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Indentation Modulus and Hardness of Whisker-Reinforced Heat-Cured Dental Resin Composites



H H. Xu, Douglas T. Smith, Gary E. Schumacher, F Eichmiller, Joseph M. Antonucci


Recent studies showed that ceramic whisker reinforcement imparted a nearly two-fold increase in the strength of dental resin composites. The aim of the study was to investigate the indentation response and measure the elastic modulus hardness, and brittleness of whisker-reinforced heat-cured resin composites as a function of a filler level, heat-cure temperature, and heat-cure duration. Silica particles were fused onto silicon nitride whiskers to facilitate silanization and to roughen the whiskers for improved retention in the matrix. Whisker filler mass fractions of 0, 20, 40, 60, 70, 74 and 79% were tested. Heat-cure temperature ranged from 100 to 180 C, and duration from 10 min to 24 h. A nano-identation system enabled the measurement of elastic modulus. Fracture toughness was measured and composite brittleness index was calculated. An inlay/onlay composite and a prosthetic composite were tested as controls. Whisker filler level and heat-cure duration had significant effects on composite properties, while heat-cure temperature had non-dignificant effects. The whisker composite with 79% filler level had a modulus in Gpa (mean (SD); n =6) of 26.9 (1.0), significantly higher than 15.1 (0.2) of an inlay/onlay control, and 16.1 (0.3) of a prosthetic control (Tukey's multiple comparison test; family confidence coefficient = 0.95). The fracture toughness in Mpa.m^u1/2 was 2.22 (0.26) for the whisker composite, higher than 0.95 (0.11) for inlay/onlay control, and (1.13 0.19) for prosthetic control. The brittleness index was (0.49 0.07) for whisker composite, lower than (1.02 0.12) for inlay/onlay control and (0.63 0.13) for prosthetic control. Whisker filler level had a profound influence, heat-cure duration had significant effects, while temperature did not have significant effects, on the properties of whisker composite. The whisker composite had significantly higher elastic modulus and fracture toughness, and lower brittleness than the inlay/onlay and prosthetic controls.
Journal of Dental Research


brittleness, ceramic whisker, elastic modulus, filler level, fracture toughness, heat cure, indentation, resin composite


Xu, H. , Smith, D. , Schumacher, G. , Eichmiller, F. and Antonucci, J. (2000), Indentation Modulus and Hardness of Whisker-Reinforced Heat-Cured Dental Resin Composites, Journal of Dental Research, [online], (Accessed May 18, 2024)


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Created December 31, 1999, Updated October 12, 2021