title: Comparative analysis of the shrinkage stress of composite resins.
abstract: The aim of this study was to compare the shrinkage stress of composite resins by three methods. In the first method, composites were inserted between two stainless steel plates. One of the plates was connected to a 20 kgf load cell of a universal testing machine (EMIC-DL-500). In the second method, disk-shaped cavities were prepared in 2-mm-thick Teflon molds and filled with the different composites. Gaps between the composites and molds formed after polymerization were evaluated microscopically. In the third method, the wall-to-wall shrinkage stress of the resins that were placed in bovine dentin cavities was evaluated. The gaps were measured microscopically. Data were analyzed by one-way ANOVA and Tukey's test (alpha=0.05). The obtained contraction forces were: Grandio = 12.18 +/- 0.428N; Filtek Z 250 = 11.80 +/- 0.760N; Filtek Supreme = 11.80 +/- 0.707 N; and Admira = 11.89 +/- 0.647 N. The gaps obtained between composites and Teflon molds were: Filtek Z 250 = 0.51 +/- 0.0357%; Filtek Supreme = 0.36 +/- 0.0438%; Admira = 0.25 +/- 0.0346% and Grandio = 0.16 +/- 0.008%. The gaps obtained in wall-to-wall contraction were: Filtek Z 250 = 11.33 +/- 2.160 microm; Filtek Supreme = 10.66 +/- 1.211 microm; Admira = 11.16 +/- 2.041 microm and Grandio = 10.50 +/- 1.224 microm. There were no significant differences among the composite resins obtained with the first (shrinkage stress generated during polymerization) and third method (wall-to-wall shrinkage). The composite resins obtained with the second method (Teflon method) differed significantly regarding gap formation.
authors.affiliation: Department of Operative Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil. rosanapbc@yahoo.com.br
authors.forename: Rosana Aparecida
authors.initials: RA
authors.lastname: Pereira
authors.forename: Paulo Amarante de
authors.initials: PA
authors.lastname: Araujo
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Castañeda-Espinosa
authors.forename: Rafael Francisco Lia
authors.initials: RF
authors.lastname: Mondelli
mesh_terms: D000818:Animals; D002417:Cattle; D055598:Chemical Phenomena; D003188:Composite Resins / Q000737:chemistry*; D003737:Dental Cavity Preparation; D018772:Dental Marginal Adaptation; D003764:Dental Materials / Q000737:chemistry*; D003804:Dentin / Q000648:ultrastructure; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D011138:Polytetrafluoroethylene / Q000737:chemistry; D011312:Pressure; D012833:Siloxanes / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: D003188:Composite Resins; D003764:Dental Materials; C474035:Filtek Supreme; C444701:Filtek Z250; C509998:Grandio; D008689:Methacrylates; D011108:Polymers; D012833:Siloxanes; C479084:admira; D011138:Polytetrafluoroethylene