title: 3D volumetric displacement and strain analysis of composite polymerization.
abstract: OBJECTIVE
  The present study aimed at a better understanding of the internal shrinkage patterns within different cavity sizes.
  
  
  METHODS
  Ten cylindrical cavities in two sizes were filled with a flowable composite and scanned using X-ray micro-computed tomography (μ-CT) before filling, before and after polymerization. Three-dimensional (3D) non-rigid image registration was applied to sets of two subsequent μ-CT images, before and after polymerization in order to calculate the displacements and strains caused by polymerization shrinkage.
  
  
  RESULTS
  3D volumetric displacement analysis disclosed a main vertical component for both the small and large cavities, however in the latter the downward direction reversed to an upward direction from a depth of approximately 2mm due to debonding at the bottom. Air bubbles and voids in the restorations increased upon polymerization, causing a reverse in strain in the surrounding areas.
  
  
  CONCLUSIONS
  Polymerization-induced shrinkage stress in composite restorations cannot be measured directly. This exploratory study revealed more information on cavity-size dependent shrinkage patterns and opens the way to more extensive studies using different composite materials and varying geometric cavity configurations.
authors.affiliation: KU Leuven - BIOMAT, Department of Oral Health Sciences, KU Leuven (University of Leuven) & Dentistry, University Hospitals Leuven, Leuven, Belgium.
authors.forename: Annelies
authors.initials: A
authors.lastname: Van Ende
authors.affiliation: KU Leuven - BIOMAT, Department of Oral Health Sciences, KU Leuven (University of Leuven) & Dentistry, University Hospitals Leuven, Leuven, Belgium; Department of Materials Engineering, KU Leuven (University of Leuven), Leuven, Belgium.
authors.forename: Elke
authors.initials: E
authors.lastname: Van de Casteele
authors.affiliation: ESAT - PSI, iMINDS - MIC Medical Image Computing, KU Leuven (University of Leuven), Leuven, Belgium.
authors.forename: Maarten
authors.initials: M
authors.lastname: Depypere
authors.affiliation: KU Leuven - BIOMAT, Department of Oral Health Sciences, KU Leuven (University of Leuven) & Dentistry, University Hospitals Leuven, Leuven, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: De Munck
authors.affiliation: KU Leuven - BIOMAT, Department of Oral Health Sciences, KU Leuven (University of Leuven) & Dentistry, University Hospitals Leuven, Leuven, Belgium.
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.affiliation: ESAT - PSI, iMINDS - MIC Medical Image Computing, KU Leuven (University of Leuven), Leuven, Belgium.
authors.forename: Frederik
authors.initials: F
authors.lastname: Maes
authors.affiliation: Department of Materials Engineering, KU Leuven (University of Leuven), Leuven, Belgium.
authors.forename: Martine
authors.initials: M
authors.lastname: Wevers
authors.affiliation: KU Leuven - BIOMAT, Department of Oral Health Sciences, KU Leuven (University of Leuven) & Dentistry, University Hospitals Leuven, Leuven, Belgium. Electronic address: bart.vanmeerbeek@med.kuleuven.be.
authors.forename: Bart
authors.initials: B
authors.lastname: Van Meerbeek
mesh_terms: D003188:Composite Resins / Q000737:chemistry*; D003799:Dental Stress Analysis; D021621:Imaging, Three-Dimensional / Q000379:methods*; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D058105:Polymerization; D019279:Resin Cements / Q000737:chemistry; D012984:Software; D055114:X-Ray Microtomography
chemical_list: C438313:Clearfil SE Bond; D003188:Composite Resins; D019279:Resin Cements; C111840:flowable hybrid composite
keywords: Composite materials; Image registration; Micro-computed tomography; Shrinkage