Journal of Dental Research, Vol 73, 505-510, Copyright © 1994 by International & American Associations for Dental Research Online Journals
Effect of surface etching on the flexure strength and fracture toughness of Dicor disks containing controlled flaws
J. Y. Thompson and K. J. Anusavice
Department of Dental Biomaterials, College of Dentistry, University of Florida, Gainesville 32610-0446.
Previous studies have shown an increase in the failure load of Dicor
glass-ceramic crowns of up to 97% when they were etched with NH4HF2 and
luted with a resin-based cement compared with the use of unetched crowns
luted with zinc phosphate cement. The objective of this study was to
evaluate the effect of the acid-etch treatment on the flexure strength and
fracture toughness of Dicor glass-ceramic specimens containing controlled
flaws. Annealed disks were divided into two groups of 14 each, and
microcracks were induced in the surface with a Vickers indenter. Seven
specimens from each sample set were etched with 10% NH4HF2 (Dicor etching
gel) and were fractured in air using a piston-on-three-ball biaxial
fixture. Fracture toughness values were determined from the flexure
strengths and fractographic measurements of fracture-initiating flaws.
Analysis of data by ANOVA and the Tukey's Studentized Range Test revealed
no significant difference (p > 0.05) in the mean flexure strength or
fracture toughness of the etched and unetched samples within group A or
group B. For the sample groups tested, flaw modification by etching had no
effect on the flexure strength or on the fracture toughness of Dicor
specimens containing controlled flaws.
