Evaluation of a Novel Zinc-Reinforced Glass Ionomer Cement

Research Abstract

Summary & Conclusion This study was designed to evaluate and compare microstructure, flexural strength, diametral tensile strength, fluoride release, solubility and water sorption and wear resistance of the new encapsulated zinc reinforced glass ionomer cement to encapsulated conventional and resin modified glass ionomer cements. A total number of one hundred forty four specimens were fabricated. Specimens were divided into three equal main groups (forty eight each), according to type of materials used; conventional glass ionomer (Ketac molar, 3M), resin modified glass ionomer (Photac fil, 3M) and zinc reinforced glass ionomer cements (Chem Fil Rock, Dentsply). For each material: three specimens were randomly selected for scanning electron microscope and EDX evaluation as one day dry specimen, one week dry specimen and one week wet specimen. The remaining forty five specimens of each group were distributed according to testing methods; fifteen specimens for flexural strength test, fifteen specimens for diametral compressive test for tension, then both were further subdivided into three subgroups (five each); according to storage period; one day, one week and one month. Five specimens for fluoride release assessment, five specimens for solubility and water sorption tests and five specimens for wear resistance test. For flexural strength test; bar-shaped specimens were fabricated in split Teflon mold. Specimens were stored in distilled water till the storage period. The test was performed using universal testing machine at a crosshead speed of 1.0 mm/min. For compressive test for tension; disc-shaped specimens were fabricated in split Teflon mold. Specimen were stored in distilled water till the storage period. The test was performed using universal testing machine at a crosshead speed of 0.5 mm/min. For fluoride release assessment; the specimens were stored in 3ml of distilled water and fluoride release was measured using fluoride ion selective electrode daily for the first week then weekly for the two months. For solubility and water sorption tests; the specimens were stored in a desiccator, at (37±1)°C for 24 hours, they were weighed on digital analytical balance (0.0001 g accuracy). This is the initial dry weight (W1). Specimens were then immersed distilled water at (37±1) °C for 1 week in an incubator then weighed one minute after removal from water in the balance (W2). The specimens then dehydrated in a desiccators at (37±1) °C for 24 h and weighed again. This is final dry weight (W3). For wear test; the specimens were stored in distilled water for 14 days at (37±1) °C in an incubator then weighed in digital analytical balance, this is the initial weight (M1). Each specimen subjected to wear testing using TNO-TRIBO Meter Wear testing machine. Test conditions were 0.1 bar wet pressure, the speed of rotation 120 rpm and the time duration for the rotation 10 minutes under constant distilled water irrigation as lubricant. Then specimen was weighed in digital analytical balance and considered as final weight of specimen (M2). The data was collected, recorded and tabulated. Statistical analysis was carried out using SPSS program. One way ANOVA was used to test the effect of group within each time on different measurements. Duncan Post-Hoc Comparisons at p≤0.05 was used for means comparison. The results of this study showed that zinc reinforced glass ionomer cement showed less cracks and voids, intermediate flexural strength, highest initial diametral tensile strength and intermediate fluoride release compared to conventional and resin modified glass ionomer cements. Moreover, the highest wear resistance was observed in zinc reinforced GIC. However, the highest solubility and water sorption were observed in zinc reinforced glass ionomer cement followed by resin modified GIC and conventional GIC, respectively. Within the limitation of this study and after analysis of its results, following could be concluded; 1- Zinc reinforced glass ionomer cement is a promising dental filling material. 2- The present of zinc in zinc reinforced glass ionomer cement produced a minimum surface cracks and voids comparable to conventional and resin modified glass ionomer cements. 3- Flouride release from glass ionomer cements is a compositional properties. 4- Although presence of zinc in zinc reinforced glass ionomer cement improved its mechanical properties, yet, a dramatic increase in solubility and water sorption were obvious .

Research Keywords

zinc glass ionomer