Effects of Preheating and Precooling on the Hardness and Shrinkage of a Composite Resin Cured with QTH and LED
| Autor: | F H Osternack, Janaina Bertoncelo de Almeida, Danilo Biazzetto de Menezes Caldas, Rui Fernando Mazur, Evelise Machado de Souza |
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| Rok vydání: | 2013 |
| Předmět: |
Dental Stress Analysis
Curing Lights Dental Hot Temperature Materials science Surface Properties Composite number medicine.disease_cause Composite Resins Polymerization law.invention Dental Materials Optical microscope Hardness law Mold Materials Testing medicine Humans Composite material General Dentistry Curing (chemistry) Light-Curing of Dental Adhesives Shrinkage Humidity Darkness Cold Temperature Knoop hardness test Stress Mechanical |
| Zdroj: | Operative Dentistry. 38:E50-E57 |
| ISSN: | 1559-2863 0361-7734 |
| DOI: | 10.2341/11-411-l |
| Popis: | 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 |
| Databáze: | OpenAIRE |
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