title: Influence of the curing method on the post-polymerization shrinkage stress of a composite resin.
abstract: The aim of this study was to evaluate the effect of different curing methods on the stress generated by the polymerization shrinkage of a restorative composite in two moments: immediately after light exposure and after 5 min. Photoactivation was performed using two different light sources: (1) xenon plasma arc (PAC) light (1,500 mW/cm2 - 3s) and (2) a quartz-tungsten-halogen (QTH) light with three light-curing regimens: continuous exposure (40 s at 800 mW/cm2 - CL); soft-start (10 s at 150 mW/cm2 and 30 s at 800 mW/cm2 - SS) and intermittent light [cycles of 4 s (2 s with light on at 600 mW/cm2 and 2 s of light off), for 80s - IL]. The composite resin was applied between two 5-mm diameter metallic rods, mounted in a servohydraulic machine. The maximum stress was recorded immediately after light exposure (FF) and after 5 min (5F). The results were submitted to ANOVA and Tukey's test (5%). For each method, the results obtained in FF and 5F were, respectively: CL (3.58 and 4.46 MPa); SS (2.99 and 4.36 MPa); IL (3.11 and 4.32 MPa) and PAC (0.72 and 3.27 MPa). The stress generated by the polymerization shrinkage during light exposure can be associated with the photoactivation method used. A significant increase in the stress level was observed during the post-curing period up to 5 min, for all evaluated methods.
authors.affiliation: Department of Prosthodontics, University of Taubaté, Taubaté, SP, Brazil. leonardogcunha@yahoo.com
authors.forename: Leonardo Gonçalves
authors.initials: LG
authors.lastname: Cunha
authors.forename: Roberta Caroline Bruschi
authors.initials: RC
authors.lastname: Alonso
authors.forename: Eduardo José Carvalho
authors.initials: EJ
authors.lastname: de Souza-Junior
authors.forename: Ana Christina Elias Claro
authors.initials: AC
authors.lastname: Neves
authors.forename: Lourenço
authors.initials: L
authors.lastname: Correr-Sobrinho
authors.forename: Mário Alexandre Coelho
authors.initials: MA
authors.lastname: Sinhoreti
mesh_terms: D003188:Composite Resins / Q000528:radiation effects*; D055117:Curing Lights, Dental; D003799:Dental Stress Analysis; D006219:Halogens; D055115:Light-Curing of Dental Adhesives / Q000379:methods*; D008422:Materials Testing; D044367:Phase Transition; D019279:Resin Cements / Q000528:radiation effects*; D013997:Time Factors; D014978:Xenon
chemical_list: D003188:Composite Resins; C444701:Filtek Z250; D006219:Halogens; D019279:Resin Cements; C084018:Scotchbond Multi-Purpose; D014978:Xenon