title: Assessment of curing behavior of light-activated dental composites using intensity correlation based multiple reference optical coherence tomography.
abstract: OBJECTIVE
  Monitoring the curing kinetics of light-activated resin is a key area of research. These resins are used in restorative applications and particularly in dental applications. They can undergo volumetric shrinkage due to poor control of the depth dependent curing process, modulated by the intensity and duration of the curing light source. This often results in the formation of marginal gaps, causing pain and damage to the restoration site. In this study, we demonstrate the capabilities of a correlation method applied using a multiple references optical coherence tomography (MR-OCT) architecture to monitor the curing of the resin.
  
  
  METHODS
  A MR-OCT system is used in this study to monitor the curing of the resin. The system operates at the center wavelength of 1310 nm with an A-scan rate of 1200 A-scans per second. The axial and lateral resolution of the system is ∼13 μm and ∼27 μm. The method to determine the intensity correlation between adjacent B-frames is based on the Pearson correlation coefficient for a region of interest. Calculating the correlation coefficient for multiple B-frames related to the first B-frame at regular spaced time points, shows for a noncured resin a reduction of the correlation coefficient over time due to Brownian motion. The time constant of the reduction of the correlation value is a measure for the progress of the polymerization during LED light irradiation of the resin. The proposed approach is potentially a low-cost, powerful and unique optical imaging modality for measuring the curing behavior of dental resin and other resins, coatings, and adhesives in medical and industrial applications.
  
  
  RESULTS
  To demonstrate the proposed method to monitor the curing process, a light-activated resin composite from GRADIA DIRECT ANTERIOR (GC Corporation, Japan) is studied. The curing time of resin was measured and monitored as a function of depth. The correlation coefficient method is highly sensitive to Brownian motion. The process of curing results in a change in intensity as measured by the MR-OCT signal and hence can be monitored using this method.
  
  
  CONCLUSIONS
  These results show that MR-OCT has the potential to measure the curing time and monitor the curing process as a function of depth. Moreover, MR-OCT as a product has potential to be compact, low-cost and to fit into a smartphone. Using such a device for monitoring the curing of the resin will be suitable for dentists in stationary and mobile clinical settings.
authors.affiliation: Tissue Optics and Microcirculation Imaging Group, School of Physics, National University of Ireland, Galway, Ireland.
authors.forename: Roshan
authors.initials: R
authors.lastname: Dsouza
authors.affiliation: Tissue Optics and Microcirculation Imaging Group, School of Physics, National University of Ireland, Galway, Ireland.
authors.forename: Hrebesh
authors.initials: H
authors.lastname: Subhash
authors.affiliation: Tissue Optics and Microcirculation Imaging Group, School of Physics, National University of Ireland, Galway, Ireland.
authors.forename: Kai
authors.initials: K
authors.lastname: Neuhaus
authors.affiliation: Smiles Dental, 21 Middle Street, Galway, Ireland.
authors.forename: Ramakrishna
authors.initials: R
authors.lastname: Kantamneni
authors.affiliation: Tissue Optics and Microcirculation Imaging Group, School of Physics, National University of Ireland, Galway, Ireland.|Compact Imaging Ireland Ltd., Galway, Ireland.
authors.forename: Paul M
authors.initials: PM
authors.lastname: McNamara
authors.affiliation: Compact Imaging, Inc., 897 Independence Ave., Suite 5B, Mountain View, California, 94043.
authors.forename: Josh
authors.initials: J
authors.lastname: Hogan
authors.affiliation: Compact Imaging, Inc., 897 Independence Ave., Suite 5B, Mountain View, California, 94043.
authors.forename: Carol
authors.initials: C
authors.lastname: Wilson
authors.affiliation: Tissue Optics and Microcirculation Imaging Group, School of Physics, National University of Ireland, Galway, Ireland.|Royal College of Surgeons (RCSI), Dublin, Ireland.
authors.forename: Martin
authors.initials: M
authors.lastname: Leahy
mesh_terms: D003188:Composite Resins / Q000493:pharmacokinetics*; D055117:Curing Lights, Dental; D041623:Tomography, Optical Coherence
chemical_list: D003188:Composite Resins
keywords: CD/DVD ROM pickup head; correlation coefficient; light-activated resin; multiple reference optical coherence tomography