Water sorption and dimensional stability of an experimental glass-ionomer cement

Objective : The purpose of this study was to obtain information about the amount of water sorption and dimensional stability of an experimental conventional glass-ionomer cement modified with hydrophilic monomers, and compare with three commercially available products.

Methods: Five disks (6 ×3 mm) of each material (Durelon [PC, 3M ESPE], NX3 Nexus [RC, Kerr], and FujiCEM [RMGIC, GC] were prepared according to the manufacturers’ instructions. The terpolymer of acrylic acid (AA)–itaconic acid (IA)–N-vinylcaprolactam (NVC) with 8:1:1 and 7:1:2 (AA: IA: NVC) molar ratios were synthesized by free radical polymerization. Experimental GIC specimens were made from a 50% solution of the NVC -containing terpolymer with Fuji IX powder in a 3.6:1 P/L ratio. Specimens were first desiccated until a consistent mass was obtained. The thickness and diameter of each specimen were determined at 3 points with a digital micrometer and the volume (V) was calculated in mm³. Specimens were immersed for 7 days in distilled water at 37^oC. The water sorption and dimensional stability of each specimen were calculated according to the change in the weight and volume. The mean data obtained from measurements were subjected to one and two- way ANOVA (α=.05).

Results:  FujiCEM exhibited the highest values for water sorption and dimensional stability (P<0.05), followed by Nexus3. The experimental cement and the polycaroxylate cement showed significantly low values of water sorption in comparison to the resin cement and the resin modified cement. However, according to the statistical analysis of data no significant difference was found between the durelon cement and the NVC-containing experimental glass-ionomer cement in terms of dimensional stability (P>0.05).

Conclusion: NVC containing glass-ionomers are promising dental restorative materials with improved mechanical properties. The experimental cement exhibited comparable water sorption and dimensional stability in comparison to the commercial available products.