Chemical durability of Dicor and lithia-based glass-ceramics.

Abstract

OBJECTIVES:

The aim of this study was to analyze the effect of a nucleation agent (P2O5) and a colorant/nucleation agent (AgNO3) on the chemical durability of Li2O-Al2O3-CaO-SiO2(LACS) glass-ceramics in 4% HAc solution, deionized-distilled water, and in pH buffer solutions of pH 1, pH 9, and pH 11.

METHODS:

Glass powder [27.8 mol% Li2O, 2.5% Al2O3, 5.9% CaO, and 63.8% SiO2(LACS)] was melted, poured into a cylindrical graphite mold (16 mm diameter), cooled, cut into 2.2 mm thick disks, polished through 1200 grit SiC, nucleated at 510 degrees C for 3 h, and crystallized at 650 degrees C for 6 h. Dynamic corrosion tests of LACS glass-ceramic, LACS glass-ceramic containing 1.0 mol% P2O5 (LACSP), LACS glass-ceramic containing 0.78 mmol% AgNO3(LACSAg), and Dicor control specimens were performed in a shaker-bath unit at 80 degrees C at a shaker speed of 30 cycles/min for periods of up to 15 d. Differences in mean weight loss and ionic concentration were analyzed for statistical significance (p = 0.05) using ANOVA and the Tukey's Studentized Range Test.

RESULTS:

The mean weight loss over 15 d in 4% HAc increased in the following order: LACS (0.21 +/- 0.02 mg/cm2), LACSAg (0.25 +/- 0.05 mg/ cm2), and Dicor (0.27 +/- 0.05 mg/cm2). The differences in mean values were not statistically significant (p > 0.05). The amounts of Li+ leached in 32 mL of pH1 and pH11 buffer solutions were 3.1 +/- 0.3 microgram/cm2/mL and 243 +/- 49.0 micrograms/cm2/mL, respectively, for the LACS group, and 3.0 +/- 0.6 microgram/cm2/mL and 166 +/- 28.0 micrograms/cm2/mL for the LACSAg group. The differences in mean values are not statistically significant (p > 0.05). The high chemical durability in acidic environments of LACS glass-ceramics without P2O5 and their decreased durability at pH values of 9 and above were confirmed by SEM observations of the exposed surfaces.

SIGNIFICANCE:

The weight loss for the three glass-ceramic systems was highest in pH 11 buffer solution, which represents an unlikely in vivo environment. From a toxicological viewpoint, the maximum amount of Li+ released from 28 fully dissolved crowns of LACS glass-ceramic at a temperature of 80 degrees C (which is greater than any temperature experienced in the oral cavity) is approximately 1.2 mg; this amount appears to be below the daily limit of 2 mg allowable from food sources.

• Authors: K J Anusavice, N Z Zhang
• Journal: Dental materials : official publication of the Academy of Dental Materials (Dent Mater) Vol. 13 Issue 1 Pg. 13-9 (Jan 1997) ISSN: 0109-5641 [Print] England
• PMID: 9467318 (Publication Type: Comparative Study, Journal Article, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Aluminum Silicates
• Dicor ceramic
• Ions
• Lithium Compounds
• Oxides
• Phosphorus Compounds
• Dental Porcelain
• phosphorus pentoxide
• Glass ceramics
• Silver Nitrate

Topics

• Aluminum Silicates (chemistry)
• Analysis of Variance
• Ceramics (chemistry)
• Corrosion
• Dental Porcelain (chemistry)
• Hydrogen-Ion Concentration
• Ions
• Lithium Compounds (chemistry)
• Materials Testing
• Microscopy, Electron, Scanning
• Oxides (chemistry)
• Phosphorus Compounds (chemistry)
• Silver Nitrate (chemistry)