title: Effect of surface etching on the flexure strength and fracture toughness of Dicor disks containing controlled flaws.
abstract: 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.
authors.affiliation: Department of Dental Biomaterials, College of Dentistry, University of Florida, Gainesville 32610-0446.
authors.forename: J Y
authors.initials: JY
authors.lastname: Thompson
authors.forename: K J
authors.initials: KJ
authors.lastname: Anusavice
mesh_terms: D000134:Acid Etching, Dental; D064751:Ammonium Compounds; D000704:Analysis of Variance; D002516:Ceramics / Q000737:chemistry*; D001840:Dental Bonding / Q000379:methods*; D003776:Dental Porcelain / Q000737:chemistry*; D004548:Elasticity; D005459:Fluorides / Q000737:chemistry; D006245:Hardness Tests; D008422:Materials Testing / Q000379:methods; D008855:Microscopy, Electron, Scanning; D000644:Quaternary Ammonium Compounds; D013499:Surface Properties
chemical_list: D064751:Ammonium Compounds; C047475:Dicor ceramic; D000644:Quaternary Ammonium Compounds; D003776:Dental Porcelain; C024822:ammonium fluoride; D005459:Fluorides