title: Impact of curing protocol on conversion and shrinkage stress.
abstract: Since considerable shrinkage stress develops during the curing of dental composites, various soft-start photocuring protocols, aiming to lower stress but not compromise conversion, have been proposed. We hypothesized that utilizing soft-start photocuring will result in not only reduced stress, but also decreased conversion. We evaluated the impact of 3 protocols (soft-start, pulse, and standard) on the stress development and polymerization extent of an experimental composite. A novel set-up capable of simultaneous shrinkage stress, conversion, and temperature measurements on the same specimen was utilized. Analysis of the data shows that stress rises dramatically as a function of conversion in the vitrified state, and the utilization of soft-start or pulse curing results in specimens with reduced final conversion and shrinkage stress, compared with specimens cured according to the standard full-intensity protocol. Finally, this study demonstrates that the predominant reason for the reduced shrinkage stress attained with soft-start or pulse curing is a modest decrease in final conversion.
authors.affiliation: Department of Chemical & Biological Engineering, Engineering Center, University of Colorado at Boulder, 80309-0424, USA.
authors.forename: H
authors.initials: H
authors.lastname: Lu
authors.forename: J W
authors.initials: JW
authors.lastname: Stansbury
authors.forename: C N
authors.initials: CN
authors.lastname: Bowman
mesh_terms: D000704:Analysis of Variance; D017438:Bisphenol A-Glycidyl Methacrylate / Q000528:radiation effects; D003188:Composite Resins / Q000737:chemistry / Q000528:radiation effects*; D003799:Dental Stress Analysis; D006244:Hardness; D008027:Light; D015394:Molecular Structure; D044367:Phase Transition; D011092:Polyethylene Glycols / Q000528:radiation effects; D011109:Polymethacrylic Acids / Q000528:radiation effects; D013674:Technology, Dental
chemical_list: D003188:Composite Resins; D011109:Polymethacrylic Acids; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate