A study of polymerization shrinkage kinetics using digital image correlation. Issue 4 (April 2015)

• Record Type: Journal Article
• Authors: Lau, Andrew; Li, Jianying; Heo, Young Cheul; Fok, Alex
• Is Part Of: Dental materials. Volume 31:Issue 4(2015)
• Page Start: 391
• Page End: 398
• Publication Date: 2015-04
• Subjects: Resin composite -- Polymerization shrinkage kinetics -- Digital image correlation (DIC) -- Inversely synchronized shutter -- Real-time measurement; Dentistry -- Periodicals; Dental materials -- Periodicals; 617.695
• DOI: 10.1016/j.dental.2015.01.001
• Languages: English
• ISSNs: 0109-5641

Abstract

Highlights: A technique for measuring real-time shrinkage strain in composite resin is proposed. An inversely synchronized external shutter allows for measurement during irradiation. Polymerization shrinkage kinetics parameters are calculated for Filtek LS and Z100. Full-field strain contour plots and shrinkage strain time series are presented. Abstract: Objective: To investigate the polymerization shrinkage kinetics of dental resin composites by measuring in real time the full-field shrinkage strain using a novel technique based on digital image correlation (DIC). Methods: Polymerization shrinkage in resin composite specimens (Filtek LS and Z100) was measured as a function of time and position. The main experimental setup included a CCD camera and an external shutter inversely synchronized to that of the camera. The specimens (2 mm × 4 mm × 5 mm) were irradiated for 40 s at 1200 mW/cm 2, while alternating image acquisition and obstruction of the curing light occurred at 15 fps. The acquired images were processed using proprietary software to obtain the full-field strain maps as a function of time. Results: Z100 showed a higher final shrinkage value and rate of development than LS. The final volumetric shrinkage for Z100 and LS were 1.99% and 1.19%, respectively. The shrinkage behavior followed an established shrinkage strain kinetics model. The corresponding characteristic time and reaction order exponent for LS and Z100 were calculated to be approximately 23 s and 0.84, and 14 s and 0.7, respectively, at a distance of 1.0 mm from the irradiated surface, the position where maximum shrinkage strain occurred. Thermal expansion from the exothermic reaction could have affected the accuracy of these parameters. Significance: The new DIC method using an inversely synchronized shutter provided realtime, full-field results that could aid in assessing the shrinkage strain kinetics of dental resin composites as a function of specimen depth. It could also help determine the optimal curing modes for dental resin composites.