title: The effect of irradiation wavelength bandwidth and spot size on the scraping depth and temperature rise in composite exposed to an argon laser or a conventional quartz-tungsten-halogen source.
abstract: OBJECTIVE
  The purpose of this study was to investigate the effect of the spectral distribution of the curing irradiation near the maximum excitation wavelength of the photo-initiator and the effect of the irradiation spot size on the scraping depth-of-cure and temperature rise in a resin composite for both an argon laser and a quartz-tungsten-halogen lamp.
  
  
  METHODS
  Using bandpass filters, the spectral outputs of an argon laser and a quartz-tungsten-halogen lamp were restricted to pass selected wavelengths on to a commercial camphorquinone-based resin composite and the depth-of-cure, using scraping methods, was measured. The temperature rise in composite was measured for some of the above-mentioned sources. The spot sizes for both sources were varied and the scraping depth was measured. Lateral curing or the extent of curing away from the focused spot was also measured.
  
  
  RESULTS
  For constant power density and exposure time, an irradiation spectral distribution closer to the photo-initiator excitation peak yielded a higher scraping depth than a broadband spectral distribution for both sources. Under similar conditions, the argon laser resulted in a lower temperature rise in the composite than the lamp. For the same total energy imparted to the resin composite, the scraping depth increased with reducing spot size of the curing irradiation. Furthermore lateral curing of the composite well beyond the irradiation spot size was observed.
  
  
  CONCLUSIONS
  The spectral and spatial characteristics of the curing irradiation need to be carefully considered as these affect the scraping depth-of-cure and temperature rise in a resin composite.
authors.affiliation: Applied Optics Center of Delaware and Department of Physics, Delaware State University, 1200 N DuPont Hwy, Dover, DE 19901, USA.
authors.forename: R D
authors.initials: RD
authors.lastname: Pradhan
authors.forename: N
authors.initials: N
authors.lastname: Melikechi
authors.forename: F
authors.initials: F
authors.lastname: Eichmiller
mesh_terms: D001128:Argon; D003188:Composite Resins / Q000737:chemistry / Q000528:radiation effects*; D004735:Energy Transfer; D005374:Filtration / Q000295:instrumentation; D006219:Halogens; D006801:Humans; D007834:Lasers; D008027:Light; D008422:Materials Testing; D010777:Photochemistry; D011108:Polymers / Q000737:chemistry / Q000528:radiation effects; D011791:Quartz; D013499:Surface Properties; D013696:Temperature; D013729:Terpenes / Q000737:chemistry; D013997:Time Factors; D014414:Tungsten
chemical_list: D003188:Composite Resins; D006219:Halogens; D011108:Polymers; C420128:Spectrum composite resin; C113300:TPH hybrid; D013729:Terpenes; D011791:Quartz; C048339:camphoroquinone; D001128:Argon; D014414:Tungsten