Aim: To investigate (a) variability in powder/liquid proportioning
(b) effect of the extremes of any such variability on diametral tensile strength
(DTS), in a commercial zinc phosphate cement. Statistical analyses (a = 0.05) were by Student¿s
t-test in the case of powder/liquid ratio and one-way ANOVA and Tukey HSD for for pair-wise comparisons of mean DTS. The Null
hypotheses were that (a) the powder-liquid mixing ratios observed would not
differ from the manufacturer¿s recommended ratio (b) DTS of the set cement
samples using the extreme powder/liquid ratios observed would not differ from
those made using the manufacturer¿s recommended ratio.
Methodology: Thirty-four undergraduate dental students
dispensed the components according to the manufacturer¿s instructions. The maximum
and minimum powder/liquid ratios (m/m), together with the manufacturer¿s
recommended ratio (m/m), were used to prepare cylindrical samples (n = 3 x 34) for DTS testing.
Results: Powder/liquid ratios ranged from 2.386 to
1.018.The mean ratio (1.644 (341) m/m) was not significantly different from the
manufacturer¿s recommended value of 1.718 (p=0.189). DTS values for the maximum
and minimum ratios (m/m), respectively, were both significantly different from
each other (p<0.001) and from the mean value obtained from the manufacturer¿s
recommended ratio (m/m) (p<0.001).
exists in powder/liquid ratio (m/m) for
hand dispensed zinc phosphate
cement. This variability can affect the DTS of the set material.