Preparation and evaluation of acrylic acid, itaconic acid, and N-methacryloylglutamic acid copolymers for use in glass-ionomer type dental restoratives

A series of copolymers containing various molar ratios of acrylic acid, ita conic acid and N-methacryloylglutamic acid were prepared in aqueous solutio n, using standard free-radical polymerization conditions. Specimens for mec hanical property studies were prepared by mixing water solutions of the cop olymers (50:50, wt:wt) with a commercial, calcium-fluoroaluminosilicate gla ss powder, with curing or hardening achieved by salt-bridge formation. The glass powder used in the formulation(s) was the same as that used in Fuji I I (GC America) glass-ionomer. The working and setting times df the various formulations were evaluated. The compressive strength was used as the basic screening property to find the optimum molar ratio of the three monomers. The diametral tensile strength, flexural strength and Knoop surface hardnes s of the cured materials were also determined. All mechanical properties we re measured after the specimens were conditioned in distilled water for 7 d ays at 37 degrees C. Based on the compressive strength (CS), poly (AA-co-IA -co-MGA) with a monomers ratio of 8:1:1, respectively, showed the highest C S (269.9 MPa). The 8:1:1 copolymer with different molecular weights were al so prepared to evaluate the effect of MW on the compressive strength. The o ptimum MW copolymer gave a glass-ionomer having the compressive strength im proved by 30%, compared to Fuji II (293.9 MPa vs. 224.9 MPa). The same poly mer solution was also mixed with glass powders used in other commercial gla ss-ionomers, i. e., Ketac-Molar (ESPE, Seefeld, Germany), alpha-Fil and alp ha-Silver (DMG, Hamburg, Germany) to produce conventional glass-ionomers te st specimens. The mechanical properties of these materials were also obtain ed and compared to the Fuji II, Ketac-Molar, alpha-Fil and alpha-Silver con trols.