Objective: The purpose of this work was to study the effect of addition of silanized zirconia
powder on flexural strength, deflection, modulus, toughness and micro-hardness of heat-polymerized
poly methyl methacrylate (PMMA) denture base resin.
Materials and Methods: One hundred specimens of heat-polymerized PMMA were prepared
for flexural and hardness tests, fifty for each. Zirconia (ZrO2) powder was treated with silane
coupling agent then added to acrylic powder in percentage of 0%(control), 0.5%, 1%, 2% and 5%
by weight. Specimens for flexural test were prepared in the shape of flat strips with dimensions of
(65×10×2.5mm) using compression molding technique. Flexural test was performed by three-point
bending test using universal testing machine. Flexural strength, flexural deflection, flexural modulus
and toughness were obtained from the software of the testing machine. Specimens for microhardness
test were prepared in dimensions of (10×10×3mm). Micro-hardness was determined
using Vickers Micro-hardness Tester. Digital microscope was used to capture photomicrographs
at x500 magnification of the surface of randomly selected specimen for each group to show the
distribution of different percentages of zirconia. One-way Anova followed by Scheffe's post hoc
multiple comparison test was performed with 5% level of significance for testing the significance
between the means of tested groups.
Results: There is a significant difference among the mean values of flexural deflection, flexural
modulus, toughness and micro-hardness (P<0.05%). The mean values of flexural strength were not
significantly different (P>0.05%). The digital microscope has shown nearly even distribution of
zirconia particles within the acrylic matrix at 0.5% and 1%, while clusters started to form at 2%,
and 5% zirconia.
Conclusion: Silanized zirconia powder could be used to improve the properties of heatpolymerized
acrylic denture base resin. The most appropriate percentages were 1% and 2%.