title: Kinetics of polymerization and contraction stress development in self-adhesive resin cements.
abstract: OBJECTIVE
  The aim of the study was to evaluate the contraction stress, microhardness and polymerization kinetics of three self-adhesive cements vs. conventional dual-cure resin cement.
  
  
  METHODS
  Cements tested were: RelyX Unicem (3M ESPE, St. Paul, MN, USA), MaxCem Elite (Kerr, Orange, CA, USA), Clearfil SA Cement (Kuraray, Tokyo, Japan) and Duolink (Bisco Inc., Schaumburg, IL, USA). Cements were irradiated with a LED-curing unit (bluephase, IvoclarVivadent) for 20 or 40 s and the contraction forces (N) generated during polymerization were continuously recorded for 6 h with a universal testing machine. Polymerization kinetics were monitored using micro-Raman spectroscopy and degree of conversion was calculated. Vickers microhardness was also recorded. All measurements were performed at 10 min and 6h. Data were statistically analyzed by three-way ANOVA with repeated measures and Tukey's post hoc test (α=0.05).
  
  
  RESULTS
  Irrespective of exposure time, stress analysis ranked in the following order: Clearfil SA Cement<MaxCem<RelyX Unicem≤Duolink (p<0.05). Stress was correlated with microhardness values (p<0.05). Kinetic curves showed that maximum degree of conversion was attained more quickly than maximum stress after light activation.
  
  
  CONCLUSIONS
  The conventional resin-based cement showed higher stress values than the self-adhesive cements. The results were material-dependent and probably correlated to the composition of each material.
authors: Department of Medical Sciences, University of Trieste, Italy.
authors: A
authors: A
authors: Frassetto
authors: C O
authors: CO
authors: Navarra
authors: G
authors: G
authors: Marchesi
authors: G
authors: G
authors: Turco
authors: R
authors: R
authors: Di Lenarda
authors: L
authors: L
authors: Breschi
authors: J L
authors: JL
authors: Ferracane
authors: M
authors: M
authors: Cadenaro
mesh_terms: D000704:Analysis of Variance; D003799:Dental Stress Analysis / Q000295:instrumentation / Q000379:methods*; D006244:Hardness / Q000528:radiation effects*; D008422:Materials Testing / Q000295:instrumentation / Q000379:methods*; D058105:Polymerization / Q000528:radiation effects; D019279:Resin Cements / Q000737:chemistry* / Q000493:pharmacokinetics / Q000528:radiation effects
chemical_list: D019279:Resin Cements