title: Influence of curing rate on softening in ethanol, degree of conversion, and wear of resin composite.
abstract: OBJECTIVE
  To investigate the effect of curing rate on softening in ethanol, degree of conversion, and wear of resin composites.
  
  
  METHODS
  With a given energy density and for each of two different light-curing units (QTH or LED), the curing rate was reduced by modulating the curing mode. Thus, the irradiation of resin composite specimens (Filtek Z250, Tetric Ceram, Esthet-X) was performed in a continuous curing mode and in a pulse-delay curing mode. Wallace hardness was used to determine the softening of resin composite after storage in ethanol. Degree of conversion was determined by infrared spectroscopy (FTIR). Wear was assessed by a three-body test. Data were submitted to Levene's test, one and three-way ANOVA, and Tukey HSD test (alpha = 0.05).
  
  
  RESULTS
  Immersion in ethanol, curing mode, and material all had significant effects on Wallace hardness. After ethanol storage, resin composites exposed to the pulse-delay curing mode were softer than resin composites exposed to continuous cure (P< 0.0001). Tetric Ceram was the softest material followed by Esthet-X and Filtek Z250 (P< 0.001). Only the restorative material had a significant effect on degree of conversion (P< 0.001): Esthet-X had the lowest degree of conversion followed by Filtek Z250 and Tetric Ceram. Curing mode (P= 0.007) and material (P< 0.001) had significant effect on wear. Higher wear resulted from the pulse-delay curing mode when compared to continuous curing, and Filtek Z250 showed the lowest wear followed by Esthet-X and Tetric Ceram.
authors.affiliation: University North of Parani (UNOPAR) Center of Biological and Health Sciences, Av. Paris 675, Jd. Piza, 86041-140, Caixa Postal 401, Londrina PR, Brazil. anabenetti@hotmail.com
authors.forename: Ana Raquel
authors.initials: AR
authors.lastname: Benetti
authors.forename: Anne
authors.initials: A
authors.lastname: Peutzfeldt
authors.forename: Erik
authors.initials: E
authors.lastname: Asmussen
authors.forename: Ulla
authors.initials: U
authors.lastname: Pallesen
authors.forename: Eduardo Batista
authors.initials: EB
authors.lastname: Franco
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D055117:Curing Lights, Dental; D019554:Dental Restoration Wear; D003799:Dental Stress Analysis; D000431:Ethanol; D006244:Hardness; D055115:Light-Curing of Dental Adhesives / Q000379:methods*; D008422:Materials Testing; D058105:Polymerization; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D003188:Composite Resins; C466112:Esthet-X; C444701:Filtek Z250; C121818:Tetric ceram; D000431:Ethanol