title: Simultaneous measurement of polymerization stress and curing kinetics for photo-polymerized composites with high filler contents.
abstract: OBJECTIVE
  Photopolymerized composites are used in a broad range of applications with their performance largely directed by reaction kinetics and contraction accompanying polymerization. The present study was to demonstrate an instrument capable of simultaneously collecting multiple kinetics parameters for a wide range of photopolymerizable systems: degree of conversion (DC), reaction exotherm, and polymerization stress (PS).
  
  
  METHODS
  Our system consisted of a cantilever beam-based instrument (tensometer) that has been optimized to capture a large range of stress generated by lightly-filled to highly-filled composites. The sample configuration allows the tensometer to be coupled to a fast near infrared (NIR) spectrometer collecting spectra in transmission mode.
  
  
  RESULTS
  Using our instrument design, simultaneous measurements of PS and DC are performed, for the first time, on a commercial composite with ≈80% (by mass) silica particle fillers. The in situ NIR spectrometer collects more than 10 spectra per second, allowing for thorough characterization of reaction kinetics. With increased instrument sensitivity coupled with the ability to collect real time reaction kinetics information, we show that the external constraint imposed by the cantilever beam during polymerization could affect the rate of cure and final degree of polymerization.
  
  
  CONCLUSIONS
  The present simultaneous measurement technique is expected to provide new insights into kinetics and property relationships for photopolymerized composites with high filler content such as dental restorative composites.
authors.affiliation: Biosystems and Biomaterials Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, United States.
authors.forename: Zhengzhi
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Department of Chemistry, Penn State University - York Campus, York, PA 17403, United States.
authors.forename: Forrest A
authors.initials: FA
authors.lastname: Landis
authors.affiliation: American Dental Association Foundation, Dr. Anthony Volpe Research Center, National Institute of Standards and Technology, Gaithersburg, MD 20899, United States.
authors.forename: Anthony A M
authors.initials: AA
authors.lastname: Giuseppetti
authors.affiliation: Biosystems and Biomaterials Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, United States.
authors.forename: Sheng
authors.initials: S
authors.lastname: Lin-Gibson
authors.affiliation: Biosystems and Biomaterials Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, United States. Electronic address: martin.chiang@nist.gov.
authors.forename: Martin Y M
authors.initials: MY
authors.lastname: Chiang
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry / Q000528:radiation effects; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects; D003764:Dental Materials / Q000737:chemistry* / Q000528:radiation effects; D004867:Equipment Design; D005898:Glass / Q000737:chemistry / Q000528:radiation effects; D007700:Kinetics; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing / Q000295:instrumentation; D058105:Polymerization; D017550:Spectroscopy, Fourier Transform Infrared; D019265:Spectroscopy, Near-Infrared / Q000295:instrumentation; D013314:Stress, Mechanical; D013696:Temperature; D013821:Thermometers
chemical_list: D000538:Aluminum Silicates; D003188:Composite Resins; D003764:Dental Materials; C000590993:TPH Spectra
keywords: Degree of conversion; Dental composites; Infrared spectroscopy; Polymerization shrinkage stress; Tensometer