Physico-mechanical properties of a fast-set highly viscous GIC restorative

The fast-setting reaction of 'fast-set' highly viscous glass-ionomer cements (GIC) may result in superior mechanical properties and good wear resistance as the material can theoretically achieve sufficient strength to resist masticatory loads within a shorter time. The aim of this study was to determine the hardness, strength (compressive and diametral tensile) and wear resistance of a 'fast-set' highly viscous GIC (Fuji IX GP Fast). Its regular set counterpart (Fuji IX GP) was used for comparison. The glass powders of the two cements were also characterized. Hardness testing [Vickers' hardness number (VHN)] was performed with a digital hardness tester (load=50 g; dwell time=30 s) and compressive/diametral tensile strength testing (MPa) was conducted based upon British Standards specification for GICs (BS6039, 1981). Wear testing was conducted using a reciprocal compression-sliding wear instrumentation at 20 MPa contact stress against SS304 counter-bodies with distilled water as lubricant. All specimens were immersed in distilled water at 37 degrees C and tested 24 h after start of mixing. Further mechanical tests (hardness and strength) were conducted with specimens stored for 1 week in distilled water at 37 degrees C. The glass powders were characterized using laser particle sizing, standard electron microscope (SEM) and energy dispressure X-ray (EDX) analysis. Results were analysed using multiple analysis of variance (manova) and independent samples t-test at significance level 0.05. No significant difference in hardness, compressive and diametral tensile strength was observed between Fuji IX GP and Fuji IX GP Fast at 1 day. There was also no significant difference in wear at all cyclic intervals. Although the difference in strength was not significant between the two cements at 1 week, Fuji IX GP Fast was significantly harder than Fuji IX GP. Particle size of both cements ranged from 0.3 to 200 microm. The mean particle sizes were, however, different and were 13.43 and 7.13 microm for Fuji IX GP and Fuji IX GP Fast, respectively. Fuji IX GP Fast offers no other advantage over Fuji IX GP with the exception of improved hardness.

Besides being harder, the fast-set highly viscous GIC restorative offers no other physico-mechanical advantage over its regular set counterpart.