HIGH VISCOSITY BULK-FILL GIOMER AND ORMOCER-BASED RESIN COMPOSITES : AN IN-VITRO COMPARISON OF THEIR MECHANICAL BEHAVIOUR
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Figure 2 . Micro-mechanical properties – a ) Martens Hardness ; b ) Vickers Hardness ; c ) Indentation modulus , YHU ; d ) Creep
specimens were polished with a grinding system ( EXAKT 400 CS , EXAKT , Norderstedt , Germany ) using silicon carbide paper P 2500 followed by P 4000 . Measurements were done on the top ( n = 10 ) of the slabs with 6 measurements per sample . The test procedure was carried out force-controlled , where the test load increased and decreased with constant speed between 0.4 and 500 mN . The load and the penetration depth of the indenter ( Vickers pyramid : diamond right pyramid with a square base and an angle of α = 136 ° between the opposite faces at the vertex ) were continuously measured during the load-unload hysteresis . Universal hardness ( HM ) is defined as the test force divided by the apparent area of indentation under the applied test force . From a multiplicity of measurements stored in a database supplied by the manufacturer , a conversion factor ( 0.0945 ) between HM and HV was calculated by the manufacturer and entered into the software so that the measurement results were also indicated in the more familiar HV units . Y HU was calculated from the slope of the tangent adapted at the beginning ( at maximum force ) of the nonlinear indentation depth curve upon unloading . By measuring the change in indentation depth with a constant test force , a relative change in the indentation depth can be calculated . This is a value for the creep of the materials .
2.3 Statistical Analysis The Kolmogoroff-Smirnoff test was applied to verify the data were normally distributed . Results were compared using one-way ANOVAs and Tukey ’ s HSD post hoc test ( α = 0.05 ). A multivariate analysis ( general linear model ) assessed the effect
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