@inproceedings{prahl11b,
  author = {Scott A. Prahl},
  title = {Using Light To Quantitatively Monitor Composites During Photocuring},
  booktitle = {European Chapter of the Tissue Engineering and Regenerative Medicine International Society},
  year = {2011, abstract only},
  volume = {},
  abstract = {\textbf{Introduction}: Photocured polymers are widely used in dental applications and as tissue engineering constructs. The physical and mechanical properties of the composite change during curing; the appearance of the composite also changes. This talk summarizes insights gained into the photopolymerization process by quantitatively monitoring appearance.\\[3mm] \textbf{Methods}: The composite were 50:50 weight ratio of BIS-GMA:TEGDMA mixed with various sizes of strontium glass as filler and different concentrations (0--0.175 wt\%) of camphorquinone (CQ). The curing irradiance was 100--400\,mW/cm2. Total reflection and total transmission spectra of filled and unfilled 1\,mm thick composite samples were measured before and after curing. Total transmittance was measured every 50\,ms from 400--900\,nm during curing. The refractive index of the unfilled resins was also measured during curing using an Abb{\'e} refractometer. Before and after reflectance and transmittance values were converted to scattering and absorption properties using the inverse adding-doubling technique. Transmission data during curing was analyzed by using red light to monitor changes in scattering and blue light to assess changes in absorption.\\[3mm] \textbf{Results}: The absorption spectrum of uncured composite measured matched the absorption spectrum of CQ in unfilled resin. Uncured composite with and without CQ had the same scattering coefficient spectrum. The absorption and scattering coefficient at 469\,nm of composites with five different CQ concentrations decayed exponentially as a function of radiant exposure. The refractive index increased with radiant exposure.\\[3mm] \textbf{Conclusion}: The optical properties of a composite affect the light distribution within the composite during curing. Changes is absorption are caused by changes in CQ absorption. Mie scattering calculation indicate that scattering changes are directly attributable to index of refraction changes of the resin during curing.},
}