Comparative evaluation of the physical properties of a reinforced glass ionomer dental restorative material.

STATEMENT OF PROBLEM: While glass ionomer cements have many unique properties and advantages, they still lack favorable mechanical properties. EQUIA Forte Fil is a newly developed glass ionomer cement (GIC) with improved mechanical strength. However, research and data on the physical properties of EQUIA Forte Fil are lacking. PURPOSE: The purpose of this in vitro study was to evaluate and compare the compressive, diametral tensile, and flexural strengths of EQUIA Forte Fil with Fuji IX GP and ChemFil Rock, restorative GICs commonly used in dentistry. Moreover, fluoride-releasing properties and surface hardness of the GICs were also assessed. MATERIAL AND METHODS: Ten disk-shaped specimens of each GIC (EQUIA Forte Fil, Fuji IX GP, and ChemFil Rock) were fabricated for mechanical and surface hardness tests by using polydimethylsiloxane (PDMS) molds. The specimens were tested after 24 hours and 7 days of immersion in distilled water at 37 °C. By using a mechanical testing machine, the compressive, diametral tensile, and flexural strengths of each GIC were measured. Fluoride-releasing properties were also evaluated (10 specimens per group). A microhardness tester was used to measure the surface hardness. The mean data were analyzed by using 1- and 2-way ANOVA (α=.05). RESULTS: EQUIA Forte Fil glass ionomer cements exhibited significantly greater (P<.05) flexural strength and surface hardness than Fuji IX GIC specimens. However, no significant difference (P>.05) was observed between the compressive and diametral tensile strength of EQUIA Forte Fil and Fuji IX GIC specimens. ChemFil Rock exhibited higher flexural strength than EQUIA Forte Fil (P>.05) but significantly lower compressive strength and microhardness (P<.05). Tested GICs matured after 1 week of immersion in distilled water, demonstrating a significant improvement in their mechanical properties. All the examined glass ionomers exhibited comparable initial fluoride-releasing properties, whereas EQUIA Forte Fil exhibited significantly higher (P<.05) amounts of fluoride release from the bulk of the material after 4 weeks. CONCLUSIONS: EQUIA Forte Fil is a promising restorative material with superior flexural strength and surface hardness compared with its predecessor, Fuji IX GP, or other commercially available glass ionomers.

Effects of an etching solution on the adhesive properties and surface microhardness of zirconia dental ceramics.

STATEMENT OF PROBLEM: Conventional approaches to adhesive bonding are not applicable to zirconia restorations. Recently, an etching solution, Zeta Etching Solution (ZES), has been introduced for etching the surface of zirconia. The effects of this etching solution on the bond strength and mechanical properties of zirconia are unknown. PURPOSE: The purpose of this in vitro study was to examine the effects of ZES on the bond strength and surface hardness of zirconia. MATERIAL AND METHODS: Two different types of partially stabilized tetragonal polycrystalline zirconia (TZP), Prettau zirconia (group P) and anterior Prettau (group AP), were evaluated with and without ZES etching. Each group was bonded to a zirconia substrate by using an adhesive resin cement. After 24 hours of storage in distilled water, the bond strength of the zirconia was analyzed. Vickers hardness was determined by using a microhardness tester. Scanning electron microscopy was used to analyze the surface microstructure and determine the mode of failure for each specimen. Results were analyzed and compared using 1-way ANOVA and Student t tests (α=.05). RESULTS: Scanning electron microscopy analysis showed that etching the surface of zirconia with ZES etching solution for 60 minutes changed the morphological characteristics and microstructure of zirconia, making the surface more irregular. The changes were more pronounced for AP specimens. Etching with ZES significantly increased the shear bond strength of zirconia (P<.05) in AP specimens. The bond strength of Prettau (P group) specimens after ZES etching did not increase significantly (P>.05). An adhesive failure mode was observed for P zirconia specimens, whereas zirconia specimens exhibited a cohesive mode of failure. No significant decrease (P>.05) was observed in the mean Vickers hardness numbers. CONCLUSIONS: Within the limitations of this in vitro study, it was concluded that etching in ZES for 30 minutes significantly enhanced the shear bond strength of highly translucent anterior Prettau (AP) zirconia restorations. Moreover, etching with ZES did not adversely affect the surface hardness of the zirconia specimens tested.