Journal of Dental Research, Vol 78, 1304-1311, Copyright © 1999 by International & American Associations for Dental Research Online Journals

ARTICLES

Dental composite resins containing silica-fused ceramic single-crystalline whiskers with various filler levels

H. H. Xu
Paffenbarger Research Center, American Dental Association Health Foundation, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.

Currently available direct-filling composite resins are susceptible to fracture and hence are not recommended for use in large stress-bearing posterior restorations involving cusps. The glass fillers in composites provide only limited reinforcement because of the brittleness and low strength of glass. The aim of the present study was to use ceramic single-crystalline whiskers as fillers to reinforce composites, and to investigate the effect of whisker filler level on composite properties. Silica particles were fused onto the whiskers to facilitate silanization and to roughen the whiskers, thereby improving retention in the matrix. The composite flexural strength, elastic modulus, hardness, and degree of polymerization conversion were measured as a function of whisker filler mass fraction, which ranged from 0% to 70%. Selected composites were polished simulating clinical procedures, and the surface roughness was measured with profilometry. The whisker composite with a filler mass fraction of 55% had a flexural strength (mean +/- SD; n = 6) of 196+/-10 MPa, significantly higher than 83+/-14 MPa of a microfill and 120+/-16 MPa of a hybrid composite control (family confidence coefficient = 0.95; Tukey's multiple comparison). The composite modulus and hardness increased monotonically with filler level. The flexural strength first increased, then plateaued with increasing filler level. The degree of conversion decreased with increasing filler level. The whisker composite had a polished surface roughness similar to that of a conventional hybrid composite (p>0.1; Student's t). To conclude, ceramic whisker reinforcement can significantly improve the mechanical properties of composite resins; the whisker filler level plays a key role in determining composite properties; and the reinforcement mechanisms appear to be crack pinning by whiskers and friction from whisker pullout resisting crack propagation.

This article has been cited by other articles:

				J.L. Drummond Degradation, Fatigue, and Failure of Resin Dental Composite Materials J. Dent. Res., August 1, 2008; 87(8): 710 - 719. [Abstract] [Full Text] [PDF]

				H.H.K. Xu, M.D. Weir, L. Sun, S. Takagi, and L.C. Chow Effects of Calcium Phosphate Nanoparticles on Ca-PO4 Composite J. Dent. Res., April 1, 2007; 86(4): 378 - 383. [Abstract] [Full Text] [PDF]

				H.H. K. Xu, J.B. Quinn, and A.A. Giuseppetti Wear and Mechanical Properties of Nano-silica-fused Whisker Composites J. Dent. Res., December 1, 2004; 83(12): 930 - 935. [Abstract] [Full Text] [PDF]

				H.H.K. Xu Long-term Water-aging of Whisker-reinforced Polymer-Matrix Composites J. Dent. Res., January 1, 2003; 82(1): 48 - 52. [Abstract] [Full Text] [PDF]