title: Influence of light-curing protocols on polymerization shrinkage and shrinkage force of a dual-cured core build-up resin composite.
abstract: This study investigated the influence of time delay and duration of photo-activation on linear polymerization shrinkage, shrinkage force, and hardening of a dual-cured core build-up resin composite. The test material (Rebilda DC) was light-cured for 20 or 60 s either early (2 min) or late (7 min) after the start of mixing. Non-irradiated self-cured specimens served as controls. Linear shrinkage and shrinkage force were measured for 60 min using custom-made devices. Knoop hardness was determined at the end of the observation period. Self-cured controls, showing a linear shrinkage similar to that of specimens early light-cured for 20 s generated the lowest shrinkage force and hardness. A shorter light exposure time (20 s vs. 60 s) reduced linear shrinkage, shrinkage force, and hardness when early light-curing was performed, but did not affect the three properties in specimens light-cured late after the start of mixing. Late photo-activation increased linear shrinkage, irrespective of irradiation time, and resulted in a higher shrinkage force and hardness for short light exposure time. A moderate correlation was found between the two shrinkage properties studied (r(2) = 0.65). In conclusion, improvements in shrinkage behavior of the tested core build-up material were associated with inferior hardening, making it important to adapt curing protocols to the clinical situation.
authors.affiliation: Department of Preventive Dentistry, Periodontology and Cariology, University of Zurich, Zurich, Switzerland. tobias.tauboeck@zzmk.uzh.ch
authors.forename: Tobias T
authors.initials: TT
authors.lastname: Tauböck
authors.forename: Tissiana
authors.initials: T
authors.lastname: Bortolotto
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Buchalla
authors.forename: Thomas
authors.initials: T
authors.lastname: Attin
authors.forename: Ivo
authors.initials: I
authors.lastname: Krejci
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry / Q000528:radiation effects; D003188:Composite Resins / Q000737:chemistry / Q000528:radiation effects*; D055117:Curing Lights, Dental / Q000145:classification*; D003764:Dental Materials / Q000737:chemistry / Q000528:radiation effects*; D017220:Dentin-Bonding Agents / Q000737:chemistry / Q000528:radiation effects; D006244:Hardness; D006801:Humans; D008689:Methacrylates / Q000737:chemistry / Q000528:radiation effects; D055668:Photochemical Processes; D011108:Polymers / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry / Q000528:radiation effects; D011140:Polyurethanes / Q000737:chemistry / Q000528:radiation effects; D055116:Self-Curing of Dental Resins / Q000379:methods*; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors
chemical_list: D003188:Composite Resins; D003764:Dental Materials; D017220:Dentin-Bonding Agents; D008689:Methacrylates; D011108:Polymers; D011109:Polymethacrylic Acids; D011140:Polyurethanes; C529053:rebilda DC; C098757:1,12-dodecanediol dimethacrylate; C029824:urethane dimethacrylate luting resin; D017438:Bisphenol A-Glycidyl Methacrylate