title: [Evaluation of laser triangulation method for measurement of post-gel shrinkage and post-vitrification shrinkage in composite resins].
abstract: OBJECTIVE
  To employ a laser triangulation method for measuring post-gel and post-vitrification polymerization shrinkage of composite resins.
  
  
  METHODS
  A novel experimental set-up capable of measuring real-time shrinkage strain was utilized. Total shrinkage of the five composite resins was measured. The measurements of post-gel and post-vitrification linear shrinkage as a function of the gel-point and vitrification transition point were also carried out in the study.
  
  
  RESULTS
  Gel point of the five composite resins ranged from 0.77 s to 1.59 s, while vitrification transition point ranged from 1.99 s to 6.33 s. Post-gel shrinkage ranged from 33.35 µm to 53.18 µm and post-vitrification shrinkage ranged from 16.43 µm to 30.58 µm. Total shrinkage ranged from 39.25 µm to 64.84 µm. Significant differences in the gel point and vitrification transition point among the five composite resins were found (P < 0.01). Significant differences in the post-gel shrinkage, post-vitrification shrinkage and total shrinkage among the five composite resins were found (P < 0.01). The ranking of post-gel and post-vitrification shrinkage of these composite was different from that of their total shrinkage.
  
  
  CONCLUSIONS
  Laser triangulation method is suitable for measuring clinically significant post-gel and post-vitrification shrinkage.
authors.affiliation: Department of Dental Materials, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors.forename: Bo-tao
authors.initials: BT
authors.lastname: Gao
authors.forename: Gang
authors.initials: G
authors.lastname: Zheng
authors.forename: Hong
authors.initials: H
authors.lastname: Lin
authors.forename: Yong-xiang
authors.initials: YX
authors.lastname: Xu
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D004548:Elasticity; D005782:Gels / Q000737:chemistry; D007834:Lasers; D008422:Materials Testing; D044367:Phase Transition; D058105:Polymerization; D013314:Stress, Mechanical; D013499:Surface Properties; D058989:Vitrification
chemical_list: C084111:Charisma composite resin; D003188:Composite Resins; D005782:Gels; C039734:Durafill