Photopolymerization of dental materials: Types and characteristics of the light sources

Light from the polymerization source which initiates photopolymerization in the material has its determined wavelength. Photoinitiator, such as camphorhinone, excited by light, can be activated with any of the wavelength from its absorption spectrum. To obtain successful photopolymerization, light source should emit waves of adequate wavelength; light intensity has to be optimal, to have sufficient time of exposure and material up to 2 mm thickness. Photoinitiator inside the material should match light source spectrum and work regime. Halogen lamps have wide spectra of wavelengths in the visible part of the light spectrum. Their spectra are similar to absorption spectrum of camphorhinone. Plasma (xenon) lamps emit blue light. Though their diapason is low, spectra have great intensity. Adequate diapason and easy excitation allow them to have short time of exposure. LED lamps have blue diodes as light source. They do not need filters due to narrow emission spectrum. Laser (argon) lamps are the only that emit linear spectra. Ultraviolet (mercury) lamps are not in use any more in dentistry; theirs initiators were activated by UV light. LED lamps have longer life time; do not change the spectra during time, warm less, do not need filters, allow change of the source for more powerful, more efficient and more advantageous two steps or impulse illumination mode. However, LED lamps can not be used for a material that has photoinitiator(s) activated by light with wavelength above the maximum of the LED spectra. Svetlost lampe za polimerizaciju koja aktivira inicijator polimerizacije (fotoinicijator) u materijalu ima odredjenu talasnu duzinu za linije emisionog spektra lampe. Fotoinicijatori poput kamforhinona, koje svetlost samo pobudjuje, mogu se aktivirati svakom talasnom duzinom iz opsega svog apsorpcionog spektra. Da bi fotopolimerizacija bila uspesna, potrebno je da emisioni spektar lampe sadrzi pogodne talasne duzine, da intenzitet svetlosti bude optimalan, da vreme osvetljavanja bude dovoljno dugo i da debljina materijala ne bude veca od 2 mm. Za dobru polimerizaciju neophodno je uskladjivanje fotoinicijatora u materijalu, spektra lampe i rezima osvetljavanja. Halogene lampe imaju sirok spektar u opsegu vidljive svetlosti. Njihov spektar je slican apsorpcionom spektru kamforhinona. Plazma- lampe (ksenonske lampe) emituju svetlost plave boje. Uprkos uskom opsegu, njihov spektar je velikog intenziteta. Pogodan opseg i velika eksitanca plazma- lampi dozvoljavaju