,500?,600?,700??on the properties of the GIC that the powers headed for 2h.DSC and XRD showed that the glass transition temperature first increased and then decreased with the increase of TiO₂ content in the glass components.X-ray diffraction peak of glass powder was glass-like"steamed bread".It shows that the glass is amorphous,and Ti⁴⁺enters into the glass structure,playing a role of"aggregation”.When the TiO₂ content was 5wt%,the curing time and strength of GIC reached the maximum.This experiment powder best heat treatment temperature is 400?,low temperature heat treatment?below 400??repaired cracks on the surface of the glass particle,and became lower reactivity;Improving the heat treatment temperature?above500??,there were aggregation,adhesion between powder or the phenomenon of agglomeration,and there were a large number of CaF2 microcrystalline in glass structure at the same time,affecting the interface combination of GIC.Glass of SiO₂-?0.6-x?Al₂O₃-0.8CaF₂-0.1P₂O₅-xLa₂O₃?x=0,0.005,0.025,0.05,0.1,0.2 and 0.3?system was prepared by melting method,to study the influence of La/Al on GIC,and XRD,SEM and EDS were used for microscopic characterization of glass powder and GIC.DSC and XRD tests showed that as the glass component La/Al increased,the diffraction peak of CaF₂ crystal of glass powder increased,and the glass transition temperature first increased and then decreased.The presence of La³⁺effectively prolongs the curing time of glass ionic cement,which reaches the maximum when La/Al is 3:2.However,the effect on mechanical strength and acid resistance first increased and then decreased,and the optimal mix ratio was La/Al=1:9.EDS showed that the loss of La³⁺was low and GIC containing La exhibited excellent acid resistance because La³⁺has large radius,high coordination number and high electric field intensity.Tetracalcium phosphate?TTCP?and anhydrous calcium hydrophosphate were prepared by solid phase sintering.Different contents of TTCP/DCPA?0%,3wt%,7wt%,10wt%and 13wt%?were added into glass powder?SiO₂-Al₂O₃-CaF₂-P₂O₅?.GIC of curing time increased with the increase of TTCP/DCPA incorporation.The14d strength of GIC exceeded that of G0.Wear resistance was improved by incorporation of a small amount of TTCP/DCPA?3wt%and 7wt%?,but Acid resistance decreased by incorporation of TTCP/DCPA?3wt%-13wt%?.TTCP/DCPA provides a large amount of Ca²⁺and PO₄³⁺for GIC system,polycarboxylate generates more ionic bonds,the degree of network cross-linking increases,and the structure of organic and inorganic network cross-linking is formed.