An assessment of visible-light polymerizing sources.
Measurements were made of the spectral distribution of light emitted from five commercially available visible-light polymerization units. All emissions peaked between 400 and 500 nm but the 'functional' irradiance varied by a factor of 20 for the sources investigated. Timer checks revealed errors of up to 20%. Light output was plotted as a function of time and, after 60 s, varied from-15% to +38% of the initial level. The decrease in irradiance with distance from the end of the guide was such that irradiance at 20 mm was between 20% and 40% of that at 2 mm. The light distribution across the face of each light guide was investigated and significant inhomogeneities discovered. An ultraviolet light (UV) hazard assessment was performed and it was concluded that none of the light sources presented a hazard to the operator in normal use.