title: Micro-Raman spectroscopic analysis of the degree of conversion of composite resins containing different initiators cured by polywave or monowave LED units.
abstract: OBJECTIVE
  To determine the degree of conversion (DC) over 48 h post-curing of resin mixtures containing trimethylbenzoyl-diphenylphosphine oxide (TPO) initiator cured by a polywave or a monowave LED light-curing unit (LCU).
  
  
  METHODS
  In resin mixtures based on equal weight percent (wt%) of BisGMA and TEGDMA the following initiators were added: 0.2 wt% camphorquinone (CQ)+0.8 wt% ethyl-4-dimethylaminobenzoate (EDMAB) (Group 1); 1 wt% TPO (Group 2) and 0.1 wt% CQ+0.4 wt% EDMAB+0.5 wt% TPO (Group 3). Half of the samples in each group (n=5) were cured using a polywave (bluephase(®) G2, Ivoclar Vivadent) or a monowave LED LCU (bluephase(®), Ivoclar Vivadent). The DC was measured using micro-Raman spectroscopy within 5 min and then 1, 3, 6, 24 and 48 h post-irradiation. The data were analysed using general linear model and two-way ANOVA for the factors 'time', 'material', 'surface' and 'LCU' at α=0.05.
  
  
  RESULTS
  The initial DC values obtained upon light curing remained similar over a 48 h period. bluephase(®) G2 produced the highest DC in Group 2 followed by Group 3, and Group 1. bluephase(®) resulted in the highest DC in Group 1, followed by Group 2 and Group 3 (p<0.05).
  
  
  CONCLUSIONS
  Unfilled resin materials containing both TPO- and CQ-amine initiators are effectively cured using bluephase(®) G2. Resin mixture with the same wt% of initiators is better cured when TPO is the only initiator, compared to CQ-amine only or combined TPO and CQ-amine system. After initial light cure, no additional conversion of uncured monomers was detected in an unfilled resin material over 48 h at 37°C.
authors.affiliation: University of Belgrade, School of Dental Medicine, Department of Restorative Odontology and Endodontics, Rankeova 4, Belgrade, Serbia.
authors.forename: Vesna
authors.initials: V
authors.lastname: Miletic
authors.forename: Ario
authors.initials: A
authors.lastname: Santini
mesh_terms: D010129:4-Aminobenzoic Acid / Q000737:chemistry; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002164:Camphor / Q000031:analogs & derivatives / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D055117:Curing Lights, Dental / Q000145:classification*; D003764:Dental Materials / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing; D010720:Phosphines / Q000737:chemistry; D058567:Photoinitiators, Dental / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry; D058105:Polymerization; D011109:Polymethacrylic Acids / Q000737:chemistry; D011829:Radiation Dosage; D013056:Spectrophotometry, Ultraviolet; D013059:Spectrum Analysis, Raman / Q000379:methods; D013499:Surface Properties; D013997:Time Factors; D062366:para-Aminobenzoates
chemical_list: C520678:(2,4,6-trimethylbenzoyl) diphenylphosphine oxide; D003188:Composite Resins; D003764:Dental Materials; D010720:Phosphines; D058567:Photoinitiators, Dental; D011109:Polymethacrylic Acids; C523330:ethyl 4-N,N-dimethylaminobenzoate; D062366:para-Aminobenzoates; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; D002164:Camphor; C553149:camphorquinone; D010129:4-Aminobenzoic Acid