School of Dentistry


Minnesota Dental Research Center for Biomaterials and Biomechanics

Digital Image Correlation

Digital Image Correlation

A new method – image correlation method – has been developed to measure the polymerization shrinkage of dental composites. The method provides an optical, non-contact technique whereby free shrinkage of dental composites can be achieved during measurement. Also, instead of an overall average shrinkage value, this method can provide a full-field shrinkage strain measurement over the surface of the specimen, including the depth of cure.

The setup of the experiment includes a CCD camera, an illumination light, curing light and the specimen. The surface of the specimen facing the camera is spray-painted to produce patterns for ease of tracking the deformation.

Image Correlation - Picture 1

During polymerization, a series of images of the specimen are taken using the CCD camera. Then, the deformation of the specimen could be analyzed using specialist software to determine the shrinkage strain distribution on the specimen surface.

The picture below shows the shrinkage strain distribution within a composite specimen. The curing light was applied from the left. Red indicates more shrinkage.

Image Correlation - Picture 3

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  • Last modified on August 29, 2012