title: The effect of combining photoinitiator systems on the color and curing profile of resin-based composites.
abstract: To evaluate the effect of combining camphorquinone (CQ) and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) on the color and curing profile of resin-based composites.
  
  
  
  Experimental composites were produced with different CQ and TPO molar concentrations: CQ-only, 3CQ:1TPO, 1CQ:1TPO, 1CQ:3TPO, and TPO-only. Polywave LED was characterized using a beam profiler. Block-shaped samples (5mm×5mm×3mm depth) were cured in a custom-designed mold with a polywave LED positioned to compare the regions exposed to the 420-495nm and 380-420nm LED emittances. To map the cure profile, degree of conversion (DC) of longitudinal cross-sections from each block were evaluated by FT-NIR. Color, light-transmittance and light-absorption during curing were evaluated on specimens 1-3mm thick. Data were analyzed using ANOVA/Tukey's test (α=0.05; β=0.2).
  
  
  
  Though the polywave LED beam profile was non-uniform, up to a depth of 2mm no differences in DC were found among the composites containing CQ with TPO added up to 50%, regardless of the position under the curing tip. Composites with higher TPO concentration showed a decrease in DC beginning with a depth of 1mm, while composites with higher or similar CQ concentrations did not show decreased DC until a depth of 3mm. Higher TPO concentration reduced initial yellowness and color change after curing; and lower CQ concentration decreased light-absorption at greater depths.
  
  
  
  The combination of CQ with TPO added up to 50% reduced the yellowness and color change of composites after curing without affecting cure efficiency up to a depth of 2mm.
authors.affiliation: Department of Biomaterials, School of Dentistry, Oregon Health & Science University, 2730 SW Moody Avenue, 27201 Portland, OR, USA; Department of Restorative Dentistry, Piracicaba Dental School, State University of Campinas, Av. Limeira, 900, 13414-903 Piracicaba, SP, Brazil. Electronic address: oliveira.day@icloud.com.
authors.forename: Dayane Carvalho Ramos Salles
authors.initials: DCRS
authors.lastname: de Oliveira
authors.affiliation: Department of Biomaterials, School of Dentistry, Oregon Health & Science University, 2730 SW Moody Avenue, 27201 Portland, OR, USA; Department of Restorative Dentistry, Piracicaba Dental School, State University of Campinas, Av. Limeira, 900, 13414-903 Piracicaba, SP, Brazil.
authors.forename: Mateus Garcia
authors.initials: MG
authors.lastname: Rocha
authors.affiliation: Department of Prosthesis and Dental Materials, School of Dentistry, Federal University of Rio de Janeiro, Avenida Brigadeiro Trompowski, s/n(o), Ilha do Fundão, Cidade Universitária, 21949-900 Rio de Janeiro, RJ, Brazil.
authors.forename: Ivo Carlos
authors.initials: IC
authors.lastname: Correa
authors.affiliation: Department of Restorative Dentistry, Piracicaba Dental School, State University of Campinas, Av. Limeira, 900, 13414-903 Piracicaba, SP, Brazil.
authors.forename: Américo Bortolazzo
authors.initials: AB
authors.lastname: Correr
authors.affiliation: Department of Biomaterials, School of Dentistry, Oregon Health & Science University, 2730 SW Moody Avenue, 27201 Portland, OR, USA.
authors.forename: Jack L
authors.initials: JL
authors.lastname: Ferracane
authors.affiliation: Department of Restorative Dentistry, Piracicaba Dental School, State University of Campinas, Av. Limeira, 900, 13414-903 Piracicaba, SP, Brazil.
authors.forename: Mario Alexandre Coelho
authors.initials: MAC
authors.lastname: Sinhoreti
mesh_terms: D002164:Camphor / Q000031:analogs & derivatives; D003116:Color; D003188:Composite Resins; D008027:Light; D008422:Materials Testing; D010720:Phosphines
chemical_list: C520678:(2,4,6-trimethylbenzoyl) diphenylphosphine oxide; D003188:Composite Resins; D010720:Phosphines; D002164:Camphor; C553149:camphorquinone
keywords: Color; Cure profile; Degree of conversion; Light transmittance; Photoinitiator