Influence of Various Whisker-Silica Fillers on the Reinforcement of Dental Resin Composites

Objectives: Whiskers were recently used to reinforce dental composites to improve the strength and fracture toughness for large stress-bearing restorations. This study aimed to investigate the effects of different types of whiskers with various whisker:silica ratios on composite properties. Methods: Silicon nitride and silicon carbide whiskers were each mixed with silica particles at whisker:silica mass ratios of 0:1, 1:5, 1:2, 1:1, 2:1, 5:1, and 1:0. Silica particles were thermally fused onto the whiskers at 800 °C to facilitate silanization and to roughen the whisker surface for improved retention in the polymer matrix. The composite specimens were heat-cured at 140 °C. Strength and fracture toughness were measured in flexure; modulus and hardness were measured with nano-indentation. Two non-whisker control composites were also tested: an inlay/onlay composite, and a prosthetic composite. Results: The silicon nitride and silicon carbide composites reached strengths (mean ą SD; n=6) of (246 ą 33) MPa and (210 ą 14) MPa, respectively; both were nearly twice of (114 ą 18) MPa of prosthetic control and (109 ą 23) MPa of inlay/onlay control. Fracture toughness was also doubled due to whisker reinforcement. Whisker type and whisker:silica ratio had significant effects on composite properties (Two-way ANOVA; p < 0.001). Silicon nitride whiskers increased the composite strength and toughness more than silicon carbide. Silicon carbide whiskers increased the modulus and hardness more than silicon nitride. With increasing whisker:silica ratio, the composite strength and work-of-fracture increased rapidly and then decreased; toughness increased and plateaued; modulus increased monotonically but hardness plateaued. Conclusions: Whisker type and whisker:silica ratio are key microstructural parameters that can be varied to tailor the composite properties. Reinforcement with silica-fused whiskers results in composites that possess substantially higher strength and fracture toughness than non-whisker control composites. Supported by NIDCR R29 DE12476, ADAHF, and NIST.

*3143 Influence of Various Whisker-Silica Fillers on the Reinforcement of Dental Resin Composites*
H.H.K. XU¹, J.B. QUINN¹, D.T. SMITH², A.A. GIUSEPPETTI¹, G.E. SCHUMACHER¹, J.M. ANTONUCCI², and F.C. EICHMILLER¹, ¹American Dental Association Health Foundation, Gaithersburg, MD, USA, ²National Institute of Standards and Technology, Gaithersburg, MD, USA Objectives: Whiskers were recently used to reinforce dental composites to improve the strength and fracture toughness for large stress-bearing restorations. This study aimed to investigate the effects of different types of whiskers with various whisker:silica ratios on composite properties. Methods: Silicon nitride and silicon carbide whiskers were each mixed with silica particles at whisker:silica mass ratios of 0:1, 1:5, 1:2, 1:1, 2:1, 5:1, and 1:0. Silica particles were thermally fused onto the whiskers at 800 °C to facilitate silanization and to roughen the whisker surface for improved retention in the polymer matrix. The composite specimens were heat-cured at 140 °C. Strength and fracture toughness were measured in flexure; modulus and hardness were measured with nano-indentation. Two non-whisker control composites were also tested: an inlay/onlay composite, and a prosthetic composite. Results: The silicon nitride and silicon carbide composites reached strengths (mean ą SD; n=6) of (246 ą 33) MPa and (210 ą 14) MPa, respectively; both were nearly twice of (114 ą 18) MPa of prosthetic control and (109 ą 23) MPa of inlay/onlay control. Fracture toughness was also doubled due to whisker reinforcement. Whisker type and whisker:silica ratio had significant effects on composite properties (Two-way ANOVA; p < 0.001). Silicon nitride whiskers increased the composite strength and toughness more than silicon carbide. Silicon carbide whiskers increased the modulus and hardness more than silicon nitride. With increasing whisker:silica ratio, the composite strength and work-of-fracture increased rapidly and then decreased; toughness increased and plateaued; modulus increased monotonically but hardness plateaued. Conclusions: Whisker type and whisker:silica ratio are key microstructural parameters that can be varied to tailor the composite properties. Reinforcement with silica-fused whiskers results in composites that possess substantially higher strength and fracture toughness than non-whisker control composites. Supported by NIDCR R29 DE12476, ADAHF, and NIST.
Seq #288 - Polymer Materials: Reinforced Resin Materials 9:00 AM-11:00 AM, Saturday, 9 March 2002 San Diego Convention Center Room 3 (Upper Level)
Back to the Dental Materials: VI - Polymer Materials-Mechanical Properties and Degradation Program Back to the IADR/AADR/CADR 80th General Session (March 6-9, 2002)
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