title: Light polymerization during cavity filling: influence of total energy density on shrinkage and marginal adaptation.
abstract: The aim of the study was to evaluate the marginal adaptation and shrinkage stress development of a micro hybrid restorative composite as a function of energy density. Linear displacement and shrinkage forces were measured with custom-made devices for energies of 4,000, 8,000, 16,000 and 32,000 mJ/cm(2) at a constant power density of 800 mW/cm(2). Marginal adaptation of composite restorations cured with the same energy density was evaluated before and after mechanical loading with 300,000 cycles at 70 N. The group "4,000 mJ/cm(2)" showed the lowest shrinkage force [2.9(0.2) kg] and linear displacement [23.5(0.7) μm] but led to the worst marginal adaptation after loading [46.4(23.5) %CM] probably due to under-curing. When the maximum energy of 32,000 mJ/cm(2) was applied, a slight increase in shrinkage forces [3.6(0.2) kg and 29.2(0.8) μm], and a slight decrease in marginal adaptation after loading [75.4(11.5) %CM] were observed, but these changes were not significantly different in comparison to groups cured with energies of 8,000 and 16,000 mJ/cm(2). For the resin composite tested in this study, no differences in marginal adaptation could be detected above the energy threshold of 8,000 mJ/cm(2).
authors.affiliation: Division of Cariology and Endodontics, School of Dental Medicine, University of Geneva, 19 Rue Barthelemy Menn, 1205, Geneva, Switzerland, tissiana.bortolotto@unige.ch.
authors.forename: Tissiana
authors.initials: T
authors.lastname: Bortolotto
authors.forename: Federico
authors.initials: F
authors.lastname: Prando
authors.forename: Didier
authors.initials: D
authors.lastname: Dietschi
authors.forename: Ivo
authors.initials: I
authors.lastname: Krejci
mesh_terms: D003188:Composite Resins; D055117:Curing Lights, Dental; D008422:Materials Testing; D058105:Polymerization
chemical_list: D003188:Composite Resins