Document Detail

Isothermal anneal effect on leucite content in dental porcelains.
MedLine Citation:
PMID:  7629334     Owner:  NLM     Status:  MEDLINE    
Porcelain thermal expansion behavior is a function of leucite content, and leucite changes can produce porcelain-metal incompatibilities. The purpose of the present study was to determine whether isothermal anneal treatments (such as are encountered during "post-soldering" operations) could result in alterations of leucite content of dental porcelain. Six commercial dental porcelains and the "Component No. 1" frit of the Weinstein et al. patent (1962) were studied. Twenty-eight coupon specimens of each porcelain were fired and divided randomly into seven groups of four specimens each. One group served as a control, while the other six groups were subjected to isothermal anneal treatments--three groups at 500 degrees C and three groups at 750 degrees C, for 4, 8, and 16 min, respectively. Leucite volume fraction was measured via quantitative x-ray diffraction. From an equation for the growth of particles in competition for diffusing material, an expression was derived for the potential simultaneous processes of leucite crystallization and reaction of leucite+glass to form sanidine or other compounds. This exponential growth/decay curve was fit through the experimental data for each porcelain by minimization of the sum of the squares of the residuals through iteration. For each porcelain, a statistically significant correlation was obtained between leucite volume fraction and isothermal anneal duration at 750 degrees C (p < 0.01), whereas at 500 degrees C, only CII exhibited a statistically significant correlation (p < 0.01). The control (non-annealed) leucite volume fractions for the commercial porcelains ranged from (mean +/- SD) 0.155 +/- 0.002 for WIL to 0.442 +/- 0.003 for Component No. 1. The 750 degrees C isothermal anneal increased the leucite volume fraction by between 6.1% and 21.3%.(ABSTRACT TRUNCATED AT 250 WORDS)
J R Mackert; S W Twiggs; A L Evans-Williams
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Journal of dental research     Volume:  74     ISSN:  0022-0345     ISO Abbreviation:  J. Dent. Res.     Publication Date:  1995 Jun 
Date Detail:
Created Date:  1995-09-06     Completed Date:  1995-09-06     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0354343     Medline TA:  J Dent Res     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1259-65     Citation Subset:  D; IM    
Department of Oral Rehabilitation, Medical College of Georgia, Augusta 30912-1260, USA.
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MeSH Terms
Aluminum Silicates / chemistry*
Dental Porcelain / chemistry*
Dental Soldering*
Dental Stress Analysis
Hot Temperature
Least-Squares Analysis
Materials Testing
Metal Ceramic Alloys / chemistry
Prosthesis Failure
X-Ray Diffraction
Grant Support
Reg. No./Substance:
0/Aluminum Silicates; 0/Metal Ceramic Alloys; 12001-21-7/Dental Porcelain; 1302-34-7/leucite

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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