title: Consistency in the amount of linear polymerization shrinkage in syringe-type composites.
abstract: OBJECTIVE
  The purpose of this study was to investigate whether the composite resin in a syringe showed a consistent shrinkage through its content. Additionally, the amount of linear shrinkage was compared between materials.
  
  
  METHODS
  Five brands of syringe-type and one brand of carpule-type composite resins were used in this study. To each brand, two to three syringes were assigned. In the carpule-type composite, 15 carpules were used. The linear polymerization shrinkage was measured using a custom-made linometer. In this linometer, the amount of displacement of an aluminum disk, which was caused by the linear shrinkage of composite resin, was recorded by a computer every second for 90 s.
  
  
  RESULTS
  The syringe-type composites showed similar consistencies in the amount of linear shrinkage except one. The linear shrinkage of the carpule-type Tetric Ceram showed more consistency compared with syringe-type composites. The amount of linear polymerization shrinkage varied between materials.
  
  
  CONCLUSIONS
  This investigation demonstrates that the use of carpule-type composites is recommended instead of syringe-types, because of the consistency in its linear shrinkage. The custom-made linometer provides an effective way to study polymerization shrinkage.
authors.affiliation: Department of Conservative Dentistry, Yonsei University, Seoul, South Korea. suhghopark@yumc.yonsei.ac.kr
authors.forename: S H
authors.initials: SH
authors.lastname: Park
authors.forename: I
authors.initials: I
authors.lastname: Krejci
authors.forename: F
authors.initials: F
authors.lastname: Lutz
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry*; D008422:Materials Testing / Q000295:instrumentation; D014677:Pharmaceutical Vehicles; D011108:Polymers / Q000737:chemistry; D013594:Syringes
chemical_list: D003188:Composite Resins; D014677:Pharmaceutical Vehicles; D011108:Polymers