@inproceedings{prahl11a,
  author = {Scott A. Prahl and Chelsea Y. Chen and Ville Ker{\"a}nen and Jack L. Ferracane},
  title = {Dynamic Optical Properties of Dental Composites},
  booktitle = {IADR/AADR/CADR 89th General Session},
  year = {2011, abstract only},
  volume = {90A},
  abstract = {Depth of cure of composites is a function of light transport through the material as it polymerizes. Objectives: To measure the scattering and absorption properties of unfilled resins and composites during photo-activated curing. Methods: The composite was 50:50 weight ratio of BIS-GMA:TEGDMA mixed with 25 wt\% strontium glass (avg.\ 2 micron). The total reflection and total transmission spectra of unfilled resin and composite samples (1\,mm thick $\times$ 25\,mm diameter) were measured during light curing (150mW/cm$^2$ for varied times). The composites were prepared with six different concentrations (0, 0.044, 0.058, 0.088, 0.116, and 0.175 wt\%) of camphorquinone (CQ). The refractive index of the unfilled resins with four equivalent CQ concentrations was measured during curing with an Abbe refractometer. Results: The absorption spectrum of uncured composite matched the absorption spectrum of CQ in unfilled resin. Uncured composite with and without CQ had the same scattering coefficient spectrum. The extinction coefficient of CQ in composite was 4:5$\pm$0.1mm$^{-1}$/(mol/L), equal to that of CQ in unfilled resin. The absorption and scattering coefficients at 469\,nm of composites with five different CQ concentrations decayed exponentially as a function of radiant exposure (figure). The refractive index increased with radiant exposure; Mie scattering calculations suggest that the index of refraction changes are responsible for scattering changes in the composite. Conclusion: The optical properties of a composite affect the light distribution within the composite during curing. Changes in absorption are caused by changes in CQ absorption. Changes in scattering are directly attributable to index of refraction changes of the resin during curing. Supported by NIH/NIDCR Grant 1R21-DE016758.},
}