Dental Materials
Volume 25, Issue 3 , Pages 314-320, March 2009

3D mapping of polymerization shrinkage using X-ray micro-computed tomography to predict microleakage☆

  • Jirun Sun

      Affiliations

    • Polymers Division, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899-8543, USA
    • ,
  • Naomi Eidelman

      Affiliations

    • American Dental Association Foundation, Paffenbarger Research Center, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
    • ,
  • Sheng Lin-Gibson

      Affiliations

    • Polymers Division, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899-8543, USA
    • Corresponding Author InformationCorresponding author. Tel.: +1 301 975 6765; fax: +1 301 975 4977.

Received 25 April 2008; received in revised form 18 July 2008; accepted 18 July 2008.

Abstract 

Objectives

The objectives of this study were to (1) demonstrate X-ray micro-computed tomography (μCT) as a viable method for determining the polymerization shrinkage and microleakage on the same sample accurately and non-destructively, and (2) investigate the effect of sample geometry (e.g., C-factor and volume) on polymerization shrinkage and microleakage.

Methods

Composites placed in a series of model cavities of controlled C-factors and volumes were imaged using μCT to determine their precise location and volume before and after photopolymerization. Shrinkage was calculated by comparing the volume of composites before and after polymerization and leakage was predicted based on gap formation between composites and cavity walls as a function of position. Dye penetration experiments were used to validate μCT results.

Results

The degree of conversion (DC) of composites measured using FTIR microspectroscopy in reflectance mode was nearly identical for composites filled in all model cavity geometries. The shrinkage of composites calculated based on μCT results was statistically identical regardless of sample geometry. Microleakage, on the other hand, was highly dependent on the C-factor as well as the composite volume, with higher C-factors and larger volumes leading to a greater probability of microleakage. Spatial distribution of microleakage determined by μCT agreed well with results determined by dye penetration.

Significance

μCT has proven to be a powerful technique in quantifying polymerization shrinkage and corresponding microleakage for clinically relevant cavity geometries.

Keywords: Composites, Dental restorative material, FTIR microspectroscopy, Microleakage, Photopolymerization, Polymerization shrinkage, X-ray micro-computed tomography

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☆ Official contribution of the National Institute of Standards and Technology; not subject to copyright in the United States.

PII: S0109-5641(08)00201-7

doi:10.1016/j.dental.2008.07.010

Dental Materials
Volume 25, Issue 3 , Pages 314-320, March 2009

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