title: [Polymerization shrinkage by 4 different types of dental materials].
abstract: Forces developing during polymerisation of dental resins cause tension in the material to increase, with possible subsequent distortion of the bond. This study was undertaken to determine and compare polymerisation shrinkage in four different light-cured dental resins. A modified dilatometer was used to determine volumetric changes during polymerisation in 60 seconds of Z250 and Filtec flow from 3 M, and DyractAP and Dyract from Dentsply. Statistical analysis revealed that Dyract Flow shrinks significantly more (P < 0.05) during polymerisation in the first, as well as the last 10 seconds when compared with the other three materials and Z250 significantly less. An increase in the amount of fillers in the composition of the material leads to a decrease in polymerisation shrinkage, while an increase in the monomer concentration gives rise to more shrinkage. Stress, that builds up during the polymerisation process, is reduced by the elasticity of the material. The shrinkage of the flowables is therefore counteracted by their reduced rigidity.
authors.affiliation: Departement Toegepaste Mondheelkunde, Skool vir Mondheelkunde, Fakulteit Gesondheidswetenskappe, Universiteit van Stellenbosch, Tygerberg, Suid-Afrika. tgo@sun.ac.za
authors.forename: T G
authors.initials: TG
authors.lastname: Oberholzer
authors.forename: S R
authors.initials: SR
authors.lastname: Grobler
authors.forename: R J
authors.initials: RJ
authors.lastname: Rossouw
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D020770:Compomers / Q000737:chemistry*; D003188:Composite Resins / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D004548:Elasticity; D006801:Humans; D008027:Light; D008689:Methacrylates / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry; D017640:Silicates / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D013223:Statistics as Topic; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors; D015040:Zirconium / Q000737:chemistry
chemical_list: D000538:Aluminum Silicates; D020770:Compomers; D003188:Composite Resins; D003764:Dental Materials; C088486:Dyract; C444701:Filtek Z250; D008689:Methacrylates; D011108:Polymers; D011109:Polymethacrylic Acids; D011140:Polyurethanes; D017640:Silicates; C029824:urethane dimethacrylate luting resin; C020946:triethylene glycol dimethacrylate; C041979:2,2-bis-(4-(2-methacryloxyethoxy)phenyl)propane; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; D012822:Silicon Dioxide; D015040:Zirconium