Document Detail


Effects of Preheating and Precooling on the Hardness and Shrinkage of a Composite Resin Cured With QTH and LED.
MedLine Citation:
PMID:  23088189     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
SUMMARY The aim of this study was to evaluate in vitro the hardness and shrinkage of a pre-cooled or preheated hybrid composite resin cured by a quartz-tungsten-halogen light (QTH) and light-emitting diode (LED) curing units. The temperature on the tip of the devices was also investigated. Specimens of Charisma resin composite were produced with a metal mold kept under 37°C. The syringes were submitted to 4°C, 23°C, and 60°C (n=20) before light-curing, which was carried out with the Optilux 501 VCL and Elipar FreeLight 2 units for 20 seconds. The specimens were kept under 37°C in a high humidity condition and darkness for 48 hours. The Knoop hardness test was carried out with a 50 gram-force (gf) load for 10 seconds, and the measurement of the shrinkage gap was carried out using an optical microscope. The data were subjected to analysis of variance and the Games-Howell test (α=0.05). The mean hardness of the groups were similar, irrespective of the temperatures (p>0.05). For 4°C and 60°C, the top surface light-cured by LED presented significantly reduced shrinkage when compared with the bottom and to both surfaces cured by QTH (p<0.05). It was concluded that the hardness was not affected by pre-cooling or preheating. However, polymerization shrinkage was slightly affected by different pre-polymerization temperatures. The QTH-curing generated greater shrinkage than LED-curing only when the composite was preheated. Different temperatures did not affect the composite hardness and shrinkage when cured by a LED curing unit.
Authors:
Fh Osternack; Dbm Caldas; Jb Almeida; Em Souza; Rf Mazur
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-10-22
Journal Detail:
Title:  Operative dentistry     Volume:  -     ISSN:  0361-7734     ISO Abbreviation:  Oper Dent     Publication Date:  2012 Oct 
Date Detail:
Created Date:  2012-10-23     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7605679     Medline TA:  Oper Dent     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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