Ablation ability of an erbium laser with a 2.64-μm wavelength during preparation of dental tissues

Abstract

Using electronic microscope we have studied the opportunity to apply YAG:Cr,Tm-Er laser irradiation (=2.64 jtm) for preparation of the enamel and dentine in different modes of operation. High efficiency of enamel and dentine preparation was shown when using 50 J/sm2 energy density and frequency of pulses proceeding 3-5 n. There were no damaged effects involved teeth hard tissues in our experiences.The opportunity to apply laser irradiation to odontopreparation in therapeutic stomatology was one of the early ideas in laser applied science4"°"3"5'7. There was a point ofview, that anyone could be able to realize effectively working up of the teeth hard tissues without any pain. Many authors have made several experiences in this theme using hard-materials, gas and eximer lasers, which generated irradiation in lengths of waves in different regions of the spectrum by continuous or pulse-frequently modes of operation5'6'8"2"9'20. The results of these studies did not allow to employ the lasers in therapeutic stomatology for teeth preparation because of influence of laser irradiation results to fissurae and enamel damages, carbonization of the dentine near the zone of incidence of the ray, damages and irreversible alterations in teeth pulp''7'8'18. The search of optimal approaches to solve the problem, result to elaboration of the Er:YAG laser, thich generated irradiation in ?.=2.69 !.tm and X2.69 tm. These irradiation are very similar to one of the basic absorbability maximums of waters, so, they influence both teeth tissues and molecules of water inculcated into the tissue, that allow to its' effectively ablation during preparation, and give the opportunity to avoid chapness ofenamel and dentine, and alteration ofteeth pulp9"4 Resent elaboration in this region of science is creation of YAG:Cr,Tm-Er laser (GOl institute named of SI. Vavilov), which generates irradiation with X=2.64 tm. The of this study is to research the application opportunities of YAG: Cr,TmEr laser irradiation in odontopreparation. MATERIALS AND METHODSThe investigation was performed with 80 human teeth, extracted by different reasons, which were devoted to 16 groups by 5 teeth in each. Preparation of enamel and dentine was made by YAG:Cr,Tm-Er laser irradiation (50 and 120 JIsm2 energy density, 3 and 5 n, pulse time 400 ms ) with teeth water irrigation and without any irrigation. Before experience teeth were kept in 0.9 % solution of natrium chioridi at temperature 37 °C during 24 hours. After preparation the teeth were set into the 2.5 % solution of glutartic aldegidis with cacodilatic buffer at temperature 4 °C during 2 hours. Then, the specimens were put into the 2 % osmium fixing solution, were washed away with saccharose solution and were dehydrated by rising concentration spirits battery. Definitive drying was performed in lipophilic dry chamber. Then teeth were fixed in microscope tables and were coat with copper. To investigate the teeth tissues we used the scanned microscope Hitachi H-300>> (Japan) with 100 A resolution. We have studied 80 ...