title: Effect of modulated photo-activation on polymerization shrinkage behavior of dental restorative resin composites.
abstract: This study investigated the influence of modulated photo-activation on axial polymerization shrinkage, shrinkage force, and hardening of light- and dual-curing resin-based composites. Three light-curing resin composites (SDR bulk-fill, Esthet X flow, and Esthet X HD) and one dual-curing material (Rebilda DC) were subjected to different irradiation protocols with identical energy density (27 J cm(-2) ): high-intensity continuous light (HIC), low-intensity continuous light (LIC), soft-start (SS), and pulse-delay curing (PD). Axial shrinkage and shrinkage force of 1.5-mm-thick specimens were recorded in real time for 15 min using custom-made devices. Knoop hardness was determined at the end of the observation period. Statistical analysis revealed no significant differences among the curing protocols for both Knoop hardness and axial shrinkage, irrespective of the composite material. Pulse-delay curing generated the significantly lowest shrinkage forces within the three light-curing materials SDR bulk-fill, Esthet X flow, and Esthet X HD. High-intensity continuous light created the significantly highest shrinkage forces within Esthet X HD and Rebilda DC, and caused significantly higher forces than LIC within Esthet X flow. In conclusion, both the composite material and the applied curing protocol control shrinkage force formation. Pulse-delay curing decreases shrinkage forces compared with high-intensity continuous irradiation without affecting hardening and axial polymerization shrinkage.
authors.affiliation: Department of Preventive Dentistry, Periodontology and Cariology, Center for Dental Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: Tobias T
authors.initials: TT
authors.lastname: Tauböck
authors.forename: Albert J
authors.initials: AJ
authors.lastname: Feilzer
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Buchalla
authors.forename: Cornelis J
authors.initials: CJ
authors.lastname: Kleverlaan
authors.forename: Ivo
authors.initials: I
authors.lastname: Krejci
authors.forename: Thomas
authors.initials: T
authors.lastname: Attin
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D017220:Dentin-Bonding Agents; D006244:Hardness; D006801:Humans; D055115:Light-Curing of Dental Adhesives / Q000379:methods*; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D058105:Polymerization; D011109:Polymethacrylic Acids / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry; D011829:Radiation Dosage; D055116:Self-Curing of Dental Resins / Q000379:methods; D013499:Surface Properties; D013997:Time Factors
chemical_list: D003188:Composite Resins; D003764:Dental Materials; D017220:Dentin-Bonding Agents; C466112:Esthet-X; C510276:Esthet-X Flow; D008689:Methacrylates; D011109:Polymethacrylic Acids; D011140:Polyurethanes; C529053:rebilda DC; C029824:urethane dimethacrylate luting resin; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; C074277:ethoxylated bis-phenol A dimethacrylate
keywords: flowable resin composite; polymerization contraction; pulse-delay; shrinkage stress; soft-start