The Effect of Variability in the PowderLiquid Ratio on the Strength of Zinc Phosphate Cement

Abstract EN

Aim.

To investigate (a) variability in powder/liquid proportioning and (b) effect of variability on diametral tensile strength (DTS), in a zinc phosphate cement.

Statistical analyses (α=0.05) were by Student’s t-test in the case of powder/liquid ratio and one-way ANOVA and Tukey HSD for pair-wise comparisons of mean DTS.

The Null hypotheses were that (a) the powder-liquid mixing ratios would not differ from the manufacturer’s recommended ratio (b) DTS of the set cement samples using the extreme powder/liquid ratios would not differ from those made using the recommended ratio.

Methodology.

34 dental students dispensed the components according to the manufacturer’s instructions.

The maximum and minimum powder/liquid ratios, together with the manufacturer’s recommended ratio, were used to prepare samples for DTS testing.

Results.

Powder/liquid ratios ranged from 2.386 to 1.018.

The mean ratio (1.644) was not significantly different from the recommended value of 1.718 (P=0.189).

DTS values for the maximum and minimum ratios were both significantly different from each other (P<0.001) and from the mean value obtained from the recommended ratio (P<0.001).

Conclusions.

Variability exists in powder/liquid ratio for hand dispensed zinc phosphate cement.

This variability can affect the DTS of the set material.