Measurement of microstrains across loaded resin–dentin interfaces using microscopic moiré interferometry

Wood, Judy D.; Sobolewski, Paul; Thakur, Varun; Arola, Dwayne; Nazari, Ahmed; Tay, Franklin R.; Pashley, David H.

doi:10.1016/j.dental.2007.10.005

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Volume 24, Issue 7 , Pages 859-866, July 2008

Measurement of microstrains across loaded resin–dentin interfaces using microscopic moiré interferometry

Judy D. Wood
- Mechanical Engineering Department, Clemson University, Clemson, SC, USA
Paul Sobolewski
- Mechanical Engineering Department, Clemson University, Clemson, SC, USA
Varun Thakur
- Mechanical Engineering Department, Clemson University, Clemson, SC, USA
Dwayne Arola
- Department of Mechanical Engineering, University of Maryland Baltimore County, Baltimore, MD, USA
Ahmed Nazari
- Department of Mechanical Engineering, University of Maryland Baltimore County, Baltimore, MD, USA
Franklin R. Tay
- Department of Oral Biology, School of Dentistry, Medical College of Georgia, 1120 15th Street, CL-2112, Augusta, GA 30912-1129, USA
David H. Pashley
- Department of Oral Biology, School of Dentistry, Medical College of Georgia, 1120 15th Street, CL-2112, Augusta, GA 30912-1129, USA
- Corresponding author. Tel.: +1 706 721 2033; fax: +1 706 721 6252.

Received 6 September 2007; received in revised form 10 October 2007; accepted 13 October 2007.

Abstract

Little is known about the mechanical behavior of resin–dentin interfaces during loading. The presence of relatively compliant hybrid and adhesive layers between stiffer dentin and resin composite should deform more during compressive loading.

Objective

The objective of this study was to measure changes in microstrain across bonded dentin interfaces in real time using a recently developed microscope moiré interferometer.

Method

This system used a miniature moiré interferometer, using two CCD cameras for simultaneous recording of longitudinal and transverse deformation fields, a piezotransducer for fringe shifting and use of a microscope objective with magnification up to 600×. Small beams (1mm×2mm×6mm) of moist resin-bonded dentin covered with cross-lined diffraction grating replica were placed in a miniature compression tester to allow controlled loading from 2 to 37N while imaging the interference fringe patterns.

Results

Resin-dentin interfaces created by bonding dentin with Single Bond/Z100, under compressive loading, exhibited comparatively large strains across the adhesive–hybrid interface. When the wrapped phase maps were unwrapped to permit conversion of fringe order to displacements, the 2-D profiles of strain fields revealed non-uniform strains across the adhesive interface. In the adhesive/hybrid layer zone, the negative strain was larger (i.e. −6000μɛ) than that seen in the adjacent resin composite or underlying mineralized dentin. The changes were elastic because they disappeared when the load was removed.