title: Comparison of polymerization contraction stresses between self- and light-curing composites.
abstract: OBJECTIVE
  The objective of this study was to examine the distributions and the magnitudes of the internal stresses in self- and a light-curing composite restorations resulting from polymerization shrinkage.
  
  
  METHODS
  Butt-joint box-shaped cavities (5.0 x 2.0 mm2, 2.0 mm in depth) prepared in composite molds were filled with either a self- or light-curing transparent resin composite. The restorations were cross-sectioned perpendicular to the longitudinal axes of the cavities and observed using polarizing microscopes. The principal stresses in the restorations, normal and shear stresses at the cavity wall were evaluated by photoelastic analysis.
  
  
  RESULTS
  The distributions of the principal stresses and the stresses generated at the cavity wall in both the self- and the light-curing composite restorations were similar. The maximum stress generated at the cavity wall in the light-curing composite restorations was twice as large as that seen in the self-curing restorations.
  
  
  CONCLUSIONS
  The results of this study indicated that the difference in the magnitude of the internal stresses between self- and light-curing composites was not related to the distribution of the stresses. The velocity of polymerization appeared to be the most important factor contributing to the magnitude of the internal stresses generated in the composite restorations in this study.
authors.affiliation: Department of Conservative Dentistry, Osaka University Faculty of Dentistry, Japan. kinomoto@dent.osaka-u.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Kinomoto
authors.forename: M
authors.initials: M
authors.lastname: Torii
authors.forename: F
authors.initials: F
authors.lastname: Takeshige
authors.forename: S
authors.initials: S
authors.lastname: Ebisu
mesh_terms: D001718:Birefringence; D003188:Composite Resins / Q000737:chemistry*; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D004548:Elasticity; D008027:Light; D008422:Materials Testing; D008859:Microscopy, Polarization; D011108:Polymers / Q000737:chemistry; D013314:Stress, Mechanical; D013997:Time Factors
chemical_list: D003188:Composite Resins; D011108:Polymers; C074539:Palfique Light