title: Study of visible light activated polymerization in BisGMA-TEGDMA monomers with Type 1 and Type 2 photoinitiators using Raman spectroscopy.
abstract: The goal of the study was to characterize the efficiency of polymerization of Type 1 and Type 2 initiators for visible light cure of a BisGMA-TEGDMA monomer mixture.
  
  
  
  Raman spectroscopy was used to follow conversion during polymerization of a BisGMA-TEGDMA mixture using a Type I photoinitiator diphenyl(2,4,6 dimethylbenzoyl)phosphine oxide (TPO) and a Type II photoinitiator camphorquinone (CQ) and an amine, both initiators at 0.5wt.%. Different light exposure times and storage times after light curing were used as variables.
  
  
  
  There was a significant difference between the relative exposure times of TPO and CQ/amine (5s for TPO vs. 20s for CQ/Amine) for attaining maximum % conversion (78% in TPO vs. 65% in CQ/Amine). There was also a significant difference in the effect of storage time (no effect in TPO vs. increased % conversion with CQ/Amine). These effects are attributed to differences in the rate controlling steps of free radical generation in Type 1/Type 2 initiators, and the potential for radiative and non-radiative energy losses in CQ/Amine in its excited state.
  
  
  
  The results confirm that photo-polymerization of BisGMA is much more efficient with TPO than with CQ/amine. Both exposure and storage times were important variables in CQ/amine, but not in TPO.
  
  
  
  TPO photolysis generates significantly more free radicals with potentially very little radiative and non-radiative energy loss in comparison with CQ/amine. The resulting improved monomer conversion is of major importance in resisting chemical and mechanical degradation and preventing toxicological adverse effects.
authors.affiliation: Department of Restorative Dentistry, Rutgers School of Dental Medicine, Newark, NJ 07103, United States. Electronic address: vaidyatk@hotmail.com.
authors.forename: Tritala K
authors.initials: TK
authors.lastname: Vaidyanathan
authors.affiliation: Department of Restorative Dentistry, Rutgers School of Dental Medicine, Newark, NJ 07103, United States.
authors.forename: Jayalakshmi
authors.initials: J
authors.lastname: Vaidyanathan
authors.affiliation: Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology (SCTIMST), Thiruvananthapuram, India.
authors.forename: Pambadikandathil Philipose
authors.initials: PP
authors.lastname: Lizymol
authors.affiliation: Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology (SCTIMST), Thiruvananthapuram, India.
authors.forename: Saraswathy
authors.initials: S
authors.lastname: Ariya
authors.affiliation: Biomedical Technology Wing, Sree Chitra Tirunal Institute for Medical Sciences and Technology (SCTIMST), Thiruvananthapuram, India.
authors.forename: Kalliyana Venketeswaran
authors.initials: KV
authors.lastname: Krishnan
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate; D003188:Composite Resins; D055117:Curing Lights, Dental; D008027:Light; D008422:Materials Testing; D011092:Polyethylene Glycols; D058105:Polymerization; D011109:Polymethacrylic Acids; D013059:Spectrum Analysis, Raman
chemical_list: D003188:Composite Resins; D011109:Polymethacrylic Acids; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate
keywords: % Conversion; BisGMA based monomer; Raman spectroscopy; Type 1 and Type 2 initiators