Verlängerung der Verarbeitungszeit von Kompositen mit einer neuartigen weißen LED-Arbeitsfeldbeleuchtung

Most light-curing composites for dental fillings contain the photoinitiator camphorquinone, which can be cured by a polymerisation lamp with blue light. However, the same range of wavelengths is also emitted by common operating lamps, so that the composite hardens unintentionally earlier. The surface of the composite becomes brittle and cracks appear when modelling is continued so that the material has to be replaced. The current solution to this problem is to reduce the illuminance of the light source. Alternatively, the critical spectrum below 500 nm can be filtered out or a yellow LED with a spectrum above 500 nm can be used. Both solutions of extending the working time create an uncomfortable lighting condition and reduce the perceptibility of contrasts for the dentist. Based on this problem, a phosphor-conversion light emitting diode (LED) is developed in the presented study, which emits white light and offers a longer working time of composites with camphorquinone than conventional LED headlamps. First, the excitation LED of the phosphor-conversion white LED was set with an emission maximum at 425 nm. It emits light in a range where the ratio between a low excitation of the photoinitiator camphorquinone and a high excitation of the S-cone in the eye is particularly favourable. Based on this LED, a fluorescent substance was selected for combination with it that emits light above 500 nm. The evaluation of the LEDs was carried out by the working time of composites containing camphorquinone with an acoustic measuring system at an illuminance of 10,000 lx. The colour temperature and spectra were taken into account in the analysis of the LEDs. Based on the results of the preliminary tests, a white LED was developed and produced by OSA Opto Light GmbH. The working time with this LED was between 6:40 min and 13:20 min at an illuminance of 10,000 lx for different composites. Compared to a headlamp, this is an extension of the working time by a factor of 3 to 5.5. The colour temperature is 3,000 K and is perceived as white. This white LED enables the dentist to model light-curing composites for filling teeth with a sufficiently long working time. In addition to the increased working time, the modelling is supported by a white working light.