title: Dielectric analysis of depth dependent curing behavior of dental resin composites.
abstract: OBJECTIVE
  The aim of this study is to investigate depth dependent changes of polymerization process and kinetics of visible light-curing (VLC) dental composites in real-time. The measured quantity - "ion viscosity" determined by dielectric analysis (DEA) - provides the depth dependent reaction rate which is correlated to the light intensity available in the corresponding depths derived from light transmission measurements.
  
  
  METHODS
  The ion viscosity curves of two composites (VOCO Arabesk Top and Grandio) were determined during irradiation of 40s with a light-curing unit (LCU) in specimen depths of 0.5/0.75/1.0/1.25/1.5/1.75 and 2.0mm using a dielectric cure analyzer (NETZSCH DEA 231 with Mini IDEX sensors). The thickness dependent light transmission was measured by irradiation composite specimens of various thicknesses on top of a radiometer setup.
  
  
  RESULTS
  The shape of the ion viscosity curves depends strongly on the specimen thickness above the sensor. All curves exhibit a range of linear time dependency of the ion viscosity after a certain initiation time. The determined initiation times, the slopes of the linear part of the curves, and the ion viscosities at the end of the irradiation differ significantly with depth within the specimen. The slopes of the ion viscosity curves as well as the light intensity values decrease with depth and fit to the Lambert-Beer law. The corresponding attenuation coefficients are determined for Arabesk Top OA2 to 1.39mm(-1) and 1.48mm(-1), respectively, and for Grandio OA2 with 1.17 and 1.39mm(-1), respectively. For thicknesses exceeding 1.5mm a change in polymerization behavior is observed as the ion viscosity increases subsequent to the linear range indicating some kind of reaction acceleration.
  
  
  CONCLUSIONS
  The two VLC composites and different specimen thicknesses discriminate significantly in their ion viscosity evolution allowing for a precise characterization of the curing process even with respect to the polymerization mechanism.
authors.affiliation: Faculty of Technology, Department of Production Engineering, Tomas Bata University in Zlín, Zlín, Czech Republic; Department of Natural Sciences, Bonn-Rhine-Sieg University of Applied Sciences, Rheinbach, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Steinhaus
authors.affiliation: Department of Natural Sciences, Bonn-Rhine-Sieg University of Applied Sciences, Rheinbach, Germany.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Moeginger
authors.affiliation: Department of Natural Sciences, Bonn-Rhine-Sieg University of Applied Sciences, Rheinbach, Germany.
authors.forename: Mandy
authors.initials: M
authors.lastname: Grossgarten
authors.affiliation: Regensburg University Medical Center, Department of Prosthetic Dentistry, Regensburg, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Rosentritt
authors.affiliation: Faculty of Technology, Department of Production Engineering, Tomas Bata University in Zlín, Zlín, Czech Republic. Electronic address: hausnerova@ft.utb.cz.
authors.forename: Berenika
authors.initials: B
authors.lastname: Hausnerova
mesh_terms: D003188:Composite Resins; D055117:Curing Lights, Dental; D001840:Dental Bonding
chemical_list: D003188:Composite Resins
keywords: Composite resin; Curing depth; Dental material; Dielectric analysis; Light attenuation; Real-time measurement; Restorative composite; Visible light-curing