Study of Generation of Singlet Oxygen in Human Saliva <i>in vitro</i> Under the Action of Nanosecond Pulsed Laser Radiation

Abstract

Background. The development of new laser devices for use in the treatment of complex dental pathology and microsurgery of the oral cavity with unique parameters with the ability to generate nanosecond pulsed radiation in a quasi-monochromatic radiation band is necessary. The high peak output power per pulse allows laser light to penetrate deeper into biological media without significant heating. The possibility of excitation of singlet oxygen without the use of endogenous photosensitizers is an indisputable advantage of such laser generators.
 Aims study of singlet oxygen generation in human oral fluid in vitro depending on the parameters of nanosecond pulsed laser radiation with a wavelength of ~1265 nm.
 Methods. We used a laser device with a main infrared (IR) emitter with a wavelength approximately corresponding to the oxygen absorption maximum (~1265 nm) with the generation of nanosecond pulsed radiation. A study was carried out to study the generation of singlet oxygen in the human oral fluid and the washing out of the oral fluid by the fading of the trap in solutions under the action of laser radiation before irradiation, after 30 and 60 min. The laser radiation parameters were set as follows: power 1 W, nanosecond pulsed radiation with a pulse duration of 400 ns and a frequency of 0.5, 1.0, 1.5 and 2.0 MHz in comparison with the continuous radiation mode.
 Results. It has been established that nanosecond laser radiation leads to the oxidation of a chemical singlet oxygen trap solubilized with sodium dodecyl sulfate (0.05 M SDS) detergent in the oral fluid and saliva flushing from the oral cavity. In pulsed nanosecond modes, laser radiation is more efficient than in continuous mode. With an increase in the repetition frequency, an increase in the effect by an average of 10% compared to a lower frequency was observed and the effect with a maximum frequency of 2.0 MHz was almost 50% higher than when using continuous radiation in all studies. A decrease in optical density at 414 nm was reliably observed in samples with oral fluid washing, the effect was 0.07 0.01 for 60 min of exposure. In the oral fluid, the effect with the same parameters was slightly lower and amounted to 0.05 0.03.
 Conclusions. The rate of fading of the trap in the saliva wash turned out to be 1.3 times faster than in water with detergent, which may indicate the activation of photoacceptors and their oversaturation with oxygen when using aqueous dilution of the oral fluid. The maximum effect was observed when using laser radiation with a pulse repetition rate of 2.0 MHz.