Measuring polymerization shrinkage of dental composite by using PhS-OCT

Abstract

A method based on phase-sensitive optical coherence tomography (PhS-OCT) was developed to investigate the depth-resolved polymerization shrinkage of dental composites. The method uses optical coherence tomography (OCT) system to acquire the interference spectra during dental composite polymerization and then estimate the refractive index variation and shrinkage strain from the phase variations of the acquired spectrum. Since OCT is a tomographic imaging technique, PhS-OCT is also available for imaging full-field polymerization behavior inside dental composites. For validation, the polymerization processes of three dental composites, FiltekTM Z350, FiltekTM Z250 and FiltekTM P60, were monitored with PhS-OCT. The strain results agree with the reference values and the relative errors are less than 10%. In addition, the vitrification-point delayed curves were measured, revealing the vitrification-point retardation phenomenon. Finally, the flowable dental composite that polymerized inside the human artificial tooth was also measured, successfully demonstrating the depth-resolved full-field polymerization behavior inside the dental composite.