title: Development of a low-color, color stable, dual cure dental resin.
abstract: Dual-cure (DC) resins are mainly used as cements due to high initial color (generally yellow) and large color shift (ΔE*) after polymerization as compared to light-cured resins. However, even as cements, this color shift is clinically unacceptable, especially when used to cement thin veneers.
  
  
  OBJECTIVE
  To develop a novel DC initiator system with both lower initial color (less yellow, i.e., whiter) and smaller ΔE*.
  
  
  METHODS
  The effect of using an allyl thiourea (T)/cumene hydroperoxide (CH) self-cure (SC) initiator system in combination with a photo-co-initiator, p-octyloxy-phenyl-phenyl iodonium hexafluoroantimonate (OPPI), in a commercial DC resin cement (PermaFlo DC, Ultradent Products, Inc.) was investigated. Initial color and ΔE* were assessed for 6 weeks in vitro under accelerated aging conditions (75°C water bath). Rockwell15T hardness was used to assess degree of cure (DoC) and the three-point bending test was used to assess mechanical properties.
  
  
  RESULTS
  PermaFlo DC (control) was significantly harder than all experimental groups without OPPI but had up to three times higher initial color and four times greater color shift (ΔE*=27 vs. 8). With OPPI, hardness in the experimental groups increased significantly and several were comparable to the controls. Initial color and ΔE* increased slightly (ΔE*=9), but was still 3 times less than that of PermaFlo DC. DC samples containing OPPI had comparable modulus and ultimate transverse strengths to those of the controls.
  
  
  CONCLUSIONS
  DC resins that use the T/CH initiator system are weaker but have extremely low color and ΔE*. The addition of OPPI increases DoC and mechanical properties to clinically acceptable levels and maintains extremely low color and ΔE*.
  
  
  CONCLUSIONS
  With this novel initiator system, DC resins potentially can now have comparable color and color stability to light-cure resins and be used in broader esthetic dental applications to improve color stability and reduce shrinkage stress in restorative composites.
authors: Division of Research, Department of Comprehensive Dentistry, University of Texas Health Science Center San Antonio, 7703 Floyd Curl Drive, San Antonio, TX 78229-3900, USA.
authors: James D
authors: JD
authors: Oei
authors: Maged
authors: M
authors: Mishriky
authors: Nasser
authors: N
authors: Barghi
authors: H Ralph
authors: HR
authors: Rawls
authors: H Lee
authors: HL
authors: Cardenas
authors: Rene
authors: R
authors: Aguirre
authors: Kyumin
authors: K
authors: Whang
mesh_terms: D000704:Analysis of Variance; D003116:Color; D006244:Hardness; D006861:Hydrogen Peroxide / Q000737:chemistry*; D055115:Light-Curing of Dental Adhesives; D009861:Onium Compounds / Q000737:chemistry*; D058567:Photoinitiators, Dental / Q000138:chemical synthesis*; D058105:Polymerization; D019279:Resin Cements / Q000138:chemical synthesis*; D055116:Self-Curing of Dental Resins; D013890:Thiourea / Q000737:chemistry*
chemical_list: D009861:Onium Compounds; D058567:Photoinitiators, Dental; D019279:Resin Cements; D006861:Hydrogen Peroxide; D013890:Thiourea