ABSTRACT
Laser irradiation on hard tissue has produced a resistant surface that is likely to prevent caries. In this study, human enamel and dentine were exposed to nanosecond pulsed Nd:YAG laser with energy densities of 20-40 J/cm(2) and pulse width of 6 ns inducing chemical changes in these tissues. Infrared analysis of human dental enamel and dentine was performed using the KBr method (2mg sample/300 mg KBr). A correlation between non-lased and lased spectra was performed that gives an indication of the changes in organic and inorganic compounds after laser-tissue interaction. Spectra of teeth simultaneously show the inorganic and organic parts of the tissue. The principal bands: amide bands A, I, II, and III from the collagen-matrix, phosphate from the mineral content, and carbonate bands were identified. The normalized area of peak versus peak position was determined. Changes of the bands attributed to the collagen matrix were verified after Nd:YAG irradiation. The present results suggest a chemical modification of organic and mineral compounds by laser. The spectral results indicated an alteration in the absorption bands relative to, essentially, organic compounds.
Subject(s)
Dental Enamel/chemistry , Dental Enamel/radiation effects , Dentin/chemistry , Dentin/radiation effects , Lasers/adverse effects , Humans , Spectrophotometry, Infrared/methodsABSTRACT
The purpose of this study is to evaluate the possibility of using a pulsed Ho:YLF laser for endodontic surgery access, preparation of cavities, etching of dental enamel, and treatment of dental caries. Specimens were irradiated with a prototype of pulsed Ho:YLF laser (2,065 microns). Laser energies in the range of 120-750 mJ per pulse were used. The study of morphological changes on enamel and dentine was conducted on light and scanning electron microscopes. Perforation of approximately 4 mm depth with homogeneous and smooth aspect of its wall surfaces was obtained. There was no carbonization. Irradiation with low energy results in melted and recrystalized surface with small and shallow pits. In accordance with our results the Ho:YLF laser produces surfaces that are white in appearance in contrast to the Nd:YAG modified enamel and dentine surfaces, that were darkened. These are indications that the holmium laser may be useful for dentistry in the future.
Subject(s)
Holmium/therapeutic use , Laser Therapy , Tooth/radiation effects , Dentistry/trends , Humans , Tooth/pathologyABSTRACT
Passive stable mode locking of a pulsed Nd:YAG laser was achieved with a long-decay-time saturable absorber in a coupled-cavity longitudinal scheme. In this configuration the saturable absorber (LiF:F(2) ) also behaves as an active medium in intracavity pumping and is the load for the Nd laser. This arrangement provides proper lasing conditions for the F(2) color centers so that the cavity photon lifetime of the color centers is much shorter than the cavity round-trip time of the Nd laser. In this way the Nd pulses are simultaneously Q switched and mode locked. The pulses show a stable temporal profile, with an envelope of 160 ns and a train of mode-locked pulses of less than 200-ps duration.
