ABSTRACT
INTRODUCTION Photoactivation is routinely used in Odontology to start the hardening reaction of clinical materials, such as "tooth colored" materials or composites. Normally, the lamps used have an emission of 400 to 510 nm, with peaks adjusted to an absorption maximum of camphorquinone, the photoinitiator most commonly used in dental materials. Traditionally, the light-curing units (LCUs) for the polymerization of oral biomaterial in dentistry have used halogen bulbs, but in recent years, the market is including light-emitting diodes (LEDs). Studies have shown that powerful LED LCUs have the potential to replace conventional halogen LCUs. However, it has also been demonstrated that LED LCUs with relatively low irradiances sold on the market may result in insufficiently cured composites and, therefore, inferior mechanical properties of the restoration [1]. In addition, not all dental composites are yet adapted to the LED-curing technology. The emitted light spectrum of LED LCUs differs from that of halogen LCUs and, therefore, the photoinitiator systems of some composites need to be adjusted to the spectrum of this new light. The clinical performance of light-polymerized dental composite is greatly influenced by the quality of the light-curing unit (LCU) used [2]. One of the determining factors in the quality of these lamps involves radiometric properties (form of emission, spectral irradiance for the application time, emission peak, etc.) [3]. In addition, the problems inherent in any lamp, such as stability or reproducibility of the emission, also heavily influence their clinical efficiency. The aim of the present study is to evaluate the temporal stability characteristics and the reproducibility of the radiometric properties (emission, peak, etc.) of high-power light-emitting diode (LED) arrays and halogen-light polymerization of oral biomaterial, which will enable the study of the suitability of LEDs LCUs in comparison with halogen light, in this field.
