Effect of mixing methods on the physical properties of GIC

Objectives: Mixing of dental cements by auto-mix system is faster and easier than hand-mixing. However, the influence on physical properties of the cements hasn't been elucidated. The aim of this study was to evaluate the effect of the mixing methods on physical properties of glass-ionomer-cement(GIC).

Methods: The trial material FL-901 paste type GIC(GC) by hand-mix(FL-HM) and that by auto-mix(FL-AM) were evaluated. The latter were mixed by using the mixing tip. RelyX™ Luting Plus Cement(RXLP) paste type GIC(3M ESPE) in the clicker dispenser and RelyX™ Luting Cement(RXL) powder/liquid type GIC(3M ESPE), both were evaluated by hand-mix. All were mixed according to manufacturer's instructions. The following tests were applied to evaluate the physical properties(n=10): working-time(WT) at (23±1)°C and setting-time(ST) at (37±1)°C (ISO 4049), compressive test (ISO 9917-1), flexural test (ISO 9917-2). Compressive strength(CS) and compressive modulus(CM) were calculated from the result of compressive test, and flexural strength(FS), flexural modulus(FM) and fracture toughness(FT) were computed from the result of flexural test. The results were analyzed by one-way ANOVA and Turkey test.

Results: Mean values and S.D. were shown in the following table. Although there was significant difference of physical properties in among the different materials(p<0.01), the mixing method had no significant difference on physical properties in the same material.

	WT	ST	CS(MPa)	CM(GPa)	FS(MPa)	FM(GPa)	FT(N.cm)
FCX-HM	2'43''(±0'07'')a	2'02''(±0'09'')b	107.7(±10.2)c	0.87(±0.10)d	35.0(±3.3)e	4.65(±0.68)g,h	0.23(±0.06)i
FCX-AM	1'53''(±0'11'')a	1'56''(±0'08'')b	94.8(±3.3)c	0.91(±0.10)d	37.8(±3.3)e,f	4.13(±0.33)g	0.32(±0.06)i
RXLP	4'20''(±0'24'')	2'24''(±0'08'')b	103.1(±8.6)c	0.52(±0.03)	27.5(±4.4)	3.29(±0.52)	0.26(±0.04)i
RXL	12'18''(±1'00'')	5'08''(±0'37'')	87.9(±9.4)c	0.79(±0.31)d	41.3(±5.6)f	4.93(±0.82)h	0.29(±0.08)i
*Letters (a-i) denote statistically significant differences(p<0.01) between the groups in the same column.

Conclusions: In this study, there was no significant difference of physical properties in the mixing method. Therefore, it is thought that auto-mix system is useful like hand-mixing in clinical.