title: Phase, compositional, and morphological changes of human dentin after Nd:YAG laser treatment.
abstract: Although techniques for repairing root fracture have been proposed, the prognosis is generally poor. If the fusion of a root fracture by laser is possible, it will offer an alternative to extraction. Our group has attempted to use lasers to fuse a low melting-point bioactive glass to fractured dentin. This report is focused on the phase, compositional, and morphological changes observed by means of X-ray diffractometer, Fourier transforming infrared spectroscopy, and scanning electron microscopy-energy dispersive X-ray spectroscopy in human dentin after exposure to Nd:YAG laser. The irradiation energies were from 150 mJ/ pulse-10 pps-4 s to 150 mJ/pulse-30 pps-4 s. After exposure to Nd:YAG laser, dentin showed four peaks on the X-ray diffractometer that corresponding to a-tricalcium phosphate (TCP) and beta-TCP at 20 = 30.78 degrees/34.21 degrees and 32.47 degrees/33.05 degrees, respectively. The peaks of a-TCP and beta-TCP gradually increased in intensity with the elevation of irradiation energy. In Fourier transforming infrared analysis, two absorption bands at 2200 cm(-1) and 2015 cm(-1) could be traced on dentin treated by Nd:YAG laser with the irradiation energies beyond 150 mJ/pulse-10 pps-4 s. The energy dispersive X-ray results showed that the calcium/phosphorus ratios of the irradiated area proportionally increased with the elevation of irradiation energy. The laser energies of 150 mJ/ pulse-30 pps-4 s and 150 mJ/pulse-20 pps-4 s could result in the a-TCP formation and collagen breakdown. However, the formation of glass-like melted substances without a-TCP at the irradiated site was induced by the energy output of 150 mJ/ pulse-10 pps-4 s. Scanning electron micrographs also revealed that the laser energy of 150 mJ/ pulse-10 pps-4 s was sufficient to prompt melting and recrystallization of dentin crystals without cracking. Therefore, we suggest that the irradiation energy of Nd:YAG laser used to fuse a low melting-point bioactive glass to dentin is 150 mJ/ pulse-10 pps-4 s.
authors.affiliation: Department of Endodontics, School of Dentistry, National Taiwan University, Taipei, Republic of China.
authors.forename: C P
authors.initials: CP
authors.lastname: Lin
authors.forename: B S
authors.initials: BS
authors.lastname: Lee
authors.forename: F H
authors.initials: FH
authors.lastname: Lin
authors.forename: S H
authors.initials: SH
authors.lastname: Kok
authors.forename: W H
authors.initials: WH
authors.lastname: Lan
mesh_terms: D000538:Aluminum Silicates; D001672:Biocompatible Materials / Q000528:radiation effects / Q000627:therapeutic use; D002118:Calcium / Q000032:analysis; D002130:Calcium Phosphates / Q000032:analysis / Q000528:radiation effects / Q000627:therapeutic use; D003094:Collagen / Q000032:analysis; D003460:Crystallization; D003804:Dentin / Q000737:chemistry / Q000293:injuries / Q000528:radiation effects* / Q000648:ultrastructure; D004577:Electron Probe Microanalysis; D005898:Glass / Q000528:radiation effects; D006801:Humans; D053685:Laser Therapy; D008855:Microscopy, Electron, Scanning; D009354:Neodymium; D010758:Phosphorus / Q000032:analysis; D011829:Radiation Dosage; D017550:Spectroscopy, Fourier Transform Infrared; D014082:Tooth Fractures / Q000628:therapy; D014092:Tooth Root / Q000293:injuries; D014961:X-Ray Diffraction; D015019:Yttrium
chemical_list: D000538:Aluminum Silicates; D001672:Biocompatible Materials; D002130:Calcium Phosphates; C485828:alpha-tricalcium phosphate; C485817:beta-tricalcium phosphate; C485830:tetracalcium phosphate; D010758:Phosphorus; D009354:Neodymium; D015019:Yttrium; C485838:calcium phosphate, monobasic, anhydrous; D003094:Collagen; C020243:calcium phosphate; C018392:tricalcium phosphate; C485829:calcium phosphate, dibasic, anhydrous; D002118:Calcium