Three-Point Bending Test Parameters For Dental Materials Evaluation

Method: Polyvinyl-siloxane molds with five different dimensions were filled with nanofill composite-resin (Filtek Supreme, 3M-ESPE), covered with a glass slide and photoactivated using a quartz-tungsten halogen light for 40s. The 5 different beam sizes were based on dimensions published or specified in ISO standards. The specimens were tested in three-point bending (n=5) and E was determined. E measurements using Knoop microhardness were carried out as control (n=5). Data were analyzed using one-way ANOVA, Tukey’s and Dunnett’s tests (p<.05). Three-dimensional models of the experimentally tested specimens and supports were generated for non-linear finite element analyses (FEA). The materials were assumed as homogeneous, linear-elastic and isotropic. Deflection at the load application point and the maximum tensile stress in the beams were calculated.

Result: Results indicated significant higher E-values with the microhardness method and significant variations between the E-values obtained with the different three-point bending test designs (Table-1). FEA confirmed differences in stress distribution patterns for the different bending test designs evaluated.

Table-1: Elastic modulus for experimental tests.

Letters indicate significant difference between rows; *Indicates significant difference between control and experimental groups (p<.05).

Conclusion: Significant different E-values were obtained using the same test-type with different parameters. These discrepancies can lead to complications when using mechanical properties from the literature in inter-study comparisons or finite element stress analyses.