title: Degree of conversion of nano-hybrid resin-based composites with novel and conventional matrix formulation.
abstract: OBJECTIVE
  This study aimed to determine the degree of conversion (DC) of two nano-hybrid resin-based composites (RBCs) with novel monomer composition based on dimer acid derivates (hydrogenated dimer acid) and tricyclodecane-urethane structure compared to three nano-hybrid materials containing conventional matrices. DC was evaluated at 0.1, 2, and 6 mm depth at varying irradiation times (10, 20, and 40 s) and layering techniques (bulk and incremental).
  
  
  METHODS
  DC was measured in real time by a Fourier transform infrared spectroscopy (FTIR) spectrometer with attenuated total reflectance accessory. The FTIR spectra were recorded on the bottom of the samples in real time for 5 min from photoinitiation. Results were compared using one- and multiple-way ANOVA, Tukey's HSD post hoc test (α = 0.05), and partial eta-squared statistic.
  
  
  RESULTS
  After 5 min of measurement, DC showed no significant difference by varying cure time for specimens of 0.1 mm thickness. At 2 mm depth, the DC significantly increased after a cure time of 20 s compared to 10 s, remaining equal after 40 s of irradiation. At 6 mm depth, bulk curing showed significantly lower DC compared to incremental curing for all polymerization times. Specimen geometry revealed a strong effect on DC (η (2) = 0.90) followed by curing time (η (2) = 0.39).
  
  
  CONCLUSIONS
  The RBCs containing the dimer acid and tricyclodecane-urethane structure showed a relatively low decrease of DC with increasing incremental thickness compared to the conventionally formulated materials. The former reached the highest DC among the tested materials.
  
  
  CONCLUSIONS
  For the tested RBCs, increments of 2 mm and irradiation time of at least 20 s may be recommended for clinical practice. The two materials containing novel monomer composition might be applied for enlarged increments because of the low decrease of DC they demonstrated for 6-mm increments.
authors.affiliation: Department of Restorative Dentistry, Dental School of Ludwig-Maximilians-University, Goethestr. 70, 80336 Munich, Germany.
authors.forename: Karina E
authors.initials: KE
authors.lastname: Frauscher
authors.forename: Nicoleta
authors.initials: N
authors.lastname: Ilie
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002626:Chemistry, Pharmaceutical; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects; D043822:Cyclodecanes / Q000737:chemistry / Q000528:radiation effects; D003764:Dental Materials / Q000737:chemistry* / Q000528:radiation effects; D006801:Humans; D006865:Hydrogenation; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry / Q000528:radiation effects; D053761:Nanocomposites / Q000737:chemistry* / Q000528:radiation effects; D011092:Polyethylene Glycols / Q000737:chemistry; D058105:Polymerization; D011109:Polymethacrylic Acids / Q000737:chemistry; D011140:Polyurethanes / Q000737:chemistry / Q000528:radiation effects; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D013997:Time Factors
chemical_list: D003188:Composite Resins; D043822:Cyclodecanes; D003764:Dental Materials; D008689:Methacrylates; C551012:N'Durance composite resin; D011109:Polymethacrylic Acids; D011140:Polyurethanes; C510232:Simile composite resin; C507210:premise composite resin; C029824:urethane dimethacrylate luting resin; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate